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Originally Posted by rc_cola1323
Sdcantrell, I was not sure if UHMW was strong enough for the application. What other materials are strong enough for the application and lighter than aluminum? Plastics?? (McMaster Carr #'s Help)
Thanks everyone. 
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You have to stop and separate the material strength and the shape/design of the wheel. You could make wheel designs where probably even glass is strong enough, and you can make wheel designs where only extremely strong steels and titaniums would be strong enough.
It's not a simple matter of saying, okay, we have a wheel designed, lets just make it out of 7068. That may work in this case, but is extreme overkill. In the workforce, if you immediately jumped to a more expensive material (compare the cost of 6061 vs 7068) , you'd probably be out of a job really quick.
I think, rather than trying to pick a material to suit this specific wheel design. Lets start over with an entirely new wheel design. First, pick the material, as it's much easier to design around a known material rather than designing a part and going "oh, I guess material XYXY" would be strong enough (and if it is, it might not be the most efficient way).
So, lets make a wheel. A real efficient design, not much heavier than it needs to be, not much more expensive than it needs to be, not more difficult to make than it needs to be (much leaves room for safety).
Okay, so in this new wheel design lets imagine the kind of stresses put on the wheel. First, you have the weight of the robot pushing from the point of contact to the hub. Second, you have the torque being transferred from the hub to the outer surface of the wheel. Finally, let's just lump in all the random forces that will happen in a match; wheel getting hit from the side, robot being twisted which would twist the wheel as well, and so on.
Now, in an ideal world you'd have an engineer on your team would know how to reasonably approximate these forces, and use a method of testing the wheel design to make sure it can withstand them (plus a safety factor). Now, you can do what I did in high school and just run Cosmos on it; but when you get older you'll realize that yeah, I got cosmos to run and give me an answer and a nice purdy graph, but in the end I had *No Idea* what I was doing really, and have no idea if those answers were reliable. Now that I've had classes that have covered some of those concepts, it really shows me how ignorant I was.
^If you have one of those engineers, go ask for his help now, and maybe stop reading the rest of this post.
So, assuming you don't we have to go assumptions; luckily there is a huge sample size of wheels that have been tested through a season for you to look at (as most robots have been wheeled pretty much since FIRST started). Look at some of the more efficient designs people have used and try to analyze what they did. Was the shape efficient at transferring the robots weight from hub to floor? Was it efficient at transferring the torque? What is it efficient at surviving the rigors of a competition?
The best example I can think of is 254/968 the past two years. For 2008, they weren't any fancy material, just plain 'ol 6061 and they worked.
Sooooooooooooooooooo...... Now that you understand what the wheel has to survive, and what has/hasn't worked and how efficient it was/wasn't; Make us an improved wheel.
You've obviously proven you have the Solidworks Skills (which can be quite difficult for some people), now lets get those design skills developed real well. You've got potential, but you've got to stop and think about how you can realize it.