Automobiles

2013-12-31T23:46:00.003-08:00

Hydraulic Brake and its components

Hydraulics

The principle behind any hydraulic system is simple: forces that are applied at one point are transmitted to another point by means of an incompressible fluid. In brakes we call this brake fluid of which there are a few different varieties, but more on that later.
As is common in hydraulics the initial force which is applied to operate the system is multiplied in the process. The amount of multiplication can be found by comparing the sizes of the pistons at either end. In braking systems for example, the piston driving the fluid is smaller than the pistons operating the brake pads therefore the force is multiplied helping you to brake easily and more efficiently.
Another convenient characteristic of hydraulics is that the pipes containing the fluid can be any size, length or shape allowing the lines to be fed almost anywhere. They can also be split to enable one master cylinder to operate two or more slave cylinders if needed.

Components

Now that we understand hydraulics let's take a look at the different parts which make up the hydraulic brake. The entire braking system can be broken down into the following main parts:

· Master cylinder (Lever)

· Lines

· Fluid

· Slave cylinder (Caliper)

· Pads

· Rotor

Next we will explain these components in more detail.

Master Cylinder/Lever

The master cylinder, mounted to the handlebar, houses the brake lever and together they produce the input force needed to push hydraulic brake fluid to the slave cylinder (or caliper) and cause the brake pads to clamp the rotor.

The lever stroke can be divided into 3 categories:

1. Dead-stroke - This is the initial part of the lever stroke when the primary seal pushes fluid toward the reservoir before it goes on to push fluid on to the caliper via the brake lines.

2. Pad Gap Stroke - This is the part between the caliper beginning to push the pistons out of their housings and the pads contacting the disc (as the dead space between the pads and rotor is taken up).

3. Contact & Modulation - The pads are now clamping the rotor and by stroking the lever further, additional brake power will be generated. Modulation is rider controlled and not necessarily a characteristic of the braking system, however some brakes may allow the rider to better modulate or control the braking forces than others.

Open or Closed?

Master cylinder systems can be categorised into two groups - open and closed.

An open system includes a reservoir and bladder which allow for fluid to be added or removed from the braking system automatically during use. Reservoirs are the overflow for fluid which has expanded due to heat produced by braking. The bladder has the ability to expand and contract therefore as the fluid expands the bladder will compensate without any adverse effects on the 'feel' of the brake. Reservoirs also provide the additional fluid needed as the pads begin to wear resulting in the need for the pistons to protrude further to compensate for the reduced pad material.

A closed system also utilises a reservoir of brake fluid, however the lack of an internal bladder to compensate for the expansion in brake fluid and also to compensate for pad wear means that any adjustments to the levels of brake fluid within the working system need to be made manually.

Brake Lines

Hydraulic brake lines or hoses play the important role of connecting the two main working parts of the brake, i.e. the master cylinder and slave cylinder. We've already mentioned that hydraulic systems can be very versatile in that their lines or hoses can be routed almost anywhere so let's take a closer look.

Hose Construction

Hydraulic hoses are multi-layered in their construction and usually consist of 3 layers:

1. Inner Tube - this layer of tubing is designed to hold the fluid. Teflon is usually the material of choice here as it does not react or corrode with brake fluid.

2. Aramid (Kevlar) Layer - provides the strength and structure of the hose. This woven layer is flexible and handles the high pressures of the hydraulic system efficiently in that it should not expand. Kevlar is also very light, which is a desirable attribute for any cycle component, and also it can be cut easily and re-assembled using standard hose fittings.

3. Outer Casing - Serves as a protection layer for both the Kevlar layer and the bike frame to reduce abrasions

The layers that make up an average hydraulic brake line

Steel Braided Brake Lines

Steel braided hoses can provide some advantages over standard hydraulic hoses. Steel braided hoses are also usually a 3-layer construction, the inner most layer contains the brake fluid and there is an outer most layer which provides protection against abrasions. The key difference is in the middle layer which is made up of a stainless steel braid.

This stainless steel layer is designed to be more resistant against expansion than that of standard lines. This can be an advantage because when the brake lever is applied we want all of the force we put in to be transferred to the caliper to cause braking. Any expansion in the hydraulic line due to the pressures within will mean that some of that pressure will not be transferred to the caliper. This will be wasted effort and will require additional lever input by the rider to compensate.

Steel braided lines may also be more appealing aesthetically. Many riders believe that they look better than the standard, boring black hoses that are supplied with the vast majority of brakes on the market.

2011 Formula R1 brake with braided brake lines

Brake Fluid

Hydraulic braking systems typically use one of two types of brake fluid - DOT fluid or mineral oil. An important thing to note before we get into the properties of each is that the two fluids should never be mixed. They are made up of very different chemicals and the seals within the braking system are suited to either fluid and not both; therefor mixing or replacing one fluid with the other is likely to corrode the internals of your brake.

On the other hand, mixing fluid from the same family is allowed but not generally advised. For example you may mix DOT 4 fluid with DOT 5.1 without harming your braking system.

DOT Brake Fluid

DOT brake fluid is approved and controlled by the Department of Transportation. It has to meet certain performance criteria to be used within braking systems and is classified by its performance properties - mainly its boiling points.

DOT 3, 4 and 5.1 brake fluid are glycol-ether based and are made up of various solvents and chemicals. Glycol-ether brake fluids are hygroscopic, which means they absorb water from the environment even at normal atmospheric pressure levels. The typical absorption rate is quoted to be around 3% per year. This water content within the brake fluid will affect the performance by reducing its boiling point. Which is why it is recommended to change brake fluid every 1-2 years at most.

The table below shows DOT brake fluid in its various derivatives with its corresponding boiling temperatures. Wet boiling point refers to fluid with water content after 1 years' service.

DOT FLUID	DRY BOILING POINT	WET BOILING POINT
DOT 3	205 °C (401 °F)	140 °C (284 °F)
DOT 4	230 °C (446 °F)	155 °C (311 °F)
DOT 5	260 °C (500 °F)	180 °C (356 °F)
DOT 5.1	270 °C (518 °F)	190 °C (374 °F)

DOT brake fluid is commonly used in Avid, Formula, Hayes and Hope brakes.

DOT 5 Brake Fluid

DOT 5 brake fluid (not to be mistaken for DOT 5.1) is very different from other DOT fluids as it is silicone based and not glycol-ether based. This silicone based brake fluid is hydrophobic (non water absorbing) and must never be mixed with any other DOT brake fluid.

DOT 5 can maintain an acceptable boiling point throughout its service life although the way in which it repels water can cause any water content to pool and freeze/boil in the system over time - the main reason that hygroscopic fluids are more commonly used.

Mineral Oil

Mineral oil is less controlled as a brake fluid, unlike DOT fluid which is required to meet a specific criteria, therefore less is known regarding its performance and boiling points from brand to brand.

Manufacturers such as Shimano and Magura design their brakes around their own brand of mineral oil and should never be introduced to DOT brake fluid as this will likely have an adverse effect on the brake's seals.

An advantage of mineral oil is that, unlike most DOT fluids, it does not absorb water. This means that the brake will not need to be serviced as often, but any water content within the braking system could pool and freeze/boil adversely affecting the performance of the brake.

Mineral oil is also non-corrosive meaning handling of the fluid and spillages are less of a concern.

Slave Cylinder/Calliper

The brake callipers reside at each wheel and respond to the lever input generated by the user. This lever input is converted to clamping force as the pistons move the brake pads to contact the rotor. Callipers can be fixed by a rigid mount to the frame or floating. Fixed callipers are combined with a fixed rotor which offers the only way of achieving zero free running drag, one drawback of this design is that it is much less tolerant of rotor imperfections. Floating callipers slide axially and self-centre with each braking application.

