I want to add a motor to my dahon folding bike and tie it in with my chain. I am trying to find a motor that is about 4" thick, 48-72 volts and 500-700 watts that weighs about 6 pounds. This is difficult. Yet, a year or so ago I saw a post on another forum from a guy that was using a motor that was designed to be used to make rc airplanes fly - was 2,000 watts and 72 volts (or so) that only weighed 3 pounds I think it was called an outrunner, similar to this: http://aircraft-world.com/shopexd.asp?id=4544.
What gives? Yes, it is a high rpm motor and expensive, but the low weight would make it worthwhile, if it will work.
Bottom line is, how do I find a small powerful motor to meet the specs of my application? What search words do I put into google?
What you describe wanting resembles the cyclone kits on ebay.
Be the pack leader.
36 volt sla schwinn beach cruiser
36 volt lifepo4 mongoose mtb
24 volt sla + nicad EV Global
If you want it to fold correctly the motor you want wont work. I suggest either going a hub motor route and over volt it to compensate for the loss of speed due to wheels size... Got to have good steel drop outs and torque arms espcially on small folders. Bright side is it will have a lot of torque. Cyclones work well but they are a bit clunky and require some modification which may require some custom fabrication. It will interfer with the folding of the bike also. On smaller folding bike you want to keep the weight down or you might exceed the maximum weight on the bike and break welds and frame flex so over all if you dont want it to fold and keep it light i would choose a cyclone kit at 36-48v with a lithium pack. If you go hub motor it will go it will go 15-20mph maybe......@48v any faster you gotta add move voltage which increases your weight.