so I have a friend in our club that claims that last year he built a 35 pound bot, stuck it on direct on 4 inch wheels, and it still moved. However, by my calculations he didn’t have enough torque:

14.76(4)/2= 29.52 pounds.

4 is the number of motors, 14.76 inch pounds is the stall torque, and 2 in is the radius of the wheels.

So what I’m asking is what am I doing wrong in my calculations? Or what other force is present that gives him the five pounds?

he could’ve used an external gear ratio like a 1:7.

He didn’t though, he had it on direct.

The fact that you have a 35 pound robot doesn’t mean that you need 35 pounds of “force” to move the robot.

I presume you are considering only the case of the robot rolling along the field and not being lifted. The calculations you did are somewhat like what you would consider if you were trying to lift the robot straight up.

Merely rolling on the field would require power to overcome the forces of friction in the drive system, such as what exists at the bearings, the amount the wheels compress as they rotate, and the amount the field tiles compress as they are being driven over. If the robot were on something like an air hockey table and had suitable feet, almost the only force needed to move it would be the force needed to accelerate it, F=ma. At 35 pounds, I’m surprised the student’s axles didn’t bend really badly, though.