Construction

Calliper construction can fall into two categories - mono-block and two piece. The difference here is the 'bridge' design, the bridge is the part of the calliper above the pistons which connects the two halves together and provides the strength to endure the clamping forces generated by the pistons.

1. Mono-block - A mono-block calliper is actually a one piece design formed from one piece of material. This can offer a unique design and usually a lighter calliper as there is no need for steel bolts joining both halves as in a two piece design. Also the lack of a transfer port seal means there is one less opportunity for fluid leaks at the half way seam. Servicing a mono-block calliper can be tricky however and manufacturing and assembly are usually more difficult.

2. Two piece - These two piece callipers are constructed as two separate halves and are then held together with steel bolts which can provide additional strength over a mono-block design. Servicing, manufacturing and assembly are simplified. Steel bolts and additional seals are a means of additional weight and can be problematic during servicing.

Exploded view of an Avid two-piece calliper design

Pistons

The pistons are the cylindrical components housed within the calliper body. Upon lever input they protrude to push the brake pads which contact the rotor. The number of pistons within a calliper or brake can differ. Many hydraulic mountain bike brakes have 2 piston callipers, some may have 4 pistons. Whereas some automobile brake callipers have 6 or even 8 pistons. It is an important note that brake power is not determined by piston quantity. A more reliable indicator would be total piston contact area, e.g. 4 smaller pistons can be just as powerful as 2 larger pistons.

Pistons can be either opposed or single sided. Opposed pistons both protrude with lever input to push the brake pads equal amounts to meet the rotor at both sides. Whereas single sided calliper pistons stroke on one side and float the rotor to the opposite pad.

Brake Pads

Choosing the right brake pads can mean the difference between a great and a poor performing brake. With the sheer diversity of brake pad materials out there it is quite easy to get it wrong when the time comes to replace the pads.

Let's jump right in and take a look at the different pad materials available and their properties.

Organic

Organic brake pads contain no metal content. They are made up of a variation of materials which used to include asbestos until its use was banned. These days you will commonly find materials such as rubber, Kevlar and even glass. These various materials are then bonded with a high-heat-withstanding resin. An advantage of organic pads is that they're made up of materials that don't pollute as they wear. They are also softer than other brake pads and as a result quieter. Also they inflict much less wear upon the brakes' rotor. However organic pads wear down faster and they perform especially poorly in wet gritty conditions (UK readers take note :).

Organic pads then are probably more suited to less aggressive riding in mostly dry conditions.

Semi-metallic

The metallic content of semi-metallic pads can vary from anything between 30% and 65%. The introduction of metal content into the friction material changes things slightly. It can improve the lifespan of the pad quite significantly as metal wears slower than organic materials. Also heat dissipation is improved as it is transferred between the pad material and the backing plate. Some disadvantages can include increased noise during use and the harder compound means increased wear on the rotor.

Sintered

Sintered brake pads are made up of hardened metallic ingredients which are bound together with pressure and high temperature. The advantages of this compound are better heat dissipation, a longer lasting pad, better resistance to fading and superior performance in wet conditions. The trade-offs are more noise, longer bed-in time and a poor initial bite until the friction material has chance to warm.

Ceramic

Ceramic brake pads are now seen more and more as an alternative/upgrade mountain bike brake pad. Traditionally ceramic brake pads would only be seen on high performance racing cars with brakes which need to perform under intense heat. Heat like that is not usually a problem for the average mountain bike brake and therefor for most people ceramic pads would be overkill, however they might have other desirable properties. The advantages of a ceramic material then is one which can cope with extreme heat and keep performing strongly; this is in part down to its great dissipating abilities. They also last longer than other pads and noise is less of an issue. They're also easier on brake rotors and produce a lot less dust that other brake pad compounds.

Rotors

Rotor size has a direct effect on braking power. The larger the brake rotor the more power will be produced for any given input. This can be a concern with larger rotors as they tend to have more of a 'grabby' feel making the brake more difficult to modulate.

Mountain bike rotors tend to range in size from 160mm to 203mm, with smaller rotors geared toward XC type riding and larger rotors designed for downhill riding.

Rotor Design

Important specifications of rotor design include hardness, thickness and rub area.

The material used to manufacture rotors must be hard and durable due to the aggressive forces inflicted upon them from the pad friction material. This has a direct impact on rotor wear.

Rotors must also have no thickness variations. Differences in thickness around the circumference of the rotor can have undesired effects on the braking system including pulsing as thicker and thinner sections pass between the pads. Rotors also need to run true. Any lateral wobble in the rotor during use can cause the brake to contact the pads intermittently during riding.

Left to right: Formula Lightweight, Avid G3 Clean Sweep, Ashima AiRotor

A rotor's rub area can take the form of many different designs. The three rotors above show this in detail. Rub area design can affect the weight and strength of the rotor. It also has a direct effect on pad lifetime.

Six Bolt or CenterLock?

The two types of rotor on the market today are ISO standard 6-bolt rotors and CenterLock rotors. Both have their pros and cons.

6 Bolt - Readily available and interchangeable between many brake models, this is the most common rotor fixing system in use today and was adopted by all manufacturers in the late 1990's. With no shortage of hub options, cross-compatibility with other products is rarely a problem. However installation of six fixing bolts can be cumbersome and there is always the risk of stripping a thread on fixing bolts and hub mounting points.

CenterLock - The Shimano CenterLock system eliminates the risk of stripping threads as there are no bolts to worry about, just one centre locking ring. Installation and removal is also simplified, although you will need a CenterLock tool. Lack of mass-market adoption means that hub choices are limited and brake choice may also be limited due to odd sized rotors. CenterLock rotors are also generally slightly heavier and can come at a price premium.

Left to right: ISO standard 6-bolt, Shimano CenterLock

2-Piece Rotors

2-Piece rotors are supplied as standard with some higher priced brake sets and can also be bought separately as a brake upgrade.

In contrast to standard stainless steel rotors, 2-piece rotors combine a stainless steel rub area with an aluminium carrier (or spider). The advantage of the alloy carrier are a cooler running disc as aluminium has superior heat dissipation qualities to that of stainless steel. This will also help to keep your pads, calliper and fluid cooler. Aluminium is also lighter than stainless steel so a reduction weight can be expected.

Formula 2-Piece Stainless Steel / Aluminium Rotor

Why Brakes Fail

Hydraulic brakes can fail or temporarily stop working for numerous reasons such as a simple (but potentially catastrophic) fluid leak or eventual brake fade after prolonged use. Knowing the causes of brake failure can be valuable knowledge in curing the problem and preventing future episodes.

As we know there are a couple of important principles behind hydraulic brakes. Hydraulics rely on pressure within the system and brakes rely on friction. Absence of either will result in failure of the system. For example, a loss of brake fluid will decrease the pressure within the system as the lever has nothing to transfer the input forces to. On the other hand if brake fluid contacts the brake pads or rotor, a loss of friction will occur due to the lubricating nature of brake fluid.

The above examples should be obvious to most but what about the less obvious causes of brake failure? Earlier we mentioned brake fade, a term which I bet many of you have heard, however did you know that there are multiple types of brake fade? Below is an overview of the three different types.

Pad Fade

All friction material (the stuff your pads are made of) has a coefficient of friction curve over temperature. Friction materials have an optimal working temperature where the coefficient of friction is at its highest. Further hard use of the brake will send the friction material over the optimal working temperature causing the coefficient of friction curve to decline.

This high temperature can cause certain elements within the friction material to melt or smear causing a lubrication effect, this is the classic glazed pad. Usually the binding resin starts to fail first, then even the metallic particles of the friction material can melt. At very high temperatures the friction material can start to vaporize causing the pad to slide on a layer of vaporized material which acts as a lubricant.

