Mech Mecca

Vehicle Dynamics

2013-12-08T14:36:00.000+05:30

Dynamic Suspension Systems

Dynamic Suspension Systems

Active and semi-active suspension systems control the forces generated in an adjustable suspension component such as struts, or shock absorber. The adjustment of the damping on individual wheels enables optimization of ride characteristics, dynamic handling, pitch control, and roll-over mitigation.

Fully active systems have the ability to bi-directionally adjust the control forces in the adjustable suspension components. Semi-active systems apply force in only a single direction.

In addition to improvements in dynamic performance, functions such as variable ride height and platform levelling are easily implemented which are of great benefit in defense applications and public transport.

Active Differential Control

Pi Innovo has worked with leading automotive differential manufacturers to apply electronic control to wide range of technologies targeted at light and heavy vehicle applications.

A standard open differential allows each wheel on an axle to rotate at different speeds, such as when negotiating a turn, to avoid tire scrub. The open differential always provides the same torque to each of the two wheels on that axle. While the wheels can rotate at different speeds, they apply the same rotational force, even if one is entirely stationary and the other spinning with no traction.

By contrast, a locked differential forces both left and right wheels on the same axle to rotate at the same speed under nearly all circumstances, without regard to traction differences at either wheel. Electrically controlled differentials are a mix between an open differential and a locking differential. They can intelligently switch between fully open and fully locked. More advanced systems allow proportioning between the limits of full open and full lock. This level of control can address traction, vehicle stability and rollover. Using OpenECU differential manufacturers have been able to improve the stability and mobility of vehicles across a broader range of terrain.

Brake Based Stability

Conventional anti-lock brake (ABS) systems detect when an individual wheel stops rotating relative to the ground, due to slip. The systems then momentarily decrease the braking force until traction with the ground is regained. Conversely traction control systems momentarily apply braking force during acceleration when slip is caused by high drive torque.

Sophisticated brake based stability control takes ABS and traction control functions into two dimensions. The system can detect excessive vehicle over-steer and under-steer by using integrated inertial sensors and vehicle dynamics software models. Mitigation of the excessive under-steer or over-steer is performed by applying one or more brake calipers to induce a yaw moment on the vehicle.

The flexibility of the OpenECU concept allows proven brake based stability algorithms to be implemented in smaller dedicated ECU platforms or integrated into larger ECU platforms controlling complete powertrain or suspension systems.

Aerodynamics

When travelling at speed aerodynamic lift can have significantly reduce the down force on each wheel with obvious degradation to stability and traction.

Our engineers have developed electronic controllers, derived from OpenECU technology to control the deployment of adjustable spoilers that increase down forces when required without raising fuel consumption at lower speeds by increasing drag.

This is just one example of the versatility of the OpenECU concept.

Zircotec's Ceramic Coating

2013-11-10T23:16:00.002+05:30

It is a range of ultra high performance plasma-sprayed ceramic coatings to protect components from the effects of fire, heat, wear, abrasion and corrosion.

Our ceramic coating is highly effective when used on engine exhaust system components including exhaust manifolds, exhaust headers, cat boxes, turbochargers and tail pipes, helping to protect sensitive components from the effects of heat. As an exhaust coating they reduce underbonnet temperatures, increase engine performance, help solve engine packaging issues, and improve engine compartment safety. Based on our proprietary ThermoHold^® formulation, our ceramic coating range can only be applied by Zircotec. A series of patent applications are in progress (with two now granted) to protect our technology. Our coatings have been proven to:

Reduce underbonnet temperatures by up to 50^oC (122^oF), as independently measured & confirmed by DAMAX Race Engineering;
Increase engine performance, eg. a 30^oC drop in intake air temperature can deliver a 6% increase in power, or can increase engine efficiency leading to less fuel usage;
Extend the life of vulnerable components and thereby enhance engine reliability.

PLASMA-SPRAY PROCESSING

General Plasma Spray Processing - Plasma-spray processing is a relatively specialised high temperature industrial process that utilises an electrically generated plasma to heat and melt the feedstock material. The process is capital intensive and requires significant electrical power. It offers a method of depositing a feedstock material (the material that is being plasma-sprayed) as a solid coating over an underlying target material. It can also be used to produce free standing parts made from just the plasma-sprayed material. Deposits having a thickness from just a few micrometers (µm) up to several millimeters can be produced using a variety of feedstock materials, including metals and ceramics.

The feedstock material is normally presented to the plasma torch in the form of a powder or wire. This feedstock melts rapidly within the plasma torch, where the typical operating temperature is ~10,000^oC (18,000^oF). It is then propelled as small molten droplets via a carrier gas towards the target material. When the molten droplets contact the target material they flatten, rapidly solidify to form a deposit that remains adhered to the target material. There are a large number of parameters that influence the interaction of the feedstock with the plasma jet and the substrate, and these parameters can lead to wide variations in the final product and product quality. These parameters include feedstock type and composition, feed rate, plasma gas composition and flow rate, energy input, torch geometry, nozzle design, nozzle offset distance, substrate cooling, etc.

The plasma-sprayed deposits consist of a multitude of pancake-like 'splats', formed by flattening of the liquid droplets. As the feedstock powders typically have sizes from micrometers to above 100 micrometers, the splats have thickness in the micrometer range and lateral dimension up to hundreds of micrometers. Small voids occur between the splats thereby trapping either air or the carrier gas whilst the splats cool rapidly leading to quite rapid crystallisation and large grain size. It is also possible for the deposited material to exist in metastable phases due to rapid cooling (i.e. crystalline structures that would normally only occur at very high temperature). Small micro-cracks and regions of incomplete bonding can also occur under certain plasma-spray conditions. The deposited material can therefore have properties that are significantly different from the bulk feedstock materials, eg. lower strength, higher strain thermal and electrical conductivity. By controlling plasma-spray parameters it is possible to control and make use of these changed material properties to suit specific applications.

This technique is mostly used to produce coatings on structural materials. It can be used to provide protection against high temperatures, corrosion, erosion and wear, or to change the appearance, electrical or tribological properties of the surface. The technique can also be used to replace worn material. Free standing parts in the form of plates, tubes, shells, etc. can be produced. The technique can also be used for powder processing (spheroidisation, homogenisation,modification of chemistry, etc.). In this case, the substrate for deposition is absent and the particles solidify during flight or in a controlled environment such as water.

Design

2013-11-09T19:03:00.003+05:30

Strategy and Design

Recall from our discussion of operations strategy that product design must be consistent with the overall strategy of the firm. In general, we would expect firms that have a low-cost strategy to have fairly standard products that change very little over time. A firm with a differentiation strategy might have a large variety of products, highly innovative products, or products with many features.

Low Cost Strategy

Standardized Products
Little Change over Time

Differentiation Strategy

Customized Products
Large Product Variety
Highly Innovative Products
Products with Many Features

It is essential for designers to know the overall strategy of the firm when designing new products. Increasingly firms are using differentiation as a way to compete. We would expect the design function to be extremely important when a differentiation strategy is employed by the firm. Designers must also be aware of basic design principles that allow new products to:

Come to market quickly,

At a competitive cost, and

Of high quality

A good design process is essential for excellent product development.

The Design Process

The stages of the design process are illustrated in the diagram below:

Generally, ideas are generated, then studied for feasibility. If the product is feasible, a preliminary design is generated from performance specifications, and a prototype is built. Process planning and final design are worked out during the next stage, and final design and manufacturing specifications are spelled out. Manufacturing begins when the product and process designs are finalized.

Idea Generation

Ideas come from many sources, including:

Customers
Competitors
Suppliers
R & D and Product Development Departments

Some companies label ideas from customers as market-pull and ideas from R & D as technology push. While ideas from customers are thought to be the most important, many products come from internal units specifically designed for product development.

Example: When IBM developed its first portable computer, individuals of exceptional talent were grouped together and sent off-site to develop the new product. Many companies use the "think-tank" approach for new products. Products that are highly technical often require development to begin with technical experts since customers have not yet thought of the product. After product introduction, customer input is essential for product improvement.

Other idea tools

Feasibility Study

A feasibility study is an analysis to determine if a market exists for the product, and if so, will financial returns be adequate enough to support the product? Several of the analyses that must be done include:

Market analysis -- assesses the demand for the product through demographic studies, customer surveys, interviews, focus groups, and market tests.

Economic analysis -- examines pricing policies for the new product; compares price and cost for the sales volume, and estimates the financial return for the product

Technical and strategic analysis -- assesses any new technology needed for the product or process; evaluates the strategic fit of the product with the rest of the firm.

Preliminary Design

A prototype is built from preliminary designs and performance specifications (instructions of what the product is supposed to do). The complete design process is an iterative process that involves building, testing, changing, testing, etc. Design is concerned with both form and function.

Form -- the physical appearance of the product

Function -- the performance of the product

Final Design and Process Planning

Final design is the stage at which detailed drawings and design specifications (product size, composition, form) are produced. Detailed drawings were called blueprints in the past, but now most detailed drawings are donewith computer-aided design (CAD). If you've ever seen blueprints or CAD drawings, you know that they contain many technical details and instructions that allow anyone working with the product to understand how it is made. Some details of process planning might also be included on the drawings. Process plans indicate which parts are purchased, which machinery must be used, how products are assembled, etc. Manufacturing specifications are detailed instructions for producing the product.

Improving the Design Process

As we mentioned earlier, more firms are using differentiation to be competitive. Since differentiation often requires uniqueness in the form of exceptional products, good design processes are essential. Poor design processes result in delayed market exposure and poor product quality. One major problem with poor design processes is excessive use of engineering change orders (ECOs). ECOs are documents that detail changes that must be made to a product after final drawings have been released. They are expensive and time-consuming.

Example: Manufactured or modular homes are becoming increasingly popular for modest-priced housing. With modular homes, framing, floors, windows, doors, and walls are constructed and assembled in a factory, then transported to a homesite. The foundations, and sometimes roofs, are made at the homesite. Suppose a window was designed into the middle of a bedroom wall, but the customer notices that he will have more room for furniture if the window is placed off-center. Changing the location of the window will require an ECO -- which means changes on the architectural drawings, rework of the existing window, scrapping of existing framing, etc. Delivery of the home may be delayed, and workmanship may suffer if workers rush to make the change.

Improving Design Processes

Using multi-functional design teams
Using concurrent engineering for product and process planning
Design for manufacture (DFM) and design for assembly (DFA)
Design for the environment
Measuring design process quality
Using quality function deployment (QFD)
Designing for robustness

Design Teams

Design teams composed of marketing, manufacturing, and engineering are necessary for getting timely information from all relevant decision areas. Others who may be useful team members include customers, suppliers, dealers, lawyers, and accountants. Cross-functional teams are some of the most effective since each function has information unique to its own discipline. There is less danger that one person will duplicate another's work when cross-functional teams are used. Furthermore, early communication about particular functional needs allow for early planning to cover each detail.

Concurrent Design

Not so long ago, manufacturers used to talk about engineers "throwing the drawings over the wall" to manufacturing. This phrase was used in reference to the fact that engineers and manufacturers did not communicate about products very well. Engineers may have specified parts or production processes that were not available or were difficult to obtain. It was manufacturing's role to accomplish monumental feats of production without complaining. Today, we recognize that such failure to communicate is bad business. Concurrent engineering requires early manufacturing involvement or continuous manufacturing involvement.

Design for Manufacture

In recent years, more attention has been paid to technical methods of design improvement. Some important technical concepts are:

Design for manufacture (DFM) -- designing a product so it can be produced easily and economically.

Product simplification -- designing products using a minimum number of parts and simplest manufacturing processes.

Standardization -- using interchangeable parts on multiple products so that some parts can be manufactured in high volumes for economies of scale.

Modular design -- combining standardized building blocks, or modules, in a variety of ways to create unique finished products. Modular design can also mean building a few common "platforms," then adding different features to make customized products. It is a method of gaining the benefits of low cost standardized parts without losing the design flexibility that allows customers to choose their options.

Design for assembly (DFA) -- a set of procedures for reducing the number of parts in an assembly, evaluating methods for assembly, and determining an assembly sequence.

The figure below shows a good example of design for manufacture.

Example: Whirlpool is known for its excellent international products strategy. Appliances around the world differ substantially. Not only are there differences in size and aesthetic appearance, but technical requirements also differ dramatically. Electrical voltages and environmental requirements in each country make appliance design quite complicated. Yet Whirlpool was successful in finding those parts of appliances that are common across a number of countries and using them as platforms on which to add country-specific features. By using such a design strategy, Whirlpool is able to source its high volume parts at low cost from the best manufacturers in the world while using local manufacturers for its more unique parts.

Design for Environment (DFE)

Around the world (and particularly in Europe), concern for the environment is growing. New standards are being developed so that products can be designed to reduce their burden on the environment. Some design guidelines include:

Reduce packaging
Design for recyclability
Design for re-use
Design for easy repair
Use recycled materials
Minimize the use of materials

ISO standards for environmental design are listed under ISO 14000.

Measures of Design Quality

When we speak about quality in this section, we are not talking about product quality. We are concerned about how well a design group has followed the principles we have discussed so far when designing a product. If a group is interested in measuring how well it is following good design principles, it should measure things like:

Number of component parts and product options
Percentage of standard parts
Use of existing manufacturing processes
Cost of first production run
First-year cost of field service and repair
Total product cost
Total product sales
Sustainable development (a measure of design for environment)

Setting good design goals and measuring them is one way to ensure that design groups will seriously pursue better ways of designing products.

Quality Function Deployment (QFD)

We've discussed the importance of communications when new products are developed. One method of guaranteeing communication among departments, suppliers, and customers is to use quality function deployment (QFD). QFD offers a structured approach for matching customer requirements with technical requirements at every stage of the design and manufacturing process. QFD uses a tool called a house of quality. The Figure below shows the parts of a house of quality.

On the left-hand side of the house, marketing would determine the essential characteristics of a product important to a customer. The "voice of the customer" drives QFD. Just below the roof, the engineers and designers would list the technical requirements of the product (related to customer needs) they typically design and specify. On the far right, the design group's product is assessed against competitors' products. The center portion of the house shows the relationship between the customer needs and technical requirements, while the roof shows how each technical requirement is related to another. The important analytical portion of the house is at the bottom. Here, the data from the other parts is analyzed for cost and technical difficulty, then rated for customer importance. Where there is a gap between what the customer sees as important and where our design group's competitive assessment is low, there should be changes made. An example of a completed house of quality is illustrated below.

The house of quality actually begins a communications chain that relates requirements for the final product to a series of requirements throughout the design and production process. Product characteristics for the final product become the customer requirements for the parts suppliers. Part characteristics then become the customer requirements for the process planners, and so on. The Figure below shows the relationships between the house of quality and successive design houses. It should be obvious that this structured approach forces a great deal of thought to be put into each level of design and production.

Design for Robustness (Taguchi's Contribution to Quality)

Robust designs are product designs that allow a product to function properly under a wide variety of environmental conditions. For example, an automobile that can as smoothly in Alaska and Arizona as it can in middleAmerica is a robust design. Conditions that cause a product to operate poorly (called noise) can be separated into controllable and uncontrollable factors. From a designer's viewpoint, controllable factors are parameters typically specified by the designer -- like material used, dimensions, and processing requirements. Uncontrollable factors are under the user's control or part of the user's environment -- things like heat, humidity, settings, degree of maintenance provided, etc. The designer's job is to choose values for the controllable factors that react to the possible occurrences of the uncontrollable factors:

Robust Design: Influence of Controllable Factors > Influence of Uncontrollable Factors

IN-LINE EXERCISE

The following factors must be considered when designing refrigerators. Indicate whether each factor is controllable or uncontrollable.

Number of times the door is opened and shut
Number of BTUs of thermal energy extracted by the refrigeration unit
Number of shelves
Amount of food stored in the refrigerator
Size of the storage compartments

Answer

Reliability

Reliability -- the probability that a given part or product will perform its intended function for a specified length of time under normal conditions of use. For example, tires are expected to last for 40,000 miles when used on normal terrain. A product or system's reliability is a function of the reliabilities of its component parts and how the parts are arranged. Reliability is one of the most important measures of product quality. Reliability is often expressed as a proportion or percentage, like 90%. A reliability of 90% means that the product will operate as intended for a certain time period 90% of the time.

Let's take a look at how reliability can be used along with design for manufacture, specifically when manufacturing a system.

A system is any product composed of more than one component. Components can be connected to each other in two ways:

In series, or in such a way that all components must operate if the product or system is to operate.

A fuel tank -- connected to a fuel hose -- connected to a fuel pump -- connected to fuel injectors is a system with components in series.
If one of the components in the fuel system fails, the entire system fails to operate.
Think of a series system as water flowing through a pipe and series of valves. If one valve closes, the water flow stops.
System reliability for series systems is expressed as

R_s= R₁R₂R_{3 . . .}R_n, where n = no. of components in the system

Series Reliability

In parallel, or in such a way that if one component fails, a similar or identical component will take over its function. Parallel systems are said to be redundant.

The space shuttle has redundant computers. If one computers fails, another takes over its function.
Think of a parallel system as a pipe that branches off into two pipes with valves in them, then re-joins into a single pipe on the other side of the valves. If one valve closes, water can still flow through the other side.
System reliability for parallel systems is expressed as:

R_s = 1 - (1 - R₁)(1 - R₂). . . (1 - R _n), or

R_P=R₁+R₂(1-R₁) if only two parallel components are present

Parallel Reliability

Another way to think about computing parallel reliabilities is to reason as in the following example:

Example: If two electrical resistors are installed in parallel, and each has a 90% reliability, that means each resistor will operate 90% of the time. One resistor may fail, and that may occur 10% of the time. During that 10% of the time, the other resistor is likely to work, but only 90% of the time. If we multiply 90% times 10%, we get 0.9, or 9% of the total time that the second resistor will provide backup. This tells us that during the time when the first resistor fails, the second resistor will work 9 out of 10 times. Since failure of the first resistor occurs only 10% of the time, our second resistor covers us 9% of the total time. To summarize, the first resistor covers us 90% of the total time, and the second covers us 9% of the total time, or 90% of the 10% failure time. Adding the reliabilities together, we get 90% for the first resistor and 9% for the second resistor, for a total of 99%. Mathematically, we can say R_P=R₁+R₂(1-R₁)

EXAMPLE

We can compute system reliabilities for different systems by reducing each component into its equivalent series reliability. Suppose we have the following system:

What is the system reliability?

The first step is to reduce the parallel reliabilities into the equivalent series reliability, so we must find the reliability of the R_B - R_Bparallel system:

R_BB= 1 - (1 - R_B)(1 - R_B)
R_BB= 1 - (1 - 0.92)(1 - 0.92)
R_BB= 1 - (0.08)(0.08)
R_BB= 0.9936

The equivalent system is now:

It is now possible to compute the system reliability since all components are at their series equivalents:

R_S= R_AR_BBR_C
R_{S =}(0.95)(0.9936)(0.99)
R_S= 0.9345

Suppose we did not have the redundant component at B. Our reliability would be R_S= (0.95)(0.92)(0.99) = 0.8653. You can see that we improved our system reliability (0.9345) significantly by adding the redundant component B.

IN-LINE EXERCISE

Compute the system reliability for the system below. First compute the series equivalent for the two parallel systems, then compute the reliability for the entire system.

Compute these:

R_AA=? R_BB=? R_CC=?

Then compute R_S

Answer

Improving Reliability to Reduce Redundancy

Now, we see from the series reliability equation that it makes sense to keep the number of parts in a system as small as possible. As the number of parts in series increases, we increase the probability that one will fail. In some instances, however, system reliability may not be good enough, and the number of parts may have to be increased by putting them in parallel. Note the difference: in the case of parallel parts, we are installing an identical or similar part, not an entirely different part. Still, there are ways to improve reliability while also reducing redundancy:

�

Example: Boeing is a company that wanted to reduce the number of parts used on the Boeing 777, a wide-body jet. Its earliest wide-body jet, the Boeing 747 uses 4 engines to support the needs of the aircraft. The engines are installed in parallel so that if one engine fails, the three remaining engines will continue to operate. The Boeing 777 has only two engines -- much larger than those on the Boeing 747. Does that mean that the Boeing 777 is less reliable than the Boeing 747? No -- each individual Boeing 777 engine is made to be more reliable than each of the four engines on the Boeing 747, so the Boeing 777 is actually more reliable than the Boeing 747.

Technology in Design

New product development is increasingly necessary to maintain competitiveness. One tool that has dramatically improved the ability to design new products is the computer.

Computer-aided design (CAD) is a software system that uses computer graphics to assist in the creation, modification, and analysis of a design. Some features of CAD include:

geometric modeling - the use of basic lines, curves, and shapes to generate the geometry and topology of a part

automated drafting - the production of detailed drawings directly from the CAD database

computer-aided engineering (CAE) - simulating operating conditions of a part on the computer and analyzing it for movement, stress, interference, and thermal properties.

link to computer-aided manufacturing (CAD/CAM) - the automatic conversion of CAD design data into processing instructions for computer-controlled equipment and the subsequent manufacture of the part as it was designed.

Benefits of CAD include:

reduced lead time for new product introduction
quicker product changes
quicker product testing
real-time access to design information
improved design process through better communication
more alternatives to be considered

Service Design

We live in a service economy. The proportion of services in the GDP is large, but not as large as the proportion of labor employed in services. It is more difficult to find productivity savings in services because of the large labor content. Service design, therefore must be carefully considered. Service design has some unique characteristics that differentiate it from product design. We will review these, then discuss design concepts for service.

Characteristics of Service

Services are intangible. Services are experienced; they cannot be touched, felt, or seen. Service design is based on expectations of the experience. Many differences exist for what customers expect for the experience and from the provider.
Services have high customer contact. Customer contact makes production of the service highly visible, unlike production of tangible goods. High visibility means that a positive encounter between the customer and provider is essential.
Services are perishable. Since services cannot be stored in inventory, service design must define not only what is to be delivered, but also where and when.
Consumers do not separate the service from the delivery (production) of the service. Services are produced and consumed simultaneously. Service design must specify how the service is produced, including :

the level of customer participation in the service process
front-room (visible) vs. backroom (invisible) tasks
role and authority of the service provider
the balance of touch vs. tech (level of automation)

Services tend to be decentralized and geographically dispersed. Many small outlets make up most services. Service organizations can become large, often through franchising or "chains," but dispersion means that decision-making and control tends to be more localized.
Services are consumed more often than products, so there are more opportunities for service "moments of truth" (chances to succeed and fail).
Services can be easily emulated, so new service improvements may occur even more rapidly than product improvements

Concurrent Engineering

2013-11-09T18:57:00.001+05:30

CONCURRENT ENGINEERING: WHAT IT IS AND HOW IT WORKS

Automotive suppliers face a number of challenges. Automotive systems are becoming more advanced, while delivery timeframes are increasingly shorter. At the same time, automakers are continually calling on suppliers to reduce costs.
   To satisfy these contradictory requirements, DENSO was one of the first in the industry to adopt concurrent engineering.
   Concurrent engineering works like this: people from a variety of departments, including product planning and production engineering, are brought together in multidisciplinary teams at the start of the product design process. This collaborative approach gives everyone involved equal access to the project's concept, blueprints and objectives. Design parameters are then fine-tuned based on in-depth discussions and parallel decision making within the team, so that remedial actions are taken well before the new product advances to the manufacturing phase. Cost estimates—including everything from personnel expenses to transportation costs—efficiency and quality can also be assessed more accurately to devise the optimum procurement and manufacturing processes. Cost and delivery times are both factored into the manufacturing process during the design phase, allowing us to achieve innovative cost reductions and significantly cut delivery time.
   This differs from the conventional linear approach to manufacturing, where product planning departments create the initial concept, designers use the concept to construct blueprints, and the production engineering department designs a manufacturing process based on these plans. Each of these activities is done independently and without discussion.

The Fruits of Concurrent Engineering
In January 2001, we were asked to design a new type of alternator for the 2002 Toyota Celsior and Estima. The new alternator had two requirements—it had to be more compact, and it had to have a higher power output than its predecessor.
To increase output, our product design team proposed increasing the number of coils in the alternator. But that led to a number of issues:

The limited space available meant that engineers had to use finer wires to increase the number of coils.
Due to the higher temperatures resulting from the required increase in power output, the coil wire had to be even more resistant to heat.
Existing alternator production line equipment was incapable of manufacturing alternators with more coil windings.

Taking on these challenges, DENSO's material engineers created a new type of high-performance wire that was finer and offered greater heat resistance, while the Machinery and Tools Department successfully developed proprietary manufacturing equipment capable of attaching coils inside components with smaller dimensions. At the same time, our production engineers used simulations to develop the best manufacturing equipment and processes for smaller alternators. These cooperative and concurrent efforts allowed us to meet the customer's requirements: alternator output was boosted to 85 amps from 55, while the diameter of the alternator core was reduced to 128mm from 135. Manufacturing costs were also cut by 30 percent.

THE BENEFITS: SYSTEMIZATION, MODULARIZATION AND STANDARDIZATION

Concurrent engineering processes do more than just streamline the design and development phases of new product creation; they also lead to smaller and lighter components, systemization and modularization, and standardized components,making us more competitive.
While compact automotive components help to reduce the size and weight of vehicles and increase cabin space (benefits for our customers and end-users), they help us in our own operations as well. We can cut the amount of materials used; reduce the size of manufacturing equipment; and scale back warehousing. Naturally, this results in a lower cost base.
Systemization and modularization also benefit both suppliers and automakers. Fewer parts in a component mean materials costs are lower, assembly costs are reduced, and production lines and logistic networks are smaller. In short, we can make products with the same functionality using smaller facilities and less investment. Standardizing components, which entails using common internal devices and systems without sacrificing outward individuality and appearance, allows us to respond to automaker model changes without losing time or resources.

ENHANCING QUALITY: ADVANCED MANUFACTURING EQUIPMENT AND SKILLS

Quality has to be built into production processes. That is why we trust our highly skilled associates and our highly reliable equipment to achieve the DENSO standard of quality. These are standards other companies find hard to match.
How do we know? Our consistently strong showing at the WorldSkills Competition, formerly known as the Skill Olympics, is one way. In this competition, skilled technicians from around the world compete in a range of technical challenges that require micron-level accuracy. In the last WorldSkills Competition, DENSO associates participated in five categories, winning medals in all five competitions. In the instrument-making category, DENSO has won the gold medal six years in a row. Because most production lines are highly automated, this kind of expertise is vital in the construction of “mother machines,” core manufacturing equipment employed in our production lines. Designed and manufactured in-house by the Machinery and Tools Department, these machines allow us to make components in unique and innovative ways.

LOWERING COSTS: AIMING TO ACHIEVE A GLOBAL MINIMUM COST

Since DENSO produced its first component in the 1950s, we have consistently worked to achieve a global minimum cost lower than that set by the customer. This process is even more difficult and demanding as automakers establish competitive global cost bases and automotive component makers face ever-tougher demands to reduce unit costs.
Concurrent engineering helps us accurately set a global minimum cost—and deliver on it.
The shared knowledge flowing from concurrent engineering allows each department to provide advice on how best to reduce the final cost of the component: by altering the initial design, adapting manufacturing processes or devising optimal materials, while keeping mid-process changes to an absolute minimum. Aware that most of the cost of a new product is incurred in the initial design phases, we target this stage of the process to deliver cost reductions to our customers.

REDUCING DELIVERY TIME: INITIATIVES BEGIN AT THE DESIGN STAGE

In the conventional linear approach to manufacturing, delays occurring in one part of the process have an unplanned effect on the rest of the cycle. These incremental delays build up, putting added strain on the production process and leaving less room for maneuver.
Our unique approach to manufacturing means we avoid this pitfall. At DENSO, “delivery” means more than getting products to customers on time. It is a concept that is factored into every part of the manufacturing process. Multidisciplinary teams cooperate at all phases of the process to devise innovative ways to cut delivery times. Every department plays a crucial role. Working hand-in-hand with automakers, DENSO enhances logistics and inventory control efficiency, and speeds up delivery by carefully reviewing and fine-tuning every part of the process. This way the burden is shared, reducing pressure on the end of the process and helping us to meet tight delivery targets.

