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

[artdutra04]

loading photo ...

[rangersteve]

Thats very cool looking and good inventor work. yet, i wonder about the practicality of it. What sort of application do you plan for this to be effective for? you would have nearly no contact between the wheel and the ground depending on the surface. Small imperfections on the surface or the wheels could cause big problems in movement. I guess what the wheels are made out of will have a big effect on the practicality of it. I hope it works for you because it really does look good.

[sanddrag]

I wonder if you could do them out of wood or plastic by hand on a wood lathe.

[Hieb]

I started looking into this same idea last year after a discussion here about variable diameter wheels. Unfortunately the other mentors on my team felt it was beyond our capabilities, so I haven't had the opportunity to test it yet.

As far as making the wheels, my plan was to make a wheel model out of clay, then create a rubber mold and use liquid casting plastic for the wheels, with a section of axle embedded in the plastic. For the surface, wedge shaped sections of conveyor belting (the same type currently used by many teams) could be attached to the surface.

[Daniel_LaFleur]

Originally Posted by artdutra04

Thread created automatically to discuss this image in CD-Media.

Really nice.

Now all you need to do is figure out how to change the wheel pitch according to the wheel speed and you will have created a CVT without belts.

Really, really nice.

[Alex Cormier]

So, you bringing the finished product to Ruckus?

[Stu Bloom]

WOW Art ... FANTASTIC concept. I really like it. Please be sure to keep us posted when you start testing ...

[Greg Needel]

there is more discussion from last year on this topic available here http://www.chiefdelphi.com/forums/sh...ad.php?t=40770

[artdutra04]

Originally Posted by Alex Cormier

So, you bringing the finished product to Ruckus?

If everything goes as planned, it will be one of the Vex robots I'll bring.

[colin340]

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

[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..

[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).

[Hieb]

Originally Posted by artdutra04

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).

Also consider the flattened end of the wheel (opposite the "normal wheel" section) for a very high traction surface. In a competition where you want to stay in place and not be moved around easily, you turn your wheels 90 degrees, stop the motors, and turn your 'bot into a very nice little coffee table While the others are draining their batteries in a pushing match, you'd could be focusing on an entirely different aspect of the game.

[colin340]

sorry i did not mean to yell some time i just hit caps lock