The characteristics of pad fade are a firm, non-spongy lever feel in a brake that won't stop, even if you are squeezing as hard as you can. Usually the onset is slow giving you time to compensate but some friction materials have a sudden drop off of friction under high temperatures resulting in sudden fade.

Green Fade

Green fade is perhaps the most dangerous type of fade which manifests itself on brand new brake pads. Brake pads are made of different types of heat resistant materials bound together with a resin binder. On a new brake pad these resins will cure when used hard on their first few heat cycles and the new pad can hydroplane on this layer of excreted gas.

Green fade is considered the most dangerous as it can catch users unaware given its quick onset. Many people would consider new brake pads to be perfect and may be used hard from the word 'go'.

Correct bedding-in of the brake pads can prevent green fade. This process removes the top layer of the friction material and keys the new pad and rotor together under controlled conditions.

Fluid Fade

Fluid fade is caused by heat induced boiling of the brake fluid in the callipers and brake lines. When used under extreme conditions heat from the pads can transfer to the calliper and brake fluid causing it to boil, producing bubbles in the braking system. Since bubbles are compressible this results in a spongy lever feel and prevents the lever input from being sent to the calliper.

The major cause of fluid fade is absorbed water from the air under normal atmospheric conditions which reduces the boiling temperature of the brake fluid. DOT brake fluid has an affinity for absorbing water from the air around it, especially in hot humid conditions. This is the main reason why we replace brake fluid on an annual basis.

Fortunately fluid fade has a gradual onset giving the user time to compensate for potential loss of braking.

2013-12-31T02:37:00.000-08:00

VEHICLE WHEEL ALIGNMENT

Wheel Alignment should be checked whenever new tires are installed, suspension components installed, when the vehicle has encountered a major road hazard or curb and any time unusual tire wear patterns appear.Wheel Alignment is the Measurement of complex suspension angles and the adjustment of a variety of suspension components. It is a suspension-tuning tool which greatly influences the vehicle's handling and tire wear.

Wheel alignment consists of adjusting the angles of the wheels so that they are parallel to each other and perpendicular to the ground, thus maximizing tire life and ensures straight and true tracking along a straight and level road.

The primary static suspension angles that need to be measured and adjusted are caster, camber, toe and thrust angle.

The following are definitions Conditions and Possible Causes of each angle and its influence on a vehicle and its tires.

Camber

Camber is the angle of the wheel, measured in degrees, if the top of the wheel is tilted out then the camber is positive, if it's tilted in, then the camber is negative.

If the camber is out of adjustment, it will cause premature tire wear on one side of the tire's thread. When the camber is out of adjustment it can cause a pulling problem to the side with the more positive camber.
This usually happens when the vehicle has been involved in an accident which has caused structural damage or damage to the strut and / or spindle assembly. Camber also goes out of adjustment when the springs sag and causes ride height to change, or when ball joints and or other attached parts are worn or defective. It also varies depending on speed as aerodynamic forces changes riding height.

After repair and alignment, pulling problem could persist due to the insufficient and or uneven tire to road contact. If a tire shows camber wear pattern, moving it to the rear might be effective but replacement might be best.

Whenever camber changes, it directly affects toe.

On most front-wheel-drive vehicles, camber is not adjustable, however there are aftermarket kits that allow sufficient adjustment to compensate for accident damage or the change in alignment due to the installation of lowering springs.

Caster

Caster is the angle of the steering pivot, measured in degrees.

Viewed from the side, the caster is the tilt of the steering axis. When the wheel is in front of the load the caster is positive. Three to five degrees of positive caster is the typical range of settings, with lower angles are being used on heavier vehicles to reduce steering effort.

If the caster is out of adjustment, it can cause problems in straight-line tracking. If the caster is different from side to side, the vehicle will pull to the side with the less positive caster. If the caster is equal but too negative, the steering will be light and the vehicle will wander and be difficult to keep in a straight line. If the caster is equal but too positive, the steering will be heavy and the steering wheel may kick when you hit a bump.

Caster has little or no effect on tire wear.

One of the best ways to visualize caster is to picture the caster on a shopping cart. The pivot while not at an angle intersects the ground ahead of the wheel contact patch. When the wheel is behind the pivot at the point where it contacts the ground, it is in positive caster.

Like camber, on many front-wheel-drive vehicles, caster is not adjustable. If the caster is out of adjustment on these vehicles, it indicates that something is possibly bent from an accident, and must be repaired or replaced.

Toe

The vehicle's toe is the most critical alignment settings relative to tire wear. if the toe setting is just 1/32-inch off of its appropriate setting, each tire on that axle will scrub almost 3 1/2 feet sideways every mile, therefore reducing tire life.

Like camber, toe will change depending on vehicle speed, as aerodynamic forces changes the riding height hence affecting camber and toe due to the geometry of the steering linkage in relation to the geometry of the suspension.

The toe angle identifies the direction of the tires compared to the centerline of the vehicle. Rear-wheel drive vehicle "pushes" the front tires, as they roll along the road, resistance causes some drag resulting in rearward movement of the suspension arms against their bushings. Most rear-wheel drive vehicles use positive toe to compensate for suspension movement.

Front-wheel drive vehicle "pulls" the vehicle, resulting in forward movement of the suspension arms against their bushings. Most front-wheel drive vehicles use negative toe to compensate for suspension movement.

Toe can also be used to alter a vehicle's handling traits. Increased toe-in will reduce oversteer, steady the car and enhance high-speed stability.

Increased toe-out will reduce understeer, free up the car, especially during initial turn-in while entering a corner.

Before adjusting toe outside the vehicle manufacturer's specification to manipulate handling, be aware that toe setting influences tire wear. Excessive toe settings often causes drivability problems, especially during heavy rain. This is because most highways have tire groves from the daily use by loaded tractor trailers. These heavy vehicles leave groves that fill with water. When one of the vehicles front tire encounters a puddle, it loses some of its grip, the other tire's toe setting will push causing excessive toe-in, or pull causing excessive toe-out. This may cause the vehicle to feel unstable.

Steering Axis Inclination (SAI)

Steering Axis Inclination (SAI) is the measurement in degrees of the steering pivot line when viewed from the front of the vehicle. On a SHORT-LONG ARM (SLA) SUSPENSION the line runs through the upper and lower ball joints.

On a MacPherson strut suspension; the line runs through the lower ball joint and upper strut mount or bearing plate. This angle (SAI), when added to the camber to forms the included angle and causes the vehicle to lift slightly when the wheel is turned from a straight position. The vehicles weight pushes down and causes the steering wheel to return to the center when you let go of it after making a turn.

Like caster, it provides directional stability and also reduces steering effort by reducing the scrub radius.

If the Steering Axis Inclination (SAI) is different from side to side, it will cause a pull at very slow speeds. SAI is a nonadjustable angle, it is used with camber and the included angle to diagnose bent spindles, struts and mislocated crossmembers.

The most likely cause for Steering Axis Inclination (SAI) being out of specification is bent parts, which has to be replaced to correct the condition. On older vehicles and trucks with king pins instead of ball joints, Steering Axis Inclination (SAI) is referred to as (KPI) King Pin Inclination.

Included Angle

Included angle is the sum of the Camber and Steering Axis Inclination (SAI) angles Included angle is not directly measurable. It is used primarily to diagnose bent suspension parts.

If the camber is negative, then the included angle will be less than the Steering Axis Inclination (SAI), if the camber is positive, it will be greater.

The included angle must be the same from side to side even if the camber is different. If there is a difference, then something is bent, possibly the steering knuckle.

Scrub Radius

Scrub Radius is the distance between the extended centerline of the steering axis and the centerline of the tire where the tread contacts the road. This distance must be exactly the same from side to side or the vehicle will pull strongly.

If the steering centerline is inboard of the tire centerline, the scrub radius is positive. If the steering centerline is outboard of the tire centerline, the scrub radius is negative.

