ultra quick bike conversion

[Bill in Houston]

I have sort of wondered if you could avoid the controller, and just have an on/off. In a high enough gear, the starting shock would not be too much...

[MetroMPG]

But the current draw would be big.

One of the good things about a controller aside from the smooth, smooth goodness, is it protects the motor, wiring & battery from excessively big amps.

Of course if you instrumented the thing with an ammeter and did a little bit of testing to learn what gear/speed/grade combos work without heating up the components too much, AND you keep an eye on the meter, a simple switch would be OK.

[Bill in Houston]

Ah, yeah, I tend to forget that electric motors will happily, peacefully destroy themselves if you ask too much of them.

[MetroMPG]

Then again, you could also just put a properly sized fuse or circuit breaker in there with the switch. That'd protect the motor without a controller. (Should be a fuse in there anyway so if the controller fails, you still have motor/circuit protection).