QCD: AT THE HEART OF EFFORTS TO BOOST GLOBAL SHARE

By realizing world-leading levels of QCD performance, we are aiming to enhance customer satisfaction and ultimately increase DENSO's share of the global automotive components market. Put simply, QCD is crucial to a key objective in our current medium-term management plan: capture the leading global share in 23 automotive product categories.

N-Time Technology: Driving Productivity Improvements

N-time technology is a phrase unique to DENSO. It was created to define technologies that drive dramatic improvements in productivity, not easily expressed with ratios. Instead, the word "times" is used. Heat exchange component production lines are a good example of how we have applied this technology to significantly boost manufacturing efficiency. Other benefits include a reduction in production line area and the creation of next-generation components that deliver real improvements in performance. Specifically, we introduced N-time technology soldering
equipment that reaches its optimum operational temperature 4 times faster than earlier devices, speeding up the manufacturing process. Proprietary equipment using N-time technology was also installed at other stages of the production line, resulting in an overall increase in processing and assembly speeds of 2 to 3 times. The combined benefit of all our improvements in the heat exchange component production line was an increase in output of 1.5 times.

THE UNIVERSAL PRODUCTION SYSTEM: UNIFORM QCD PERFORMANCE

In building an optimum global manufacturing framework, we have to consider a range of local issues: the needs of automakers, workforce skills, procurement costs, and personnel expenses, to name just a few. Using this information, we rapidly adapt our universal production system to the local business environment and have it up and running with minimal investment. This tried and tested approach means we can quickly achieve uniform QCD performance wherever we operate.

THE VITAL INGREDIENT: INVESTING IN PEOPLE

No matter how advanced our facilities or materials, people are still the vital ingredient—it is DENSO associates who make the difference. They take to heart our approach to mono-zukuri, our commitment to Quality First, and help us create new manufacturing technologies.
In April 2001, we established the DENSO E&TS Training Center Corporation in Japan to evaluate skills and provide technical training. This company enhances the skills of two key groups of engineers: those involved in product development and those helping to fabricate the finished products on the factory floor. Building stronger ties between these two groups of engineers ensures that concurrent engineering remains an integral and widely accepted element of DENSO’s corporate culture. The center also supports overseas facilities through training programs designed to foster the skills that our technicians need.

Devising Optimum Equipment and Workflow Processes

Concurrent techniques are not limited to product development processes. We also use them to develop manufacturing equipment.
On the factory floor, machinery and tools, production engineering and production control departments work closely with engineers, managers and other associates to devise optimum equipment and workflow processes.
Creating simulated production lines from cardboard is one technique we use. The approach was first employed in Thailand in 2002 to boost productivity and incorporate the expertise and work-related ideas of local personnel. Prior to installing new manufacturing equipment, we build life-size production lines made from cardboard and wood that incorporate mock-ups of the new equipment currently under development. This allows us to simulate and monitor actual workflow processes, helping us to reduce startup lead times. If we notice any potential flaws in the system, we can rapidly make adjustments to fix them. Moreover, we can achieve output targets almost as soon as a new production line comes on stream, helping to further reduce costs.

Bearings

2013-06-30T23:13:00.001+05:30

A bearing is a machine element that constrains relative motion between moving parts to only the desired motion. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads (forces) applied to the parts.

Parasitic Power Losses in Hydrodynamic Bearings

Parasitic frictional losses in machines result in wasted energy and the generation of heat, which affects the life of materials, including the lubricant. A significant portion of total fluid film bearing losses in high-speed turbomachinery may be consumed simply in feeding oil to the bearings.

At surface speeds below roughly 10,000 ft/min, these extraneous parasitic losses are generally less than 10 percent of those of the oil-film frictional losses. For higher velocities, however, these losses increase rapidly with surface speed and can reach 25 to 50 percent of the total bearing loss in large turbine-generators and related machinery. This article discusses parasitic frictional losses in turbo machinery and suggests means for their reduction.

Sources of Parasitic Losses
Parasitic losses for both journal and thrust bearings (Figures 1 and 2) can be assigned to two categories: through-flow loss simply caused by the lube oil’s passage through a bearing, and surface drag between the lube oil and rotating surfaces. Due to larger diameter and large surface area, these losses are generally greater in thrust bearings.

Through-flow Loss. These losses result from three sources: acceleration of the oil as it enters feed ports, influx and outflux of lubricant to and from feed grooves, and discharge of the lubricant from the bearing (leakage). Through-flow losses for a pivoted-pad thrust bearing can be assigned to the following sources (Figure 1):

One single velocity head loss for oil entering at the shaft surface velocity. This loss is associated with the flow of the oil feed as it enters under the base ring, makes an abrupt turn, and is brought to the bulk oil velocity between the shaft outside diameter and the inside diameter of the base ring.
One single velocity head loss, calculated at the mean thrust runner diameter, for the oil as it passes into the channels between the tilting pads and into the bearing oil film.
Approximately 25 percent of discharge oil is assumed to be splashed onto the thrust runner to be reaccelerated at the runner’s outside diameter. This action is not typically encountered in conventional journal bearings.

Figure 1. Parasitic Losses in a Pivoted-pad Thrust Bearing

Referring to Figure 2, a plain cylindrical axial-groove journal bearing introduces a total parasitic loss of 1.5 velocity heads (calculated at the shaft surface velocity). This results from acceleration of the feed oil as it enters into the turbulent vortex in the feed groove and then further accelerates as it enters the bearing oil film itself. In pivoted pad journal bearings, on the other hand, vortex action and churning in the square-sided cavity between pads offers more resistance to entering feed oil.

Surface Drag Losses. Power loss from fluid friction drag on wetted shaft and thrust collar areas follows the general turbulent relation for hydraulic drag in channels where frictional loss is related to the dimensionless Reynolds number. For circular annular spaces around a journal, and for overshot internal grooves, as in the upper half of some journal bearings, the estimate of drag coefficient should be increased by 30 to 40 percent These losses would be reduced by appropriate draining of the housing to avoid fully-flooded operation.

Reducing Parasitic Losses
Several strategies may be employed to minimize parasitic losses in high-speed bearings. The simplest is to reduce the oil feed volume. A method that nearly eliminates the through-flow losses in fixed-pad bearings is discussed in the next section. For pivoted shoe bearings, feeding the oil directly to the leading edge of each bearing pad is an attractive method for decreasing parasitic power losses.

Decreased Loss with Partially Filled Grooves.When the oil feed rate drops to the extent that internal grooves in a bearing are not completely filled with oil, the parasitic drag loss in the groove also drops, frequently to a negligible level.

Figure 3. Decrease in Power Loss in a 27-inch
O.D. Tapered Land Thrust Bearing Partially Filled

Figure 3 illustrates this point for a 350-square inch tapered-land steam-turbine thrust bearing operating at 3,600 rpm, wherein a step drop in power loss was encountered with decreasing oil flow. As the design oil feed was gradually reduced, at 166 gpm the total power loss in the bearing dropped from 800 to 473 hp. At this point, the back pressure dropped in the feed grooves with simultaneous elimination of through-flow loss for the entering oil.

Combined with observation of low loss in cavitated hydrodynamic oil films themselves, surface drag losses appear to become negligible for all partially filled zones within a bearing.

Leading Edge Feed Grooves. Several pivoted-pad bearing designs use sprays or channels to feed oil directly to the leading edge of each thrust pad in a bearing cavity otherwise empty of oil. These arrangements avoid essentially all surface drag losses which would otherwise be encountered by rotating surfaces immersed in oil as well as portions of through-flow losses. Such designs are offered primarily for the surface speeds above that encountered in journal bearings with diameters approximately 10 to 12 inches operating at 3,600 rpm. For lower surface velocities, parasitic power losses become so low as not to warrant the extra cost and complexity with specially directed feed.

In high-speed bearings, leading edge oil feed grooves provide significant benefits. Oil flow rates can be as much as 60 percent lower with power loss down 45 percent. While a variety of lubrication flow arrangements, design and operating factors exert an influence, the resulting bearing temperature may be reduced by 16 to 35°F.

Figure 4. Pivoted Pad Thrust Bearing with
Leading Edge Oil Feed Grooves and Oil Lift
Pockets (Courtesy Kingsbury, Inc.)

As a surprising factor, reversing the rotation to place the oil feed groove at the trailing edge of each pad still provides satisfactory operation of a pivoted pad journal bearing at moderate speeds. This suggests that hot oil is still carried over from one pad to the next, and that absence of bulk oil from the bearing cavity is likely the major benefit to be realized from directed lubrication.

As bearing surface speeds range above approximately 10,000 ft./min., significant parasitic power losses may be encountered. At 30,000 ft./min., these losses may range up to half of the total power loss experienced in a bearing – equal to the power loss in the hydrodynamic load-supporting oil film itself. The following are factors to consider for minimizing parasitic frictional losses and achieving lower bearing temperatures:

Limit oil feed rate to the minimum required for reliable bearing operation.
Blend the shape of oil groove entrance ports and groove walls to minimize vortex flow restrictions.
Minimize unessential oil-wetted areas on rotating journal and thrust surfaces.
Minimize splashing of discharge oil onto rotating surfaces.
Utilize directed lubrication with leading edge grooves to feed tilting-pads.

Mechanical Devices

2013-06-27T23:08:00.005+05:30

Chaff Cutters

A chaff cutter is a mechanical device for cutting straw or hay into small pieces before being mixed together with other forage and fed to horses and cattle. This aids the animal's digestion and prevents animals from rejecting any part of their food.

Chaff and hay played a vital role in most agricultural production as it was used for feeding horses. Horses were extensively used in farming operations until they were replaced by tractors in the 1940's.

Chaff cutters have evolved from the basic machines into commercial standard machines that can be driven at various speeds and can achieved various lengths of cuts of chaff with respect to animal preference type. New chaff cutter machines include portable tractor driven chaff cutter - where chaff cutter can be in the field and load trolleys (if required).

Chaff Cutting Machine ( SP 10 PLAIN ):

Hand cum power operated, Covered fly wheel, Feeding tray,
Slide rail for motor, Motor pully, Machine pully, Handle, Grinder.
But without NEUTRAL & REVERSING arrangement.
R.P.M. MAX : 150
H. P. REQD : 1 : 2 H. P.
CAP.KGS. PER HOUR : 150
BLADES ARNGT : 2

Chaff Cutting Machine ( SP 10 SPECIAL ) :

Hand cum power operated, Covered fly wheel, Feeding tray,
Slide rail for motor, Motor pully, Machine pully, Handle, Grinder.
But without NEUTRAL & REVERSING arrangement.
Above machine but with NEUTRAL & REVERSING arrangement.
R.P.M. MAX : 200
H. P. REQD : 1 : 2 H. P.
CAP.KGS. PER HOUR : 200
BLADES ARNGT : 2

Chaff Cutting Machine ( SP 14 SG ) :

Power operated, Covered fly wheel from top as well as bottom,
feeding tray, Slide rail for motor, Motor pully, Machine pully &
Grinder.
R.P.M. MAX : 300
H. P. REQD : 3 : 5 H. P.
CAP.KGS. PER HOUR : 300
BLADES ARNGT : 3

Chaff Cutting Machine ( SP 14 SGDB ) :

Power operated, Covered fly wheel from top as well as bottom,
feeding tray, Slide rail for motor, Motor pully,Machine pully &
Grinder. Above machine with Downward Blower arrangement.
R.P.M. MAX : 300
H. P. REQD : 3 : 5 H. P.
CAP.KGS. PER HOUR : 300
BLADES ARNGT : 3

Chaff Cutting Machine ( SP 25/4 BLADED ) :

Power operated, Covered M. S. Plate Wheel fitted with Steel
blades, Feeding tray, Slide rail for motor & grinder. Machine
Pully, Grinder & Regrinding attachment. Downward blower.
Above machine with 4 Blades arrangement.
R.P.M. MAX : 400
H. P. REQD : 5 : 7.5 H. P.
CAP.KGS. PER HOUR : 800
BLADES ARNGT : 4

Chaff Cutting Machine ( SP 30/ 3 BLADED ) :

Power operated, Covered M. S. Plate Wheel fitted with Steel
blades, Large feeding tray, Pressing drum, Complete ball
bearings, Slide rail for Motor & Grinder. Machine Pully, Grinder
& Regrinding attachment. Downward & High level blower.
R.P.M. MAX : 600
H. P. REQD : 7.5 : 10 H. P.
CAP.KGS. PER HOUR : 1500
BLADES ARNGT : 3

Chaff Cutting Machine ( SP 30/ 3 BLADED ):

Power operated, Covered M. S. Plate Wheel fitted with Steel
blades, Large feeding tray, Pressing drum, Complete ball
bearings, Slide rail for Motor & Grinder. Machine Pully, Grinder
& Regrinding attachment. Downward & High level blower.
Above machine with 4 Blades arrangement.
R.P.M. MAX : 600
H. P. REQD : 7.5 : 10 H. P.
CAP.KGS. PER HOUR : 1500
BLADES ARNGT : 4

Chaff Cutting Machine ( SP 30/ 3 BLADED DB ):

Power operated, Covered M. S. Plate Wheel fitted with Steel
blades, Large feeding tray, Pressing drum, Complete ball
bearings, Slide rail for Motor & Grinder. Machine Pully, Grinder
& Regrinding attachment. Downward & High level blower.
with Downward blower only.
R.P.M. MAX : 600
H. P. REQD : 7.5 : 10 H. P.
CAP.KGS. PER HOUR : 1500
BLADES ARNGT : 3

Chaff Cutting Machine ( SP 30 DB 4 BLADED ) :

Power operated, Covered M. S. Plate Wheel fitted with Steel
blades, Large feeding tray, Pressing drum, Complete ball
bearings, Slide rail for Motor & Grinder. Machine Pully, Grinder
& Regrinding attachment. Downward & High level blower.
Above machine is 4 Blades arrangement.with Downward
blower only.
R.P.M. MAX : 600
H. P. REQD : 7.5 : 10 H. P.
CAP.KGS. PER HOUR : 1500
BLADES ARNGT : 4

Chaff Cutting Machine ( SP 40 ) :

Power operated, Covered M. S. Plate Wheel fitted with 4 Steel
blades, Large feeding tray, Pressing drum, Complete ball
bearings, Heay frame made out of 4" channel, Slide rail for
Motor & Grinder.'C' sec heavy machine Pully, Grinder &
Regrinding attachment. Downward & High level blower.
R.P.M. MAX : 500
H. P. REQD : 15 : 20 H. P.
CAP.KGS. PER HOUR : 3000
BLADES ARNGT : 4

Chaff Cutting Machine ( SP 25/3 BLADED ) :

Power operated, Covered M. S. Plate Wheel fitted with Steel
blades, Feeding tray, Slide rail for motor & grinder. Machine
Pully, Grinder & Regrinding attachment. Downward blower.
R.P.M. MAX : 450
H. P. REQD : 5 : 7.5 H. P.
CAP.KGS. PER HOUR : 800
BLADES ARNGT : 3

Chaff Cutting Machine ( SP 45 TRACTOR ) :

Tractor driven, Mounted on 2 wheel Trolly frame Above machine
but operated with Tractor, Having machine level blower only.
R.P.M. MAX : 500
H. P. REQD : TRACTOR
CAP.KGS. PER HOUR : 3000
BLADES ARNGT : 4

Chaff Cutting Machine ( SP 45 TRACTOR ) :

Tractor driven, Mounted on 2 wheel Trolly frame Above machine
but operated with Tractor, Having machine level & high blower
R.P.M. MAX : 500
H. P. REQD : TRACTOR
CAP.KGS. PER HOUR : 3000
BLADES ARNGT : 4

Worlds Largest Helicopters

2013-06-24T23:43:00.001+05:30

The article you mention discusses several of the largest planes in the world. It also describes how aircraft are typically ranked by weight rather than by physical dimensions like length or wingspan. The same holds true for helicopters. Although the diameter of the rotor is often a useful measure of a helicopter's size, these vehicles are most often ranked by maximum takeoff weight. As was also true of the largest planes, the ranks of largest helicopters are largely dominated by craft originally built in the Soviet Union. Perhaps that should be no surprise given the vast size of that nation and the need to transport large cargoes to distant and remote locations.

1. Mil V-12 : 231,485 lb (105,000 kg)

Mil V-12, largest helicopter in the world
The largest helicopter ever built was a massive aircraft developed in the Soviet Union during the 1960s called the Mil V-12. The V-12 was a rather unusual test vehicle that featured two rotors mounted side by side at the ends of a large wing. Each rotor had a diameter of nearly 115 ft (35 m). The helicopter was so enormous that the distance from the edge of one rotor disk to the other was almost 220 ft (67 m), even wider across than the wingspan of a Boeing 747!
Even more remarkable was the lifting capacity of this powerful craft. The V-12 had a maximum takeoff weight of 231,485 lb (105,000 kg), nearly twice that of the second largest helicopter, and set a record in 1969 for carrying a payload of 88,635 lb (40,205 kg). So massive was the V-12 that this payload weight alone is greater than the maximum takeoff weight of the third biggest helicopter in the world! These impressive figures have earned the V-12 the record as the world's largest helicopter according to the FAI and the Guinness Book of World Records.

Only two V-12 prototypes were built, yet despite its amazing size and lifting power, the design was considered a failure by its manufacturer and Soviet authorities. The V-12 was simply too big and difficult to maneuver to be a practical machine. A production model would have been called the Mi-12, but these plans were cancelled following evaluation of the two test vehicles. One of the V-12 prototypes was retired to the Russian Air Force Museum in Monino while the second is kept at the Mil factory near Moscow.

2. Mil Mi-26 : 123,455 lb (56,000 kg)

Mil Mi-26 recovering an American CH-47 Chinook helicopter
Because the V-12 had been judged unsatisfactory, Mil was again tasked with designing a large heavy-lift helicopter for military and civil use. The resulting Mi-26 was far more compact than the V-12 due to advancements in propulsion technology, making the Mi-26 much less cumbersome to operate. With a maximum takeoff weight of 123,455 lb (56,000 kg), the Mi-26 is the world's second largest helicopter overall and the largest ever to go into production as well as the largest flying today.
though substantially smaller than the V-12, the Mi-26 carries a considerable payload up to 44,000 lb (20,000 kg). The Mi-26 has proven much more powerful and efficient than its predecessors thanks in part to its eight-bladed main rotor. This rotor is only 106 ft (32 m) in diameter compared to the 115 ft (35 m) diameter rotors used aboard other giant Russian helicopters but can lift greater loads due to improvements in engines and blade design. Over 200 examples of the Mi-26 were built and the type remains in use throughout Russia. Several have also been sold to civilian firms and foreign nations.

An inside view of Mil Mi-26

Rare and Front view of Mi-26

In September, 1996, one Mi-26 set a world record when lifted 224 paratroopers at the height of 6500 m (four miles).

3. Mil Mi-6 : 97,000 lb (44,000 kg)

The third and fourth largest helicopters are also Mil designs that helped prepare the way for the V-12 and Mi-26. The Soviet's first attempt to create an enormous heavy-lift helicopter came during the mid-1950s with the introduction of the Mi-6. Designed for many of the same duties as the improved Mi-26 some 25 years later, the Mi-6 had a maximum takeoff weight of 97,000 lb (44,000 kg) and could carry up to 24,250 lb (11,000 kg) of payload. The rotor used on the Mi-6 was the same 115 ft (35 m) diameter rotor system that would also be used on the V-12.
The Mi-6 was the world's largest helicopter when it was first built and retained the title for many years until the appearance of the V-12. The Mi-6 proved quite successful for its time as illustrated by the large number built. Some 860 were manufactured between 1960 and 1981 primarily for the Soviet Air Force and the civil airline Aeroflot. Additional models were also exported to several Soviet allies. These helicopters remained in use for over 40 years but are finally being phased out. In spite of its age, the Mi-6 still remains a remarkable vehicle and one of the largest helicopters ever conceived

4. Mil Mi-10 : 83,775 lb (38,000 kg)

Mil Mi-10 showing its long landing gear legs
Yet another member of this related family of giant helicopters was the Mi-10. The Mi-10 was a specialized variant of the Mi-6 called a flying crane. The Mi-10 borrowed the engine and dynamic systems of the Mi-6 but these were mounted within a new fuselage. Unlike the wide Mi-6 fuselage that featured hinging doors for loading cargo internally, the Mi-10 fuselage was instead configured for passengers. This fuselage
stood atop four widely spaced, extended-length landing gear legs designed to straddle large, bulky payloads carried below the helicopter.
Both the Mi-6 and Mi-10 shared the same 115 ft (35 m) diameter rotor that was also used aboard the V-12. Compared to the Mi-6, however, the Mi-10 had a reduced maximum takeoff weight of 83,775 lb (38,000 kg) ranking it as the fourth largest helicopter ever built. Only about 55 Mi-10 helicopters were made and the type saw relatively little use. Both its flying crane mission and the transport duties of the Mi-6 have since been taken over by the far superior Mi-26.

5. Sikorsky CH-53E : 73,500 lb (33,340 kg)

Coming in as the fifth largest helicopter in the world is the biggest ever built in the United States, the Sikorsky CH-53E Super Stallion. The CH-53E is an enlarged model of the earlier CH-53 Sea Stallion. Both vehicles were originally developed as heavy-lift helicopters for the US Marine Corps, and they have also been used by the Navy, Air Force, and allied countries. The largest variant of the CH-53 family developed so far is the CH-53E with a maximum takeoff weight of 73,500 lb (33,340 kg). Though comparable in physical dimensions to other H-53 models with a main rotor 79 ft (24.1 m) in diameter, the CH-53E and related MH-53E are equipped with an extra engine of increased power to lift a significantly greater payload.

CH-53E Super Stallion lifting an F-15 Eagle fighter

Approximately 115 examples of the CH-53E and MH-53E Sea Dragon variant were built, and these remain the largest helicopters in military service in the West. However, a new version of the venerable H-53 design is currently under development. Known as the CH-53K, this improved model will carry more powerful engines and new rotor blades to increase maximum takeoff weight to 84,700 lb (38,420 kg). Once this enhanced variant becomes available, the CH-53K should narrowly beat the Mi-10 to become the world's fourth largest helicopter.

6. Boeing Vertol MH-47E/G : 54,000 lb (24,495 kg)

The next largest helicopter is the Boeing Vertol CH-47 Chinook also developed in the United States. The H-47 family began development during the late 1950s as an enlarged variant of the CH-46 Sea Knight and has proven to be one of the most successful series of military heavy-lift helicopters. The design features a long, spacious fuselage powered by two engines driving a pair of tandem rotors 60 ft (18.3 m) in diameter. The type is widely used for transporting troops, carrying heavy military equipment like artillery slung underneath the fuselage, and resupply missions. Though the primary users are the US Army and British Royal Air Force, the CH-47 has been sold to over 20 nations as well as civilian operators

The single largest versions of the H-47 developed to date are the MH-47E and MH-47G special operations models. While most CH-47 variants have a maximum takeoff weight around 50,000 lb (22,680 kg), the MH-47E/G have been upgraded to 54,000 lb (24,495 kg). Over 1,000 Chinooks have been built to date and production of newer CH-47F, MH-47G, and HH-47 models continues today.

7. Hughes XH-17 : 50,000 lb (22,680 kg)

Coming in as the seventh largest helicopter is a unique prototype called the XH-17 Sky Crane. The Sky Crane was the first helicopter built by Hughes Aircraft, the same company that had also built the behemoth Spruce Goose flying boat during the 1940s. Shortly thereafter, Howard Hughes became interested in helicopter technology and purchased a design for a giant transport helicopter from the Kellett company. Similar to the Russian Mi-10, the Sky Crane was equipped with four long landing gear legs to straddle large oversized payloads carried underneath the fuselage. The H-17 was lifted by a massive two-blade rotor system 134 ft (40.8 m) across, still the record for the largest rotor ever flown

Construction of a single XH-17 prototype began during the late 1940s for use as a research vehicle. The craft was completed by 1952 when it began a three-year testing period. The maximum takeoff weight ever attempted aboard the Sky Crane was over 50,000 lb (22,680 kg) during a flight in 1953. However, the research program concluded the design was too large and cumbersome to be useful and no further models were built. Hughes also designed an enlarged variant called the H-28 that would have doubled the maximum weight to nearly 104,000 lb (47,000 kg), but further development was cancelled following experience with the XH-17.

8. Sikorsky CH-54 : 47,000 lb (21,320 kg)

Rounding out this list of large helicopters is another American design called the Sikorsky CH-54 Tarhe. Like the Mi-10 and XH-17, the CH-54 was a flying crane helicopter designed to haul large payloads slung below the fuselage. The unusual looking helicopter featured an upper spine containing the engines driving the 72 ft (21.9 m) diameter main rotor. At the front of this spine was the cockpit with windows facing both forward and aft allowing crew to monitor the payload. This minimal fuselage structure made the CH-54 a very efficient design compatible with various cargo modules that could be hoisted into position behind the cockpit for low drag.

CH-54 Tarhe recovering a damaged F-4 Phantom II

With a maximum takeoff weight of 47,000 lb (21,320 kg), the CH-54 was designed primarily for transporting military cargoes like artillery, ground vehicles, and other bulky supplies. Its lifting capabilities were frequently used during the Vietnam War to move aircraft or recover downed planes and helicopters. A civil model called the S-64 Skycrane was also developed and became popular with the logging industry and for firefighting. About 105 of these helicopters were built, and though retired from military service, several remain in civilian use.

Summary

Further illustrating just how large the helicopters described above are is the fact that no other helicopter exceeds a maximum weight of 35,000 lb (15,875 kg). The majority of helicopters are indeed quite small next to these giants since there is relatively little demand for such enormous vehicles compared to more moderately sized designs. Yet even among these giants, the size differential between them is hard to comprehend. The following diagram compares the Russian V-12 and Mi-26 to the American CH-53E. Despite its enormous size relative to any other Western helicopter, the Super Stallion almost seems a toy next to the two largest helicopters ever built.

Material Handling Systems

2013-05-16T13:39:00.004+05:30

Excavators

Excavators are heavy construction equipment consisting of a boom, stick, bucket and cab on a rotating platform (known as the "house"). The house sits atop an undercarriage with tracks or wheels. A cable-operated excavator uses winches and steel ropes to accomplish the movements. They are a natural progression from the steam shovels and often called power shovels. All movement and functions of a hydraulic excavator are accomplished through the use of hydraulic fluid, with hydraulic cylinders and hydraulic motors. Due to the linear actuation of hydraulic cylinders, their mode of operation is fundamentally different from cable-operated excavators.

Backhoe

What is a Backhoe Loader?

Backhoe loaders have a very unique appearance -- they have components sticking out every which way. It's obvious what adump truck does just by looking at it; but what are the different appendages of a backhoe used for?

A backhoe loader is an interesting invention because it is actually three pieces of construction equipment combined into one unit. A backhoe loader is:

A tractor
A loader
A backhoe

Each piece of equipment is suited to a particular sort of work. On a typical construction site, the backhoe operator usually uses all three components to get the job done.

The Tractor

The core structure of a backhoe loader is the tractor. Just like the tractors that farmers use in their fields, the backhoe tractor is designed to move easily over all kinds of rough terrain. It has a powerful,turbocharged diesel engine, large, rugged tires and a cab with basic steering controls (a steering wheel, brakes, etc.). Backhoe cabs are either completely enclosed or have an open canopy structure to give the operator protection.

The Loader

The loader is attached in the front and the backhoe is attached in the back. These two components serve very different functions.

The loader can do several different things. In many applications, you use it like a big, powerful dustpan or coffee scoop. You usually don't dig with it; you mostly use it to pick up and carry large amounts of loose material. It's also used to smooth things over like a butter knife, or to push dirt like a plow. The operator controls the loader while driving the tractor.

The Backhoe

The backhoe is the main tool of the backhoe loader. It's used to dig up hard, compact material, usually earth, or to lift heavy loads, such as a sewer box. It can lift this material and drop it in a pile to the side of the hole.

Basically, the backhoe is a big, extremely powerful version of your arm or finger. It has three segments:

The boom
The stick
The bucket

This arrangement is very similar to your arm. Your arm has three segments -- your upper arm, forearm and hand.

The backhoe segments are connected by three joints, comparable to your wrist, elbow and shoulder. The backhoe moves in pretty much the same way as your arm. In a Caterpillar® backhoe, the boom is bent upward to make it easier to dig with obstacles in the way. This design also provides extra space for the bucket when the operator curls it in with a full load.