Rear-wheel drive cars and trucks generally have a positive scrub radius while FWD cars usually have zero or a negative scrub radius because they have a higher Steering Axis Inclination (SAI), angle.

Using different wheels other than stock can alter the scrub radius.

Riding Height

Riding height is usually measured in inches, from the rocker panel to the ground. A good wheel alignment charts should provide specs, but the main thing is that the measurements should be within one inch from side to side and front to rear.

Riding height is not usually adjustable except on vehicles with torsion bar type springs, coil-over and some air suspensions.

On a nonadjustable type suspensions, springs replacement is best way to fix this problem.

Note: Springs should only be replaced in pairs. Changes in riding height affect camber and toe, so if springs are replaced or torsion bars are adjusted, the wheel must be aligned to avoid tire wear.

Set Back

Set back is when one front wheel is set further back than the other. With alignment equipment that measures toe by using only the front instruments, any setback will cause an uncentered steering wheel. Any good 4-wheel aligner will reference the rear wheels when setting toe in order to eliminate this problem.

Some good alignment equipment will measure set back and give you a reading in inches or millimeters.
Some manufacturers consider a set back of less than 1/4-inch normal tolerance. More than that and there is a good chance that something is bent.

Setback is Caused By: Manufacture or Collision.

Thrust Angle

Thrust angle is the direction that the rear wheels are pointing in relation to the centerline of the vehicle.

The vehicle will "dog track" if the thrust angle is not zero and the steering wheel will not be centered.

The best solution is to first adjust the rear toe to the centerline and then adjust the front toe. This is done during a all wheel alignment if the rear toe is adjustable. If the rear is not adjustable, then the front toe must be set to compensate for the thrust angle, allowing the steering to be centered.

If the thrust angle is not correct on a vehicle with a solid rear axle, it often requires a frame straightening shop to correctly reposition the rear axle.

A vehicles with independent rear suspension, the toe must be adjusted individually until it has reached the appropriate setting for its side of the vehicle, incorrect thrust angle is often caused by an out-of-position suspension or incorrect toe settings.

So in addition to the handling problems that are the result of incorrect toe settings, thrust angles can also cause the vehicle to handle differently when turning left vs. right.

Alignment Ranges

The vehicle manufacturers' alignment specifications usually identify a "preferred" angle for camber, caster and toe (with preferred thrust angle always being zero). The manufacturers also provide the acceptable "minimum" and "maximum" angles for each specification. The minimum and maximum camber and caster specifications typically result in a range that remains within plus or minus 1-degree of the preferred angle.

If for whatever reason your vehicle can't reach within the acceptable range, replacing bent parts or an aftermarket alignment kit will be required. Fortunately there is a kit for almost every popular vehicle due to the needs of body and frame shops doing crash repairs and driving enthusiasts tuning the suspensions on their cars.

Steering Center

Steering center is that the steering wheel is centered when the vehicle is traveling down a straight and level road. However most roads are crowned to allow for water drainage, this may cause the vehicle to drift to the right so the steering wheel will appear to be off-center to the left on a straight road. to compensate for this

· The left caster should be more negative than the right, but not more than 1/2 degree within the specified range.

· The left camber should be more positive than the right camber. Check the specs to see what the allowable differences.

A crooked steering wheel is one of the most common complaints after a wheel alignment. Steering center is controlled by the front and rear toe settings, when setting steering center, the rear toe should be set first bringing the Thrust Angle as close to the vehicle centerline as possible. the steering wheel is then locked in a straight-ahead position in order to set the front toe. Please note; before locking the steering wheel, the engine should be started and the wheel turned right and left a couple of times. This will take any stress off the power steering valve. Repeat the above starting and turning of the steering after setting front toe to ensure that the steering valve wasn't loaded again due to the tie rod adjustments.

Toe Out on Turns

When you steer a car through a turn, the outside front wheel has to navigate a wider arc than the inside wheel. For this reason, the inside front wheel must steer at a sharper angle than the outside wheel.

Toe-out on turns is measured by the turning angle gauges (turn plates) that are a part of every wheel alignment machine. The readings are either directly on the turn plate or they are measured electronically and displayed on the screen. Wheel alignment specifications will usually provide the measurements for toe-out on turns. They will give an angle for the inside wheel and the outside wheel such as 20º for the inside wheel and 18º for the outside wheel. Make sure that the readings are at zero on each side when the wheels are straight ahead, then turn the steering wheel so that the inside wheel is at the inside spec. then check the outside wheel. The toe-out angles are accomplished by the angle of the steering arm. This arm allows the inside wheel to turn sharper than the outside wheel. The steering arm is either part of the steering knuckle or part of the ball joint and is not adjustable. If there is a problem with the toe-out, it is due to a bent steering arm that must be replaced.

Wheel Offset

The offset of a wheel is the distance from its hub mounting surface to the centerline of the wheel. The offset can be one of three types.

Zero Offset

The hub mounting surface is even with the centerline of the wheel.

Positive

The hub mounting surface is toward the front or wheel side of the wheel. Positive offset wheels are generally found on front wheel drive cars and newer rear drive cars.

Negative

The hub mounting surface is toward the back or brake side of the wheels centerline. "Deep dish" wheels are typically a negative offset.

If the offset of the wheel is not correct for the car, the handling can be adversely affected. When the width of the wheel changes, the offset also changes numerically. If the offset were to stay the same while you added width, the additional width would be split evenly between the inside and outside. For most cars, this won't work correctly.

Load on stationary vehicle

2013-07-16T04:25:00.001-07:00

Load on stationary vehicle

What are the Forces on a Moving Car?

The forces acting on a moving car are thrust and drag
as well as the same forces that act on a stationary car.

Drag is the force of air resistance (a form of friction)
pushing against the front of the car while it is moving.

Thrust is the force pushing the car forwards. Thrust comes from the engine turning the wheels.

How do Wheels make a Car go Forwards?

Tyres on the wheels push backwards against the road as they try to turn, causing an equal and opposite force which pushes the car forwards.

The tyres must have good grip (a high friction)
so that they do not slide on the road surface.

If the forces of thrust and drag are equal,
then the forces are balanced and
the car will move with a constant velocity.

If the forces of thrust and drag are not equal, then
the forces are unbalanced and the car will accelerate.
The car will get faster if thrust is bigger than drag,
and slower if the drag is bigger than the thrust.

Crankshaft position sensor

2013-04-29T09:51:00.001-07:00

Crankshaft Position Sensor

The functional objective for the crankshaft position sensor is to determine the position and/or rotational speed (RPM) of the crank. Engine control unit use the information transmitted by the sensor to control parameters such as ignition timing and fuel injection timing. The sensor output can also be related to other sensor data including the cam position to derive the current combustion cycle, this is very important for the starting of a four stroke engine. The Crankshaft Position Sensor (CPK) is always located somewhere on the engine in close proximity to the crankshaft, usually near the harmonic balancer or in the engine block aligned with a toothed wheel connected to the crankshaft. The CPK provides the data that is used to compute the engine's revolutions per minute (RPM), which is essential for proper transmission gear selection in relationship to vehicle speed and load.

Failure Symptoms

There are three primary engine malfunction symptoms that may be indicators of CPK malfunction. If the vehicle engine is experiencing cylinder misfires, the CPK may not be providing the computer with accurate information on piston position. If the vehicle hesitates during acceleration, the CPK may not be providing cylinder position data to the computer fast enough to fire the appropriate cylinder to accelerate the vehicle in response to driver input. The most serious indication of CPK malfunction is intermittent start, and eventually no start. When the sensor fails, the computer will register a malfunction code and illuminate the check engine light on the instrument panel. There may be an indication of sensor failure due to defective electrical connections such as high resistance, or an open condition in the circuit going to the sensor or returning to the vehicle engine control module.

oxygen sensor

2011-04-08T21:58:00.000-07:00

Introduction
The O2 sensor is mounted in the exhaust manifold to monitor how much unburned oxygen is in the exhaust as it exits the engine. Monitoring oxygen levels in the exhaust is a way it gauges the fuel mixture. The sensor tells the ECU if the fuel mixture is burning rich (less oxygen) or lean (more oxygen).

