Group 03-05: Rittenhouse Clock Design

Week 8 Activity

2012-05-30T10:22:00.001-07:00

This week the group concluded with the computer modeling and tweeked any rough edges of the orrery mechanism after Deepak reviewed the 3D parts. The final STL files were submitted to be printed. All parts should be ready to be assembled by week 9 lab. The group also constructed the plexiglass box for which the gear system will reside in. The box was made out of 1/4in plexiglass with dimensions 14in x 12in x 4.15in. Slight modifications to the box will need to be made in week 9 lab once the printed parts are assembled. These modifications will allow the parts to rest securley in the plexiglass box so the mechanism will not fall apart once in motion. The group also mentioned the final report and delagated specific sections that are to be completed by each member.

These are videos of the orrery mechanism

Week 7 Activity

2012-05-20T16:08:00.001-07:00

This week the group submitted the parts to Deepak for review and printing. The group will now be working on creating the working mechanism of the clock's orrery system in ProE. This mechanism will be created by week 8 lab. The group will also be assembling the acrylic box that the gear system will be constructed into. Other components that are left to create are the spacers between each gear along with the bearings. These parts will most likely be bought after the gears have been printed. The group also must decide of a way to mount the gear system inside the acrylic box taking into consideration the drive motor, batteries, and the physical planet attachments to the gear system.

This video shows an enlarged view of gears in motion

Week 6 Activity

2012-05-14T10:37:00.000-07:00

The group started the meeting off with presenting what each member had completed. There was a general consensus that there was something wrong with the calculations in the processes of making the gear teeth for each planet. This error threw off every gear tooth that was made, so every tooth had to be remade from scratch again. The entirety of the meeting was spent with a joint effort to remake the gear teeth in record time. Most off the 12 teeth were made during the lab and the remainder were submitted to Sam for assembly. The slight skew in the group's progress did not hinder their ability to sufficiently get what was required done. All assembly has been completed and the only thing left to do is render a working proE mechanism, rapid prototype the gears, and obtain ball bearings to divide each gear stack. Weak 7 will entail converting the assembly to a mechanism, making sure all the parts are in order, and hopefully submitting the gears to be made.

Week 5 Activity

2012-05-06T18:49:00.001-07:00

This week the group finalized calculations needed to model the gear teeth of each planet. There is much to be completed to reach the final printing stage. The group has divided the gear modeling up amongst its members and final gear products will be done by week 6. One dilemma that the group is running into is scaling. The calculations and information obtained in the books are a 1:1 ratio. In week six the group will analyze the system to determine the appropriate scale for the gears. This is so that all the gears will meet size constraints in the rapid prototype machine. Printing is expected in week 8.

This screenshot shows all the calculations done to model each gear tooth

Week 4 Activity

2012-04-25T13:43:00.003-07:00

Week 4 composed of a lot of mathematical work for the group. The group verified, based on calculations, that the diameter talked about in the book, The Most Important Clock in America, is with respect to the pitch of the gear. [shown in Figure 1 and 2] The group also stated that the final product would be made out of plastic from the rapid prototyping material and not metal. This was because of the time constraints placed on the group and the cost of custom parts. The group also modeled a quick mock up of a gear in ProE to show the basics behind creating a gear. Each member will be required to make 2 gears each that match the gear pitch and tooth count described in the book. These parts will be completed by week 5. This will give the group enough time to work out any scaling issues and/or flaws in each gear before assembling each gear into a ProE mechanism.

Figure 1

Figure 2

Diagram of Orrery Design

Calculations of Gear teeth, rations, and diameter

Calculations Cont. Showing % error

Calculations cont.

Week 3 Activity

2012-04-20T12:41:00.000-07:00

The group talked over the basic structure of the orrery and how each gear fits in with one another to control the whole mechanism. There were some difficulties understanding the particular gear ratios in the book and deciphering what was meant by the radius of each gear. The problem was knowing if the radius was measured to the bottom landing of the gear or if it was measured to the circular pitch. Further calculations this week will be done to verify what Rittenhouse interpreted the radius as.

The group also talked about making a final design that has custom metal gears that would be ordered instead of making plastic gears from the rapid prototyping machine. The only factor that would change this plan is the time constraint.

The following picture shows how the internal gear mechanism of this orrery will be constructed.
Note: The gear ratios of this orrery are not the exact ratios that the group will be using.

Source: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1938PA.....46..567B&db_key=AST&page_ind=4&data_type=GIF&type=SCREEN_VIEW&classic=YES

Design Proposal

2012-04-17T20:40:00.000-07:00

Project Overview

The goal of this project is to model the orrery system that can be found in the Rittenhouse Clock at Drexel University. An orrery is a mechanical system that models the motion of the planets. An orrery will be designed and printed using rapid prototyping that will mimic the orrery in the Rittenhouse Clock. The orrery model will be housed in a clear Plexiglas box that will allow people to observe how the gearing runs the planetary system. The new design will give insight into how the Rittenhouse Clock was constructed in the late 18^th century. Today there are only a few drawings and pictures that show how the Rittenhouse Clock functions. Also, if time allows, the time keeping function of the Rittenhouse Clock will also be designed and printed using rapid prototyping.