The backhoe can dig all sorts of holes, but is especially suited for digging ditches. To use the backhoe, the operator has to park the tractor and turn the seat around.

So what do the tractor, loader and backhoe have to do with each other? The tractor component is for moving the other two components from place to place, and the operator also maneuvers it when using the loader. The loader and backhoe components are a natural combination for all sorts of jobs. When you dig up a lot of dirt to make a ditch or any other sort of hole, you generally need a loader to either move the dirt out of the area or to fill the dirt back in once you've got the pipes, power lines, etc. in position. The most common application for a backhoe loader is this basic job -- digging a trench with the backhoe and then back-fillingit with the loader.

The Stabilizer Legs

The other appendages you'll typically notice on a backhoe loader are the two stabilizer legs just behind the rear wheels. These legs are crucial to backhoe operation because they take the brunt of the weight when a backhoe is digging. Without the stabilizer legs, the weight of a heavy load or the downward force of digging into the ground would strain the wheels and tires, and the whole tractor would bounce constantly. The stabilizers keep the tractor steady, minimizing the jostling effect of digging with the backhoe. They also secure the tractor so that it won't slip into the ditch or hole.

The stabilizer legs have two types of "shoes," so that they can be planted securely on both dirt and pavement. The grouser shoe side digs into the dirt for a better grip, but would tear up the pavement if you were to use it on a road. For a good grip on asphalt, the operator simply flips the rubber-padded shoe into position.

Hydraulic Power

If you've ever watched a backhoe at work, you know that it is an extraordinarily powerful tool. An experienced operator can dig a 5-foot-deep, 10-foot-long ditch in less than 15 minutes. Just think how long it would take you to do that with only a shovel! Amazingly, all of this work is done withhydraulics -- pumping liquid to move pistons.

The concept of hydraulic machinery may seem pretty bizarre -- how can pumping liquid give you such power? -- but it's actually very simple. First, let's look at the basic idea of a hydraulic system, and then we'll see how a backhoe uses these systems to dig and load such huge amounts of dirt.

Hydraulic systems simply transmit forces from point to point through fluid. Most systems use anincompressible fluid, a fluid that is as dense as it can get. This sort of fluid transmits nearly all of the original force instead of absorbing some of it. The most commonly used incompressible fluid in hydraulic machinery is oil.

In the very simple hydraulic machine shown below, the operator pushes on the oil with one piston so that the oil pushes on another piston, raising it up.

Hydraulic multiplication

Because the second piston has a larger diameter than the first piston, the second piston moves a shorter distance but pushes up with greater force.

The basic concept at work is a trade between distance and force. The work you do in pressing down on the piston on the left has two components -- the amount of force you apply and how far you push the piston. This pushes down a certain amount of fluid. Since the fluid is incompressible, it can't absorb the force you apply, so it pushes up on the piston on the right. The fluid has the same pressure (pounds per square inch) at every point in the system. Since the pressure at the piston on the right is working on a larger area, that piston pushes upward with a greater force.

It's pretty easy to figure out the exact multiplication factor. Assume that the piston on the left has a 2-inch diameter (1-inch radius), while the piston on the right has a 6-inch diameter (3-inch radius). The area of each piston is Pi * r². The area of the left piston is therefore 3.14 (3.14 * 1²), while the area of the piston on the right is 28.26 (3.14 x 3²). The piston on the right is nine times larger than the piston on the left. This means that any force applied to the left-hand piston will be nine times greater on the right-hand piston. So, in the illustration above, the 100-pound downward force applied to the left piston creates a 900-pound upward force on the right piston. But, in keeping with the force-distance trade-off, you've moved the left-hand piston 9 inches and raised the right-hand piston only 1 inch.

In the backhoe loader shown above, the hydraulic system pumps oil at up to 3,300 pounds per square inch, and the cylinder pistons in the backhoe arm have a diameter of up to 5.25 inches. This gives each cylinder piston a force of 70,000 pounds!

Different Types of Material Handling Equipment

Material handling equipment encompasses a diverse range of tools, vehicles, storage units, appliances and accessories involved in transporting, storing, controlling, enumerating and protecting products at any stage of manufacturing, distribution consumption or disposal.

Categories of Material Handling Equipment

The four main categories of material handling equipment include: storage, engineered systems, industrial trucks and bulk material handling.

Storage and Handling Equipment

Storage equipment is usually limited to non-automated examples, which are grouped in with engineered systems. Storage equipment is used to hold or buffer materials during “downtime's,” or times when they are not being transported. These periods could refer to temporary pauses during long-term transportation or long-term storage designed to allow the buildup of stock. The majority of storage equipment refers to pallets, shelves or racks onto which materials may be stacked in an orderly manner to await transportation or consumption. Many companies have investigated increased efficiency possibilities in storage equipment by designing proprietary packaging that allows materials or products of a certain type to conserve space while in inventory.

Examples of storage and handling equipment include:

Racks, such as pallet racks, drive-through or drive-in racks, push-back racks, and sliding racks

Stacking frames

Shelves, bins and drawers

Mezzanines

Engineered Systems

Engineered systems cover a variety of units that work cohesively to enable storage and transportation. They are often automated. A good example of an engineered system is an Automated Storage and Retrieval System, often abbreviated AS/RS, which is a large automated organizational structure involving racks, aisles and shelves accessible by a “shuttle” system of retrieval. The shuttle system is a mechanized cherry picker that can be used by a worker or can perform fully automated functions to quickly locate a storage item’s location and quickly retrieve it for other uses.

Other types of engineered systems include:

Conveyor systems

Robotic delivery systems

Automatic guided vehicles (AGV)

Industrial Trucks

Industrial trucks refer to the different kinds of transportation items and vehicles used to move materials and products in materials handling. These transportation devices can include small hand-operated trucks, pallet-jacks, and various kinds of forklifts. These trucks have a variety of characteristics to make them suitable for different operations. Some trucks have forks, as in a forklift, or a flat surface with which to lift items, while some trucks require a separate piece of equipment for loading. Trucks can also be manual or powered lift and operation can be walk or ride, requiring a user to manually push them or to ride along on the truck. A stack truck can be used to stack items, while a non-stack truck is typically used for transportation and not for loading.

There are many types of industrial trucks:

Hand trucks

Pallet jacks

Pallet trucks

Walkie stackers

Platform trucks

Order picker

Sideloader

Many types of AGV

Bulk Material Handling Equipment

Bulk material handling refers to the storing, transportation and control of materials in loose bulk form. These materials can include food, liquid, or minerals, among others. Generally, these pieces of equipment deal with the items in loose form, such as conveyor belts or elevators designed to move large quantities of material, or in packaged form, through the use of drums and hoppers.

Conveyor belts

Stackers

Reclaimers

Bucket elevators

Grain elevators

Hoppers

Silos

Car Engines

2013-04-25T09:37:00.003+05:30

There are a number of different types of car engines in today's road and race cars, and the number is growing especially with emerging technologies like Hybrids.

Most cars these days use what is called a four-stroke combustion cycle to convert gasoline into kinetic motion. This four-stroke approach is known as the the Otto cycle, in honor of Nikolaus Otto who invented it in 1867.

Intake stroke- air and fuel are taken into the cylinder as the piston moves downwards.

Compression stroke- where the air and fuel are compressed by the upstroke of the cylinder.

Combustion stroke- compressed mixture is ignited and the expansion forces the cylinder downwards.

Exhaust stroke- waste gases are forced out of the cylinder.

The intake and outlet ports open and close to allow air to be drawn into the cylinder and exhaust gases to be expelled.

So we understand that the engine is effectively a device which sucks in air, compresses it, ignites it and then blows the air out again to create power to the road wheels. In terms of the performance gains possible, there are a vast multitude of different techniques and technologies.

First of all lets get a understanding of the different types of engine layouts commonly found in cars today. As Engines can come in an array of different designs, including Straight/Inline, V Type, Boxer, Rotary Wankel and even Diesel:

Straight/ Inline Engines
V Type Engines
Boxer/ Flat Engines
Wankel/ Rotary Engines
Diesel Engines

Straight/ Inline Engines

In-line engines have the cylinders arranged, one after the other, in a straight line. Almost all four cylinder engines are A straight/Inline engine is considerably easier to build than an otherwise equivalent Boxer or V type engines because the cylinder bank and crankshaft can be milled from a single metal casting and it requires fewer cylinder heads and camshafts.

This ultimately means lower production and maintenance costs. Also due to their smaller and more lightweight construction, this is the preferred Engine design for FF cars (Front Wheel Drive). The design can be extremely fuel efficient compared to V type, Boxer and Rotary engine designs.

There are some five and six cylinder Straight/ Inline design engines, which are mainly found in European cars from the likes of Audi and BMW for example.

Reasonable performance can be achieved with performance levels in the 0'9 Ford Focus RS around 300 BHP. This is mostly due to Turbo Charging and boost pressure used, but it is common for a 2.0 Litre 16 Value inline 4 to produce 200 BHP plus.

The engines are not generally thought to be as smooth as the V type and Boxer engine designs and the structure has it's limitations in terms of durability and strength. Inline engines can sometimes be a little rough in lower revs, but work well for smaller cars and do respond well to Tuning.

V Type Engines

The V-type of engine has two rows of cylinders set normally at a ninety degree angle to each other. Advantages include it's short length, great rigidity of the block, its heavy crankshaft, and attractive low profile. This is a tried and tested engine design with huge performance potential.

In sports applications, having the engine as low to the floor as possible increases the car's handling characteristics, as it will naturally have a lower centre of gravity. Also having a strong engine with built in rigidity can mean the difference in endurance races, making the V type engine design an ideal choice for Motorsport applications.

With this type of engine it is possible to have a very high compression ratios, without block distortion under load.

This makes it a strong and robust design for high performance applications and is used in F1 for instance. Also with it's resistance to torsional vibration, the engine characteristics produce a smooth and refined engine.

Another attribute for this compact engine design is a shorter car length without losing passenger room. In 1914, Cadillac was the first company in the United States to use a V-8 engine in its cars. From there America has fallen in love with the V type engine and the 50's and 60's produced some of the best Muscle cars.

Boxer/ Flat Engines

In 1896, Karl Benz invented the first internal combustion engine with it's horizontally opposed pistons. This Boxer/Flat engine is an design with multiple pistons that all move in the horizontal plane. The most popular and significant layout has cylinders arranged in two banks on either side of a single crankshaft, generally known as "boxers". This is because the two pistons join together in the middle of TDC ( Top Dead Centre).

This is similar to two boxers touching gloves at the beginning of a bout and is the origins of the name appointed to the engine design.

Flat engines have a lower center of gravity than any other common configuration, so vehicles using them should benefit from better stability and control during cornering. But they are also wider than more traditional configurations and the extra width causes problems fitting the engine into the engine bay of a front-engined car. Subaru have been producing AWD front engined cars for some time now, so where there's a will they is a way.

Boxer engines are one of only three cylinder layouts that have a natural dynamic balance; the others being the Straight/Inline 6 cylinder and the V12 design. This makes for a smooth and harmonious engine at idle.

Boxer/Flat engines tend to be nosier then other designs due to the lack of airboxes and other components in the engine bay. They have a engine characteristic of smoothness throughout the rev range and when combined with a mounting position immediately ahead of the rear axle, offer a low center of gravity and largely neutral handling characteristics.

Wankel/ Rotary Engines

The Rotary Wankel engine was an early type of internal-combustion engine in which the crankshaft remained stationary and the entire cylinder block rotated around it.

The Rotary/ Wankel engine has no pistons, it uses rotors instead. This engine is small, compact and has a curved, oblong inner shape. Its central rotor turns in one direction only, but it produces all four OTTO strokes (intake, compression, power and exhaust) effectively.

The only production car to still have a Rotary/ Wankel engine design in production today is the Masda RX-8 and previous RX-7 models.

The Rotary/ Wankel engine is limited by its inherent restriction on breathing capacity due to the need for the fuel/air mixture to be aspirated through the hollow crankshaft and crankcase, which directly affected its volumetric efficiency, also low torque levels are a known problem and the engine has design limitations. Turbocharging this engine is one of the easiest ways around these deficiencies and was seen in the RX-7.

The rotational forces of the mass of the Rotary/ Wankel engine's weight produce a powerful gyroscopic flywheel effect. This smooths out the power delivery and reduces vibration. Vibration had been such a serious problem on conventional piston engines that heavy flywheels had to be added to the overall engine design to help counteract the effects.

The cylinders themselves functioned as a flywheel, Rotary engines gained a substantial power-to-weight ratio advantage over more conventional engines. Another advantage was improved cooling, as the rotating cylinder block created its own fast-moving airflow, even at standstill.

Dispensing with separate cylinders, pistons, valves and crankshaft, the rotary engine applies power directly to the transmission. It's construction allows it to provide the power of a conventional engine that is twice its size and weight and that has twice as many parts.

The Rotary/ Wankel burns as much as 20% more fuel than the conventional engine and is potentially a higher polluter, but its small size allows the addition of emission-control parts more conveniently than does the piston engine.

The basic unit of the rotary engine is a large combustion chamber in the form of a pinched oval. Within this chamber all four functions of a piston take place simultaneously in the three pockets that are formed between the rotor and the chamber wall. Just as the addition of cylinders increases the horsepower of a piston-powered engine, so the addition of combustion chambers increases the power of a rotary engine. Larger cars may eventually use rotaries with three or four rotors.

Mazda have had numerous success with this design, especially with the RX-7 and RX-8 models. By adding a turbocharger as discussed previously, the torque deficiencies are some what over come and also engine power greatly increased. This combined with the lower weight made a effective and competitive performance package.

Diesel Engines

The Diesel engine was first invented by Rudolf Diesel, of German ethnicity born in Paris. Although quite similar in design to petrol internal combustion engines, Diesel engines use compression to ignite the compressed fuel to air mixture prior to injecting it into the combustion chamber, with out the need for spark plugs.

Advantages over Petrol Engines:

45% efficiency in converting fuel into mechanical energy compared to Petrol at 30%.
Engine life expectancy is twice as long compared to petrol engines, due to the stronger internal design to cope with higher pressures under combustion.
No need for HT leads, spark plugs and coils, meaning greater reliability especially in damp environments.
Diesel engines are immune to vapour lock and the fuel is not explosive like petrol.
No proportionate decrease in fuel efficiency compared to petrol engines, at higher engine loads.
Produce less heat in cooling and exhaust.
Produce less carbon monoxide and can be used in underground applications.
Can accept turbo/supercharging with out risk of detonation, unlike petrol engines at higher pressure levels.
Higher torque lower in the rev range.
Diesel fuel is denser then petrol and contains roughly 15% more energy.

Disadvantages over Petrol Engines:

Lower power to weight ratio then petrol engines, due to the increased internal component strength.
Lower power and rev band range compared to petrol engines, although turbo/ super charging has helped to combat this in the last decade.
Normally noisier and rougher in operation compared to petrol counter parts, although diesels are almost on par with technological advancements.
More expensive to purchase and run compared to petrol alternatives, due to increase in stronger components and more regular service schedules.

Straight/ Inline Engines

This ultimately means lower production and maintenance costs. Also due to their smaller and more lightweight construction, this is the preferred Engine design for FF cars (Front Wheel Drive). The design can be extremely fuel efficient compared to V type, Boxer and Rotary engine designs.

There are some five and six cylinder Straight/ Inline design engines, which are mainly found in European cars from the likes of Audi and BMW for example.

Reasonable performance can be achieved with performance levels in the 0'9 Ford Focus RS around 300 BHP. This is mostly due to Turbo Charging and boost pressure used, but it is common for a 2.0 Litre 16 Value inline 4 to produce 200 BHP plus.

V Type Engines

In sports applications, having the engine as low to the floor as possible increases the car's handling characteristics, as it will naturally have a lower centre of gravity. Also having a strong engine with built in rigidity can mean the difference in endurance races, making the V type engine design an ideal choice for Motorsport applications.

With this type of engine it is possible to have a very high compression ratios, without block distortion under load.

This makes it a strong and robust design for high performance applications and is used in F1 for instance. Also with it's resistance to torsional vibration, the engine characteristics produce a smooth and refined engine.

Boxer/ Flat Engines

This is similar to two boxers touching gloves at the beginning of a bout and is the origins of the name appointed to the engine design.

Flat engines have a lower center of gravity than any other common configuration, so vehicles using them should benefit from better stability and control during cornering. But they are also wider than more traditional configurations and the extra width causes problems fitting the engine into the engine bay of a front-engined car. Subaru have been producing AWD front engined cars for some time now, so where there's a will they is a way.

Boxer engines are one of only three cylinder layouts that have a natural dynamic balance; the others being the Straight/Inline 6 cylinder and the V12 design. This makes for a smooth and harmonious engine at idle.

Boxer/Flat engines tend to be nosier then other designs due to the lack of airboxes and other components in the engine bay. They have a engine characteristic of smoothness throughout the rev range and when combined with a mounting position immediately ahead of the rear axle, offer a low center of gravity and largely neutral handling characteristics.

Wankel/ Rotary Engines

The Rotary Wankel engine was an early type of internal-combustion engine in which the crankshaft remained stationary and the entire cylinder block rotated around it.

The Rotary/ Wankel engine has no pistons, it uses rotors instead. This engine is small, compact and has a curved, oblong inner shape. Its central rotor turns in one direction only, but it produces all four OTTO strokes (intake, compression, power and exhaust) effectively.

The only production car to still have a Rotary/ Wankel engine design in production today is the Masda RX-8 and previous RX-7 models.

The Rotary/ Wankel engine is limited by its inherent restriction on breathing capacity due to the need for the fuel/air mixture to be aspirated through the hollow crankshaft and crankcase, which directly affected its volumetric efficiency, also low torque levels are a known problem and the engine has design limitations. Turbocharging this engine is one of the easiest ways around these deficiencies and was seen in the RX-7.

The rotational forces of the mass of the Rotary/ Wankel engine's weight produce a powerful gyroscopic flywheel effect. This smooths out the power delivery and reduces vibration. Vibration had been such a serious problem on conventional piston engines that heavy flywheels had to be added to the overall engine design to help counteract the effects.

The cylinders themselves functioned as a flywheel, Rotary engines gained a substantial power-to-weight ratio advantage over more conventional engines. Another advantage was improved cooling, as the rotating cylinder block created its own fast-moving airflow, even at standstill.

Dispensing with separate cylinders, pistons, valves and crankshaft, the rotary engine applies power directly to the transmission. It's construction allows it to provide the power of a conventional engine that is twice its size and weight and that has twice as many parts.

The Rotary/ Wankel burns as much as 20% more fuel than the conventional engine and is potentially a higher polluter, but its small size allows the addition of emission-control parts more conveniently than does the piston engine.

The basic unit of the rotary engine is a large combustion chamber in the form of a pinched oval. Within this chamber all four functions of a piston take place simultaneously in the three pockets that are formed between the rotor and the chamber wall. Just as the addition of cylinders increases the horsepower of a piston-powered engine, so the addition of combustion chambers increases the power of a rotary engine. Larger cars may eventually use rotaries with three or four rotors.

Mazda have had numerous success with this design, especially with the RX-7 and RX-8 models. By adding a turbocharger as discussed previously, the torque deficiencies are some what over come and also engine power greatly increased. This combined with the lower weight made a effective and competitive performance package.

Diesel Engines

Advantages over Petrol Engines:

45% efficiency in converting fuel into mechanical energy compared to Petrol at 30%.
Engine life expectancy is twice as long compared to petrol engines, due to the stronger internal design to cope with higher pressures under combustion.
No need for HT leads, spark plugs and coils, meaning greater reliability especially in damp environments.
Diesel engines are immune to vapour lock and the fuel is not explosive like petrol.
No proportionate decrease in fuel efficiency compared to petrol engines, at higher engine loads.
Produce less heat in cooling and exhaust.
Produce less carbon monoxide and can be used in underground applications.
Can accept turbo/supercharging with out risk of detonation, unlike petrol engines at higher pressure levels.
Higher torque lower in the rev range.
Diesel fuel is denser then petrol and contains roughly 15% more energy.

Disadvantages over Petrol Engines:

Lower power to weight ratio then petrol engines, due to the increased internal component strength.
Lower power and rev band range compared to petrol engines, although turbo/ super charging has helped to combat this in the last decade.
Normally noisier and rougher in operation compared to petrol counter parts, although diesels are almost on par with technological advancements.
More expensive to purchase and run compared to petrol alternatives, due to increase in stronger components and more regular service schedules.

Frictionless Compressor Technology

2013-04-25T08:43:00.001+05:30

Frictionless Compressor Technology is one of the fast growing Technology in the mechanical engineering field. In the case of Traditional centrifugal compressors, we use roller bearings & hydrodynamic bearings, both of them consumes power & require oil & lubrication system. This can being overcome by introduction of the new compressor technology which is called as frictionless compressor technology.

The frictionless compressor technology is the compressor with which the application of the magnetic bearings & permanent magnet synchronous motor. In the frictionless compressor instead of the roller bearings & hydrodynamic bearings, magnetic bearings will be use. Magnetic bearings consume less power & there is no need for the oil and lubrication systems. Permanent magnet brushless synchronous motor has the permanent magnet instead of the copper windings.

Advantages :

This compressor has the high efficiency, reliability, less maintenance cost & the staff. With help of the digital control system, controlling & monitoring of the work is very easy.

The frictionless compressor technology makes new revolutions in the field of air conditioning,refrigeration.

Engineering Drawing

2013-04-01T22:25:00.000+05:30

Introduction

One of the best ways to communicate one's ideas is through some form of picture or drawing. This is especially true for the engineer. The purpose of this guide is to give you the basics of engineering sketching and drawing.
We will treat "sketching" and "drawing" as one. "Sketching" generally means freehand drawing. "Drawing" usually means using drawing instruments, from compasses to computers to bring precision to the drawings.
This is just an introduction. Don't worry about understanding every detail right now - just get a general feel for the language of graphics.
We hope you like the object in Figure 1, because you'll be seeing a lot of it. Before we get started on any technical drawings, let's get a good look at this strange block from several angles.

Figure 1 - A Machined Block

Isometric Drawing

The representation of the object in figure 2 is called an isometric drawing. This is one of a family of three-dimensional views called pictorial drawings. In an isometric drawing, the object's vertical lines are drawn vertically, and the horizontal lines in the width and depth planes are shown at 30 degrees to the horizontal. When drawn under these guidelines, the lines parallel to these three axes are at their true (scale) lengths. Lines that are not parallel to these axes will not be of their true length.

Figure 2 - An Isometric Drawing

Any engineering drawing should show everything: a complete understanding of the object should be possible from the drawing. If the isometric drawing can show all details and all dimensions on one drawing, it is ideal. One can pack a great deal of information into an isometric drawing. However, if the object in figure 2 had a hole on the back side, it would not be visible using a single isometric drawing. In order to get a more complete view of the object, an orthographic projection may be used.

Orthographic or Multiview Drawing

Imagine that you have an object suspended by transparent threads inside a glass box, as in figure 3.

Figure 3 - The block suspended in a glass box

Then draw the object on each of three faces as seen from that direction. Unfold the box (figure 4) and you have the three views. We call this an "orthographic" or "multiview" drawing.

Figure 4 - The creation of an orthographic multiview drawing

Figure 5 shows how the three views appear on a piece of paper after unfolding the box.

Figure 5 - A multiview drawing and its explanation

Which views should one choose for a multiview drawing? The views that reveal every detail about the object. Three views are not always necessary; we need only as many views as are required to describe the object fully. For example, some objects need only two views, while others need four. The circular object in figure 6 requires only two views.

Figure 6 - An object needing only two orthogonal views

Dimensioning

Figure 7 - An isometric view with dimensions

We have "dimensioned" the object in the isometric drawing in figure 7. As a general guideline to dimensioning, try to think that you would make an object and dimension it in the most useful way. Put in exactly as many dimensions as are necessary for the craftsperson to make it -no more, no less. Do not put in redundant dimensions. Not only will these clutter the drawing, but if "tolerances" or accuracy levels have been included, the redundant dimensions often lead to conflicts when the tolerance allowances can be added in different ways.
Repeatedly measuring from one point to another will lead to inaccuracies. It is often better to measure from one end to various points. This gives the dimensions a reference standard. It is helpful to choose the placement of the dimension in the order in which a machinist would create the part. This convention may take some experience.

Sectioning

There are many times when the interior details of an object cannot be seen from the outside (figure 8).

Figure 8 - An isometric drawing that does not show all details

We can get around this by pretending to cut the object on a plane and showing the "sectional view". The sectional view is applicable to objects like engine blocks, where the interior details are intricate and would be very difficult to understand through the use of "hidden" lines (hidden lines are, by convention, dotted) on an orthographic or isometric drawing.
Imagine slicing the object in the middle (figure 9):

Figure 9 - "Sectioning" an object

Figure 10 - Sectioning the object in figure 8

Take away the front half (figure 10) and what you have is a full section view (figure 11).

Figure 11 - Sectioned isometric and orthogonal views

The cross-section looks like figure 11 when it is viewed from straight ahead.

Drawing Tools

To prepare a drawing, one can use manual drafting instruments (figure 12) or computer-aided drafting or design, or CAD. The basic drawing standards and conventions are the same regardless of what design tool you use to make the drawings. In learning drafting, we will approach it from the perspective of manual drafting. If the drawing is made without either instruments or CAD, it is called a freehand sketch.

Figure 12 - Drawing Tools

"Assembly" Drawings

An isometric view of an "assembled" pillow-block bearing system is shown in figure 13. It corresponds closely to what you actually see when viewing the object from a particular angle. We cannot tell what the inside of the part looks like from this view.
We can also show isometric views of the pillow-block being taken apart or "disassembled" (figure 14). This allows you to see the inner components of the bearing system. Isometric drawings can show overall arrangement clearly, but not the details and the dimensions.

Figure 13 - Pillow-block (Freehand sketch)

Figure 14 - Disassembled Pillow-block

Cross-Sectional Views

A cross-sectional view portrays a cut-away portion of the object and is another way to show hidden components in a device.
Imagine a plane that cuts vertically through the center of the pillow block as shown in figure 15. Then imagine removing the material from the front of this plane, as shown in figure 16.

Figure 15 - Pillow Block	Figure 16 - Pillow Block

This is how the remaining rear section would look. Diagonal lines (cross-hatches) show regions where materials have been cut by the cutting plane.

Figure 17 - Section "A-A"

This cross-sectional view (section A-A, figure 17), one that is orthogonal to the viewing direction, shows the relationships of lengths and diameters better. These drawings are easier to make than isometric drawings. Seasoned engineers can interpret orthogonal drawings without needing an isometric drawing, but this takes a bit of practice.
The top "outside" view of the bearing is shown in figure 18. It is an orthogonal (perpendicular) projection. Notice the direction of the arrows for the "A-A" cutting plane.

Figure 18 - The top "outside" view of the bearing

Half-Sections

A half-section is a view of an object showing one-half of the view in section, as in figure 19 and 20.

Figure 19 - Full and sectioned isometric views

Figure 20 - Front view and half section

The diagonal lines on the section drawing are used to indicate the area that has been theoretically cut. These lines are called section lining or cross-hatching. The lines are thin and are usually drawn at a 45-degree angle to the major outline of the object. The spacing between lines should be uniform.
A second, rarer, use of cross-hatching is to indicate the material of the object. One form of cross-hatching may be used for cast iron, another for bronze, and so forth. More usually, the type of material is indicated elsewhere on the drawing, making the use of different types of cross-hatching unnecessary.

Figure 21 - Half section without hidden lines

Usually hidden (dotted) lines are not used on the cross-section unless they are needed for dimensioning purposes. Also, some hidden lines on the non-sectioned part of the drawings are not needed (figure 12) since they become redundant information and may clutter the drawing.

Sectioning Objects with Holes, Ribs, Etc.

The cross-section on the right of figure 22 is technically correct. However, the convention in a drawing is to show the view on the left as the preferred method for sectioning this type of object.

Figure 22 - Cross section

Dimensioning

The purpose of dimensioning is to provide a clear and complete description of an object. A complete set of dimensions will permit only one interpretation needed to construct the part. Dimensioning should follow these guidelines.

