[Gui Cavalcanti]

Thanks to everyone that responded so far, I'm learning a lot (everything from rolling friction to why people's robots didn't work as they intended... ;-) )

Lloyd, can you walk through a physics problem combining all of these concepts into one? This is what I think it would look like:

First, find your place on the motor torque/efficiency/speed chart. Then, re-calculate the torque by multiplying it times the gear ratios in your drive train. Then, convert the radius of your wheel into whatever units of length your torque is in (ft-lbs, oz-in, n-m) and divide torque by the covnerted length. Now you have the torque of your wheel.

Now lets see if we can cheat with the units a little bit... you would then proceed to say (if you used the metric newton-meter) "For every meter I move, I can push with such and such newtons of force". You would then take that and subtract the losses to rolling friction, and would get a pretty good estimate of the pushing force of your robot.

To see if you can push another robot, you would take the force you have available for pushing and compare to either their "static" friction, if they are standing still and not pushing their motors, or you would do the same calculations for their drive train and compare the pushing forces - the robots would move in the direction of whoever has the greater pushing force, and the force of them moving in that direction would be equal to the difference of forces in their drive trains.

Yes, no, maybe?

I did take a year of physics, but right now I'm flying by ear.