Quote:
Originally posted by M. Krass
Well, thanks 
What I've settled on, I think, is two pieces of 3/8" polycarbonate cut to a similar pattern and bolted together to form a 3/4" wide wheel. Then, we can attach belting to its circumference, or whatever other material suits our needs.
I'll post a screen shot of what I have in mind this evening. I decided to do it this way because it can be made from sheet stock, rather than looking for enormous round stock that is still kit legal. They're also reasonably light (.5 lbs each), which is also good - especially when there may be 10. ( )
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The bot is only as strong as the strongest material.
With that stated, how are you going to attach the polycarbonate wheel to your shaft? Keyway? Setscrew?
Although polycarb has a very high impact strength, I am unfamiliar with its tolerance of high forces for long periods (tensile strength). If a keyway is used, will it hold as the shaft rotates and high forces are created? This is one of the things you will need to figure out.
This webpage might help you to evaluate this.
http://homepages.which.net/~paul.hil...rialsBody.html -table form, easy to read, but you may have to look up some terms
http://students.villanova.edu/robotics/howto.htm -more pros/cons
http://www.matweb.com/ -material specifications for pros
If you look on the first site, Polycarbonate has a maximum working temperature of 138 degrees C before it loses much of its tensile strength. Will friction approach this temperature, allowing your keyways to melt through the polycarb like butter? You'll have to find this out. It's better to figure it out now, then to figure it out when your shafts are rotating but your bot is going nowhere during the match.
One problem with 10 wheels is turning the robot. One thing you could do is like we did last year. We used pneumatics to lower a caster that raised the front wheels up. Granted, you will be able to turn mor accurately if the caster is on the rear wheels, you might want to try something like this. It used a wedge design to gain strength to lift the 130lb bot with a small 3/4" cylinder capable of only lifting a maximum of 30lbs. This is the only picture available, but if you look at the preship video, or the regionals video, there are better shots of the robots systems.
Drive picture Team 93 website