Hi.
I am preparing for Tug of war lessons. I built basebot myself and found that it motors are too powerful: if I use simple base bot, it can pull quite heavy object and then wheels begin to slip. If I add more weight to basebot, it can pull even more, but at the end wheels begin to slip again. Whatever I am doing - either basebot pull or wheels slip. At the end I decided to stop experiments, because additional weight on top of basebot was too high (kilograms).
I tried on different surfaces - same observation.
Is it expected? I would expect that base bot shouldn’t be able to pull so easily and then kids should use gears to increase the torque. At present, it just doesn’t make sense - the problem is slipping wheels.
Any ideas? What I didn’t take into account?
Hi @Dmitrii_Filippov Welcome to the community. What you’re seeing is expected, and it’s actually a great lesson in itself.
A robot’s pull is limited by two things: how much torque the motors have, and how much grip the wheels have. Grip depends on the weight pressing down on the drive wheels. The IQ motors are strong enough that on most surfaces the wheels lose grip before the motors stall. Once the wheels are slipping, adding gear reduction won’t help, because the robot already has more torque than the tires can use.
If you want students to see the effect of gearing, set things up so the motors run out of strength before the tires lose grip. Lowering the motor’s max torque in code is one way to do that.
Your weight experiments are worth keeping, too. Ask students why adding weight helped and then stopped helping. That leads right into friction and the idea that pulling force can’t exceed what the tires can grip.
