pic: Variable Diameter Wheels? In Vex?! - pic 3

[artdutra04]

Originally Posted by yongkimleng

wow that looks cool... done it in solidworks I guess?
I'm wondering where u get more templates for vex parts. I have used those from their website.. but many parts arent available for CAD such as omniwheels, wheels and the quarter-of-a-circle steel piece you used? wonder if you manually did them..

Nope, I used Inventor 7, which is the only CAD software I have on my home computer.

Everything that I could not download I had to model myself. Most of the Vex stuff is not hard to model, especially if you have a decent set of calipers. (Even then, all the Vex parts use a repeating pattern for their holes and the like, so it becomes easy to model everything once you've done a few.)

Originally Posted by colin340

MAYBE YOU SHOULD MOVE THE FLAT SPOT TO THE HIGH TORQUE DIAMETER

I did consider doing that, but in order to do that I would have to increase the diameter of the wheel. Also, the flat spot really is not one-hundred percent necessary, as traction comes from the friction something has, which is directly affected by the amount of force pushing down upon it. So point contact would normally be fine. This is why steel railroad wheels on steel tracks can pull huge trains weighing thousands of tons, because there is so much force (mass of locomotive) pushing down on the drive wheels.

The only reason why I put the flat spot there, was to possible included recessed roughtop or wedgetop traction material, just to experiment with a "normal wheel" mode (the angles of the wheels do not change), and then the "variable diameter wheel mode" (the angle changes dynamically).