Accuracy: correct values must be given.
Clearness: dimensions must be placed in appropriate positions.
Completeness: nothing must be left out, and nothing duplicated.
Readability: the appropriate line quality must be used for legibility.

The Basics: Definitions and Dimensions

The dimension line is a thin line, broken in the middle to allow the placement of the dimension value, with arrowheads at each end (figure 23).

Figure 23 - Dimensioned Drawing

An arrowhead is approximately 3 mm long and 1 mm wide. That is, the length is roughly three times the width. An extension line extends a line on the object to the dimension line. The first dimension line should be approximately 12 mm (0.6 in) from the object. Extension lines begin 1.5 mm from the object and extend 3 mm from the last dimension line.
A leader is a thin line used to connect a dimension with a particular area (figure 24).

Figure 24 - Example drawing with a leader

A leader may also be used to indicate a note or comment about a specific area. When there is limited space, a heavy black dot may be substituted for the arrows, as in figure 23. Also in this drawing, two holes are identical, allowing the "2x" notation to be used and the dimension to point to only one of the circles.

Where To Put Dimensions

The dimensions should be placed on the face that describes the feature most clearly. Examples of appropriate and inappropriate placing of dimensions are shown in figure 25.

Figure 25 - Example of appropriate and inappropriate dimensioning

In order to get the feel of what dimensioning is all about, we can start with a simple rectangular block. With this simple object, only three dimensions are needed to describe it completely (figure 26). There is little choice on where to put its dimensions.

Figure 26 - Simple Object

We have to make some choices when we dimension a block with a notch or cutout (figure 27). It is usually best to dimension from a common line or surface. This can be called the datum line of surface. This eliminates the addition of measurement or machining inaccuracies that would come from "chain" or "series" dimensioning. Notice how the dimensions originate on the datum surfaces. We chose one datum surface in figure 27, and another in figure 28. As long as we are consistent, it makes no difference. (We are just showing the top view).

Figure 27 - Surface datum example

Figure 28 - Surface datum example

In figure 29 we have shown a hole that we have chosen to dimension on the left side of the object. The Ø stands for "diameter".

Figure 29 - Exampled of a dimensioned hole

When the left side of the block is "radiuses" as in figure 30, we break our rule that we should not duplicate dimensions. The total length is known because the radius of the curve on the left side is given. Then, for clarity, we add the overall length of 60 and we note that it is a reference (REF) dimension. This means that it is not really required.

Figure 30 - Example of a directly dimensioned hole

Somewhere on the paper, usually the bottom, there should be placed information on what measuring system is being used (e.g. inches and millimeters) and also the scale of the drawing.

Figure 31 - Example of a directly dimensioned hole

This drawing is symmetric about the horizontal centerline. Centerlines (chain-dotted) are used for symmetric objects, and also for the center of circles and holes. We can dimension directly to the centerline, as in figure 31. In some cases this method can be clearer than just dimensioning between surfaces.

MEMS Technology

2013-03-16T22:25:00.001+05:30

MEMS Technology

Knowles' Micro Electro-Mechanical Systems (MEMS) technology platform brings you smaller product design possibilities and related cost advantages, including silicon-based, surface mount manufacturing.

Traditional uses of silicon involve creating pathways for electricity within components such as integrated circuits. In contrast, MEMS transforms silicon into mechanically moving parts. During the past decade, this process has become useful in an increasing number of industries. For example, the automotive market uses MEMS accelerometers to sense crashes and deploy airbags.

Our research in MEMS led to the introduction of the world's first surface mount microphone in 2001 to 2002, the SiSonic™ series. We have since helped major brands design breakthrough cell phone and consumer electronics products, while eliminating the cost of traditional offline ECM microphone subassemblies.

MicroElectroMechanical Systems (MEMS) and Microrobotics research spans design methodologies, physical investigations and manufacturing techniques involving various microsensors, microactuators and other microsystems. Selected applications include inertial sensor suites for control and guidance, miniature wall-climbing robots using micro/nano-fiber adhesives, arrayed MEMS probe manipulators for tip-based nanomanufacturing, gas chemical sensor arrays for early warning systems, and ultra-compliant neural probes for brain-computer interfaces.

MEMS and Microrobotics RI faculty have developed strong multidisciplinary research programs on integrated MEMS design and fabrication (Fedder), micro and nanorobotic systems (Sitti), and implantable medical microsystems (Fedder, Weiss). This research links the RI to many departments throughout the University through active collaborations with faculty from across CIT and MCS as well as with Pitt and UPMC. These RI faculty members also have joint appointments in other entities. Expanded research in micro-inertial navigation technologies (Kelly and Fedder) is also planned to target new DOD initiatives.

The future for research in MEMS and microrobotics remains bright, with trends toward use of the technology to access and manipulate nano-scale phenomena as well as to enable emerging biomedical applications. RI faculty are taking leads in these areas in collaboration with faculty throughout the University. One of the challenges faced is to merge systems across macro-, micro-, and nano-scales. CMU's planned Nano/Bio/Energy Building (2014 expected date of completion) for nano- and biotechnologies will facilitate efforts in this area by providing state-of-the-art shared infrastructure for nano/microfabrication. In addition, a budding collaboration in multi-scale factory automation (Hollis, Fedder) is leveraging renewed efforts in reconfigurable, high-precision minifactories (Hollis).

There are several different broad categories of MEMS technologies, outlined below:

Bulk Micromachining:

Bulk micromachining is a fabrication technique which builds mechanical elements by starting with a silicon wafer, and then etching away unwanted parts, and being left with useful mechanical devices. Typically, the wafer is photo patterned, leaving a protective layer on the parts of the wafer that you want to keep. The wafer is then submersed into a liquid etchant, like potassium hydroxide, which eats away any exposed silicon. This is a relatively simple and inexpensive fabrication technology, and is well suited for applications which do not require much complexity, and which are price sensitive.

Today, almost all pressure sensors are built with Bulk Micromachining. Bulk Micromachined pressure sensors offer several advantages over traditional pressure sensors. They cost less, are highly reliable, manufacturable, and there is very good repeatability between devices.

All new cars on the market today have several micromachined pressure sensors, typically used to measure manifold pressure in the engine.

The small size and high reliability of micromachined pressure sensors make them ideal for a variety of medical applications as well.

Surface Micromachining:

While Bulk micromachining creates devices by etching into a wafer, Surface Micromachining builds devices up from the wafer layer-by-layer.

A typical Surface Micromachining process is a repetitive sequence of depositing thin films on a wafer, photopatterning the films, and then etching the patterns into the films. In order to create moving, functioning machines, these layers are alternating thin films of a structural material (typically silicon) and a sacrificial material (typically silicon dioxide). The structural material will form the mechanical elements, and the sacrificial material creates the gaps and spaces between the mechanical elements. At the end of the process, the sacrificial material is removed, and the structural elements are left free to move and function.

For the case of the structural level being silicon, and the sacrificial material being silicon dioxide, the final "release" process is performed by placing the wafer in Hydrofluoric Acid. The Hydrofluoric Acid quickly etches away the silicon dioxide, while leaving the silicon undisturbed.

The wafers are typically then sawn into individual chips, and the chips packaged in an appropriate manner for the given application.

Surface Micromachining requires more fabrication steps than Bulk Micromachining, and hence is more expensive. It is able to create much more complicated devices, capable of sophisticated functionality. Surface Micromachining is suitable for applications requiring more sophisticated mechanical elements.

LIGA:

LIGA is a technology which creates small, but relatively high aspect ratio devices using x-ray lithography. The process typically starts with a sheet of PMMA. The PMMA is covered with a photomask, and then exposed to high energy x-rays. The mask allows parts of the PMMA to be exposed to the x-rays, while protecting other parts. The PMMA is then placed in a suitable etchant to remove the exposed areas, resulting in extremely precise, microscopic mechanical elements.

LIGA is a relatively inexpensive fabrication technology, and suitable for applications requiring higher aspect ratio devices than what is achievable in Surface Micromachining.

Deep Reactive Ion Etching:

Deep reactive ion etching is a type of Bulk Micromachining which etches mechanical elements into a silicon wafer. Unlike traditional Bulk Micromachining, which uses a wet chemical etch, Deep Reactive Ion Etching micromachining uses a plasma etch to create features. This allows greater flexibility in the etch profiles, enabling a wider array of mechanical elements. The fabrication tools needed to perform Deep Reactive Ion etching are somewhat expensive, to this technology is typically more expensive than traditional Bulk Micromachining based on wet etching.

Integrated MEMS Technologies

Since MEMS devices are created with the same tools used to create integrated circuits, in some cases it is actually possible to fabricate Micromachines and Microelectronics on the same piece of silicon. Fabricating machines and transistors side by side enables machines that can have intelligence. A number of exciting products are already taking advantage of this capability.

The micro mechanical device embedded with electronics/electrical system fabricated through a mix of integrated circuit manufacturing and micro-machining process where material is shaped by etching away micro layers is called Micro Electro Mechanical System (MEMS). The intelligent electronic system part is integrated in the same way of IC device fabrication. The most popular material used for MEMS is Silicon for it's semiconductor , physical and commercial properties.

Micro-Electro-Mechanical Systems consists of mechanical elements, sensors, actuators, and electrical and electronics devices on a common silicon substrate.

The sensors in MEMS gather information from the environment through measuring mechanical, thermal, biological, chemical, optical, and magnetic phenomena. The electronics then process the information derived from the sensors and through some decision making capability direct the actuators to respond by moving, positioning, regulating, pumping, and filtering, thereby controlling the environment for some desired outcome or purpose. The advantages of semiconductor IC manufacturing such as low cost mass production, reliability are also integral to MEMS devices.
The size of MEMS sub-components is in the range of 1 to 100 micrometers and the size of MEMS device itself measure in the range of 20 micrometers to a millimeter.

Some of the advantages of MEMS devices are,

1. Very small size, mass, volume
2. Very low power consumption
3. Low cost
4. Easy to integrate into systems or modify
5. Small thermal constant
6. Can be highly resistant to vibration, shock and radiation
7. Batch fabricated in large arrays
8. Improved thermal expansion tolerance
9. Parallelism

Typical Applications:

There are plenty of applications for MEMS. As a breakthrough technology, MEMS is building synergy between previously unrelated fields such as biology and microelectronics, many new MEMS and Nanotechnology applications will emerge, expanding beyond that which is currently identified or known.

MEMS technology finds applications in the below general domains

Automotive domain:
1. Airbag Systems
2. Vehicle Security Systems
3. Intertial Brake Lights
4. Headlight Leveling
5. Rollover Detection
6. Automatic Door Locks
7. Active Suspension

Consumer domain:
1. Appliances
2. Sports Training Devices
3. Computer Peripherals
4. Car and Personal Navigation Devices
5. Active Subwoofers

Industrial domain:
1. Earthquake Detection and Gas Shutoff
2. Machine Health
3. Shock and Tilt Sensing

Military:
1. Tanks
2. Planes
3. Equipment for Soldiers

Biotechnology:

1. Polymerase Chain Reaction (PCR) microsystems for DNA amplification and identification
2. Micromachined Scanning Tunneling Microscopes (STMs)
3. Biochips for detection of hazardous chemical and biological agents
4. Microsystems for high-throughput drug screening and selection
5. Bio-MEMS in medical and health related technologies from Lab-On-Chip to biosensor & chemosensor.

The commercial applications include:

1. Inkjet printers, which use piezo-electrics or thermal bubble ejection to deposit ink on paper.
2. Accelerometers in modern cars for a large number of purposes including airbag deployment in    collisions.
3. Accelerometers in consumer electronics devices such as game controllers, personal media players     / cell phones and a number of Digital Cameras.
4. In PCs to park the hard disk head when free-fall is detected, to prevent damage and data loss.
5. MEMS gyroscopes used in modern cars and other applications to detect yaw; e.g. to deploy a roll     over bar or trigger dynamic stability control.
6. Silicon pressure sensors e.g. car tire pressure sensors, and disposable blood pressure sensors.
7. Displays e.g. the DMD chip in a projector based on DLP technology has on its surface several      hundred thousand micromirrors.
8. Optical switching technology, which is, used for switching technology and alignment for data      communications.
9. Interferometric modulator display (IMOD) applications in consumer electronics (primarily displays for     mobile devices).
10. Improved performance from inductors and capacitors due the advent of the RF-MEMS technology

MEMS devices:

Few examples of real MEMS products are,

1. Adaptive Optics for Ophthalmic Applications
2. Optical Cross Connects
3. Air Bag Accelerometers
4. Pressure Sensors
5. Mirror Arrays for Televisions and Displays
6. High Performance Steerable Micromirrors
7. RF MEMS Devices
8. Disposable Medical Devices
9. High Force, High Displacement Electrostatic Actuators
10. MEMS Devices for Secure Communications

MEMS devices used in Space exploration field include:

1. Accelerometers and gyroscopes for inertial navigation
2. Pressure sensors
3. RF switches and tunable filters for communication
4. Tunable mirror arrays for adaptive optics
5. Micro-power sources and turbines
6. Propulsion and attitude control
7. Bio-reactors and Bio-sensors, Microfluidics
8. Thermal control
9. Atomic clocks

Mechanical Measuring Tools

2013-03-14T21:42:00.002+05:30

Different Types of Mechanical Measuring Tools:-
Measuring instruments and gauges are used to measure various parameters such as clearance, diameter, depth, ovality, trueness etc. These are important engineering parameters which describes the condition of the working machinery.

Popular mechanical gauges and tools used are:

1. Ruler and scales :
They are used to measure lengths and other geometrical parameters. They can besingle steel plate or flexible tape type tool.

2. Callipers :
They are normally of two types- inside and outside calliper. They are used to measure internal and external size (for e.g. diameter) of an object. It requires external scale to compare the measured value. Some callipers are provided with measuring scale. Other types are odd leg and divider calliper.

3. Venire calliper :
It is a precision toolused to measure a small distance with high accuracy. It has got two different jaws to measure outside and inside dimension of an object.It can be a scale, dial or digital type venire calliper.

4. Micrometer :
It is a fine precision tool which is used to measure small distances and is more accurate than the venire calliper. Another type is a large micrometer calliper which is used to measure large outside diameter or distance.

5. Feeler gauge :
Feelers gauges are a bunch of fine thickened steel strips with marked thickness which are used to measure gap width or clearance between surface and bearings.

6. Telescopic feeler gauge :
It is also known as tongue gauge and it consists of long feeler gauge inside acover with tongue or curved edge. The long feeler strips protrude out ofthe cover so that it can be inserted into remote places where feeler gauge access is not possible.

7. Poker gauge :
This gauge is used to measure propeller stern shaft clearance, also known as propeller wear down.

8. Bridge gauge :
Bridge gauges are used to measure the amount of wearof Main engine bearing. Normally theupper bearing keep is removed and clearance is measured with respect to journal. Feeler gauge can be used to complete the process.

9. Liner measurement tool :
Liner measurement tool is a set of straightassembled rod with marked length in each set. It is used to measure the wear down or increase in the diameter of the engine liner.

10. American Wire Gauge :
American wire gauge or AWG is a standard tool which is circular in shape and has various slots of different diameter in its circumference. It is used to measure cross section of an electric cable or wire.

11. Bore Gauge:
A tool to accurately measure size of any hole is known asbore gauge, It can be a scale, dial or digital type instrument .

12. Depth gauge:
A depth gauge is used to measure the depth of a slot, hole or any other surface of an object. It can be of scale, dial or digital type.

13. Angle plate or tool :
It is a right angle plate or tool used to measure the true right angle of two objects joined together.

14. Flat plate :
Flat plate is a precised flat surface used to measure flatness of an object when it is kept over the flat plate.

15. Dial Gauge :
Dial gauge is utilised in different tools as stated above and can be separately used to measure the trueness of the circular object, jumping of an object etc.

16. Lead Wire :
It is a conventional method to used soft lead wire or lead balls to measure the wear downor clearance between two mating surfaces. The lead wire or balls of fixed dimension is kept between two surfaces and both are tightened against each just as in normal condition. The increase in the width of the lead wire or ball will shoe the clearance or wear down.

Vocabulary Term	Definition
Accumulated Error	The collected inaccuracy in measurement that can occur when multiple elements are combined.
Accuracy	The difference between a measurement reading and the true value of that measurement.
Air Gage	A variable, non-contact pneumatic instrument that uses pressurized air to inspect the ID of holes.
Air Regulator	The part of a pneumatic inspection system by which pressurized air is controlled.
Backflow Pressure	Movement of pressurized air in the direction opposite to which it was pushed out of the device. In an air gage, backflow pressure is caused by resistance from the sides of the hole.
Bore Gage	A hole inspection gage that makes three points of contact within the hole. Bore gages are handheld, mechanical or electronic contact instruments with variable measuring systems.
Borescope	A non-contact optical inspection device consisting of a rigid or flexible tube with an eyepiece at one end and a magnifying lens at the other. Borescopes provide a view of hole interiors that are otherwise difficult or impossible to see.
Caliper	A handheld, variable contact instrument that functions as a precision slide ruler. The indicators on the top of the instrument expand to measure internal diameters.
Capable	A gage's predictable range of ability, even when under the influence of natural variation due to common causes.
Comparison Device	A measuring instrument that adjusts to assume the size of a feature.
Concavity	A curved surface condition like the inside of a ball.
Contact Instrument	A measuring device that actually touches the part in order to obtain its measured value.
Contact Probe	The main measuring member on a coordinate measuring machine that communicates its position on a workpiece to the CMMs control panel or computer. A probe often has a sphere of ruby at its tip.
Continuous Scanning	An inspection method used by a coordinate measuring machine in which the probe slides along the surface of the workpiece to collect seamless data in the form of a series of numerous points.
Coordinate Measuring Machine	A sophisticated electronic measuring instrument with a flat polished table that inspects parts in three-dimensional space using either a contact or a non-contact probe. All CMMs are variable devices.
Dial Indicator	A measuring instrument with a contact point attached to a spindle and gears that move a pointer on the dial. Dial indicators have graduations that allow you to read different measurement values.
Digital Readout	An indicator on a measuring device that presents data through a numerical display.
Electronic Instruments	Inspection devices that use electrical impulses to report either position changes or contact between the inspection device and the part.
Extension	A piece that is added to the head of an inside micrometer to expand it to the width of the hole.
Eyepiece	The part of a boroscope through which the inspector views the interior of the workpiece.
Flowmeter Tube	A cylindrical indicating device on a pneumatic measuring instrument that looks similar to a thermometer.
Gaging Instrument	An inspection device of a standard size that determines fit but does not determine actual measurement value.
Go-No Go Gage	An instrument that determines whether a part feature simply passes or fails inspection. No effort is made to determine the exact degree of error.
Indicator	A device, often numerical, that displays a measurement. An indicator may be a dial with a needle or a digital readout.
Inner Diameter	ID. The interior surface of a hole in a workpiece.
Inside Micrometer	A mechanical or electronic, variable, handheld contact instrument, usually cylindrically shaped, used to measure the inside diameter of larger holes.
Laser System	A non-contact, variable, optical inspection method that uses light to examine the inside diameter of holes. Laser systems send out a single light wave on a straight line that is detected by sensors and converted into an electrical signal.
Light Wave	A form of visible energy used by lasers.
Linear Scale	A series of parallel lines that represent a measurement standard. A ruler contains a linear scale.
Linearity	The amount of error change throughout an instrument's measurement range. Linearity is also the amount of deviation from an instrument's ideal straight-line performance.
Lobing	A condition in which the manufacturing process creates a rounded projection out from what would otherwise be a circular hole. A hole may have more than one lobe.
Master Gage	A measuring device of a standard size that is used to calibrate other measuring instruments.
Mechanical Device	A measuring instrument that must be physically manipulated by the inspector. Mechanical devices may be go-no go or variable.
Micrometer Head	The main component of an inside micrometer that includes the scale and indicating device. Extensions are added to the micrometer head.
Non-Contact Instrument	A measuring device that is able to obtain the measured value of the part without making physical contact. An air gage is an example of a non-contact instrument.
Optical Comparator	A sophisticated measuring instrument that projects an image of a part onto a screen to compare the shape, size, and location of its features. Optical comparators are non-contact, variable, optical inspection devices.
Optical Instruments	Inspection devices that use light and lenses to inspect parts. The part may be viewed directly through the lense or displayed on a screen.
Outside Micrometer	A handheld device consisting of an anvil, a shaft, and an indicator that is used to measure outside diameters.
Ovality	A condition in which a hole that should be round has two opposing lobes, resulting in an egg shape.
Pin Gage	A cylindrically shaped length of metal of a specific diameter used as a gaging inspection device. A pin gage is a handheld mechanical contact instrument.
Plug Gage	A hardened, cylindrical gage used as a handheld mechanical contact instrument to inspect the size of a hole. Plug gages are available in standard diameters and are often two-sided, with a "go" side and a "no go" side.
Pneumatic Instrument	A measuring device that uses a pressurized gas, such as air, to function.
Precision	The degree to which an instrument will repeat the same measurement over a period of time.
Probe Cable	The portion of a laser system that transmits information and power to and from the tip of the device and the computer.
Ring Gage	A circular measuring device of a standard size that is used to calibrate other instruments or inspect cylindrical parts.
Rotary Laser	An inspection device that projects a light wave on the surface of the part's internal diameter as it turns.
Scale	A standard of measurement that is often displayed as a series of lines.
Setting Gage	A measuring device of a standard size that is used to check or prepare a working gage for use. Bore gages often come with matching setting ring gages.
Split-Ball Gage	A cylindrical device with an expanding, flat-ended ball on one end and a locking device on the other. A split-ball gage is a handheld, mechanical contact instrument that is used for comparison measurement. It is also called a small-hole gage.
Taper	A gradual narrowing of an inside or outside surface.
Telescoping Gage	A T-shaped measuring device that has two spring-loaded measuring arms and a lock in the base. A telescoping gage is a handheld, mechanical contact instrument used for comparison measurement.
Thimble	A ring or cylinder that fits around the spindle of a micrometer. To advance the spindle, you turn the thimble.
Tolerance	The acceptable variation from a specified dimension.
Tolerance Range	The expected range of measurements produced by a given operation. It is also known as a tolerance zone.
Variable Instrument	An inspection device calibrated in standard measurement units. Variable inspection reveals the degree of variation from a given standard.
Video Borescope	A borescope that contains a video camera rather than an eyepiece.
Working Gage	A measuring device of a standard size that is used to inspect parts.

Rapid Prototyping

2013-03-04T10:25:00.000+05:30

1 Overview of Rapid Prototyping
The term rapid prototyping (RP) refers to a class of technologies that can automatically construct physical models from Computer-Aided Design (CAD) data. These "three dimensional printers" allow designers to quickly create tangible prototypes of their designs, rather than just two-dimensional pictures. Such models have numerous uses. They make excellent visual aids for communicating ideas with co-workers or customers. In addition, prototypes can be used for design testing. For example, an aerospace engineer might mount a model airfoil in a wind tunnel to measure lift and drag forces. Designers have always utilized prototypes; RP allows them to be made faster and less expensively.
In addition to prototypes, RP techniques can also be used to make tooling (referred to as rapid tooling) and even production-quality parts (rapid manufacturing). For small production runs and complicated objects, rapid prototyping is often the best manufacturing process available. Of course, "rapid" is a relative term. Most prototypes require from three to seventy-two hours to build, depending on the size and complexity of the object. This may seem slow, but it is much faster than the weeks or months required to make a prototype by traditional means such as machining. These dramatic time savings allow manufacturers to bring products to market faster and more cheaply. In 1994, Pratt & Whitney achieved "an order of magnitude [cost] reduction [and] . . . time savings of 70 to 90 percent" by incorporating rapid prototyping into their investment casting process. ⁵
At least six different rapid prototyping techniques are commercially available, each with unique strengths. Because RP technologies are being increasingly used in non-prototyping applications, the techniques are often collectively referred to as solid free-form fabrication, computer automated manufacturing, or layered manufacturing. The latter term is particularly descriptive of the manufacturing process used by all commercial techniques. A software package "slices" the CAD model into a number of thin (~0.1 mm) layers, which are then built up one atop another. Rapid prototyping is an "additive" process, combining layers of paper, wax, or plastic to create a solid object. In contrast, most machining processes (milling, drilling, grinding, etc.) are "subtractive" processes that remove material from a solid block. RP’s additive nature allows it to create objects with complicated internal features that cannot be manufactured by other means.
Of course, rapid prototyping is not perfect. Part volume is generally limited to 0.125 cubic meters or less, depending on the RP machine. Metal prototypes are difficult to make, though this should change in the near future. For metal parts, large production runs, or simple objects, conventional manufacturing techniques are usually more economical. These limitations aside, rapid prototyping is a remarkable technology that is revolutionizing the manufacturing process.

2 The Basic ProcessAlthough several rapid prototyping techniques exist, all employ the same basic five-step process. The steps are:

Create a CAD model of the design
Convert the CAD model to STL format
Slice the STL file into thin cross-sectional layers
Construct the model one layer atop another
Clean and finish the model

CAD Model Creation: First, the object to be built is modeled using a Computer-Aided Design (CAD) software package. Solid modelers, such as Pro/ENGINEER, tend to represent 3-D objects more accurately than wire-frame modelers such as AutoCAD, and will therefore yield better results. The designer can use a pre-existing CAD file or may wish to create one expressly for prototyping purposes. This process is identical for all of the RP build techniques.
Conversion to STL Format: The various CAD packages use a number of different algorithms to represent solid objects. To establish consistency, the STL (stereolithography, the first RP technique) format has been adopted as the standard of the rapid prototyping industry. The second step, therefore, is to convert the CAD file into STL format. This format represents a three-dimensional surface as an assembly of planar triangles, "like the facets of a cut jewel." ⁶ The file contains the coordinates of the vertices and the direction of the outward normal of each triangle. Because STL files use planar elements, they cannot represent curved surfaces exactly. Increasing the number of triangles improves the approximation, but at the cost of bigger file size. Large, complicated files require more time to pre-process and build, so the designer must balance accuracy with manageablility to produce a useful STL file. Since the .stl format is universal, this process is identical for all of the RP build techniques.
Slice the STL File: In the third step, a pre-processing program prepares the STL file to be built. Several programs are available, and most allow the user to adjust the size, location and orientation of the model. Build orientation is important for several reasons. First, properties of rapid prototypes vary from one coordinate direction to another. For example, prototypes are usually weaker and less accurate in the z (vertical) direction than in the x-y plane. In addition, part orientation partially determines the amount of time required to build the model. Placing the shortest dimension in the z direction reduces the number of layers, thereby shortening build time. The pre-processing software slices the STL model into a number of layers from 0.01 mm to 0.7 mm thick, depending on the build technique. The program may also generate an auxiliary structure to support the model during the build. Supports are useful for delicate features such as overhangs, internal cavities, and thin-walled sections. Each PR machine manufacturer supplies their own proprietary pre-processing software.
Layer by Layer Construction: The fourth step is the actual construction of the part. Using one of several techniques (described in the next section) RP machines build one layer at a time from polymers, paper, or powdered metal. Most machines are fairly autonomous, needing little human intervention.
Clean and Finish: The final step is post-processing. This involves removing the prototype from the machine and detaching any supports. Some photosensitive materials need to be fully cured before use. Prototypes may also require minor cleaning and surface treatment. Sanding, sealing, and/or painting the model will improve its appearance and durability.

3 Rapid Prototyping TechniquesMost commercially available rapid prototyping machines use one of six techniques. At present, trade restrictions severely limit the import/export of rapid prototyping machines, so this guide only covers systems available in the U.S.
3.1 StereolithographyPatented in 1986, stereolithography started the rapid prototyping revolution. The technique builds three-dimensional models from liquid photosensitive polymers that solidify when exposed to ultraviolet light. As shown in the figure below, the model is built upon a platform situated just below the surface in a vat of liquid epoxy or acrylate resin. A low-power highly focused UV laser traces out the first layer, solidifying the model’s cross section while leaving excess areas liquid.

