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BrianG · 10.18.2011, 11:18 AM

FWIW, I tried a 2 speed setup in an Ofna Ultra GTP and didn't like it. The tires would break loose when it shifted and control was difficult to say the least. Electric motors simply produce too much torque. You can try to minimize the difference in rpms when it shifts by narrowing the ratio between 1st and 2nd gears (motor rpms don't drop as much), but I still had a really hard time keeping the tires from spinning.

Personally, simply using a large motor and gearing up high enough to get your desired speed would be the way to go. However, when geared very high, startups can be rough with sensorless systems (not enough motor revs per inch of vehicle movement for the ESC to get a good feedback for commutation). It would be nice if there were large sensored motors available, and when coupled with a sensored ESC (like a Tekin RX8), startups are much smoother and controllable, yet can still spin at high rpms.

	(#17)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	10.18.2011, 11:18 AM FWIW, I tried a 2 speed setup in an Ofna Ultra GTP and didn't like it. The tires would break loose when it shifted and control was difficult to say the least. Electric motors simply produce too much torque. You can try to minimize the difference in rpms when it shifts by narrowing the ratio between 1st and 2nd gears (motor rpms don't drop as much), but I still had a really hard time keeping the tires from spinning. Personally, simply using a large motor and gearing up high enough to get your desired speed would be the way to go. However, when geared very high, startups can be rough with sensorless systems (not enough motor revs per inch of vehicle movement for the ESC to get a good feedback for commutation). It would be nice if there were large sensored motors available, and when coupled with a sensored ESC (like a Tekin RX8), startups are much smoother and controllable, yet can still spin at high rpms.