The O2 sensor works like a miniature generator and produces its own voltage when it gets hot. Inside the vented cover on the end of the sensor that screws into the exhaust manifold is a zirconium ceramic bulb. The bulb is caoted on the outside with a porous layer of platinum.Inside the bulb are two strips of platinum that serve as electrodes or contacts.Between the electrodes is a solid-state electrolyte made up of a zirconic ceramic material that acts like a galvanic battery electrolyte under certain conditions. When the sensing element is cold, the zirconia material behaves similar to an insulator . At elevated temperatures, the zirconia material performs more like a semiconductor, and can generate a characteristic voltage output on the sensor connections. The outside of the bulb is exposed to the hot gases in the exhaust while the inside of the bulb is vented internally through the sensor body to the outside atmosphere. Newer-style O2 sensors breathe through their wire connectors and have no vent hole. This is why grease should never be used on O2 sensor connectors because it can block the flow of air.

Automobiles: Air brake system

2011-04-08T21:54:00.000-07:00

Automobiles: Air brake system: "Air Brake system Compressed air brake systems are typically used on heavy trucks and buses . The system consists of service brakes, parking..."

Air brake system

2011-03-12T20:45:00.000-08:00

Air Brake system

Compressed air brake systems are typically used on heavy trucks and buses . The system consists of service brakes, parking brakes, a control pedal, an engine-driven air compressor and a compressed air storage tank. Compressed air brake system used both disc or drum brake arrangement. Most types of truck air brakes are drum units, though there is an increasing trend towards the use of disc brakes in this application. The air compressor air draws filtered air from the atmosphere and forces it into high-pressure reservoirs at around 120 PSI. Most heavy vehicles have a gauge within the driver's view, indicating the availability of air pressure for safe vehicle operation, often including warning tones or lights. Setting of the parking/emergency brake releases the pressurized air pressure in the lines between the compressed air storage tank and the brakes, thus actuating the (spring brake) parking braking hardware. An air pressure failure at any point would apply full spring brake pressure immediately.

Brakes are applied by pushing down the brake pedal. (It is also called the foot valve.) Pushing the pedal down harder applies more air pressure. Letting up on the brake pedal reduces the air pressure and releases the brakes. Releasing the brakes lets some compressed air go out of the system, so the air pressure in the tanks is reduced. It must be made up by the air compressor. Pressing and releasing the pedal unnecessarily can let air out faster than the compressor can replace it. If the pressure gets too low, the brakes won't work.These large vehicles also have an emergency brake system, in which the compressed air holds back a mechanical force (usually a spring) which will otherwise engage the brakes. Hence, if air pressure is lost for any reason, the brakes will engage and bring the vehicle to a stop.

A compressed air brake system is divided into a supply system and a control system. The supply system compresses, stores and supplies high-pressure air to the control system as well as to additional air operated auxiliary truck systems (gearbox shift control, clutch pedal air assistance servo, etc.).

Component of air brake system

Air Compressor

The air compressor pumps air into the air storage tanks (reservoirs). The air compressor is connected to the engine through gears or a v-belt. The compressor may be air cooled or may be cooled by the engine cooling system. It may have its own oil supply or be lubricated by engine oil. If the compressor has its own oil supply, check the oil level before driving.

Air Compressor Governor

The governor controls when the air compressor will pump air into the air storage tanks. When air tank pressure rises to the "cut-out" level (around 125 pounds per-square-inch or "psi"), the governor stops the compressor from pumping air. When the tank pressure falls to the "cut-in" pressure (around 100 psi), the governor allows the compressor to start pumping again.

Air Storage Tanks

Air storage tanks are used to hold compressed air. The number and size of air tanks varies among vehicles. The tanks will hold enough air to allow the brakes to be used several times, even if the compressor stops working.

Air Tank Drains

Compressed air usually has some water and some compressor oil in it, which is bad for the air brake system. For example, the water can freeze in cold weather and cause brake failure. The water and oil tend to collect in the bottom of the air tank. Be sure that you drain the air tanks completely. Each air tank is equipped with a drain valve in the bottom. There are two types:

· Manually operated by turning a quarter turn or by pulling a cable. You must drain the tanks yourself at the end of each day of driving. See Figure 5.1.

· Automatic--the water and oil are automatically expelled. These tanks may be equipped for manual draining as well.

Automatic air tanks are available with electric heating devices. These help prevent freezing of the automatic drain in cold weather

Alcohol Evaporator

Some air brake systems have an alcohol evaporator to put alcohol into the air system. This helps to reduce the risk of ice in air brake valves and other parts during cold weather. Ice inside the system can make the brakes stop working.

Check the alcohol container and fill up as necessary, every day during cold weather. Daily air tank drainage is still needed to get rid of water and oil. (Unless the system has automatic drain valves.)

Safety Valve

A safety relief valve is installed in the first tank the air compressor pumps air to. The safety valve protects the tank and the rest of the system from too much pressure. The valve is usually set to open at 150 psi. If the safety valve releases air, something is wrong. Have the fault fixed by a mechanic.

The Brake Pedal

You put on the brakes by pushing down the brake pedal. (It is also called the foot valve or treadle valve.) Pushing the pedal down harder applies more air pressure. Letting up on the brake pedal reduces the air pressure and releases the brakes. Releasing the brakes lets some compressed air go out of the system, so the air pressure in the tanks is reduced. It must be made up by the air compressor. Pressing and releasing the pedal unnecessarily can let air out faster than the compressor can replace it. If the pressure gets too low, the brakes won't work.

Foundation Brakes

Foundation brakes are used at each wheel. The most common type is the s-cam drum brake. The parts of the brake are discussed below.

Brake Drums, Shoes, and Linings. Brake drums are located on each end of the vehicle's axles. The wheels are bolted to the drums. The braking mechanism is inside the drum. To stop, the brake shoes and linings are pushed against the inside of the drum. This causes friction, which slows the vehicle (and creates heat). The heat a drum can take without damage depends on how hard and how long the brakes are used. Too much heat can make the brakes stop working.

S-cam Brakes. When you push the brake pedal, air is let into each brake chamber. Air pressure pushes the rod out, moving the slack adjuster, thus twisting the brake camshaft. This turns the s-cam (so called because it is shaped like the letter "S"). The s-cam forces the brake shoes away from one another and presses them against the inside of the brake drum. When you release the brake pedal, the s-cam rotates back and a spring pulls the brake shoes away from the drum, letting the wheels roll freely again. See Figure 5.2.

Wedge Brakes. In this type of brake, the brake chamber push rod pushes a wedge directly between the ends of two brake shoes. This shoves them apart and against the inside of the brake drum. Wedge brakes may have a single brake chamber, or two brake chambers, pushing wedges in at both ends of the brake shoes. Wedge type brakes may be self-adjusting or may require manual adjustment.

Disc Brakes. In air-operated disc brakes, air pressure acts on a brake chamber and slack adjuster, like s-cam brakes. But instead of the s-cam, a "power screw" is used. The pressure of the brake chamber on the slack adjuster turns the power screw. The power screw clamps the disc or rotor between the brake lining pads of a caliper, similar to a large c-clamp.

Wedge brakes and disc brakes are less common than s-cam brakes.

Supply Pressure Gauges

All vehicles with air brakes have a pressure gauge connected to the air tank. If the vehicle has a dual air brake system, there will be a gauge for each half of the system. (Or a single gauge with two needles.) Dual systems will be discussed later. These gauges tell you how much pressure is in the air tanks.