Figure 1: Schematic diagram of stereolithography. ⁷

Next, an elevator incrementally lowers the platform into the liquid polymer. A sweeper re-coats the solidified layer with liquid, and the laser traces the second layer atop the first. This process is repeated until the prototype is complete. Afterwards, the solid part is removed from the vat and rinsed clean of excess liquid. Supports are broken off and the model is then placed in an ultraviolet oven for complete curing.
Stereolithography Apparatus (SLA) machines have been made since 1988 by 3D Systems of Valencia, CA. To this day, 3D Systems is the industry leader, selling more RP machines than any other company. Because it was the first technique, stereolithography is regarded as a benchmark by which other technologies are judged. Early stereolithography prototypes were fairly brittle and prone to curing-induced warpage and distortion, but recent modifications have largely corrected these problems.

3.2 Laminated Object ManufacturingIn this technique, developed by Helisys of Torrance, CA, layers of adhesive-coated sheet material are bonded together to form a prototype. The original material consists of paper laminated with heat-activated glue and rolled up on spools. As shown in the figure below, a feeder/collector mechanism advances the sheet over the build platform, where a base has been constructed from paper and double-sided foam tape. Next, a heated roller applies pressure to bond the paper to the base. A focused laser cuts the outline of the first layer into the paper and then cross-hatches the excess area (the negative space in the prototype). Cross-hatching breaks up the extra material, making it easier to remove during post-processing. During the build, the excess material provides excellent support for overhangs and thin-walled sections. After the first layer is cut, the platform lowers out of the way and fresh material is advanced. The platform rises to slightly below the previous height, the roller bonds the second layer to the first, and the laser cuts the second layer. This process is repeated as needed to build the part, which will have a wood-like texture. Because the models are made of paper, they must be sealed and finished with paint or varnish to prevent moisture damage.

Figure 2: Schematic diagram of laminated object manufacturing. ⁸

Helisys developed several new sheet materials, including plastic, water-repellent paper, and ceramic and metal powder tapes. The powder tapes produce a "green" part that must be sintered for maximum strength. As of 2001, Helisys is no longer in business.

3.3 Selective Laser SinteringDeveloped by Carl Deckard for his master’s thesis at the University of Texas, selective laser sintering was patented in 1989. The technique, shown in Figure 3, uses a laser beam to selectively fuse powdered materials, such as nylon, elastomer, and metal, into a solid object. Parts are built upon a platform which sits just below the surface in a bin of the heat-fusable powder. A laser traces the pattern of the first layer, sintering it together. The platform is lowered by the height of the next layer and powder is reapplied. This process continues until the part is complete. Excess powder in each layer helps to support the part during the build. SLS machines are produced by DTM of Austin, TX.

Figure 3: Schematic diagram of selective laser sintering. ⁹

3.4 Fused Deposition ModelingIn this technique, filaments of heated thermoplastic are extruded from a tip that moves in the x-y plane. Like a baker decorating a cake, the controlled extrusion head deposits very thin beads of material onto the build platform to form the first layer. The platform is maintained at a lower temperature, so that the thermoplastic quickly hardens. After the platform lowers, the extrusion head deposits a second layer upon the first. Supports are built along the way, fastened to the part either with a second, weaker material or with a perforated junction.
Stratasys, of Eden Prairie, MN makes a variety of FDM machines ranging from fast concept modelers to slower, high-precision machines. Materials include ABS (standard and medical grade), elastomer (96 durometer), polycarbonate, polyphenolsulfone, and investment casting wax.

Figure 4: Schematic diagram of fused deposition modeling. ¹⁰

3.4 Solid Ground Curing
Developed by Cubital, solid ground curing (SGC) is somewhat similar to stereolithography (SLA) in that both use ultraviolet light to selectively harden photosensitive polymers. Unlike SLA, SGC cures an entire layer at a time. Figure 5 depicts solid ground curing, which is also known as the solider process. First, photosensitive resin is sprayed on the build platform. Next, the machine develops a photomask (like a stencil) of the layer to be built. This photomask is printed on a glass plate above the build platform using an electrostatic process similar to that found in photocopiers. The mask is then exposed to UV light, which only passes through the transparent portions of the mask to selectively harden the shape of the current layer.

Figure 5: Schematic diagram of solid ground curing. ¹¹ After the layer is cured, the machine vacuums up the excess liquid resin and sprays wax in its place to support the model during the build. The top surface is milled flat, and then the process repeats to build the next layer. When the part is complete, it must be de-waxed by immersing it in a solvent bath. SGC machines are distributed in the U.S. by Cubital America Inc. of Troy, MI. The machines are quite big and can produce large models.

3.6 3-D Ink-Jet PrintingInk-Jet Printing refers to an entire class of machines that employ ink-jet technology. The first was 3D Printing (3DP), developed at MIT and licensed to Soligen Corporation, Extrude Hone, and others. The ZCorp 3D printer, produced by Z Corporation of Burlington, MA (www.zcorp.com) is an example of this technology. As shown in Figure 6a, parts are built upon a platform situated in a bin full of powder material. An ink-jet printing head selectively deposits or "prints" a binder fluid to fuse the powder together in the desired areas. Unbound powder remains to support the part. The platform is lowered, more powder added and leveled, and the process repeated. When finished, the green part is then removed from the unbound powder, and excess unbound powder is blown off. Finished parts can be infiltrated with wax, CA glue, or other sealants to improve durability and surface finish. Typical layer thicknesses are on the order of 0.1 mm. This process is very fast, and produces parts with a slightly grainy surface. ZCorp uses two different materials, a starch based powder (not as strong, but can be burned out, for investment casting applications) and a ceramic powder. Machines with 4 color printing capability are available.
3D Systems' (www.3dsystems.com) version of the ink-jet based system is called the Thermo-Jet or Multi-Jet Printer. It uses a linear array of print heads to rapidly produce thermoplastic models (Figure 6d). If the part is narrow enough, the print head can deposit an entire layer in one pass. Otherwise, the head makes several passes.
Sanders Prototype of Wilton, NH (www.solid-scape.com) uses a different ink-jet technique in its Model Maker line of concept modelers. The machines use two ink-jets (see Figure 6c). One dispenses low-melt thermoplastic to make the model, while the other prints wax to form supports. After each layer, a cutting tool mills the top surface to uniform height. This yields extremely good accuracy, allowing the machines to be used in the jewelry industry.
Ballistic particle manufacturing, depicted in Figure 6b, was developed by BPM Inc., which has since gone out of business.

Figure 6: Schematic diagrams of ink-jet techniques. ¹²

4 Applications of Rapid PrototypingRapid prototyping is widely used in the automotive, aerospace, medical, and consumer products industries. Although the possible applications are virtually limitless, nearly all fall into one of the following categories: prototyping, rapid tooling, or rapid manufacturing.
4.1 PrototypingAs its name suggests, the primary use of rapid prototyping is to quickly make prototypes for communication and testing purposes. Prototypes dramatically improve communication because most people, including engineers, find three-dimensional objects easier to understand than two-dimensional drawings. Such improved understanding leads to substantial cost and time savings. As Pratt & Whitney executive Robert P. DeLisle noted: "We’ve seen an estimate on a complex product drop by $100,000 because people who had to figure out the nature of the object from 50 blueprints could now see it." ¹³ Effective communication is especially important in this era of concurrent engineering. By exchanging prototypes early in the design stage, manufacturing can start tooling up for production while the art division starts planning the packaging, all before the design is finalized.
Prototypes are also useful for testing a design, to see if it performs as desired or needs improvement. Engineers have always tested prototypes, but RP expands their capabilities. First, it is now easy to perform iterative testing: build a prototype, test it, redesign, build and test, etc. Such an approach would be far too time-consuming using traditional prototyping techniques, but it is easy using RP.
In addition to being fast, RP models can do a few things metal prototypes cannot. For example, Porsche used a transparent stereolithography model of the 911 GTI transmission housing to visually study oil flow. ¹⁴ Snecma, a French turbomachinery producer, performed photoelastic stress analysis on a SLA model of a fan wheel to determine stresses in the blades. ¹⁵

4.2 Rapid ToolingA much-anticipated application of rapid prototyping is rapid tooling, the automatic fabrication of production quality machine tools. Tooling is one of the slowest and most expensive steps in the manufacturing process, because of the extremely high quality required. Tools often have complex geometries, yet must be dimensionally accurate to within a hundredth of a millimeter. In addition, tools must be hard, wear-resistant, and have very low surface roughness (about 0.5 micrometers root mean square). To meet these requirements, molds and dies are traditionally made by CNC-machining, electro-discharge machining, or by hand. All are expensive and time consuming, so manufacturers would like to incorporate rapid prototyping techniques to speed the process. Peter Hilton, president of Technology Strategy Consulting in Concord, MA, believes that "tooling costs and development times can be reduced by 75 percent or more" by using rapid tooling and related technologies. ¹⁶ Rapid tooling can be divided into two categories, indirect and direct.

4.2.1 Indirect Tooling
Most rapid tooling today is indirect: RP parts are used as patterns for making molds and dies. RP models can be indirectly used in a number of manufacturing processes:

Vacuum Casting: In the simplest and oldest rapid tooling technique, a RP positive pattern is suspended in a vat of liquid silicone or room temperature vulcanizing (RTV) rubber. When the rubber hardens, it is cut into two halves and the RP pattern is removed. The resulting rubber mold can be used to cast up to 20 polyurethane replicas of the original RP pattern. A more useful variant, known as the Keltool powder metal sintering process, uses the rubber molds to produce metal tools. ¹⁷ Developed by 3M and now owned by 3D Systems, the Keltool process involves filling the rubber molds with powdered tool steel and epoxy binder. When the binder cures, the "green" metal tool is removed from the rubber mold and then sintered. At this stage the metal is only 70% dense, so it is infiltrated with copper to bring it close to its theoretical maximum density. The tools have fairly good accuracy, but their size is limited to under 25 centimeters.
Sand Casting: A RP model is used as the positive pattern around which the sand mold is built. LOM models, which resemble the wooden models traditionally used for this purpose, are often used. If sealed and finished, a LOM pattern can produce about 100 sand molds.
Investment Casting: Some RP prototypes can be used as investment casting patterns. The pattern must not expand when heated, or it will crack the ceramic shell during autoclaving. Both Stratasys and Cubital make investment casting wax for their machines. Paper LOM prototypes may also be used, as they are dimensionally stable with temperature. The paper shells burn out, leaving some ash to be removed.

Injection molding: CEMCOM Research Associates, Inc. has developed the NCC Tooling System to make metal/ceramic composite molds for the injection molding of plastics. ¹⁸ First, a stereolithography machine is used to make a match-plate positive pattern of the desired molding. To form the mold, the SLA pattern is plated with nickel, which is then reinforced with a stiff ceramic material. The two mold halves are separated to remove the pattern, leaving a matched die set that can produce tens of thousands of injection moldings.

4.2.2 Direct Tooling
To directly make hard tooling from CAD data is the Holy Grail of rapid tooling. Realization of this objective is still several years away, but some strong strides are being made:

RapidTool: A DTM process that selectively sinters polymer-coated steel pellets together to produce a metal mold. The mold is then placed in a furnace where the polymer binder is burned off and the part is infiltrated with copper (as in the Keltool process). The resulting mold can produce up to 50,000 injection moldings.

In 1996 Rubbermaid produced 30,000 plastic desk organizers from a SLS-built mold. This was the first widely sold consumer product to be produced from direct rapid tooling. ¹⁹ Extrude Hone, in Irwin PA, will soon sell a machine, based on MIT’s 3D Printing process, that produces bronze-infiltrated PM tools and products. ²⁰

Laser-Engineered Net Shaping (LENS) is a process developed at Sandia National Laboratories and Stanford University that can create metal tools from CAD data. ²¹ Materials include 316 stainless steel, Inconel 625, H13 tool steel, tungsten, and titanium carbide cermets. A laser beam melts the top layer of the part in areas where material is to be added. Powder metal is injected into the molten pool, which then solidifies. Layer after layer is added until the part is complete. Unlike traditional powder metal processing, LENS produces fully dense parts, since the metal is melted, not merely sintered. The resulting parts have exceptional mechanical properties, but the process currently works only for parts with simple, uniform cross sections. The system has been commercialized by MTS corporation (www.mts.com)

Direct AIM (ACES Injection Molding): A technique from 3D Systems in which stereolithography-produced cores are used with traditional metal molds for injection molding of high and low density polyethylene, polystyrene, polypropylene and ABS plastic. ²² Very good accuracy is achieved for fewer than 200 moldings. Long cycle times (~ five minutes) are required to allow the molding to cool enough that it will not stick to the SLA core.

In another variation, cores are made from thin SLA shells filled with epoxy and aluminum shot. Aluminum’s high conductivity helps the molding cool faster, thus shortening cycle time. The outer surface can also be plated with metal to improve wear resistance. Production runs of 1000-5000 moldings are envisioned to make the process economically viable.

LOMComposite: Helysis and the University of Dayton are working to develop ceramic composite materials for Laminated Object Manufacturing. LOMComposite parts would be very strong and durable, and could be used as tooling in a variety of manufacturing processes.

Sand Molding: At least two RP techniques can construct sand molds directly from CAD data. DTM sells sand-like material that can be sintered into molds. Soligen (www.3dprinting.com) uses 3DP to produce ceramic molds and cores for investment casting, (Direct Shell Production Casting).

4.3 Rapid ManufacturingA natural extension of RP is rapid manufacturing (RM), the automated production of salable products directly from CAD data. Currently only a few final products are produced by RP machines, but the number will increase as metals and other materials become more widely available. RM will never completely replace other manufacturing techniques, especially in large production runs where mass-production is more economical.
For short production runs, however, RM is much cheaper, since it does not require tooling. RM is also ideal for producing custom parts tailored to the user’s exact specifications. A University of Delaware research project uses a digitized 3-D model of a person’s head to construct a custom-fitted helmet. ²³ NASA is experimenting with using RP machines to produce spacesuit gloves fitted to each astronaut’s hands. ²⁴ From tailored golf club grips to custom dinnerware, the possibilities are endless.
The other major use of RM is for products that simply cannot be made by subtractive (machining, grinding) or compressive (forging, etc.) processes. This includes objects with complex features, internal voids, and layered structures. Specific Surface of Franklin, MA uses RP to manufacture complicated ceramic filters that have eight times the interior surface area of older types. The filters remove particles from the gas emissions of coal-fired power plants. ²⁵ Therics, Inc. of NYC is using RP’s layered build style to develop "pills that release measured drug doses at specified times during the day" and other medical products. ²⁶

5 Future DevelopmentsRapid prototyping is starting to change the way companies design and build products. On the horizon, though, are several developments that will help to revolutionize manufacturing as we know it.
One such improvement is increased speed. "Rapid" prototyping machines are still slow by some standards. By using faster computers, more complex control systems, and improved materials, RP manufacturers are dramatically reducing build time. For example, Stratasys recently (January 1998) introduced its FDM Quantum machine, which can produce ABS plastic models 2.5-5 times faster than previous FDM machines. ²⁷Continued reductions in build time will make rapid manufacturing economical for a wider variety of products.
Another future development is improved accuracy and surface finish. Today’s commercially available machines are accurate to ~0.08 millimeters in the x-y plane, but less in the z (vertical) direction. Improvements in laser optics and motor control should increase accuracy in all three directions. In addition, RP companies are developing new polymers that will be less prone to curing and temperature-induced warpage.
The introduction of non-polymeric materials, including metals, ceramics, and composites, represents another much anticipated development. These materials would allow RP users to produce functional parts. Today’s plastic prototypes work well for visualization and fit tests, but they are often too weak for function testing. More rugged materials would yield prototypes that could be subjected to actual service conditions. In addition, metal and composite materials will greatly expand the range of products that can be made by rapid manufacturing.
Many RP companies and research labs are working to develop new materials. For example, the University of Dayton is working with Helisys to produce ceramic matrix composites by laminated object manufacturing. ²⁸ An Advanced Research Projects Agency / Office of Naval Research sponsored project is investigating ways to make ceramics using fused deposition modeling. ²⁹ As mentioned earlier, Sandia/Stanford’s LENS system can create solid metal parts. These three groups are just a few of the many working on new RP materials.
Another important development is increased size capacity. Currently most RP machines are limited to objects 0.125 cubic meters or less. Larger parts must be built in sections and joined by hand. To remedy this situation, several "large prototype" techniques are in the works. The most fully developed is Topographic Shell Fabrication from Formus in San Jose, CA. In this process, a temporary mold is built from layers of silica powder (high quality sand) bound together with paraffin wax. The mold is then used to produce fiberglass, epoxy, foam, or concrete models up to 3.3 m x 2 m x 1.2 m in size. ³⁰
At the University of Utah, Professor Charles Thomas is developing systems to cut intricate shapes into 1.2 m x 2.4 m sections of foam or paper. ³¹ Researchers at Penn State’s Applied Research Lab (ARL) are aiming even higher: to directly build large metal parts such as tank turrets using robotically guided lasers. Group leader Henry Watson states that product size is limited only by the size of the robot holding the laser. ³²
All the above improvements will help the rapid prototyping industry continue to grow, both worldwide and at home. The United States currently dominates the field, but Germany, Japan, and Israel are making inroads. In time RP will spread to less technologically developed countries as well. With more people and countries in the field, RP’s growth will accelerate further.
One future application is Distance Manufacturing on Demand, a combination of RP and the Internet that will allow designers to remotely submit designs for immediate manufacture. Researchers at UC-Berkeley, among others, are developing such a
system. ³³ RP enthusiasts believe that RP will even spread to the home, lending new meaning to the term "cottage industry." Three-dimensional home printers may seem far-fetched, but the same could be said for color laser printing just fifteen years ago.
Finally, the rise of rapid prototyping has spurred progress in traditional subtractive methods as well. Advances in computerized path planning, numeric control, and machine dynamics are increasing the speed and accuracy of machining. Modern CNC machining centers can have spindle speeds of up to 100,000 RPM, with correspondingly fast feed rates. ³⁴ Such high material removal rates translate into short build times. For certain applications, particularly metals, machining will continue to be a useful manufacturing process. Rapid prototyping will not make machining obsolete, but rather complement it.

Bose Suspension System

2013-03-03T17:03:00.001+05:30

While there have been enhancements and improvements to both springs and shock absorbers, the basic design of car suspensions has not undergone a significant evolution over the years. But all of that's about to change with the introduction of a brand-new suspension design conceived by Bose -- the same Bose known for its innovations in acoustic technologies. Some experts are going so far as to say that the Bose suspension is the biggest advance in automobile suspensions since the introduction of an all-independent design.

How does it work? The Bose system uses a linear electromagnetic motor (LEM) at each wheel in lieu of a conventional shock-and-spring setup. Amplifiers provide electricity to the motors in such a way that their power is regenerated with each compression of the system. The main benefit of the motors is that they are not limited by the inertia inherent in conventional fluid-based dampers. As a result, an LEM can extend and compress at a much greater speed, virtually eliminating all vibrations in the passenger cabin. The wheel's motion can be so finely controlled that the body of the car remains level regardless of what's happening at the wheel. The LEM can also counteract the body motion of the car while accelerating, braking and cornering, giving the driver a greater sense of control.

Unfortunately, this paradigm-shifting suspension won't be available until 2009, when it will be offered on one or more high-end luxury cars. Until then, drivers will have to rely on the tried-and-true suspension methods that have smoothed out bumpy rides for centuries.

Casting Process

2013-01-25T00:49:00.005+05:30

Casting Process

Consider the casting process at 645 B.C, the first traces of the Sand Molding was found. Now consider the state-of-the-art Electromagnetic casting process. Truly, the Casting process has traversed a long path and impacted human civilization for nearly five millennia. With technological advances, metal casting is playing a greater role in our everyday lives and is more essential than it has ever been.

Selecting the Right Metal Casting Process

For any Metal Casting Process, selection of right alloy, size, shape, thickness, tolerance, texture, and weight, is very vital.
Special requirements such as, magnetism, corrosion, stress distribution also influence the choice of the Metal Casting Process.
Views of the Tooling Designer; Foundry / Machine House needs, customer's exact product requirements, and secondary operations like painting, must be taken care of before selecting the appropriate Metal Casting Process.
Tool cost.
Economics of machining versus process costs.
Adequate protection / packaging, shipping constraints, regulations of the final components, weights and shelf life of protective coatings also play their part in the Metal Casting process.

The Metal Casting or just Casting process may be divided into two groups:
Hot Forming Process

Examples are Centrifugal casting, Extrusion, Forging, Full mold casting, Investment casting, Permanent or Gravity Die casting, Plaster mold casting, Sand Casting, Shell Mold casting. The method to be used depends upon the nature of the products to be cast.

Cold Forming Process

Examples are Squeeze casting, Pressure die casting, Gravity die casting, Burnishing, Coining, Cold forging, Hubbing, Impact Extrusion, Peening, Sizing, Thread rolling.

Comparative Advantages, Disadvantages and Applications for Various Casting Methods :

Sand Casting
Advantages	Disadvantages	Recommended Application
Least Expensive in small quantities (less than 100) Ferrous and non - ferrous metals may be cast Possible to cast very large parts. • Least expensive tooling	Dimensional accuracy inferior to other processes, requires larger tolerances Castings usually exceed calculated weight Surface finish of ferrous castings usually exceeds 125 RMS	Use when strength/weight ratio permits Tolerances, surface finish and low machining cost does not warrant a more expensive process
Permanent and Semi-permanent Mold Casting
Less expensive than Investment or Die Castings Dimensional Tolerances closer than Sand Castings Castings are dense and pressure tight	Only non-ferrous metals may be cast by this process Less competitive with Sand Cast process when three or more sand cores are required Higher tooling cost than Sand Cast	Use when process recommended for parts subjected to hydrostatic pressure Ideal for parts having low profile, no cores and quantities in excess of 300
Plaster Cast
Smooth "As Cast" finish (25 RMS) Closer dimensional tolerance than Sand Cast • Intricate shapes and fine details including thinner "As Cast" walls are possible • Large parts cost less to cast than by Investment process	More costly than Sand or Permanent Mold-Casting Limited number of sources Requires minimum of 1 deg. draft	Use when parts require smooth "As Cast" surface finish and closer tolerances than possible with Sand or Permanent Mold Processes
Investment Cast
Close dimensional tolerance Complex shape, fine detail, intricate core sections and thin walls are possible Ferrous and non-ferrous metals may be cast As-Cast" finish (64 - 125 RMS)	Costs are higher than Sand, Permanent Mold or Plaster process Castings	Use when Complexity precludes use of Sand or Permanent Mold Castings The process cost is justified through savings in machining or brazing Weight savings justifies increased cost
Die Casting
Good dimensional tolerances are possible Excellent part-part dimensional consistency Parts require a minimal post machining	Economical only in very large quantities due to high tool cost Not recommended for hydrostatic pressure applications For Castings where penetrant (die) or radiographic inspection are not required. Difficult to guarantee minimum mechanical properties	Use when quantity of parts justifies the high tooling cost Parts are not structural and are subjected to hydrostatic pressure

Bike Description

2013-01-23T12:09:00.000+05:30

How do bike engines work

Introduction

A while ago, I wondered “how does an engine really work”. I wasn’t just thinking of explosion in cylinders pushing pistons up and down. I was thinking of the little details. This file is a tidied up version of my random notes and questions.

How does an engine work

We want the engine to turn the back wheel. Or, more practically, to turn the gearbox since we want the bike to move both a very slow speeds and very fast speeds. The range of engine speeds available is roughly 1000 to 10,000 rpm which is a factor of ten. We want to ride a motorbike at anything from 1 to 100mph which is a factor of 100. So, we need a gearbox to provide a suitable range of gears. The engine drives the gearbox which drives the wheel. How do we get rotational motion from the engine?

We do this by a piston which provides periodic linear motion, connected by a con-rod to a crankshaft which turns the linear motion into rotation. The piston experiences a downward force on the ignition stage, which increases its monentum. The crankshaft acts as a flywheel which moves the piston through the other three stages (exhaust, intake and compression).

What affects the force on the piston when we ignite the fuel/air mixture?

Combustion is not instantaneous. A flame spreads from the spark plug across the cylinder. This takes a significant amount of time. Remember that an engine running at 10,000 rpm completes one revolution in 0.006 secs.
Combustion isn’t always complete. The fuel/air mixture might now have completely burned by the time it gets punted out of the exhaust port.
The amount of fuel/air mixture ignited. We can get more energy in each explosion by having more fuel and oxygen molecules in the cylinder to react together. This is why turbos and supercharges make an engine more powerful – they squeeze more fuel and air molecules into the cylinder. Nitros add an oxygen-rich chemical into the cylinder, which means we can burn more fuel.
The fuel/air ratio. Different proportions of fuel and air will affect combustion. Let’s look more at petrol first …

What goes into petrol?

Petrol contain mostly hydrocarbons. Hydrocarbons are basically anything which contain carbon atoms and hydrogen atoms. They’re useful as a fuel, because a carbon atom can combine with two oxygen atoms to make carbon dioxide, and two hydrogens can comine with an oxygen to make water (H2O). Actually, as well as the carbon dioxide reaction, you get get a single carbon reacting with a single oxygen to make carbon monoxide (CO). This can then go on to react with more oxygen to make carbon dioxide. All these reactions release energy, which is what makes our piston move downwards.

Petrol is a mixture of about 500 different hydrocarbons, which contain between 3 and 12 carbon atoms. These hydrocarbons are liquid (obviously, since petrol is liquid) and they boil between 30 and 220 degree celcius. So, on a hot day the smallest molecules are going to start evaporating off if they’re not in a sealed container.

Hydrocarbons are either saturated (only contain single bonds) or unsaturated (contains at least one double bond). Saturated hydrocarbons tend to burn cleanly, whereas unsaturated hydrocarbons burn smokily and are unstable.

Now, you want to get the biggest possible bang out of your fuel/air mixture, and you can do this by compressing it before igniting it. This pushes all of the fuel and air molecules closer together. A compression ratio of 6:1 gives 25% efficiency, whereas raising it to 12:1 gives 35% efficiency.

However, when you compress the mixture it gets hotter – up to 600 degrees celcius in a running engine.. If you compress it too much, it’ll get hot enough to ignite itself, which is bad! If this happens in a running engine, it’s called knocking or preignition and it can damage your pistons. Of course, if the engine is hot to start with, it’ll heat up the mixture and make preignition more likely. We’ll return to this in a minute.

So, the efficiency of your engine is related to the compression ratio, which is how much you squish the fuel air mixture before igniting it. The fuel/air mixture gets sucked into the cylinder on the intake stroke when the inlet value is open. Then it gets squished during the compression stoke, until the piston reaches its highest point. If there is 400 cubic centimetres above the piston at it’s lowest point, but only 100cc at it’s highest point then you have a compression ratio of 4:1. A real engine would have a compression ratios of something like 12:1.

We’d ideally want to have the compression ratio as high as possible, but we’ve seen that that’ll cause the fuel/air mixture to ignite early (before the spark plug has sparked) and damage our engine. So, we look for some magic ingredient to stop this happening.

One such magic ingredient is Tetra-ethyl lead, which gives leaded fuel it’s name. It reduces the tendency of the mixture to preignite. Unfortunately, it’s bad for the environment and has been phased out in the UK. TEL acts to lubricate the exhaust value, so there’s some concern that switching to unleaded fuel can lead to the exhaust valve being lubricated less.

Another problem with using tetra-ethyl lead (TEL) is that it would eventually gum up the engine and exhaust with lead, so you also have to add scavengers to the petrol. Scavengers are chemicals which react with the lead to make a volatile chemical which can pass out of the exhaust. An example would be lead halide salts.

It’s worth noting that petrol usually contains some Sulphur before it gets refined. Sulphur defeats the anti-knock properties of TEL and so has to be removed. It’s hard to remove it all though, and the sulphur which is left in the fuel reacts with air to form sulphur dioxide. The sulphur dioxide gets into the atmosphere via your exhaust and dissolves in water to form sulphuric acid – causing acid rain.

Fuel/air ratio

The carburettor controls the fuel/air mixture on a motorbike, and you often hear ‘lean’ and ‘rich’ being used to describe the fuel/air mixture. Let’s look at what effect this ratio has on the engine.

Firstly, there’s a theoretically optimal fuel/air mixture. This is called the stoichiometric mass/volume and it tells you how much air (ie. oxygen) you need to completely burn an amount of fuel. If you have less air than this, the mixture is rich. If you have too much air, the mixture is lean. You can look at it in terms of fuel. Too much fuel gives a rich mixture, too little gives a lean mixture.

