I was looking at a VEX Robot Speed Chart and noticed that some speeds were considered to be in the red or yellow zone. What does this mean? For example, if I gear my robot to have the the driving gear be 84T and the driven be 12T, then my robot speed is 8.41-ft/sec., which is considered to be in the ‘Red Zone.’ What does this mean? My motor has a shaft RPM of 100, which gets divided by the gear reduction of 12/84 or 0.14, to give me a 2.75-in. wheel speed of 8.41-ft/sec. Why is this considered red? Is this due to the load on the wheel wanting to draw too much amperage on the motor? What exactly is going on at this high speed? I realize the motor has a certain Power rating, and that Power = Torque x Speed. Please explain in detail if possible! Thanks!

RPM = 100 = RPS*60
RPS = 1.67
1.67*0.14=0.23

On drive wheel, .23 rotations per second

.23

*2.75*pi=1.987

I think you confused rotations per minute and rotations per second, because as it stands you are only going about 1/6 of a foot per second

Thanks for responding! Yes, I misprinted RPM. I meant RPS. But regardless, what about my question about the red and yellow zone? Do you have a very detailed answer, in terms of what’s going on with the motor in terms of Torque, Speed, and gear ratio as related to the current that it’s drawing to go into the yellow and red zone?

I’m not 100% sure on this, but I believe the yellow and red zones are rough indicators of what is “safe” to gear the motor to. When the chart indicates a particular gearing is in the red zone, it is saying that you have a lot of speed and not much torque in that gear ratio, and you may run into problems as a result. If you do that 1:7 over-gear, you’ll have a very fast mechanism with very little torque, so under any significant load it could overheat the motor or pop a breaker.