Gear operation

2011-01-05T20:45:00.000-08:00

Introduction

In a manual transmission for a rear-wheel drive vehicle, the gear train is
built up on three shafts. The input shaft extends from the front of the transmission.

An external parallel-splined section engages with internal splines on the clutch-driven plate.A main-drive gear is an integral part of the shaft. It meshes constantly with a mating gear on a counter-shaft which has a number of gears
formed on it.These gears mesh with mating gears on the mainshaft, or output. These mainshaft gears are supported on bearings on the shaft. They can rotate
without turning the output.

Each mainshaft gear has an external toothed section on one side. The
teeth face an internally-toothed engagement sleeve located on a central
hub, which is itself splined to the mainshaft. The engagement sleeve can slide in either direction to engage the external teeth on the appropriate gear. This locks the gear through the sleeve and hub, to the mainshaft.

The engagement sleeve can slide in either direction to engage the external
teeth on the appropriate gear. This locks the gear through the sleeve and
hub, to the mainshaft.Before engagement of the components occurs, a synchromesh devicebetween the sleeve and gear synchronizes them.
The gears constantly in mesh, have their teeth cut on a helix, at an angle
to the gear center line.This reduces gear noise and distributes load more evenly, as several teeth are in contact at any one time. Teeth on the reverse idler are normally straight cut or spur gears, cut parallel to the gear center line.
When reverse is selected, this connects the reverse idler with mating
gears on the countershaft and mainshaft. The reverse idler rotates on a plain shaft fixed in the casing. It transfers the drive from one shaft to the other, and reverses the direction of rotation of the mainshaft.

Differential

2011-01-05T20:32:00.003-08:00

Introduction

Car wheels spin at different speeds, especially when turning . wheel travels a different distance through the turn, and that the inside wheels travel a shorter distance than the outside wheels. For the non-driven wheels There is no connection between them, so they spin independently. But the driven wheels are linked together so that a single engine and transmission can turn both wheels. If your car did not have a differential, the wheels would have to be locked together, forced to spin at the same speed. . This would make turning difficult and hard on your car: For the car to be able to turn, one tire would have to slip. With modern tires and concrete roads, a great deal of force is required to make a tire slip. That force would have to be transmitted through the axle from one wheel to another, putting a heavy strain on the axle components.

How Differential Work

The drive shaft ends in a pinion gear inside the differential. When the drive shaft turns, the pinion drives a ring gear that is part of the differential housing, so that both housing and ring gear rotate together. Inside the housing are two pinion gears and two side gears; each side gear is connected, via an axle, to a drive wheel. When the car drives straight ahead and the axle shafts turn at the same speed, the differential housing rotates, but no differential action occurs. When the car negotiates a turn, however, the differential must compensate for the difference in distance traveled by the drive wheels. The opinions roll around the side gears, allowing the inside wheel to turn more slowly and the outside wheel to turn more slowly and the outside wheel to turn faster.

1. The differential on a vehicle, be it a front- or rear-wheel drive, is the final gear reduction for the transmission. It not only reduces the ratio, but supplies the engine power to the drive wheels. The picture above illustrates the gear locations within the carrier.

2. The power from the engine is transmitted through the pinion gear at the top. The pinion gear turns the large ring gear, which changes the direction of the power 90 degrees so that it can be transmitted to the wheels. The drawing depicts the axles and tires on both sides. These axles have splines on the ends, and are inserted into the side gears in the differential (marked in yellow). The axles are held in the side gears by the splines so that the side gear and axle move as one.

3. The spider gears are the small gears in the top and bottom of the chunk. They are in between and mesh with both side gears. When the vehicle is going straight, both axles turn at the same speed and the spider gears do not rotate. All they do is lock up both axles so they turn at the same speed. When the vehicle turns, the spider gears will rotate, allowing one axle to turn at a different speed than the other--hence the name, "differential."

4. This is a depiction of an open differential, which is commonly found in most vehicles. They are quite trouble-free, but do have one disadvantage. On a dry road with good traction, the power is evenly applied to both wheels. When one of the tires hits ice or a slippery surface, it begins to spin and the majority of torque is directed to the spinning wheel, leaving very little for the wheel with the good traction. This is how vehicles can get stuck in snow or mud.

5. Another type of differential is the limited slip differential, which is an option on most new cars. It has a distinct advantage by having a set of clutches and springs within the differential. Their function is to apply pressure to the side gears should one of the tires begin to slip. By applying pressure to the opposite wheel from the one spinning, it allows for more torque to be applied to the wheel with traction. If is far superior to the open differential when it comes to traction in bad weather.

Extending Turbo Charger life

2010-12-30T09:43:00.000-08:00

Tips

Turbo lag

The time required to bring the turbo up to a speed where it can function effectively is called turbo lag

EXTENDING TURBOCHARGER LIFE
The major causes of turbocharger failures are attributed to:
Lack of lube oil (quick starts and hot shutdowns)

Oil contamination

Ingestion of foreign objects

Restricted oil drainage

Abnormally high exhaust temperatures

1) Lack of Lube oil
Oil not only lubricates the turbocharger's spinning shaft and bearings, it also carries away heat. When oil folw stops or is reduced, heat is immediately transferred from the hot turbine wheel to the bearings, which are also heating up because of the increased friction due to the lack of oil. This combination causes the turbocharger shaft temperature to increase rapidly.
if oil flow down not increase and the process continues, bearings will fail. Once the bearings fail (which can happen in just seconds) seals, shft, turbine and compressore sheels can also be damaged.
The principle causes of turbocharger bearing lubrication problems are low oil pressure , a bent, plugged or undersized oil lube supply line, plugged or restricted oil galleries in the turbocharger, or improper machine start-up and shutdown procedure.
Oil lelvels and pressure should always be closedly monitored and all worn hoses and lines should be replaced. The turbocharger oil supply line should be checked frequently to make sure it is not kinked or bent and it should always be replaced with a line of equal size, length and strength.
The easiest way to damage a turbocharger is through improper start-up and shutdown procedures. Always idle the engine for at least 30 seconds (no load) after start-up and before shutdown. Warming the engine up before applying a load allows oil pressure to build up and lines to fill with oil.
Idling the engine before shutdown allows the engine and turbocharger to cool. "Hot" shutdowns can cause the turbocharger to fail because after high-speed operation the turbocharger will continue to rotate lone after the engine has been shut off and oil pressure has dropped to zero. This will cause heat to build up and possible hearing damage. It can also cause carbon and varnish deposits to form.

2) Oil Contamination
A second cause of turbocharger failures is contaminated oil. it can be caused by a worn or damaged oil filter or not changing the lube oil at recommended intervals. Expecting the oil filter to remove dirt, sand, metal chips, etc. from the oil before they reach the engine or turbocharger can be a costly mistake because contaninated oil may completely bypass the engine oil filter if the oil filter or oil cooler is clogged, if the filter element is improperly installed, or if the oil is thick during cold weather.
Four good ways of avoiding oil contamination are:

Always inspect the engine thoroughly during major overhaul. Look especially for any sludge or debris left in lube oil galleries.

Change lube oil at recommended intervals. Analysis of oil samples at filter chane periods can help identify potentially harmful contaminants in the oil.

Clean the area around the oil fill cap before adding oil.

3) Ingetion of Foreign Objects
The third cause of turbocharger damage is the ingestion of foreign objects. Foreign objects or particaes can be ingested and cause damage to the turbocharger on both compressor and turbine sides. This easy to avoid.
On the compressore side, foreign objects usually take the form of dust, sand, or shreds of air cleaner element that enter through improperly installed air cleaner elements. Leak air inlet piping (loose clamps or torn rubber joints) or torn pleats in dry-type air cleaner elements also create problems.
The result is erosion of compressor blades that can cause the delicately balance wheel to wobble.

