Electric Bike - Now With Chain-snapping Power!

Last weekend I decided to put a big electric motor I have onto my bike. I had all the parts already from various projects. The only parts I needed to buy were the U-bolts. The motor is a 36V PMDC motor, rated at 3.0HP ~= 2.2kW. No, I don't know where to get another one, or even who the manufacturer is- the name is scratched off on the nameplate. Control is simple on/off control with a White-Rodgers contactor. In the first beta build, I ran it at 12v because I didn't want to die. That proved to be boring enough that I stepped it up to 24v immediately, which worked okay on half-dead batteries but threw and snapped chains incessantly on a full charge, making it unridable. Some of the pictures show a LiPo on the bike- when the batteries were wired for 12v, I needed some extra voltage to throw the 24v control coil. It is plenty quick at 24v, but with this design the pedals spin just as fast as you're going. Imagine pedalling fast enough to go 25MPH in the lowest gear on your bike. That's how fast the pedals are spinning- keep your legs out the the way. This weekend, I will take the ubermotor off and see about putting on a more reasonable 400W Kollmorgen brushless. That should be less suicidal. However, I want to drive the rear wheel directly, so it will be more complex. Probably won't get completed immediately, as I know I don't have the right rear sprocket. Please, feel free to ask questions in the comments.