The stoichiometric mass is related to the carbon/hydrogren ratio in your fuel. This makes sense, since each carbon atom needs two oxygen atoms to make CO2, and each hydrogren needs on average half an oxygen atom. So you can presumably just add up the number of carbon and hydrogen atoms and do a bit of maths to work out how many oxygen atoms you’re going to need.

If you have the ‘perfect’ amount of oxygen for your petrol you can expect to get about 45 mega-joules of energy for every kilogram of petrol you’ve got. However, engines aren’t perfectly efficient. For a start, to get the maximum amount of work out of the explosion, you’d have to let the gases expand until they’ve cooled down to the surrounding air temperature (look up Carnot cycles somewhere). In a real engine, the gases only get to expand as long as the piston is moving down. When the exhaust port opens, and the piston moves up to punt the exhaust gases out, the gases are still hot. That’s why the exhaust pipe gets hot! A normal engine has an efficiency of about 20-40%, so it only gets 20-40% of the theoretical maximum amount of energy out of each explosion. The rest of the energy goes to warm up the engine coolant, the exhaust and the engine’s surroundings.

All these hot exhaust gases go out of the cylinder, passing by the exhaust value. This makes the exhaust value pretty hot – up to 300 degrees celcius. Because of this, the exhaust value takes more of a hammering than the inlet valve, since the gases passing into the cylinder are at air temperature.

Apparently, for petrol you get stoichiometric combustion (that’s complete combustion) when you have a fuel/air ratio of 1:15 (that’s 15 parts of air to one part of fuel). You can get more power out of your engine by running a richer mixture of 13:1, but you’ll be producing some partly burned fuel leading to smoky exhaust and a gunky engine. You get maximum thermal efficiency (most energy for a given amount of fuel?) when you have a lean mixture such as 17:1.

Let’s look at what happens when the spark plug fires when you’re running a lean mixture. There’s less fuel molecules to go around, so the flame moves across the cylinder more slowly. This leaves more heat in the cylinder walls and cylinder head, which can lead to overheating. If the fuel/air mixture is very lean, then the flame can still be present when the inlet valve opens, which causes backfire!

If you’ve got a compression ratio of 12:1, with an engine speed of 1500rpm the flame will move across the cylinder at something like 15 meters per second.

As the engine speed increases, there’s less time for the mixture to burn completely. An engine running at 1000rpm spends 0.06 secs in each cycle, which drops to 0.006 secs when it’s running at 10,000rpm. One way to combat this drop in available burning time is to fire the spark plug a bit earlier when the engine is running fast – this is called the spark advance. If you increase the spark advance too much, it can cause knocking. However, if the engine is running fast then there’s less time for reactions to occur on front of the flame front, which tends to decrease the chance of knocking.

Mechanical aspects of the engine

Engines are made from metal, because it’s one of the few materials which can withstand the forces of the explosions, withstand the high temperatures and which can be made into the right shapes. The cylinder is made of metal. The piston and piston rings are made of metal. What stops this from scraping against each other in a nasty way?

The answer is oil. If you’ve got two metal surfaces rubbing against each other you need at least a thin layer of oil between them. If you run out of oil, or the oil film breaks at some place in your engine, the metal will rub together and get hot very quickly, potentially welding themselves together.

Why is oil good for this purpose? Most obvious, it’s slidy. If you have two metal surfaces sliding against each other, then putting a layer of oil between them will decrease the friction.

What is oil made from? What makes it slidy? Long molecules? Why doesn’t water work?

It has to be stable at temperature – can’t decompose quickly.

What do the different ratings mean?

Piston rings to scrape the oil, block the explosion from getting down past the piston.

What does oil encounter during its lifetime (cold start, hot operating — changes in viscosity).

If you use different metals when building an engine, you’d better be sure that they expand at roughly the same rate. If you make the piston from metal which expands faster (as the temperature increases) than the metal which the cylinder is made of, you’ll have problems.

If you’ve got a rotating shaft, you need to support the two ends of it somehow. The two ends get supported in bearings (since they bear the load) in the engine case. A bearing is just a specially chosen material which reduces the friction between the parts – such as brass. You still need oil though.

Carburettors

The carburettor is the bit of the motorbike which mixes the fuel with air. The fuel comes the tank, through a fuel tap which lets you turn the fuel on or off, then into the carburettor. Normally, we leave it up to gravity to get the fuel from the tank into the carburettor – we don’t need to pump it. This wouldn’t work in an aeroplane which has to fly upside down, but bikes spend most of their life right-way-up so it works fine. The air is sucked in from the outside world, and passes through an air cleaner before reaching the carburettor. There’s a few different types of air cleaner, but their purpose is the same. They remove grit, dust and other undesirable gunk from the air. You don’t want little bits of grit flying into your engine where they’d cause havoc.

The carburettor has its own little reserve of fuel called the float chamber. This work in the same way as a toilet cistern. When the fuel level drops, a value is opened which lets more fuel in. When the fuel level is high enough, the valve closes. You can get an idea of how much fuel is stored in the float chamber by turning the fuel tap off while the bike is still running. It’ll keep running for a minute or so.

The main purpose of the carburettor is to ‘spray’ the fuel into the air stream which passes through the carburettor. This creates a very fine mist, so that each bit of fuel is surrounded by lots of air which it can react with once it reaches the cylinder. It’s no good having big blobs of fuel, because only the fuel on the surface will be exposed to oxygen.

Let’s look at how the carburettor sprays the fuel into the air. There’s a fairly wide passage runs through the carburettor which is where the air passes through. We make a little hole in the side of this passage, and connect it to the float chamber. The idea is that the passing air will suck the fuel out of the hole, and it’ll then mix with the air.

We can make this work much better if we make the air passage narrow before it reaches the hole, and then widen afterwards. This creates a pressure difference (the Venturi effect) which acts to suck the fuel out into the air stream.

Clearly, the size of the hole is going to have a big effect on the resulting fuel/air mixture, so we use a carburettor jet. A jet is like a screw with a hole running down the middle of it. You screw the jet into the carburettor body, and the fuel goes up through the hole in the middle. You can buy jets with different sizes of hole if you want to change your fuel/air mixture.

There’s a problem with this description though. There’s not yet any way for the rider of the bike to control the fuel/air mixture. That’s going to be a problem, because the rider isn’t going to be happy with an engine which only runs at one speed. We can introduce speed control by arranging for a metal needle to sit above the jet. We can slow the engine down by moving the needle down, so that it partially blocks the hole in the jet. This throttles the fuel supply, and so it’s known as the throttle control. The right-hand grip on a motorbike simply controls the height of the needle. When you’re at full throttle, the needle is totally out of the jet. When you’re going very slowly, the needle will be blocking the jet more.

So, that’s the a pretty simple carburettor. The people who first built these things pretty quickly realized that they weren’t perfect. For a start, they didn’t work very well if the engine was running slowly. If the engine is running slowly, the piston is sucking air in at a relatively slow rate. If the air is moving past our jet very slowly, it doesn’t suck out much fuel so we end up with an overly lean mixture. We can fix this problem by putting a second, larger, hole in the carburettor called the pilot jet. This is only operational when the engine is running slowly. It’s larger size ensures that enough fuel is mixed in, even at slow speeds. At higher speeds, it’s not used.

So, what can go wrong with carburettors? Since they’ve got lots of very small fuel passages, they can get blocked quite easily. That’s why you have a fuel filter (usually in the fuel tap). That’s also why it’s a bad idea to run the bike with very little fuel. Chances are, you’ve got little bits of sediment in your fuel tank which have sunk to the bottom. If they get into the carburettor, everything is going to stop. You’ll also get problems if the fuel leaves behind any residue inside the carburettor. This gums up the insides of the carb, and you need pretty noxious cleaning fluids to get rid of it.

If it’s a cold day then starting the bike can be difficult. If the walls of the carburettor and cylinder inlets are cold, then the fuel will condense on the walls. The same thing happens if you breath out on a cold window – the water vapour in your breath condenses on the cold surface. If your fuel is all condensing before it reaches the cylinder, the mixture will be too lean to burn. You can remedy this by providing some means of making the mixture much richer when you’re starting the bike. This is what the choke lever controls. You can also see why it’s bad to run the bike with the choke lever on, since you’ll end up with an overly rich mixture. Also, if you put the choke on when you’re starting the bike on a warm day then you’ll get an overly rich mixture too, which will stop the bike starting. Taken to extremes, the fuel will start condensing in the cylinder and stop your spark plugs from doing their job.

A final carburettor problem is called carb icing. This is usually only a problem when it’s quite cold outside and there is high humidity (lots of water vapour in the air). When any liquid evaporates and turns into vapour, it takes in heat from it’s surroundings. That’s why you feel colder if you get wet – the evaporating water is sucking all your heat away. The same thing happens in the carburettor when the volatile fuel turns into fuel vapour. This makes the surfaces of the carburettor colder – by as much as 20 degrees celcius. This isn’t normally a problem, but if the carburettor is already cold then the cooling effect of the vapourizing fuel can make the carburretor body drop below freezing. If this happens on a humid day, then as we suck in air we will also be getting lots of water vapour. The water vapour can condense on the cold interior surfaces of the carb, and ultimately freeze. The ice can block the jets and stop the carb from working.

Exhaust pipes (4 strokes)

Bike builders tend not to put parts onto a bike unless they have a purpose. So what is the purpose of the exhaust pipe. Why is is it shaped like that, and what’s inside it?

You could theoretically run an engine without an exhaust pipe. It would be incredibly noisy – the exhaust valve is opened pretty quickly after there’s just been a big explosion inside the cylinder. There’s probably still some burning gases, and the whole mixture is going to still be extremely hot and would burn your legs. So, you need some way of getting these hot gases away.

The exhaust pipe serves three purposes. It takes the noxious gases which come out of the engine and moves them a bit further from the rider. We’ve already seen how carbon dioxide, carbon monoxide and water are formed during the burning of hydrocarbons. Sulphur dioxide is formed when the sulphur in the fuel is burned. Additionally, we find oxides of nitrogen in the exhaust gases. Normally nitrogen is pretty unreactive (it makes up 80% of the air we breathe) but the extremely high temperatures generated by the spark plug can cause it to react with oxygen.

Secondly, the exhaust pipe cools down the gases. It does this by allowing them to expand. The exhaust pipe is quite narrow when it leaves the engine, and then it gets wider. Allowing a gas to expand makes it cooler. Remember how compressing the fuel/air mixture with the piston made it hotter? This is the opposite effect. Once the gases have passed through the expansion chamber they are much cooler. That’s why your exhaust pipe dries out fastest near the engine when it’s been raining.

Finally, the exhaust pipe reduces the noise of the engine. Every time the exhaust valve opens, there’s a pressure wave (shockwave) travels along the exhaust pipe. If the exhaust pipe was just a straight tube, this wave would escape to the outside world and you’d have a noisy bike. To stop this, the exhaust pipe also acts as a silencer. It contains various plates with holes in them (baffles), which force the exhaust gases to take a convoluted route to the outside world. This tends to breaks up and cancel out much of the pressure waves, which results in a quieter bike. If you get a hole in your exhaust before the silencer then the exhaust gases will escape there and everything will get much noiser.

Power and Torque

The power of a bike is measured in horsepower (HP). One horsepower is the energy required to move 33,000 lbs by one foot in a minute, which is the strength of some perfect horse. It measure the rate of energy use – which is the same thing which ‘watts’ measure, eg. for lightbulbs. A human being can produce something like a quarter of a horse power. Bike engines produce anything from 10 to 200 horsepower.

In practise, you see bikes rated in brake horsepower (BHP). Brake horsepower is named after the machine which is used to measure horsepower, which is called the prony brake. The bhp rating is the maximum attainable hp for the engine. It doesn’t account for losses of energy through the gearbox, chain, wheel bearings. Even if you have a 50bhp engine, you wont be getting your full 50hp of rotation power at your back wheel if you’ve got a rusty chain and corroded wheel bearings.

An engine clearly delivers a different amount of pow

er at different speeds. When it’s going slowly, it provides less energy each second than if it was going quickly. If you look at the power graph for your bike, you’ll see what power it produces at different engine speeds (rpm).

Torque measures ability of accelerate. Again, your engine will produce different amounts of torque at different speeds. Typically, it has low torque at low revs, maximum torque at something like 60% of it’s maximum speed, and then the torque drops off as it reaches maximum speed. The more torque you have, the faster you can accelerate. That’s why bikes feel most responsive at something like 60% of peak revs – you’re at the point of maximum torque.

Solar Powered Bird Scarer

2013-01-05T10:15:00.001+05:30

The solar powered bird scarer is a device to scare birds away from different locations varying from large crop fields to airports and urban areas. This scare crow device uses natural bird distress calls to drive them away from crop fields and other populated areas. The device is powered by Photovoltaic Cells, also called solar panels. These devices are portable and water proof.

The bird movements over a wide area is detected by the device using infra red sensors. Once such a disturbance in the area is detected, the device produces distress calls to drive away the flock of birds. This system is very effective, portable and is independent of any external power supplies.

Photovoltaics: Solar PV installation, Kent

A 2.6 Kwh installation for a domestic residence.

Simon Mallett is a long term user and advocate of alternative energy having had solar water heating panels since 2003 and experimented with wind turbines over the last few years. With the introduction of Feed in Tariffs he decided that now was the time to install even more solar panels, this time as a sound financial decision to both save the planet, save money and this time make money with a clear view on a return of about 7% to 8%.

For SolarUK, of course we were keen to add to Simon's solar roof, but we had to consider that although from the outside it looked a fairly straightforward slate roof, in fact it wasn't just any old roof being a super insulated warm roof made up of jablite panels, one of the few in the UK, though Jablite warm roofs are more common in the Scandinavian countries.

Being a self builder Mr Mallett had a very clear idea of the challenges faced and SolarUK was able to work with him in developing a fixing system that would stand the test of time and preserve the roof in the best condition, something that we as solar panel installers have been doing for many years.

The 2.6kW system was decided on as being of a size that allowed for a single run of panels preserving an attractive look to the roof and avoiding a mish mash of panels every where they might just about fit.

Also, being a larger property we had to consider cable runs, the cables being run through the floor within plastic trunking, in this case prepared by Simon ready for our electrician to complete all connections.

The system is now up and running, feeding electricity into the grid and earning the Mallet family a regular Feed in Tariff income.

Manually Operated Paper Recycling Machine-Design

2013-01-05T10:13:00.002+05:30

The aim of this project is to design and construct a manually operated paper recycling machine.

As paper is one of the most used material in the world, the waste produced during its production, usage as well as disposal are very high. Since paper is made of natural materials its decomposition is easy. But if properly recycled, the material can be converted into useful products. As we know, the main raw material for the production of paper is wood and plants. The destruction of forests for obtaining these raw materials will result in an ecological unbalance. If paper can be recycled to be used again, such mass destruction of the environment can be prevented.

The paper recycling machine consists of 6 main units such as:
1. The disc Refiner
2. The Hydropupler
3. The headbox
4. The Felt Conveyor
5. The driers
6. The Rollers.

Simple Magnetic Levitation Train

2013-01-05T09:41:00.000+05:30

The world continues to expand with the increase in population. This is leading to the growth of cities and causing congestion in the present cities. If this trend continues, then the normal modes of transportation won’t be sufficient. This problem can be solved by making use of electromagnets and superconductors. These concepts can be made to design a train that floats on the track rather than on it.

This project “Simple Magnetic Levitation Train Btech Mech Project” aims to determine the effect of load on the friction force in the levitation train. In this project the principles of magnetism are applied. This project can be applied practically in today’s world as these levitation trains are low on maintenance and devoid of tracks that cause friction.

Working:

In this project Simple Magnetic Levitation Train Btech Mechanical Project Report two magnetic strips are used as rails and are glued to a long piece of wood in a manner that the north side of the strip is up. In the same manner two magnetic strips are placed at the bottom of the train. This should cause the train to levitate as the North Pole and train magnets face each other. The train also might slide to left or right but can be controlled by side rails.

In the setup of the project, the foundation of the wood track foundation is used. The plastic angles are mounted in the next step. Now comes the important part i.e. high force magnetic strips are mounted. These are mounted on the train block. This train is then set on the track.

Conclusion:

This experiment establishes the levitation project by making use of the principles of magnetism. If the magnetic strip is doubled then the magnetic levitation of the train goes faster. As distance reduces, the repelling force multiplies. The most important application of this project is Trans rapid magnetic lift trains.

Automatic Pneumatic Bumper For Four Wheeler

2012-12-29T21:17:00.000+05:30

Description: Many years ago, wheels were the part of a log and it slowly utilized for carts and wagons. The wooden wheel utilized was hard wood stakes. Trucks have become the backbone of the workforce in the world. They are large, strong and could be move on roughest of terrains. Truck rims should be placed if they are cracked.

The Automatic Pneumatic Bumper For Four Wheeler of truck rims are manufactured in the similar manner. It begins with tough hub and 4 to 6 holes for the bolts. Truck wheels require durable which carry some weight. Lighter wheels are developed by decreasing unsprung mass and permit suspension to follow the terrain and develop grip. Better heat conduction spends heat from the brakes that develops braking function in driving situations and decreases the brake failure because of overheating. The spun steel rim is saved with welds series. The rim is balanced and provided the smooth finishing.

The wheel rim is the portion of automotive. It includes static loads and fatigue loads like wheel rim moves various road profile. It improves high stresses in rim to search the serious stress point. The alloy of steel and light are important materials utilized in a wheel consisting glass-fiber. Different wheels are Wire Spoke Wheel, Steel Disc Wheel, and Light Alloy Wheel. The steel rims are present in silver and chrome and many finishes are secured for alloy wheels.

The important components of the project are,

• IR transmitter

• IR receiver

• Control Unit with Power supply

• Solenoid Valve

• Flow control Valve

• Air Tank (Compressor)

The IR TRANSMITTER circuit is to transmite the Infra-Red rays. If any obstacle is there in a path, the Infra-Red rays reflected. This reflected Infra-Red rays are received by the receiver circuit is called " IR RECEIVER".

In this project, we have to apply this breaking arrangement in one wheel as a model. The compressed air drawn from the compressor in our project. The compressed air floe through the Polyurethene tube to the flow control valve. The flow control valve is connected to the solenoid valve as mentioned in the block diagram. The application of pneumatics produces smooth operation. By using more techniques, they can be modified and developed according to the applications

Conclusion:

The wheel rim is the outer circular concept of the metal where corner of the tyre is climbed on automobiles like vehicles. The automotive steel wheel rim is created with rectangular metal. The metal plate is made curved to generate the cylindrical sleeve with the two corners of the sleeve joined together.

Solar Sail

2012-12-29T20:39:00.001+05:30

It's interesting when you look back at the history of space exploration and realize that propulsion technology hasn't really changed very much.

The earliest rocket prototypes were nothing more than elaborate versions of weapons used during World War 2 and fireworks used during civil celebrations. Even the Space Shuttle made use of solid rocket fuel technology in its pair of solid rocket boosters. But, with the liquid rocket fuel propulsion in the external tank, this combination has proved to be highly effective and launched hundreds of astronauts into space.

The approach works -- albeit not very efficiently -- and to get out of the Earth's gravitational well, it seems for now that the extra punch from exothermic processes is needed.

In deep space, however, there are alternatives receiving very serious consideration -- such as the "eco-friendly" solar sail.

What is a Solar Sail?

A solar sail, simply put, is a spacecraft propelled by sunlight. Whereas a conventional rocket is propelled by the thrust produced by its internal engine burn, a solar sail is pushed forward simply by light from the Sun. This is possible because light is made up of packets of energy known as “photons,” that act like atomic particles, but with more energy. When a beam of light is pointed at a bright mirror-like surface, its photons reflect right back, just like a ball bouncing off a wall. In the process the photons transmit their momentum to the surface twice – once by the initial impact, and again by reflecting back from it. Ever so slightly, propelled by a steady stream of reflecting photons, the bright surface is pushed forward.

A solar sail is made up of just such a reflective surface, or several surfaces, depending on the sail’s design. When the bright sails face the Sun directly, they are subjected to a steady barrage of photons that reflect off the shiny surfaces and impel the spacecraft forward, away from the Sun. By changing the angle of the sail relative the Sun it is possible to affect the direction in which the sail is propelled – just as a sailboat changes the angle of its sails to affect its course. It is even possible to direct the spacecraft towards the Sun, rather than away from it, by using the photon’s pressure on the sails to slow down the spacecraft’s speed and bring its orbit closer to the Sun.

In order for sunlight to provide sufficient pressure to propel a spacecraft forward, a solar sail must capture as much Sunlight as possible. This means that the surface of the sail must be big – very big. Cosmos 1 is a small solar sail intended only for a short mission. Nevertheless, once it spreads its sails even this small spacecraft will be 10 stories tall, as high as the rocket that will launch it. Its eight triangular blades are 15 meters (49 feet) in length, and have a total surface area of 600 square meters (6500 square feet). This is about one and a half times the size of a basketball court.

For a true exploration mission the requirements are far greater: when a NASA team in the 1970s, headed by Louis Friedman, suggested using a solar sail spacecraft for a rendezvous with Halley’s comet, they proposed a sail with a surface area of 600,000 square meters (6.5 million square feet). This is equivalent to a square of 800 meters (half-mile) by 800 meter – the size of 10 square blocks in New York City!

Even with such a gigantic surface, a solar sail spacecraft will accelerate very slowly when compared to a conventional rocket. Under optimal conditions, a solar sail on an interplanetary mission would gain only 1 millimeter per second in speed every second it is pushed along by Solar radiation. The Mars Exploration Rovers, by comparison, accelerated by as much as 59 meters (192 feet) per second every second during their launch by conventional Delta II rockets. This acceleration is 59,000 times greater than that of a solar sail!

But the incomparable advantage of a solar sail is that it accelerates CONSTANTLY. A rocket only burns for a few minutes, before releasing its payload and letting it cruise at a constant speed the rest of the way. A solar sail, in contrast, keeps on accelerating, and can ultimately reach speeds much greater than those of a rocket-launched craft. At an acceleration rate of 1 millimeter per second per second (20 times greater than the expected acceleration for Cosmos 1), a solar sail would increase its speed by approximately 310 kilometers per hour (195 mph) after one day, moving 7500 kilometers (4700 miles) in the process. After 12 days it will have increased its speed 3700 kilometers per hour (2300 mph).

While these speeds and distances are already substantial for interplanetary travel, they are insignificant when compared to the requirements of a journey to the stars. Given time, however, with small but constant acceleration, a solar sail spacecraft can reach any desired speed. If the acceleration diminishes due to an increasing distance from the Sun, some scientists have proposed pointing powerful laser beams at the spacecraft to propel it forward. Although such a strategy is not practicable with current technology and resources, solar sailing is nevertheless the only known technology that could someday be used for interstellar travel.

How do they work?

Solar Sails propel a spacecraft by utilizing the pressure created by the stream of photons (tiny units of light energy) from the sun. Once a spacecraft is in orbit, a lightweight sail would unfurl. Changing the position of the sail would increase or decrease speed. The thrust created by the photon stream is very low and interplanetary journeys would take years. For long missions, an on-board laser or microwave transmitter would be fitted to provide power when the Sun is distant.

Hundreds of space missions have been launched since the last lunar mission, including several deep space probes that have been sent to the edges of our solar system. However, our journeys to space have been limited by the power of chemical rocket engines and the amount of rocket fuel that a spacecraft can carry. Today, the weight of a space shuttle at launch is approximately 95 percent fuel. What could we accomplish if we could reduce our need for so much fuel and the tanks that hold it?

International space agencies and some private corporations have proposed many methods of transportation that would allow us to go farther, but a manned space mission has yet to go beyond the moon. The most realistic of these space transportation options calls for the elimination of both rocket fuel and rocket engines -- replacing them with sails. Yes, that's right, sails.

NASA is one of the organizations that has been studying this amazing technology called solar sails that will use the sun's power to send us into deep space.

History

On February 4, 1993, Znamya 2, a 20-meter wide aluminized-mylar reflector, was successfully tested from the Russian Mir space station. Although the deployment test was successful, the experiment only demonstrated the deployment, not propulsion. A second test, Znamaya 2.5, failed to deploy properly.

On August 9, 2004, the Japanese ISAS successfully deployed two prototype solar sails from a sounding rocket. A clover type sail was deployed at 122 km altitude and a fan type sail was deployed at 169 km altitude. Both sails used 7.5 micrometer thick film. The experiment was purely a test of the deployment mechanisms, not of propulsion.

In June 21, 2005 a Volna rocket launched from a Russian submarine in the Barents Sea launched the privately built Cosmos-1 spacecraft. However, a rocket failure prevented it from reaching its intended orbit. The Cosmos-1 spacecraft was designed to use solar sails to move through space. Had the mission been successful, it would have been the first ever orbital use of a solar sail to speed up a spacecraft, as well as the first space mission by a space advocacy group (Planetary Society).

The IKAROS probe is the world's first spacecraft to use solar sailing as the main propulsion.

LightSail-1, a second orbital spacecraft by the Planetary Socity is under construction and is expected to be ready by the end of 2010.

How It Works: The sun’s radiation exerts force on the ultrathin fabric of solar sails, much like wind propels a sailboat. These sails can clean up orbit by slowing debris enough that it deorbits. For example, an expandable 97-square-foot sail can be launched as a secondary payload on even a small 110-pound satellite, and an onboard system or ground control triggers its deployment. Conductive coils embedded in the sail control its angle, so it can maneuver a satellite out of orbit; sail and satellite disintegrate together in the atmosphere.

Pros: The material is cheap and portable.

Cons: The sail’s expansion and the spacecraft’s altitude need to be carefully calculated beforehand.

Plausibility: The technology has existed for decades, from a sail-equipped craft in the mid-1970s intended to ride along with Halley’s Comet (the craft never flew, and the project was scrapped) to large solar arrays currently affixed to the Messenger spacecraft, which are helping steer it to Mercury. Most recently, the Japan Aerospace Exploration Agency launched a solar-sail-propelled “space yacht” called Ikaros in May. But the solar sails precisely controllable enough to remove debris are still years away.

Cloud Cover: Tanks of liquid gas would emit mist that slows down objects passing through enough that the debris would fall from orbit. Kevin Hand

Space Mist

How It Works: One of the more novel solutions, first proposed by researchers at NASA’s Ames Research Center in 1990 and recently resurrected, is to use frozen mist to drag an object out of orbit. A rocket launches a tank filled with liquid gas, such as carbon dioxide, and thrusters position the tank near the path of the target object.Thousands of miles from the debris, the tank sprays a cloud of frozen mist. The droplets slow down and deorbit anything they encounter. According to the idea’s originator, aerospace engineer George Sarver of Ames, a spaceship emitting a 220-pound, 62-foot-diameter cloud of frozen mist could deorbit dense objects such as steel nuts. Larger clouds could stop less-dense items like insulation.

Pros: Once the mist dissipates, nothing remains in orbit. The tank falls back into the atmosphere, which means less clutter that could otherwise create more debris.

Cons: It requires precise aim, because each tank sprays its shot just once.

Plausibility: “We could probably test it in orbit within 18 months if NASA funded it,” says Creon Levit, the chief scientist for programs at Ames.

Astro-Velcro: Large balls with adhesive shells could stick themselves to debris and carry it out of orbit. Kevin Hand

Robots and Adhesives

How It Works: One idea to capture tumbling debris employs orbiting spacecraft that would use robotic arms to grab and release debris, essentially tossing it out of orbit so it burns up in the atmosphere. Sean Shepherd, a curriculum coordinator at Eastern New Mexico University, proposes a more novel idea, called Adhesive Synthetic Trash Recovery Orbital Spheres, or Astros—essentially a collection of sticky balls. The balls consist of a layer of metallic foam (such as silicon carbide) and an outer shell of adhesive (such as aerogels or resins). They attach themselves to debris and then dive into the atmosphere, where both are incinerated.

Pros: Spacecraft that carry and position the robotics are easier to control than tethers or sails and can remove multiple pieces of debris. Adhesives are cheap.

Cons: The adhesive balls can’t be compressed, so packing them into a rocket for launch will be difficult.