4) Restriced oil Drainage
A fourth cause of turbocharger damage is restricted lube oil drainage. Thelubricating oil carries away heat generated by friction fo the bearings and from the hot exhaust gases. If drainage back to the sump is impeded, the bearings will overheat with damage that will ultimately lead to failure.
There ar two primary reasons for restricted drainage. A blocked drain tube, due to either damage or a buildup of sludged oil or high crankcase pressure which can be due to restriced crankcase breather or excessive engine blowby.
Periodically check both the turbocharger oil drain tube and engine breather tube for damge or restriction. Correction of these conditions leads to longer turbocharger life.

5) Abnormally High Exhaust Temperatures
A fifth cause of turbocharger damge is abnormally high exhaust temperatures. Elevated exhaust temperatures cause coking of oil which can lead to bearing failure. Extreme over-temperature operation can case wheel burst.
There are two basic cause of over-temperature. The first is restricted air flow and the second is overpowering the engine. In either case the einge has more fuel than available air for proper combustion, this overfueled condition leads to elevated exhaust temperatures.
Causes of restricted air flow can include damaged inlet piping, clogged air filters, excessive exhaust restriction, or operation at extreme altitudes. Overpowering generally is due to improper fuel delivery or injection timing. If overtemperature operation has been identified, an instpection of the air inlet and exhaust systems should be perfomed. Also, check the fuel delivery and timing.

Tyre Pressure

2010-12-29T23:22:00.000-08:00

Tyre Pressure

Correct tyre pressure can help to extend the life of your tyre, improve vehicle safety and maintain fuel efficiency. Pressure is measured by calculating the amount of air that has been pumped into the inner lining of your tyre in pounds force(PSI) or BAR pressure.

Maintaining correct Tyre Pressures

There are three main reasons why maintaining the right tyre pressure is important. The first is safety. Tyres that are under inflated can overheat; and over inflated tyres can lead to poor vehicle handling on the road.
The second reason is economy. Over or under inflated tyres suffer more damage than those with the correct pressure and need to be replaced more regularly. Vehicles with under-inflated tyres have increased rolling resistance that require more fuel to maintain the same speed.
The third reason for maintaining the correct tyre pressure is the environment. Correct tyre pressures help to maintain optimum fuel efficiency. This can equate to lower Co2 emissions coming from your vehicle than those with incorrect tyre pressures and that has to be good for the environment.

Remember that tyre failure can occur due to under inflation and overloading!
One of the most dangerous conditions that can exist is the slow leak. Sometimes a small nail, screw or other object will puncture a tyre and then act as an inefficient plug. Air pressure drops slowly over a matter of hours or days, undetected by the driver. Your best defense in this circumstance is to be alert to the symptoms of this condition. Be aware of any pulling or vibration that seems unnatural. And listen for any tick-ticking sound—especially audible at slow, parking lot speeds. If you detect this, get off the road and inspect the tyres on the side of the pull, vibration or sound. A bulging sidewall and/or excessively hot tyre indicates a slow leak. Put on your spare tyre and have your Tyrepower Pro repair the punctured unit. Ask the repair technician if any sidewall damage has occurred (a powdery residue inside the tyre indicates this condition). If so, have the tyre replaced.

How To Check Air Pressure
Properly checking tyre pressure requires an accurate air gauge. Many people believe that they can check air pressure just by looking at the tyre and judging the sidewall appearance. Also, many people use the air guages at service stations, which can be grossly inaccurate due to exposure or abuse. Invest in a quality air gauge.

When checking your vehicle's tyre pressure, make sure the tyres are "cold". Cold air pressure means that the vehicle has not yet been driven one kilometer (remember that driving on a tyre as well as being in direct sunlight increases its temperature and air pressure). If you must drive more than one kilometer for air, check and record the air pressure in all your tyres before you leave. Once at the tyre dealer, measure each tyre's inflation again and then note the difference. Inflate the tyres with low pressure to a level that is equal to the recommended cold pressure plus the difference at the higher temperature.

Finally, after completing the pressure check, make sure the valves and extensions are equipped with valve caps to keep out dirt and moisture. Remember to replace the valve assembly when you replace the tyre; it's your best assurance against a sudden or consistent loss of air pressure.

Environmental Impact
How can routine air pressure maintenance impact our environment? Consider that fewer tyres per year would end up in the landfills and scrap heaps that trouble our ecology. How many tyres are we talking about? We estimate that most drivers lose from 10% to as much as 50% of tyre tread life due to underinflation. That's a significant statistic. Now consider the extra fuel we burn to push cars along on soft, underinflated tyres. Tyres do require extra energy to roll if they are under inflated. While the statistics vary widely and inconclusively, the implications are staggering. So maintaining tyre pressure is a small line item in our busy daily routines, but it adds up to big environmental consequences. We must all care and take action to do the right thing.

Other Factors Change Air Pressure
Besides the routine air check, other circumstances necessitate a visit to the air pump. Seasonal changes or altitude changes create a rise or drop in air pressure (for every 10 degrees change in temperature, tyre air pressure changes approximately 7 kpa). But perhaps the most overlooked factor is vehicle loading for trucks and 4WDs. Since these vehicles can be configured and loaded in many ways, the proper inflation pressure should be determined by actual tyre loads. This is best determined by weighing the vehicle; vehicle loading can change from trip to trip

The Benefits of Correct Air Pressure
Keeping the correct air pressure in your tyres is as important as giving your engine a tune up. The economic benefits are perhaps even greater! With the right amount of air pressure, your tyres wear longer, save fuel, enhance handling and prevent accidents. The effects of not maintaining correct air pressure are poor petrol mileage, loss of tyre life, bad handling (perhaps even loss of control), and potential vehicle overloading.

Steering system

2010-12-08T00:14:00.000-08:00

Introduction

The steering system must provide control over the direction of travel of the vehicle; good maneuverability for parking the vehicle; smooth recovery from turns, as the driver releases the steering wheel; and minimum transmission of road shocks from the road surface.
The effort by the driver is transferred from the steering wheel, down the steering column, to a steering box.
The steering box converts the rotary motion of the steering wheel, to the linear motion needed to steer the vehicle.
It also gives the driver a mechanical advantage.
The linear motion from the steering box is then transferred by tie-rods, to the steering arms at the front wheels. The tie rods have ball joints that allow steering movement, and movement of the suspension.
The steering-arm ball-joints are arranged so that movement in the suspension does not affect steering operation.

Summary
The steering system provides control over direction of travel, good manoeuvrability, smooth recovery from turns, and minimum transmission of road shocks.

Diagram of steering system

synchromesh gear system

2010-12-06T03:41:00.000-08:00

How synchromesh gear works?

If the dog teeth, make contact with the gear, but the two parts are spinning at different speeds, the teeth will fail to engage and a loud grinding sound will be heard as they clatter together. For this reason, a modern dog clutch in an automobile has a synchronizer mechanism or synchromesh, which consists of a cone clutch and blocking ring. Before the teeth can engage, the cone clutch engages first which brings the selector and gear to the same speed using friction. Moreover, until synchronization occurs, the teeth are prevented from making contact, because further motion of the selector is prevented by a blocker (or baulk) ring. When synchronization occurs, friction on the blocker ring is relieved and it twists slightly, bringing into alignment certain grooves and notches that allow further passage of the selector which brings the teeth together. Of course, the exact design of the synchronizer varies from manufacturer to manufacturer.

