Python with 'numpy' (numerical python) and 'matplotlib' is a friendly, free alternative to Matlab with similar commands for generating plots, working with matrices etc. If you have a Mac, some version of Python is already installed.

Canopy Python is a nicely bundled package of Python scientific packages. Free for academic use: https://www.enthought.com/store/
Sypder https://code.google.com/p/spyderlib/ is a another nice lightweight development environment.

4.2 Dynamic simulation programs

Working Model 2D has been used for years by ME112 students. We have several licenses for the class. Unfortunately, it was written for Windows 2000, and is getting increasingly finicky to run on modern operating systems.

If you have a Windows computer you can try installing it from one the CDs. This version wants the CD in your hard drive to run, but you can instead create an ISO image of the CD and mount that. See one of ME112 Teaching Staff about borrowing the CD and setting this up.
If you have a new Mac running Yosemite, there is a new Wineskin wrapped stand-alone application. As with Matlab, you need to have X11 or Xquartz activated on your Mac (look in Applications/utilities; download if needed). This pretty much works except that I've had trouble getting simulations to Stop. I've tried everything from clicking Stop to using Control-C, Escape, etc. The only solution seems to be to set World/Pause Control... in Working Model to enforce a timeout Pause after some period of time or a certain number of frames. Other than that it, seems to work fine :-) The first time you launch it, it will ask for the last word on certain page in the manual, which you will have to get from one of the TAs in the ME112 project room.
If you have an older Macintosh running Snow Leopard (10.6.8) or earlier, there is a older wrapped app version created using Wine. It runs well as long as you have X Windows (Utilities) installed. Download the zip file, unzip it and put anywhere.It's a stand-alone application. The first time you launch it, it will ask for the last word on certain page in the manual, which you will have to get from one of the TAs in the ME112 project room.

Algodoo is a modern alternative to Working Model and is free for Windows, Mac and Linux. It has somewhat less ability to customize the properties of objects and surfaces, but you can still build interesting simulations. The handling of collisions also seems a bit less tunable than in Working Model; as a result dynamic simulations sometims seem a bit "jumpy."

Nice example comparing the Klann and Theo Jansen linkages in Phun (older version of Algodoo)
Page comparing the linkages: http://www.mechanicalspider.com/comparison.html

5. Curated List of Helpful Links

5.1 Gears, Involute Profiles, Transmissions

Involute kinematics: http://en.wikipedia.org/wiki/Involute -- equivalent to what you get deriving from first principles.
Leonhard Euler and the involute gear: http://en.wikipedia.org/wiki/Involute_gear
Involute gear animation from How Stuff Works -- good visualization
Primitive peg gear for comparison, notice the variable rotation speed.
Planetary gears from How Stuff Works
How gears are made from How Stuff Works
Useful page on gears, gear terminology etc. from Susan Finger at CMU
- In particular figure 7.4 for gear face width, addendum, pitch circle, etc.
Make your own Lego-compatible gear using Solid Works and lasercutter
- A technique for getting more accurate involutes in Solidworks (or any CAD package): Involutes in CAD

5.2 Fatigue

Good notes page from Shawn Kelly at Virginia Tech. on dislocations in materials leading to fatigue in gears and other components.
Examples of failures in metal components
Wikipedia on fatigue http://en.wikipedia.org/wiki/Fatigue
Cool animations of plastic strain and dislocations (leading to fatigue crack growth): http://www.kochmann.caltech.edu/research_animations.html

5.3 Motors

Useful wiki page from Northwestern on brushed DC motor theory
If looking for motors you can buy, see: Motors under Final Project Materials

5.4 Linkages

Main.ME112LinkageLinks

Useful 'atlas' approach to searching for a mechanism with desired coupler curve properties.
A handy 4-bar simulatior on which you can adjust link lengths and see whether Grashof criterion is satisfied This one is also handy to drag some of the joints and coupler around and see the effect Note, if you set the velocity to zero to stop it, you can drag the coupler point location and adjust dimensions at will. Then reset the velocity to get it moving again.
OpenEdX videos on 4-bar linkage analysis and synthesis posted
Brock Engineering summary of useful linkage types, with simulations
Cool mechanical spider leg linkage Also called Klann linkage
Good chapter on different types of linkages from FUNdaMENTALS of Design by Alex Slocum at MIT.
An interesting 6 bar
- This is part of a more general library of mechanism simulations
Nice simulator for Theo Jansen walking mechanism
- Theo Jansen's very cool Strandbeests (presented at TED)
- Strandbeest website & nice video of latest versions
Disney Animatronics linkage design has recently been in the news. They mostly used a "geared 5 bar" design and vary the parameters to match a desired coupler curve to a family of designs:
- tutorial video on Youtube
- article in Machine Design
- paper presented at ACM Siggraph 2013 - this is mainly on the search and optimization algorithms
- The Disney software is not publicly available, but some other basic tools are: geared 5 bar simulation
Paddle motion linkage patent ;-)

5.5 Cams and other Mechanisms

Youtube channel with over 1000 3D animations on cool mechanisms
Cute amateur mechanisms page
- Common problems and how to fix them
Example of a 3D cam - perhaps for manufacturing equipment
Small library of mechanisms for examples for examples
Extensive library of 507 movements for mechanism inspiration

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Page last modified on March 15, 2017, at 01:15 PM