So I have been trying to work out an equation for the maximum weight a robot can hold. Does this look right?
https://drive.google.com/file/d/0B8z...ew?usp=sharing
T is torque of one motor, Mn is number of motors on one side, Wn is number of wheels on one side, Wr is wheel radius, Fs is static friction, rps is revolutions per second, m is mass.
The robot is a tank drive, with chains linking all wheels on each side to the motors.