Design Constraints

The only constraint that exists in this project is that the orrery design must be able to fit into the Rittenhouse Clock. Since the Rittenhouse Clock cannot be opened up to find out the exact dimensions that the orrery must fit in, a clock of comparable size was measured and in order to fit in the comparable clock the orrery gear box must fit in a box with dimensions of 5 1/2'” x 12” x 15”.

These constraints require the orrery to be as compact and efficient as possible.

Pre-Existing Solutions

Although the Rittenhouse Clock has been around for more than two centuries, there are few texts that describe the design of the clock in great detail. For this project, the book “The Most Important Clock in America: The David Rittenhouse Astronomical Musical Clock at Drexel University by Ronald R. Hoppes” will be used for most of the referencing because it provides many of the gear ratios, time equations, and gear assemblies that make up the Rittenhouse Clock. The information was obtained from the observations made during the most recent restoration of the clock, in which the clock was taken apart, had its components cleaned or sometimes even modified, and reassembled so that it continued functioning. Since the main focus of this project will be the modeling of the orrery dial that is located at the top of the clock's frame, much of the observations found in the section that talks about the gear trains located behind the frame can be considered a pre-existing solution due to the fact that it presents the math involved in the Rittenhouse Clock orrery mechanism. The section of “The Most Important Clock in America” that talks about the orrery, there are several drawings of the mechanism and the gears used to make the orrery dial with extremely precision considering the clock was made in the 18^th century. The orrery shows the planet alignments of Mercury, Venus, Earth, Mars, Jupiter, and Saturn, which were the only planets visible to David Rittenhouse during the 18^th century. Even with the drawings in the book this project is a first because there are no existing models of how the mechanisms inside the Rittenhouse Clock work, which is why there is not much information on the subject.

Design Goal

At the end of the ten-week period the goal is to have a working model of the orrery dial in the Rittenhouse Clock that has been made using rapid prototyping, also to have a computer model of the orrery dial in Pro/Engineer. By achieving these goals, a better understanding of the clock will be obtained. To simulate how a function of the Rittenhouse Clock works, the computer model will use the information pertaining to the orrery in “The Most Important Clock in America: The David Rittenhouse Astronomical Musical Clock at Drexel University” by Ronald R. Hoppes. In the book, equations relating to the movement of the gears, as well as the traits of all the components that make up each function are given. Using this, a computer model can be made that simulates the Rittenhouse Clock’s orrery dial.

When dissembled, the Rittenhouse Clock showed signs of previous repair attempts, which could have altered the original design that Rittenhouse created. With that in mind, the model will be a first since there has been no recreation of the complex mechanisms inside the clock. Although the model will use the information gained from “The Most Important Clock in America” by Ronald R. Hoppes, this model will be unique because it will be the first virtual and maybe even the first physical model that simulates the mechanisms that make the Rittenhouse Clock so famous.

Project Deliverables

The project deliverables are a working orrery housed in a Plexiglas case which displays how the gears in the orrery function. Also a ten-minute presentation taking about the design process, overall project, and a demonstration of the orrery in action. Another deliverable, if time allows, is a model of the time keeping function as well.

Project Schedule

Wk #	Work to this point	Deliverables for next week
3	Design Proposal, read book	Research on clock/orrery, both book and outside research
4	Research complete, design started	Create final design sketch/photos, begin modeling with Pro/Engineer if possible
5	Design complete	Model parts in Pro/Engineer
6	Design complete, Pro/Engineer model started	Continue to model parts in Pro/Engineer and compile parts into an animation
7	Working animation of clock model	Submit rapid prototype model by end of class, refine animation
8	Working animation, printed parts	Construct and test prototype, resubmit if necessary
9	Working prototype and computer model	Create PowerPoint presentation and construct prototype for demonstration
10	Presentation	-

Project Budget

To fulfill the task of modeling the Rittenhouse Clock’s orrery dial, a few items will need to be purchased. The two items that need to be purchased are a nine-volt battery to power a 3-volt DC motor. This motor will drive the gears of the assembly.

Cost

9-volt batteries~$7.00

3 Volt DC Motor~$3.80

Approximate Total Cost~$10.80

References

[1] R.Hoppes, Most Important Clock in America: The David Rittenhouse Astronomical Musical Clock at Drexel University, Scitech Book News, 2009, pp. 30-32.

Why was this project chosen?

2012-04-11T13:54:00.000-07:00

Why was this project was chosen?

The group consist mostly of mechanical engineering majors, this project consists mainly of mechanical engineering principles. Also, the history behind the clock is one of a kind. It was built in 1773 by a man named David Rittenhouse who was a renowned American astronomer, inventor, clockmaker, and mathematician. This clock is so unique not only because it is the only one of its kind and it belongs to Drexel, but because of all the functions it can perform simultaneously. The clock itself has the ability to tell the time, the date, the phases of the moon, the position of the sun and the moon, the zodiac signs, and the part that we find the most interesting, the ability to model planetary movement with respect to the sun. The shear complexity of the clock is one of its biggest draws. The goal of this project is to replicate a piece of history that is significant to Drexel, and to ultimately apply engineering principles in order to decipher, model, and create one of the most complex clocks in the world.

2012-04-10T14:27:00.002-07:00

Pictures of the clock

The Rittenhouse Astronomical Musical Clock

Clock Face