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Remember that teaser pic I released a few weeks ago? Well here is the idea I was really working on: variable diameter wheels. This is what happens when you try to combine the TechnoKats ball-drive and a CVT transmission into the same robot. 
This concept relies on the fact that a sphere, if rotated along an axis, has an infinitely variable diameter, depending on where it hits the ground. So at the "equator" of the sphere, it has the largest diameter. But if you could tip the sphere (think of how the Earth wobbles about its axis), then the diameter of where the sphere would make contact with the ground would be smaller. (Earth example, think of the earth rolling along the 60° latitude).
Also, one may notice the flat spot along the largest diameter. This is because you can assume that you will travel the most in this "high-diamter", so you can put traction material here. But the rest of the wheel has a constant radius of 4". The wheels themselves have a maximum diamater of 3", and a minimum diameter of 1/2".
The pivot point where the whole side assembly would rotate along is the exact centerpoint of the constant radius of the wheel. This is so the main chasis of the robot would always stay parallel and the same height above the ground. (The variable diameter wheels would just slip sideways.)
At this point, I expect to build a working model of this in the coming month(s), and I've been exploring two different options for creating the wheels. The first option would be to use 3D rapid-prototyping printed wheels. The latter would be to machine an aluminum cast, and pour urethane molds of the wheels. Both wheels would utilize 3D printed thrust bearings where they make contact with the Vex chassis rail.
This picture of of a sample chassis with the wheels in high-diameter "gear".
I also had to model a bunch of the Vex metal pieces myself, because I only have Inventor 7 on my home computer, and there is only a limited number of parts at vexcad.com in STEP format...
Some people may remember an this thread from here on ChiefDelphi about variable-diameter wheels from last year. The funny thing is that I had thought up the same idea about a week or two prior to that thread, which is why I refrained from posting there. 
Discussion
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07-09-2006 20:35
doukjin
Re: pic: Variable Diameter Wheels? In Vex?! - pic 1
very nice
i have a few questions
what CAD software did you use for this?
did you make the parts [motor, gear, etc] yourself?
if not, where'd you get them?
yeah i'm interested in CADing with VEX so if you could reply soon that'd b great
07-09-2006 20:53
SamC
Re: pic: Variable Diameter Wheels? In Vex?! - pic 1
If you read this thread he says he used INventor 7. And on vexlabs thier is a CAD section with some already made parts in certain formats. But on vexfan forums thier is a whole CAD forum section aswell. And also on vexforum thier is a few different VEX CAD disscussions! good-luck!
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