Plausibility: Hanspeter Schaub, the associate chair of graduate studies in the Aerospace Engineering Sciences department at the University of Colorado, says the orbiting robot concept could be tested in space within five years.

Hybrid hydraulic Vehicle

2012-12-21T23:36:00.001+05:30

Introduction To Hydraulic Hybrid Vehicles:

Hybrid vehicles use two sources of power to drive the wheels. In a hydraulic hybrid vehicle (HHV) a regular internal combustion engine and a hydraulic motor are used to power the wheels.

Hydraulic hybrid systems consist of two key components:

High pressure hydraulic fluid vessels called accumulators, and
Hydraulic drive pump/motors.

Working of Hydraulic Hybrid Systems:

The accumulators are used to store pressurized fluid. Acting as a motor, the hydraulic drive uses the pressurized fluid (Above 3000 psi) to rotate the wheels. Acting as a pump, the hydraulic drive is used to re-pressurize hydraulic fluid by using the vehicle’s momentum, thereby converting kinetic energy into potential energy. This process of converting kinetic energy from momentum and storing it is called regenerative braking.

The hydraulic system offers great advantages for vehicles operating in stop and go conditions because the system can capture large amounts of energy when the brakes are applied.

The hydraulic components work in conjunction with the primary. Making up the main hydraulic components are two hydraulic accumulator vessels which store hydraulic fluid compressing inert nitrogen gas and one or more hydraulic pump/motor units.

The hydraulic hybrid system is made up of four components.

The working fluid
The reservoir
The pump or motor
The accumulator

The pump or motor installed in the system extracts kinetic energy during braking. This in turn pumps the working fluid from the reservoir to the accumulator, which eventually gets pressurized. The pressurized working fluid then provides energy to the pump or motor to power the vehicle when it accelerates. There are two types of hydraulic hybrid systems – the parallel hydraulic hybrid system and the series hydraulic hybrid system. In the parallel hydraulic hybrid, the pump is connected to the drive-shafts through a transmission box, while in series hydraulic hybrid, the pump is directly connected to the drive-shaft.

There are two types of HHVs:

Parallel and
Series.

Parallel Hydraulic Hybrid Vehicles:

In parallel HHVs both the engine and the hydraulic drive system are mechanically coupled to the wheels. The hydraulic pump-motor is then integrated into the driveshaft or differential.

Series Hydraulic Hybrid vehicles:

Series HHVs rely entirely on hydraulic pressure to drive the wheels, which means the engine does not directly provide mechanical power to the wheels. In a series HHV configuration, an engine is attached to a hydraulic engine pump to provide additional fluid pressure to the drive pump/motor when needed.

Advantages:

Higher fuel efficiency. (25-45 percent improvement in fuel economy)
Lower emissions. (20 to 30 percent)
Reduced operating costs.
Better acceleration performance.

How to build a Solar Car

2012-07-18T14:42:00.001+05:30

Building a solar car is a very ambitious goal, but one that is achievable through hard work and commitment. One of the first things to do is to organize a group of people interested in building a car, and planning a specific goal. How much money will you need to build a solar car? If the least expensive parts are used, the cost of a solar car is about $12,000, not including trip costs to the competition. You will need a core group of fundraisers who are willing to spend the year making presentations to businesses and speaking to individuals at their home. You will also need to assess what materials and tools you need and get several people focused on building the car itself. It may be a difficult road the first year, but the things you learn along the way will last a lifetime!
Solar cars are powered by the sun's energy. The main component of a solar car is its solar array, which collect the energy from the sun and converts it into usable electrical energy. The solar cells collect a portion of the sun's energy and stores it into the batteries of the solar car. Before that happens, power trackers converts the energy collected from the solar array to the proper system voltage, so that the batteries and the motor can use it. After the energy is stored in the batteries, it is available for use by the motor & motor controller to drive the car. The motor controller adjusts the amount of energy that flows to the motor to correspond to the throttle. The motor uses that energy to drive the wheels.

Solar Array and Power Trackers
We recommend a solar array created from individual solar cells as opposed to one made of prefabricated solar panels. It enhances the students' learning and can result in a lighter solar array. Cells can be bought from either Siemens or ASE Americas. Both sell the terrestrial-grade cells that are permitted in the Winston Solar Challenge, and the cost for terrestrial-grade cells are much lower than space-grade cells, though terrestrial-grade is less efficient. Each solar cell should produce .5 volts at about 3 amps at peak sunlight. The number of cells to use depends on their size and the allowable solar area per Winston rules. Solar cells should be wired in series on a panel and should be divided into several zones. For example, if you have 750 solar cells, you might want to wire 3 sets of 250 cells, each zone producing about 125 volts. If one zone fails, two other zones are still producing power. The solar array voltage does not need to match the system voltage of the motor if you use power trackers. Power trackers convert the solar array voltage to the system voltage. They are essential in a solar car. Be sure to verify with the power tracker vendor the necessary array voltage to feed the power trackers. If the car drives underneath shade, the power trackers automatically adjusts the power to match system voltage, allowing the system to run as efficient as possible. Power trackers are available from AERL.
Batteries
The batteries store energy from the solar array and makes them available for the motor's use. Many different types of batteries are sold. Most high school teams use lead-acid batteries because they are inexpensive, but some teams use lithium-ion or nickel-cadmium. We recommend that you stick with lead-acid batteries because they are readily available and inexpensive. Another choice teams must make is running with flooded-cell batteries or gel-cell batteries. Flooded-cell batteries are the standard automotive batteries filled with liquid sulfuric acid. They are preferred because they can be overcharged without risk of blowing up, but they weigh more than gel-cell batteries. Gel-cell are sealed and lightweight, but when charging the batteries, check the battery voltage often. The number of batteries to choose depends on the motor (system) voltage. If the system voltage is 72 volts, you will need 6 12-volt batteries. Also be sure to check the rules for weight or watthour requirements. Buy batteries with as many amphours as allowed by the rules to maximize the amount of energy you can store.
Motor & Controller
Most teams use DC brush permanent magnet motors to drive their solar cars. Inexpensive and easy to hook up, these motors are desirable for high school teams with little financial support. Expect a maximum efficiency of 80-90%. For teams with more money, brushless motors increase the efficiency of the motor to the 94-99% range. Also, some motor and controller setups allow for regenerative braking, which allows the solar car to put energy back into the batteries when going downhill. For the beginning team, DC brush motors would be sufficient to get a solar car up and running. Another variable in choosing a motor is how much power it has. We have found that there is little need to have more than 5hp continuous power output on our motors. There are two manufacturers who supply most teams with motors and controllers: Solectria and Advanced DC Motors. Many college teams buy their motors from Solectria, but Advanced DC Motors have less expensive motors. Controllers usually drive a particular motor. Once you choose the motor that suits your needs, the same vendor would most likely have a matching controller.
Instrumentation
One of the most important pieces of instrumentation is a state-of-charge meter. A state-of-charge meter gives information about system voltage, amp draw, battery energy remaining, and estimates the how much time remains until the battery is out of energy. We found that the E-Meter, manufactured by Cruising Equipment, served out purpose well. It has a digital display and accurately counts the number of amp-hours remaining in the battery. The E-Meter is the do-it-all in instrumentation. Another instrument that may be useful is a speedometer. Instead of using a regular speedometer drive, use magnetic contact speedometers, found in many sports equipment stores. This option does not add drag to your car. To ensure that your batteries are running properly, you may invest in getting a voltmeter for each of your batteries. A failed battery may show the proper voltage when the car is not running, but while the battery is under load, the voltmeter will show a lower than normal battery voltage.
Steering & Suspension
We strongly recommend front wheel steering as it tends to be more stable and safer. A solar car uses energy frugally if it is to be competitive. If there are two front wheels, it is therefore advisable to work out the geometry so that they run parallel when the car is going straight ahead, but when the car is turning, the front wheels turn at different radii. If the car is turning left, the left front tire is making a smaller circle than the right front tire. If the tires remain parallel while turning, they will cause unnecessary drag, decreasing tire life and overall performance.
The only advice we can offer with respect to suspension is that it should be soft enough to protect the car and solar array from unnecessary jolts and firm enough to provide a stable ride.
Brakes
Disc brakes are desirable as they are predominantly hydraulic. Having hydraulic lines running to the wheels can be easier than mechanical brake arrangements. The most significant problem with disc brakes is that the brake pads do not back away from the brake rotors when pressure is released, they just relieve braking pressure. Because the pads don't normally back away from the rotors, they continue to have a small amount of drag. While this drag may not be noticeable on the family car, it is very inefficient on solar cars. Go kart shops now have brake calipers that are spring loaded to move the pads away from the rotors. We have found these very worthwhile.
Tires & Hubs
Tire selection will affect rolling resistance which affects how far the solar car will travel with the energy available. Tires with thicker rubber and wider tread tend to have higher rolling resistance (a bad thing). Thinner tires with higher pressuer have less rolling resistance, but are more susceptible to flats. The best tires we have found are the Bridgestone Ecopia tires made for solar cars. They are very thin and operate at over one hundred pounds/inch pressure. Unfortunately, they need to be mounted on specially made wheels and require custom made hubs. On the good side, these tires and wheels are very light. Some colege teams have experimented with bicycle tires but report limited success (bicycle tires, rims and spokes are not designed for the forces placed on them by non-tilting vechicles that weigh several hundred pounds). Motorcycle tires tend to have more resistance, although there may be high pressure tires with low resistance that we don't know about yet.
Bearing resistance can be reduced by light minimal lubrication. Bearing seals can be cut away at the contact lip to leave most of the seal protection while removing most if not all seal drag. It is a good idea to get the rolling chassis operational months before your schedule gets critical. Run the chassis as many miles as possible to prove that your bearings, axles, steering and suspension can survive.

Thermal Cycles

2012-06-28T21:15:00.003+05:30

Otto Cycle

1-2 Reversible adiabatic compression of air (W_IN)

2-3 Addition of heat at constant volume increases pressure (Q_IN)

3-4 Reversible adiabatic expansion of air (W_OUT)

4-1 Rejection of heat at constant volume reduces pressure (Q_OUT)

§ From first law

§ Thermal efficiency of a cycle usually found . Also and hence

§ Compression and expansion of air are Polytropic process with hence Where the compression ratio

§ Hence thermal efficiency is only dependant on compression ratio

Diesel cycle

1-2 Reversible adiabatic compression of air (W_IN)

2-3 Addition of heat at constant pressure increases volume (Q_IN)

3-4 Reversible adiabatic expansion of air (W_OUT)

4-1 Rejection of heat at constant volume reduces pressure (Q_OUT)

§ From first law

§ As with Otto but as heat is added at constant pressure

§ Assume heat addition 2-3 is ideal gas: but so hence the cut-off ratio

§ Thermal efficiency is dependant on compression AND cut-off ratio

Real gas turbines

§ Approximated by joule cycle.

§ Air drawn into compressor.

§ Fuel injected and ignited.

§ Hot gasses pass through turbine, providing mechanical power.

§ Exhaust gasses expelled.

Joule Cycle

§ Approximates gas turbine, like aircraft engines.

Open system so use SFEE!

1-2 Reversible adiabatic compression of air (W_IN)

2-3 Reversible addition of heat at constant p increases T (Q_IN)

3-4 Reversible adiabatic expansion of air (W_OUT)

4-1 Reversible rejection of heat at constant p reduces T (Q_OUT)

§ From first law

§ For heat transfers at constant pressure and

§ For compressor and turbine work and

§ Compression and expansion is Polytropic with such that

§ Here we have the pressure ratio

§ Thermal efficiency dependant only on the pressure ratio

Otto cycle

The Otto cycle is a first approximation to model the operation of a spark-ignition engine, first built by Nikolaus Otto in 1876, and used in many cars, small planes and small power systems (below say 200 kW) down to miniature engines. This is a reciprocating internal combustion gas engine, in contrast to the, at that time master, reciprocating or rotodynamic external combustion steam engine. The Otto engine is sketched in Fig. 5.2, where the typical terms are introduced for engine-geometry characteristics (stroke, bore, displacement and compression ratio); other terms for engine-operation characteristics are shaft speed, mean pressure, power, fuel consumption, torque, volumetric efficiency, energy efficiency, etc.

Fig. 5.2. Sketch and nomenclature for reciprocating engines: a) 4-stroke, b) 2-stroke (uni-flow).

In the ideal air-standard Otto cycle, the working fluid is just air, which is assumed to follow four processes (Fig. 5.3): isentropic compression, constant-volume heat input from the hot source, isentropic expansion, and constant-volume heat rejection to the environment.

Fig. 5.3. The ideal Otto cycle in the T-s and p-V diagram, and a practical p-V trace of four-stroke and two-stroke engines.

The main parameters of both ideal and real Otto cycles are:

· Size, measured by the displacement volume (the volume swept by the piston, V₁−V₂), usually less than 0.5 litres per cylinder, to avoid self-ignition.

· Speed, more precisely crankshaft speed, n, with a typical operation range n=1000..7000 rpm (n=20..120 Hz). The maximum value may be in the range n_max=6000..8000rpm for four-stroke engines. Two-stroke motorcycle engines run quicker (n_max=13 000 rpm), the quickest (n_max=20 000 rpm) being the smallest engines (two stroke), used in aircraft modelling.

· Compression ratio, r=V₁/V₂, with a typical range of r=8..10 (up to 14 in direct-injection spark-ignition engines), limited by the 'knock' or self-ignition problem.

· Mean effective pressure, p_me, defined as the unit work divided by the displacement, with a typical range of 0.2..1.5 MPa (the full-load value may range from p_me=1.2 MPa in two-stroke motorcycle engines, to p_me=1.7 MPa in the largest turbocharged engines). Maximum pressure may have a typical range of 4..10 MPa. Performance maps of reciprocating engines are usually presented on a p_me-n diagram, i.e. mean effective pressure versus engine speed.

Real reciprocating engines may be two-strokes or four-strokes in a cycle; the simple to model is the four-strokes engine, where one stroke is used to fill the cylinder with the air-fuel mixture through the inlet valve (the inside pressure is a little below atmospheric), a second stroke to compress the mixture with valves closed and exploding it at a precise point with a spark, a third stroke to let the product gasses to expand and do work on the crank-shaft, and a fourth stroke to force the burnt gasses out through the exhaust valve, and start a new cycle (two crank-shaft turns have elapsed). In two-stroke engines there is an overlap between intake and exhaust, with the inlet stream used to sweep the burnt gasses (throwing unburnt gases to the tailpipe!), and the whole cycle is performed in one turn of the crankshaft. In spite of the higher fuel consumption and pollutant emissions, and the difficulties for their lubrication (oil is added to the fuel), two-stroke engines have very high specific power, and thus they are used for small engines (hand-held and garden engines, motorcycles and outboard boats).

The cold-air-standard model takes as working fluid air with constant properties (those at the inlet, i.e. cold), what renders the analysis simple. The energy exchanges for the trapped control mass, m, are W₁₂/m=c_v(T₂-T₁), Q₁₂=0, W₂₃=0, Q₂₃/m=c_v(T₃-T₂), W₃₄/m=c_v(T₄-T₃), Q₃₄=0, W₄₁=0, Q₄₁/m=c_v(T₁-T₄), and the energy and exergy efficiencies are:

and (5.2)

Real spark-ignition engines do not recycle the working fluid; they are all internal combustion engines where ambient air is pumped in, and petrol fuel (gasoline) is added to prepare a homogeneous reactive mixture that at a certain point (cinematically or electronically controlled) is ignited by an electrical spark. Fuel addition can be in a carburettor by Venturi suction, or in the individual inlet duct by injection, or recently by direct injection inside the cylinder as in a diesel engine (but with a much lower injection pressure, less than 10 MPa). Gaseous fuels like coal-gas, liquefied petroleum gas (LPG), and natural gas are also used, as well as other liquid fuels like methanol, ethanol and ethers, usually added to gasoline up to a 20%. Typical energy efficiencies are low, 25% to 35% when running at nominal power, much lower at partial load, but the engine is light, very powerful and not expensive.

Diesel cycle

The Diesel cycle is a first approximation to model the operation of a compression-ignition engine, first built by Rudolf Diesel in 1893, and used in most cars, nearly all trucks, nearly all boats, many locomotives, some small airplanes, and many large electric power systems and cogeneration systems. It is the reference engine from 50 kW to 50 MW, due to the fuel used (cheaper and safer than gasoline) and the higher efficiency. This is a reciprocating internal combustion engine with the same sketch as in Fig. 5.2, but substituting the spark-plug by the fuel injector (the fuel is injected at very high pressures, up to 200 MPa, to ensure immediate vaporisation). One of its key advantages compared to Otto engines is the great load increase per cylinder associated to the higher pressures allowed (the mixture of fuel and air would detonate in Otto engines at high compressions), and the further load increase associated to charging previously-compressed air (turbocharging). Another advantage is the much better performance at part load, since there it is achieved by injecting less fuel instead of by throttling, and the torque (power divided per angular speed, M=P/w), changes less with angular speed.

In the ideal air-standard Diesel cycle, the working fluid is just air, which is assumed to follow four processes (Fig. 5.4): isentropic compression, constant-pressure heat input from the hot source, isentropic expansion, and constant-volume heat rejection to the environment.

Fig. 5.4. The ideal Diesel cycle. Practical p-V diagrams are as in Fig. 5.3.

Similarly to the Otto cycle, the main parameters of ideal and real Diesel cycles are also the size, measured by the displacement volume (that may reach more than 1 m³ per cylinder in large marine engines), the compression ratio, r=V₁/V₂ (with a typical range of 16..22, limited just by strength), the cut-off ratio, r_c, or the mean effective pressure (in the range 1..2 MPa), or the maximum pressure (in the range of 3 MPa to 20 MPa), and the speed (with a typical range of 100..6000 rpm). The energy efficiency can be expressed as:

(5.3)

Real compression-ignition engines take ambient air (often after a first stage compression) and compress it (inside the cylinder) so much, rising the temperature accordingly, that the fuel burns as it is injected (after a small initial delay due to vaporisation and combustion kinetics). The external compression is performed in a centrifugal compressor driven by a centrifugal turbine moved by the exhaust gasses (turbocharger); the air is cooled after external compression (inter-cooler) before further compression within the cylinders, to increase the efficiency, as explained in Multistage compression.

The higher pressures in Diesel than in Otto engines require a robust engine-frame and delicate fluid injection hydraulics (with injection pressure up to 200 MPa), but the wider range of fuels (from gas-oils to fuel-oils), the better fuel control, longer durability and economy are making Diesel engines to displace traditional gasoline-engines markets (for heavy-duty applications it has always been unrivalled). Typical energy efficiencies are from 30% to 54% (based on the lower heating value of the fuel), the latter, the largest of any single thermal engine, being achieved in large two-stroke marine low-speed engines with bores larger than 0.5 m: first, because the thermal losses decrease with size, and second, because the very low speed (some 100 rpm instead of the typical 3000 rpm for a car engine) allows for a more complete combustion (more time to burn, and burning nearly without volume change) and decrease friction losses (in spite of the fact that the mean piston speed stays at some 6..7 m/s for the whole range of reciprocating engines: from the 1 cm³ 50 W model, to a 1 m³ 5 MW 'three-store castle', per cylinder). Most large Diesel engines are supercharged, i.e. fed with compressed air instead of atmospheric air, usually by means of a turbocharger (a small compressor shaft-coupled to a small turbine driven at high speeds by the exhaust gases; some 10% of the fuel energy goes through that shaft), with an intermediate cooling of the compressed air before intake to the cylinders (intercooler). The two-stroke cycle is better suited to Diesel engines, since only air is used to sweep the burnt gases (scavenging), and not fresh mixture, but, because of the difficulty in lubricating, it is only used in the largest marine engines (10 MW..100 MW), where residual fuel (must be preheated to flow) can be used.

Mixed cycle

The mixed (or dual, or Sabaté, or Seiliger, or 5-point) cycle, sketched in Fig. 5.5, is a refinement to both Otto and Diesel cycles, at the expense of an additional parameter, the heat-addition pressure ratio, r_p=p₃/p₂.

Fig. 5.5. The dual or Sabaté cycle.

The energy efficiency can be expressed as:

(5.4)

Brayton cycle

The Brayton cycle, named after the American engineer George Brayton (that built a two-stroke reciprocating engine in 1876 and advanced combustion chambers at constant pressure), is a good model for the operation of a gas-turbine engine (first successfully tested by F. Whittle in 1937, and first applied by the Heinkel Aircraft Company in 1939), nowadays used by practically all aircraft except smaller ones, by many fast boats, and increasingly been used for stationary power generation, particularly when both power and heat are of interest.

In the ideal air-standard Brayton cycle, the working fluid is just air, which is assumed to follow four processes (Fig. 5.6): isentropic compression, constant-pressure heat input from the hot source, isentropic expansion, and constant-pressure heat rejection to the environment. Contrary to reciprocating engines, the gas turbine is a rotatory device working at a nominal steady state (it can hardly work at partial loads); spark ignition is used to start up, since air compressor output temperature is not high enough to inflame the fuel).

Fig. 5.6. The ideal Brayton cycle in the T-s and p-V diagram, and the regenerative Brayton cycle.

Most gas turbines are internal combustion engines where the working fluid must be renovated continuously as sketched in Fig. 5.7, but some gas turbines use a closed-loop working fluid.

Fig. 5.7. Open and closed cycle gas turbine.

The main parameters of ideal and real Brayton cycles are the turbine-inlet temperature, T₃, the compressor pressure ratio, p=p₂/p₁ (with a typical range of 4 to 30), the compressor and turbine efficiencies, and the size, measured by the air mass flow rate. The energy and exergy efficiencies for the ideal Brayton cycle (compressor and turbine efficiencies of 100%), can be expressed as:

and (5.5)

Real engine efficiencies are comparatively low, from 25% to 38%, but in combination with a bottoming vapour cycle, they reach 50..59% based on LHV; combined cycle power plants are the present standard in electricity generation. Contrary to reciprocating and steam engines, the gas turbine can only work with fine-tuned components, since it gives no net power if the compressor and turbine efficiencies fall below say 80% (modern gas turbines can have compressor efficiencies of 68% to 88%, and turbine efficiencies of 88% to 90%). It also needs high turbine-inlet temperature (modern aircraft gas turbines with blade cooling operate at up to 1700 K and at pressure ratios up to 30:1). It is easy to prove that for fixed extreme temperatures (ambient and turbine-inlet) there is a pressure ratio that maximises the work per unit mass flow rate, thus rendering the smallest engine for a given power, this optimum value being:

(5.6)

where h_C and h_T are the compressor and turbine isentropic efficiencies. .

Several improvements to the simple Brayton cycle are in use. Besides the multistage compression and expansion, the main variant is the regenerative cycle (Fig. 5.6), where heat from the exhaust gasses is used (from point 4 to 5) to heat up air before entering the combustion chamber (from point 2 to ideally up to point 2' in Fug. 5.6, although in practice the heat exchanger efficiency will limit this value). The heat recovery from the exhaust gasses may be also performed externally to the cycle, e.g. generating vapour in a heat exchanger (boiler), that may be directly used for heating applications or may even get expanded in a vapour turbine to produce further work (combined Brayton and Rankine cycles).

Stirling cycle and other gas cycles

Practical gas engines reduce to reciprocating engines and gas turbines, whose processes best represented by the dual cycle and the Brayton cycle, respectively, but there are more cycles of academic interest, as the Stirling cycle that models Stirling engines, invented in 1816 by the Scottish clergyman Robert Stirling, that, although faded away in the XIX c. against the steam and later gas engines, has got considerable attention lately.

The Stirling engine is an external combustion machine (all petrol and diesel engines, and practically all gas turbine engines, are of the internal combustion type, although, as said in the study of their cycles, they could operate as external combustion machines, in principle). The working substance may be just air or better helium, and the four processes followed are (Fig. 5.8): isothermal compression with heat input from the hot source, constant-volume compression by heat input from a regenerator (a porous solid matrix; an auxiliary displacer forces the gas through), isothermal expansion with heat rejection to the environment, and constant-volume heat rejection to the regenerator. Similar to the Stirling cycle is the Ericson cycle, where heat regeneration is isobaric instead of isometric as in the Stirling one (the regenerative Brayton cycle with infinitesimal multistage compressions and expansions approaches to the Ericson cycle). Notice that there is nothing essential to the four-process engines, and a three-process cycle (Fig. 5.8, named after J.J.E. Lenoir, a pioneer of two-strokes engines in the XIX c.) is used to model the operation of a pulse-reactor.

Fig. 5.8 The ideal Stirling cycle in the T-s and p-V diagram, and the ideal Ericson and Lenoir cycles.

Energy and exergy efficiencies of 36% and 50% respectively have been reached with prototype Stirling engines of up to 10 kW, the main problems being the regenerator loss of efficiency at high speeds (>30 Hz, i.e. >1800 rpm), the radiant heat looses at high temperature (>1000 K), incomplete exchange of gas between the hot and cold zones, and leaking at high pressure (>5 MPa).

Vapour power cycles

Rankine cycle

Most large electricity generating plants (central power stations), and very large ship engines, use water vapour (steam) as working fluid, following some variation of the basic Rankine cycle (named after the Scottish inventor William Rankine, that in 1859 wrote the first book on Thermodynamics), the only vapour power cycle in practical use since 1840 until in 1984 Alexander Kalina patented in the USA the cycle named after him.

The heat source for the boiler is usually the combustion products of a fuel (mainly coal) and air, or the primary refrigerant of a nuclear reactor, and the heat sink in the condenser is usually a water loop, open like in a river, or closed like in a cooling tower (as explained in Chapter 8). Thomas Newcomen is credited with the invention of the steam engine in 1705 for the purpose of driving the pumps used in clearing groundwater from mine shafts. Although the work-producing element was initially reciprocating cylinder-piston devices, in 1882 Gustav de Laval introduced the vapour turbine that has taken over.

Fig. 5.9. Carnot cycle within the two-phase region, basic Rankine cycle in the T-s and p-V diagram, and sketch of a vapour plant.

The four processes in a simple Rankine cycle are: isentropic compression of the liquid from 1 to 2 (Fig. 5.9), isobaric heating of the liquid, boiling and super-heating the vapour (from 2 to 3), isentropic expansion from 3 to 4, and isobaric heat rejection until full condensation of the vapour. The Rankine cycle is less efficient than the Carnot cycle (Fig. 5.9), but it is more practical since the compression is not in the two-phase region and only requires a small work, and the expansion is mainly in the gaseous phase (high-speed droplets erode turbine blades). Water is not the ideal working substance because it changes phase at relatively low temperatures (below the critical point at 647 K), generating a lot of entropy in the heat transfer from typical high-temperatures heat-sources: 1000 K in nuclear reactors up to 2000 K in conventional combustion plants. Nevertheless, water is practically the only working substance used, because of its good thermal properties and availability. A caution note is that the right-hand-side end of the two-phase region, the saturated vapour line, that for water in the T-s diagram has the shape shown in Fig. 5.9, may be more vertical and even have negative slope at low temperatures for heavier molecular substances, naturally avoiding the problem of wet-vapour at the turbine.

Since, at ambient temperature (the heat sink), water change phase at lower-than-atmospheric pressure (e.g. 5 kPa at 33 ºC) the condenser must operate under vacuum and a so-called 'deaerator' is needed to remove non-condensable gasses from the feed water or infiltration; moreover, removal of oxygen and carbon dioxide in feed water is always desirable to avoid corrosions in the circuit. Gas solubility in a liquid decreases near the pure-liquid vapour saturation curve, thus deaeration may be achieved by heating the liquid at constant pressure (e.g. adding some vapour) or by making vacuum at constant temperature (e.g. with a small jet of vapour by Venturi suction).

Maximum temperature in a steam power plant is limited by metallurgical constraints to less than 900 K (some 600 ºC), and the maximum pressure depends on the variations to the simple Rankine cycle used, with typical values of 10 MPa (supercritical Rankine cycles surpass 22 MPa). For a simple Rankine cycle with an ideal turbine exiting just at the vapour saturation point, the energy efficiency, with the perfect substance model, is:

(5.8)

where c_p=2 kJ/(kg×K) is an average isobaric thermal capacity of water vapour, and h_lv1=2400 kJ/kg the enthalpy of phase change at T₁ (Fig. 5.9).

