[Specialagentjim]

Originally posted by Ken L
The whole point of shifting gear ratio in a drive train is to trade off between speed and torque. You have constant power from the motor, and since Power = speed times force, or angular velocity times torque, you get a combinations of speed and force from the motors depending your wheel size and your gear ratio.

By switching to a different ratio, you slow down your robot but you get more pushing force, or you speed up your robot but you have weaker pushing force. Controlling it in software only limit how much power you have from the motor, and thus making the motor weaker when you slow it down, instead of trading off speed for torque.

Few ways I've seen for shifting gear ratio: Drill motor's transmission using a servo or pneumatic cylinder, that's the most simple way for a team to shift gear ratio.

Have two sets of wheels with different ratio, and lower one set at a time depending what ratio you want. You can shift on the fly that way.

Custom gear box like team 45 and 60 last year, or the 67 bot at 2001, where you use pneumatics to move gears outside the drill transmission to from one ratio to another ratio. This is much more complicated, and if your team doesn't already know how to do this, I wouldn't start right with only a few weeks left in the 6 weeks.

Or, you can add more motors to your drive system, and get more mechanical power out of it that way. You have more overall power, and thus more torque and speed at the same time.

Very nice post!