Electric Bikes - Chromoly for front motor?
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Question for all the knowledgeable electric bikers here -
Should a chromoly fork be strong enough to use with a front drive motor?
04-23-10, 01:32 PM
04-23-10, 06:25 PM
Depends on how safety conscious you are. There's a long-standing debate on the Endless Sphere forums on whether any hub motor is safe. Even hub motor aficionados there admit that a hub motor mounted on the rear wheel is safer. Why, even the drop outs on steel forks can fail after exposure to the torque of a hub motor mounted in the front wheel and there are reported occurrences of that happening in different threads on Endless Sphere. Regardless of whether you get a hub motor that's laced into a front or rear wheel, you need torque arms. Good luck. Be safe.
04-23-10, 06:45 PM
Well, you could always install torque arms, they are cheaper than the alternative.
So long as you don't use regen I see no risks...
04-23-10, 07:03 PM
I think it's pretty safe. I have two front hub motors. One on steel fork and one on a chromoly fork. The chromoly one has a hub motor that is doing about 2000 w of power and not having any trouble. If you want to be super safe, get a rear hub motor or if you really want a front one, get a 20 amp controller and use about 48v of batteries . The power would be about 48 x 20 = about 960 watts which is half of what I'm using. That'd be less torque but probably safer. I use a 35 amp controller and I have two torque arms on it. I've gotten my bike up to 37 mph. It's pretty safe I think.
04-23-10, 07:25 PM
One on steel fork and one on a chromoly fork.
Chromoly is steel - just a particular kind of steel. Steel is an alloy of iron with carbon and small amounts of other metals. Chromoly is steel where the 'other metals' are chromium and molybdenum.
But the original question is missing the main point - you can build a strong enough fork out of lots of different materials and you can also build a weak fork out of those same materials. A fork that was designed to be as light as possible while just being adequate for the forces encountered during normal cycle use may well have problems when you add a high-torque hub motor - and that'll be the case no matter what material is used.
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