The main variants of the simple Rankine cycle are reheating (a multistage expansion) and regeneration (bleeding some vapour from the middle of the turbine, and before reheating if used, to heat the feed water). These feed-water heaters may be of the open or closed type (Fig. 5.10). In an open feed-water heater, steam extracted at some turbine stage is added to the main feed water stream (that must be previously pressurised to avoid boiling). In a closed feed-water heater, the extracted steam goes through the shell of a shell-and-tubes heat-exchanger and discharges in a lower-pressure heater or the condenser. The mass fraction of vapour to be extracted is designed to be able to heat the main feed-water stream until the saturation temperature of the extracted steam.

Fig. 5.10. Open and closed feed-water heaters.

Steam turbines (notice that the term is used indistinguishable for the roto-dynamic device and for the whole power plant) are the largest thermal power plants, typically limited to 1000 MW per unit in nuclear power stations, with typical efficiencies from 30% to 40%, although supercritical power plants reach 45% (based on LHV). An advantage of steam turbines, extensive to all external combustion engines, is that any kind of fuel or other heat source may be used, contrary to internal combustion engines, where only fluid fuels, either residual to petroleum distillation but most of the times distillate fluids, can be used. The isentropic efficiency of the turbine is typically 85%, and the electromechanical efficiency of the alternator 98%. The energy and exergy balances in a typical steam power plant are presented in Table 1.

Table 1. Energy and exergy balances in a typical steam power plant

Component	Energy output	Exergy use
Combustion chamber	0	0.30
Boiler tubes heat transfer	0	0.30
Exhaust gasses (chimney)	0.15	0.01
Turbine	0	0.05
Condenser	0	0.03
Water cooling (condenser)	0.55	0.01
Shaft	0.30	0.30
	1	1

Kalina cycle

Most heat input/output to/from a plant's working fluid is from variable temperature heat sources/sinks, as the hot combustion gasses and the cold cooling water streams in the normal Rankine cycle. If, instead of using a pure fluid, a mixture were used in a Rankine cycle, due to its variable boiling/condensing temperature, the phase-change heating/cooling could better match the temperature rise/fall in the heating/cooling streams.

The only successful vapour-mixture cycle developed has been the Kalina cycle, proposed by Alexander Kalina in 1984 (the first Kalina power plant, of 3 MW, opened in 1991). Its characteristics are:

· An ammonia-water mixture (70%-NH₃ and 30%-H₂O) is used (a large know-how from absorption-refrigeration cycles existed).

· The turbine exit goes through a distillation and the heavy fraction (40%-NH₃ and 60%-H₂O) is condensed, and, once pressurised, the two fractions mix before entering the boiler again.

· Because temperature jumps across heat exchangers can be more uniform, the efficiency increases some 10% for a normal power station, but for special low-temperature applications more than 30%.

· Because ammonia lowers the boiling point, the Kalina cycle is better suited to low-temperature applications than the Rankine cycle, as in bottoming cycles (see below), geothermal power plants, and so on.

Combined power cycles

In a Rankine cycle, one single substance, like water, cannot easily match the high-temperature side (e.g. at the temperature of the combustion gasses, 1500 K to 2000 K, it is very difficult to transfer heat to water vapour), and the low-temperature side (to condense water vapour at ambient temperature is difficult because of the very low pressures and densities). The use of two Rankine cycles with different substances has been tried without success (an experimental plant was built with mercury for the top cycle and water for the bottom cycle).

The combination that has reached considerable success is the Brayton-Rankine combined cycle, where the exhaust gasses from a gas turbine are used to supply the heat in the boiler of a vapour turbine operating at not too-high temperatures. The Brayton-Kalina combination may be particularly successful in this respect. Natural-gas-fuelled combined power stations are the rule nowadays because of their low installation cost (some 450 $/kW against 1100 $/kW for coal stations), short-time operations start-up (2 years vs. 3.5 years for coal), and lower environmental impact (nuclear, coal and hydroelectric stations are on hold in Europe and USA), although wider fluctuation in gas price make the choice risky.

The turbodiesel engine can also be considered a combined Diesel-Brayton cycle (Fig.5.11).

Fig. 5.11. Combined power cycles: a) Brayton-Rankine, b) Diesel-Brayton.

There are other combined cycles, still in the developing stage, that show great promise from both the energetics and the environmental aspects, like Graz cycle in Fig. 5.12 (proposed in 1985 by Prof. H. Jericha from Graz University, Austria), where pure oxygen is used as oxidiser instead of air (to avoid NO_x-emissions and to have a pure exhaust gas), which on combustion with a fuel (e.g. natural gas) yields only water vapour and carbon dioxide as products, easily separated in a water condenser, ready to CO₂ capture, a major concern in the fight against global warming by anthropogenic greenhouse gases. Of course, CO₂ capture can be done with all traditional power cycles, e.g. by selective chemical absorption from the exhaust, but it is not competitive with oxy-fuel cycles like Graz's. Application of these air-independent propulsion concepts to submarines is evident.

Fig. 5.12. The Graz cycle, a new combined gas-steam power cycle burning fuel with pure oxygen, and capturing carbon dioxide.

Propulsion

To propel or impel is to force a body to move forwards, and it requires a push (a force) and an energy expenditure (motive power) to overcome the drag imposed in practice by the nearby objects (if there were no interactions with the surroundings, a body could move without propulsion, as in outer space). Most propulsive systems aim at moving a body over land or through a fluid at constant speed, but all propulsive systems need to accelerate the body at some stage. The power required to propel a body of mass m (e.g. a car) may be expressed as:

(5.9)

with:

(5.10)

where a is the acceleration applied, v the actual speed, q the slope of climbing, c_R a tyre-rolling coefficient (typically 10^-2), c_D a fluid-drag coefficient (typically of order 1, but may drop to 0.1 for streamlined bodies), A_F the frontal area projected by the body in the direction of motion, and r the density of the fluid medium.

The idealisation of a long rope being hauled in absence of any other interaction may be a good propulsion paradigm; because of force reciprocity, propulsion may be thought both as a pushing the environment (the rope, in the example) to the rear, and as pulling (the rope) from the front.

As a first model, for a constant-mass vehicle, the momentum balance in the direction of motion may be written as , m being the mass of the body, its acceleration, Tthe thrust force (pull or push on the rope example) and D the drag force resisting the motion (friction with the rope, frictional and pressure drag in a fluid, etc.). For these vehicles, the drag can be measured by towing at constant speed, and the thrust by breaking. For steady motion at speed v, the energy dissipated just by the motion is Dv=Tv, and a propulsion efficiency may be defined to compare this energy with the energy supplied by the engine that cause the motion, (because it is usually through a shaft), in the way:

(shaft-propeller efficiency) (5.11)

Notice that all engines consume more energy that what they supply: electrical engines, elastic engines, etc., but particularly thermal engines, where this internal energy conversion efficiency, h_e, is of the order of 30% to 50% (in electric motors it may be typically 95%).

Most propulsion systems may be considered in this way just power plants that apply a torque, M, to a shaft at a certain rotation speed, w, producing a power =Mw. The shaft then is mechanically coupled to the propeller itself, which may be the friction wheels in land vehicles, or the pressure-reaction blade-propeller in sea and air vehicles.

But there are some propulsion systems based on the change of momentum of a working fluid, notably rockets, jet-engines and water jets, which have inlets and outlets through which some fluid flow. The momentum balance for an open system is :

(5.12)

where m is the mass of the body being propelled (may be changing), is the sum of externally applied volumetric forces (gravitational or electromagnetic), the sum of externally applied surface forces at the wall, and and p_e the exit velocity and pressure through any opening of area A_e with an outward normal vector .

Rocket propulsion

For steady horizontal motion of a body with just one exit (rocket) the momentum balance, in the direction of motion, reduces to (see Eq. 5.20):

(5.13)

where p₀ is the pressure in the surrounding media (acting on the impermeable walls), that may be zero in outer space, and the propulsion efficiency, h_p, is defined as the ratio of thrust power, Tv, to whole power emanating from the body, that is the sum of thrust power, Tv (communicated to the surrounding media) and residual kinetic power of the jet relative to the surrounding media, (communicated to the jet); i.e.:

(5.14)

where the simplification of considering p_e=p₀ is always acceptable (it is true for subsonic exits, and for supersonic exits with 'adapted nozzle', and very approximate even for large pressure departures). Equation 5.14 is shown in Fig. 5.13.

Fig. 5.13. Rocket propulsion efficiency vs. flight speed to exit speed ratio.

Most rockets are heat engines because they transform the heating power of a fuel/oxidiser mixture into mechanical energy (the kinetic energy of the jet), and thus an energy efficiency may be defined by:

(5.15)

where h_P is the heating power of the fuel/oxidiser mixture per unit mass of reactants. Notice that high energy-efficiency demands high exit speed, demanding also high flight speed to keep a reasonable propulsion efficiency; i.e., rocket propulsion is inefficient at low speed. Compressed-gas rockets are also heat engines, but new magnetohydrodynamic and electrodynamic rockets are not.

Air-breathing propulsion

For steady horizontal motion of a body with one inlet and one exit (like a jet engine) the momentum balance, in the direction of motion, reduces to (see 5. 13):

(5.16)

where the approximation to neglect the additional mass flow rate of fuel is introduced. The propulsion efficiency, defined as for rockets, becomes:

(5.17)

where the approximation to consider the inlet speed equal to the flight speed has been introduced. Notice that the thrust, , may be obtained with a large Dv and small flow rate or vice versa, but the propulsion efficiency, h_p=2/(2+Dv/v), shows that it is better to have a small Dv and a large , what has been implemented in practice, where turbofans of high bypass have superseded simple turbojets.

Similarly to chemical rockets, air-breathing engines (turbojets) are heat engines that transform the heating power of a fuel into mechanical energy (the kinetic energy of the exiting jet minus the one at the inlet), and thus an energy efficiency may be defined by:

(5.18)

where h_P is the heating power of the fuel/oxidiser mixture per unit mass of fuel. Notice that the energy efficiency is based on thermal-to-mechanical conversion, and the propulsion efficiency is based on mechanical-to-propulsive ratio, thus, the efficiency using the fuel for propulsion is h_eh_p. The overall energy balance of the air-breathing engine may help to identify every term; in axes fixed to the surroundings:

(5.19)

with:

(5.20)

being the chemical enthalpy released, the propulsive power, the kinetic energy of the exit jet, and the thermal enthalpy of the exit jet.

It is important to compare air-breathing propulsion with rocket propulsion for the same fuel expenditure (notice that for rockets , whereas for turbojets is of the order of 2% of ). The quotient of respective thrusts is:

(5.21)

showing that air-breathing engines are much better than rockets (if there is air!) because typical values are v_e,turbojet~2×10² m/s, and v_erockett~5×10³ m/s.

Cogeneration

Cogeneration is the term coined for the combined generation of work and heat (and, by extension, also of cold). Any heat engine must reject a lot of heat to the environment, but this energy has no exergy (i.e. utility) in the ideal heat engine. Practical engines however reject useful heat in the exhaust gasses and in the cooling circuit, that could be directly used (as when heating the car cabin with the engine cooling water), or the engine modified to provide more useful heat at a small expense in work output.

Without cogeneration, the work needed was taken from the electrical grid, and the heat needed was generated locally in a boiler (heat is much more difficult to transport than work). Cogeneration is provided by using a heat engine (a steam turbine, a gas turbine or a reciprocating engine) to generate work and, at the same time, heat (usually in a exhaust gasses boiler). The great advantage of cogeneration is the energy saving; an additional advantage may be the autonomy gained by self-production, and the main drawback is that the ratio of work-to-heat generation is rather stiff, none can be easily accumulated, and the actual need of work and heat may vary a lot with time (that was one of the main advantages of central production: the levelling of the averaged demand). To stiffness of a cogeneration plant is relaxed by the possibility to send excess work-power to the electrical grid, a convenience that has been enforce by public authorities on account of the social benefit that saving in primary energy resources (fossil fuels) cogeneration brings.

Efficiencies of cogeneration plants are high, but care must be paid not to mix work and heat values (everybody knows that work is usually two or three times more expensive than heat, i.e. the output should be consistently measured in exergy, so that the, instead of W+Q, the output value is W+Q(1-T₀/T), where T is the temperature at which heat is delivered.

Reciprocating engine cogeneration

The useful heat-to-work ratio is around 0.6. It is only used for direct heating with the exhaust gasses or the cooling water, but not to generate vapour.

Gas turbine cogeneration

The useful heat-to-work ratio is around 2. It does not require changes in the power plant, it is a versatile cogeneration system, and its use is expanding in most industries: textile, chemical, food. Because the exhaust gasses are relatively hot (some 700 K), it is suitable for high temperature applications.

Vapour turbine cogeneration

The useful heat-to-work ratio is around 7 (suitable for the iron industry, but still low for the ceramic and glass industry). It directly provides useful vapour, either by extracting some of it at an intermediate stage in the turbine, or by not expanding to the low pressures of ambient temperatures but to higher than atmospheric pressures (it is called a back-pressure turbine), to render the whole turbine outlet vapour useful.

Efficiency in power generation with heat engines and other generators

Power cannot be generated; only converted from one form to another; what is implied is the generation of some useful power at the expense of some other less-convenient power. But recall that we have restricted here the term ‘power’ to mechanical or electrical power (i.e. excluding thermal power), so that power generation can be seen as the generation of electricity (or equivalent power) from any other energy source: thermal, chemical, nuclear, etc.

Power generation efficiency can be defined as “useful output power divided by input power”, but it is not rigorous enough since at least two choices exist for the evaluation of input power: a) heat-equivalent power, and b) work-equivalent power. Table 2 presents typical values of power generation efficiencies using the raw input power (choice a), the most commonly used, although the net input power criterion, i.e. the exergy or available energy of the raw energy source, would give a sounder measure of the ‘technological efficiency’ of the power plant.

Table 2. Some power generation efficiencies.

Energy source	Typical efficiency [%]	Typical range [%]
Photovoltaic	10	5..15
Solar thermal	15	10..25
Gas turbine	30	15..38
Spark Ignition ICE	30	25..35
Nuclear	33	32..35
Steam turbine	33	25..39
Wind turbine	40	30..50
Compression Ignition ICE	40	35..49
Fuel cell	45	40..70
Combined GT-ST	50	45..60
Hydroelectrical	85	70..90

It is without saying that power generation efficiency is not the only criterion, neither the most important, to quantify engine excellence. The generic goal of maximum power at minimum cost, should include the cost of design (e.g. new technologies), cost of manufacture (e.g. new materials), cost of implementation (e.g. size and weight), cost of operation (e.g. specific fuel consumption, but also pollutant emissions and noise level), cost of maintenance (reliability), and even the cost for disposal.

Problem 1:

Consider a piston-cylinder device, holding initially 500 cm³ of ambient air, which is to be quickly compressed to 50 cm³. We aim at analysing the four following cyclic processes (find the energy exchanges and the energy efficiency):

a) After the compression, 1 kJ of heat is added at constant volume, and then a quick expansion follows, ending with a constant volume heat release.

b) After the compression, 1 kJ of heat is added at constant volume, and then a quick expansion follows, ending with a constant pressure heat release.

c) After the compression, 1 kJ of heat is added at constant pressure, and then a quick expansion follows, ending with a constant volume heat release.

d) After the compression, 1 kJ of heat is added at constant pressure, and then a quick expansion follows, ending with a constant pressure heat release.

Solution

a) After the compression, 1 kJ of heat is added at constant volume, and then a quick expansion follows, ending with a constant volume heat release.

Let us first work out the initial compression, common to all four cycles.

From 1 to 2. It is a control-mass problem, since in air-standard cycles the mass of air is assumed to remain all the time within the cylinder. The energy balance is thus DE=W+Q. The enclosed mass, assuming p₀=10⁵ Pa and T₀=288 K, is =10⁵∙500∙10^-6/(287∙288)=0,61 g. After the isentropic compression, the state is V₂=50 cm³,p₂=p₁(V₁/V₂)^g=10⁵∙(500/50)^1.4=2.5 MPa, T₂=T₁(V₁/V₂)^g-1=288∙(500/50)^0.4=723 K. The work the gas receives is W₁₂=DE=mc_v(T₂-T₁)=0.61∙10^-3∙ (1000-287)(723-288)=190 J, and the heat is null, Q₁₂=0. Notice that W₁₂ is not the work that must be done; ambient pressure contributes, too.

Let start now with the first cycle described, that corresponds to the well-known Otto cycle, represented in Fig. 1.

Fig. 1. Otto cycle.

From 2 to 3, Q₂₃=1 kJ is received with V₃=V₂ (i.e. W₂₃=0), and, from the energy balance DE=W+Q=mc_v(T₃-T₂), T₃=T₂+Q₂₃/(mc_v)=723+1000/(0.61∙10^-3∙713)=3020 K, too high for practical combustion engines, that only reach 2000 K, but this is a simple academic exercise. Furthermore, p₃=p₂T₃/T₂=2.5∙10⁶∙3020/723=11 MPa.

From 3 to 4 there is an isentropic expansion, from V₃=50 cm³ to V₄=500 cm³, so that p₄=p₃(V₃/V₄)^g=11∙10⁶∙(50/500)^1.4=418 kPa, T₄=T₃(V₃/V₄)^g-1=3020∙(50/500)^0.4=1210 K. The work the gas delivers is W₃₄=DE=mc_v(T₄-T₃)=0.61∙10^-3∙713(1210-3020)=-790 J, and the heat is null, Q₃₄=0. Notice again that W₃₄ is not the work delivered to the shaft; ambient pressure resists, too.

From 4 to 1, heat is released at constant volume (i.e. W₄₁=0), and, from the energy balance DE=W+Q=mc_v(T₁-T₄)=0.61∙10^-3∙713(288-1210)=-400 J. Table 1 shows the summary of energy exchanges.

Table 1. Summary of energy exchanges.

Otto	DE	W	Q
1-2	190	190	0
2-3	1000	0	1000
3-4	-790	-790	0
4-1	-400	0	-400
cycle	0	-600	600

The energy efficiency of a power cycle is defined as net work delivered divided by heat input, h=W_net/Q_in, that here takes the value:

which can be compared with the well-known efficiency of the ideal Otto cycle: h=1-1/r^g-1=1-1/10^0,4=0,60, r being the compression ratio r=V₁/V₂ (with r=10 in this case).

b) After the compression, 1 kJ of heat is added at constant volume, and then a quick expansion follows, ending with a constant pressure heat release.

Fig. 2. New cycle.

From 1 to 2 has been worked at the very beginning: p₁=10⁵ Pa, T₁=288 K, p₂=2,5 MPa, T₂=723 K, Q₁₂=0 and W₁₂=190 J.

From 2 to 3 is the same as in the Otto cycle: p₂=2,5 MPa, T₂=723 K, p₃=11 MPa, T₃=3020 K, Q₂₃=1 kJ and W₂₃=0.

From 3 to 4 there is an isentropic expansion, from p₃=11 MPa to p₄=10⁵ Pa, so that V₄=V₃(p₃/p₄)^1/^g =50∙10^-6∙(11/0,1)^1/1,4=1400 cm³, T₄=T₃(V₃/V₄)^g-1=3020∙(50/1400)^0.4=800 K. The work the gas delivers is W₃₄=DE=mc_v(T₄-T₃)=0.61∙10^-3∙713(800-3020)=-970 J, and the heat is null, Q₃₄=0.

From 4 to 1, heat is released at constant pressure. The energy balance DE=W+Q takes the form Q=DH=mc_p(T₁-T₄)=0.61∙10^-3∙1000(288-800)=-310 J, whereasW₄₁=-p₁(V₁-V₄)=90 J. Table 2 shows the summary of energy exchanges.

Table 2. Summary of energy exchanges.

	DE	W	Q
1-2	190	190	0
2-3	1000	0	1000
3-4	-970	-970	0
4-1	-220	90	-310
cycle	0	-690	690

The energy efficiency now takes the value:

c) After the compression, 1 kJ of heat is added at constant pressure, and then a quick expansion follows, ending with a constant volume heat release.

This corresponds to the ideal Diesel cycle, depicted in Fig. 3.

Fig. 3. Diesel cycle.

From 1 to 2 has been worked at the very beginning: p₁=10⁵ Pa, T₁=288 K, p₂=2,5 MPa, T₂=723 K, Q₁₂=0 and W₁₂=190 J.

From 2 to 3, Q₂₃=1 kJ is received at constant pressure. The energy balance DE=W+Q takes the form Q=DH=mc_p(T₃-T₂), so thatT₃=T₂+Q₂₃/(mc_p)=723+1000/(0.61∙10^-3∙1000)=2370 K and V₃=V₂T₃/T₂=50∙10^-6∙2370/723=164∙10^-6 m³, with a work (output) of W₂₃=-p₂(V₃-V₂)=-290 J.

From 3 to 4 there is an isentropic expansion, from V₃=164 cm³ to V₄=500 cm³, so that p₄=p₃(V₃/V₄)^g=2,5∙10⁶∙(164/500)^1.4=525 kPa, T₄=T₃(V₃/V₄)^g-1=2370∙(164/500)^0.4=1520 K. The work the gas delivers is W₃₄=DE=mc_v(T₄-T₃)=0.61∙10^-3∙713(1520-2370)=-370 J, and the heat is null, Q₃₄=0.

From 4 to 1, heat is released at constant volume (i.e. W₄₁=0), and, from the energy balance DE=W+Q=mc_v(T₁-T₄)=0.61∙10^-3∙713(288-1520)=-530 J. Table 3 shows the summary of energy exchanges.

Table 3. Summary of energy exchanges.

Diesel	DE	W	Q
1-2	190	190	0
2-3	710	-290	1000
3-4	-370	-370	0
4-1	-530	0	-530
cycle	0	-470	470

The energy efficiency here takes the value:

which can be compared with the well-known efficiency of the ideal Diesel cycle:

r being the compression ratio r=V₁/V₂ as for the Otto cycle (r=10), and r_c being the cut-off ratio, r_c=V₃/V₂=3,3.

d) After the compression, 1 kJ of heat is added at constant pressure, and then a quick expansion follows, ending with a constant pressure heat release.

This corresponds to the ideal Brayton cycle, depicted in Fig. 4.

Fig. 4. Brayton cycle.

From 1 to 2 has been worked at the very beginning: p₁=10⁵ Pa, T₁=288 K, p₂=2,5 MPa, T₂=723 K, Q₁₂=0 and W₁₂=190 J.

From 2 to 3, Q₂₃=1 kJ is received at constant pressure as in the Diesel cycle above, yielding T₃=2370 K, V₃=164∙10^-6 m³, and W₂₃=-290 J.

From 3 to 4 there is an isentropic expansion, from p₃=p₂=2,5 MPa to p₄=10⁵ Pa, so that V₄=V₃(p₃/p₄)^1/^g =164∙10^-6∙(2,5/0,1)^1/1,4=1640 cm³, T₄=T₃(V₃/V₄)^g-1=2370∙(164/1640)^0.4=940 K. The work the gas delivers is W₃₄=DE=mc_v(T₄-T₃)=0.61∙10^-3∙713(940-2370)=-620 J, and the heat is null, Q₃₄=0.

From 4 to 1, heat is released at constant pressure. The energy balance DE=W+Q takes the form Q=DH=mc_p(T₁-T₄)=0.61∙10^-3∙1000(288-940)=-400 J, whereasW₄₁=-p₁(V₁-V₄)=114 J. Table 4 shows the summary of energy exchanges.

Table 4. Summary of energy exchanges.

Brayton	DE	W	Q
1-2	189	189	0
2-3	714	-286	1000
3-4	-619	-619	0
4-1	-284	114	-398
cycle	0	-602	602

The energy efficiency here takes the value:

which can be compared with the well-known efficiency of the ideal Brayton cycle:

p₁₂ being the pressure ratio p₁₂=p₂/p₁.

Problem2:

A four-cylinder four-stroke 50 kW gasoline engine, running at 3000 rpm, has a compression ratio of 9, 500 cm³ of displacement per cylinder. Evaluate:

a) The conversion efficiency, deducing it from the basic cycle states.

b) Maximum pressure and temperature in the cycle, and mean effective pressure.

Solution.

Fig. 1. Sketch of the standard Otto cycle and corresponding piston position.

a) The conversion efficiency, deducing it from the basic cycle states.

The cold-air-standard model takes as working fluid plain air with constant properties (those at the inlet, i.e. cold), what renders the analysis simple. The energy exchanges for the trapped control mass, m, are W₁₂/m=c_v(T₂-T₁), Q₁₂=0, W₂₃=0, Q₂₃/m=c_v(T₂-T₁), W₃₄/m=c_v(T₄-T₃), Q₃₄=0, W₄₁=0, Q₄₁/m=c_v(T₁-T₄), and, with the isentropic relation,TV^g^-1=constant, in terms of the compression ratio r≡V₁/V₂, the energy efficiency becomes:

with a numerical values of h_e=1-1/9^0.4=0.58. Taking as reference a Carnot cycle with the same extreme temperatures, the exergy efficiency h_x would be:

where T₃ is computed below.

b) Maximum pressure and temperature in the cycle, and mean effective pressure.

For the isentropic compression T₂=T₁r^g^-1=288×9^0.4=694 K, p₂=p₁r^g=100×9^1.4=2.2 MPa. From the mechanical power:

where =50 kW, Z=4 cylinders, m=p₁V₁/(RT₁)=100×10³×0.5×10^-3/(287×288)=0.68×10^-3 kg is the control mass per cylinder (neglecting the residual mass), and n=(3000/60)/2=25 s^-1 is the control-mass processing rate (i.e. the charge is renovated 25 times per second; remember that only half of the cycles count, in a 4-stroke engine). The maximum temperature obtained from that is T₃=1060 K, and then the maximum pressure p₃=p₂(T₃/T₂)=2.2×(1060/694)=3.3 MPa. Substitution in the exergy efficiency above, yields h_x=0.80.

The mean effective pressure, p_me, is the unit work divided by the displacement volume, i.e. the pressure difference that produces the same power:

Mech Mecca

Vehicle Dynamics

Dynamic Suspension Systems

Active Differential Control

Brake Based Stability

Aerodynamics

Zircotec's Ceramic Coating

PLASMA-SPRAY PROCESSING

Design

Concurrent Engineering

Bearings

Parasitic Power Losses in Hydrodynamic Bearings

Mechanical Devices

Worlds Largest Helicopters

Material Handling Systems

What is a Backhoe Loader?

The Tractor

The Loader

The Backhoe

The Stabilizer Legs

Hydraulic Power

Hydraulic multiplication

Different Types of Material Handling Equipment

Car Engines

Most cars these days use what is called a four-stroke combustion cycle to convert gasoline into kinetic motion. This four-stroke approach is known as the the Otto cycle, in honor of Nikolaus Otto who invented it in 1867.

Straight/ Inline Engines

V Type Engines

Boxer/ Flat Engines

Wankel/ Rotary Engines

Diesel Engines

Straight/ Inline Engines

V Type Engines

Boxer/ Flat Engines

Wankel/ Rotary Engines

Diesel Engines

Frictionless Compressor Technology

Engineering Drawing

Introduction

Isometric Drawing

Orthographic or Multiview Drawing

Dimensioning

Sectioning

Drawing Tools

"Assembly" Drawings

Cross-Sectional Views

Half-Sections

Sectioning Objects with Holes, Ribs, Etc.

Dimensioning

The Basics: Definitions and Dimensions

Where To Put Dimensions

MEMS Technology

MEMS Technology

Mechanical Measuring Tools

Rapid Prototyping

Bose Suspension System

Casting Process

Casting Process

Bike Description

How do bike engines work

Introduction

How does an engine work

What goes into petrol?

Fuel/air ratio

Other problems with engines

Mechanical aspects of the engine

Carburettors

Exhaust pipes (4 strokes)

Power and Torque

Solar Powered Bird Scarer

Photovoltaics: Solar PV installation, Kent

A 2.6 Kwh installation for a domestic residence.

Manually Operated Paper Recycling Machine-Design

Simple Magnetic Levitation Train

Working:

Conclusion:

Automatic Pneumatic Bumper For Four Wheeler

Solar Sail

Space Mist

Robots and Adhesives

Hybrid hydraulic Vehicle