Diagram of synchromesh & syncromesh ring

water cooling system

2010-12-05T09:39:00.000-08:00

Working of water cooling system

Figure illustrated above describes the functioning of cooling system of an automobile. The key components used in a cooling system are pressure cap, heater hoses, thermostat, heater core, reserve tank, lower hose, transmission cooler, water pump, fan, radiator and upper house. The cooling system of a vehicle operates or functions by directing liquid coolant via passages in the engine block and heads. After that the liquid coolant which flows through passages absorb the heat from an engine. Then this fluid passes through a rubber hose to reach to the radiator. At this stage the hot liquid is cooled by air stream entering the engine compartment via grills. Once it gets cooled, then it goes back to engine and same process repeats again.

Automotives clutch

2010-12-05T09:33:00.000-08:00

Operation: The transmission of power happens when one driving shaft (which is one contact with the crankshaft/flywheel) is brought into contact with another shaft which is being driven (The propeller shaft). This is made possible through the clutch and its supporting mechanism. The contact between the two shafts is brought about by applying strong spring loaded pressure through suitable linkage by a pedal operated by the driver.

The clutch basically consists of a clutch plate (or a series of them in larger vehicles) and a clutch assembly which is spring loaded in such a way that when the pedal is pressed, the release levels (as shown in the picture below) are pressed inward, which push against a set of springs that clamp this clutch plate to the flywheel of the engine, thereby releasing the clutch plate. This causes the engine flywheel to rotate freely (the clutch is not in contact anymore) and the gears can be shifted now or the engine can be started (if you are about to start the engine). This clutch plate is always in contact with the engine’s flywheel, by default. It is disengaged only when necessary by the action of the driver on the pedal.

4 stroke engine principle

2010-12-05T09:26:00.000-08:00

4 stroke engine principle

1. INTAKE stroke: On the intake or induction stroke of the piston , the piston descends from the top of the cylinder to the bottom of the cylinder, reducing the pressure inside the cylinder. A mixture of fuel and air is forced by atmospheric (or greater) pressure into the cylinder through the intake port. The intake valve(s) then close.

2. COMPRESSION stroke: With both intake and exhaust valves closed, the piston returns to the top of the cylinder compressing the fuel-air mixture. This is known as the compression stroke.

3. POWER stroke.: While the piston is close to Top Dead Center, the compressed air–fuel mixture is ignited, usually by a spark plug (for a gasoline or Otto cycle engine) or by the heat and pressure of compression (for a diesel cycle or CI ). The resulting massive pressure from the combustion of the compressed fuel-air mixture drives the piston back down toward bottom dead center with tremendous force. This is known as the powerstroke, which is the main source of the engine's torque and power.

4. EXHAUST stroke.: During the exhaust stroke, the piston once again returns to top dead center while the exhaust valve is open. This action evacuates the products of combustion from the cylinder by pushing the spent fuel-air mixture through the exhaust valve(s).

2 stroke engine

2010-12-05T09:18:00.000-08:00

Mode of operation of the two-stroke engine

1st stroke: The piston is at the bottom of the cylinder. A pipe at the left side is opened and lets the fuel mixture, which is already compressed a bit, flow from the lower to the upper part of the cylinder. The fresh gases expulse now the exhaust through an ejection pipe, which is not closed by the piston at this moment.

2nd stroke: After being hurried upward, the piston now covers the pipe on the left side and the ejection pipe. Because there is no way out any more, the upper, fresh gas mixture gets compressed now. At the same time in the part below fresh gas is taken in by the piston driving upward through the open suction pipe. At the upper dead-center, the compressed fuel mixture is ignited by the sparking plug, the piston is pressed downward while he compresses at the same time the fresh gas below. The process begins again as soon as the piston arrives at its lowest point.

Petrol engine principle

2010-12-05T09:09:00.000-08:00

Diagram of 4-s petrol engine cycle

This cycle have 4 cycle namely they are:

2. COMPRESSION stroke: With both intake and exhaust valves closed, the piston returns to the top of the cylinder compressing the fuel-air mixture. This is known as the compression stroke.

3. POWER stroke.: While the piston is close to Top Dead Center, the compressed air–fuel mixture is ignited, usually by a spark plug (for a gasoline or Otto cycle engine) or by the heat and pressure of compression (for a diesel cycle or compression ignition engine). The resulting massive pressure from the combustion of the compressed fuel-air mixture drives the piston back down toward bottom dead center with tremendous force. This is known as the power stroke, which is the main source of the engine's torque and power.

diesel engine

2010-12-05T08:55:00.000-08:00

inventor of diesel engine is Rudolf Diesel I n 1878.

Fig: Principle cycle of diesel engine

A diesel engine uses high compression [intake air that is compressed / squished] into a very small space inside each cylinder causing extreme heat! This is called 'Heat Of Compression' which ignites a very fine high pressure mist of diesel fuel that is injected into the cylinder at the exact time.
So you now know that a gasoline engine needs a high energy spark to run while a diesel uses 'Heat Of Compression'

THE FOUR STROKE PRINCIPLE

Every engine today runs on FOUR STROKES or FOUR CYCLES- both these terms mean the same. Here is how the four stroke diesel engine operates.
The four strokes are: INTAKE-COMPRESSION-POWER-EXHAUST. The pistons, valves and injectors work together in each cylinder in a set sequence over and over.

1} INTAKE STROKE:
Intake valves in the cylinder head open allowing pressurized air to enter each cylinder while the piston is travelling downward.{the pressurized air supply is made possible by the TURBOCHARGER which pushes air into the intake system giving the diesel engine a boost of air to keep up with instantaneous injection of fuel}

2} COMPRESSION STROKE:
When the piston starts to make it's way back upward the valves close which traps the intake air in the cylinder which allows compression to take place, the HEAT OF COMPRESSION is reached when the piston reaches the top of the cylinder, the diesel fuel is then injected into the cylinder at the precise time.

3} POWER STROKE:
After injection takes place an explosion occurs in the cylinder because of the combination of heat and atomized diesel fuel. This causes the piston to be forced downward which produces torque and the horsepower required from a typical diesel engine.

4} EXHAUST STROKE:
After the power stroke the piston moves upward once again while the exhaust valves open allowing the previously ignited gases to escape to the atmosphere out the exhaust system.

Automobile manufactures

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Alpha Sports ,Bullet, Chrysler Australia (produced the Valiant), West Coast Motors, Chrysler Canada Ltd., Chalmers Motor Car of Canada, Fisher Motor Company. Ltd., General Motors of Canada Ltd., Renault, First Automotive Works (FAW), Great Wall, Shanghai Automotive, Alpine/Alpine-Renault, Bugatti, Peugeot, Volkswagen, Audi, Skoda , Lamborghini, Bentley, Mercedes-Benz, Chrysler, Jeep, BMW, Rolls-Royce, Audi, Daimler, MAN, Opel, Porsche, Tata Motors, Reva, Premier, Mahindra, Hindustan, HeroHonda, Bajaj Tempo, Ashok Leyland, Alfa Romeo, Abarth, Ferrari, Lamberti, Daihatsu, Honda, Isuzu, Mazda, Mitsubishi, Nissan , Subaru, Subaru, Toyota Motor Corporation, Perodua, Proton, Hyundai, Kia Motors, SsangYong, Alvis Cars, Aston Martin, Aston Martin, Leyland, Jaguar, Mini/MINI, Rover, Hummer,

Automobile Introduction

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An automobile, motor car or car is a wheeled motor vehicles used for transporting passengers, which also carries its own engine or motor. Most definitions of the term specify that automobiles are designed to run primarily on roads, to have seating for one to fifty people ( Excluding driver ), It may have 2 or more wheels. Primarily automobile are
design to transport passenger & goods.The word automobile comes, via the France 'automobile' from ancient Greek.firstly automobile fuel is petrol later Diesel,bio diesel,solar,hydrogen,electricity etc ,now a days scientist
are trying on water too. The only disadvantage of automobile is it cause air pollution ,noise pollution etc.