[Retired Starman]

After having spent 26 years running a planetarium which contained dozens of solid silver slip-rings, I would rather gnaw off my right arm than try to use slip-rings on a FIRST robot. Those things are nothing but trouble!

You mostly likely will trade the solution to one problem for about a dozen other problems.

If you insist on going the slip-ring route, consider solutions to the following:
1) Dirt. It gets ground into your rings with unpredictable performance results.
2) Design rings with multiple brushes, to keep contact if one hits a clot of dirt.
3) Shield against nuts, screws, washers, bolts, shavings, etc. etc. bouncing up from the carpet. Getting metallic junk in your high-current slip-rings can have SPECTACULAR results.
4) Allow for wear. With the pressure of the brushes, some materials which are good conductors won't last long under use.
5) A damaged slip-ring may be very difficult to replace between game matches.

Sounds like a good engineering project!

Dr. Bob