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Old 03-01-2010, 04:03 PM
42blue15 42blue15 is offline
Motorized Bicycle Elite Member
Join Date: Sep 2008
Location: St Louis metro, USA
Posts: 135
Default Re: I need some input on this Frakenstein bike project

Originally Posted by View Post
... Ok well have you seen those grey hound 2.5 HP engines from harbor freight? well what if you hooked up a car alternator to it and the used the power from that alternator to power a hub motor? would that work? has any body tried this? Califorina laws say that the motor powering the bike can be no bigger then 2HP, but the motor would only act as a power supply for the 500w or 1000w hub motor.
It has been suggested before, by myself and at least a couple other people in the last couple years. I don't know that anybody (around here) has done it though.

One problem I found was that it would be fairly expensive, as you'd need both a gas engine and a motor+generator setup. A decent brand-name engine is going to cost at least $300 or so for a 4-stroke, and (at the time) I priced a 500W hub motor + generator at around $500. Car alternators aren't that expensive, but I don't know that they'd work easily, using a regulator and all. I was looking at DC generators.

It would be fairly simple--you wouldn't need a (electric motor) controller at all, unless you also had batteries to run the electric motor from. I liked the idea because I figured the electric portion of the drivetrain would provide a CVT-style action, rather like a diesel-electric locomotive. The main complaint I have with my first (Golden Eagle) bike is that it is lousy at climbing any kind of hill.

If the dual-engine setup would be any more California-legal than a plain gas engine I don't know. Both EPA and CARB regulations cover ALL engines, and usually treat vehicle engines different from utility engines. At the least you would want to use a CARB-legal engine, and even then it still may not save you.
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