I have a wiper motor from some car or van that has a shaft on it. When I apply 12 volts to it, with no load on it, it seems to spin at about 125 RPMs. I vaguely remember that when I load it, it can draw up to about 10 amps (10A). I suspect it can output maybe 100 watts of power or so. It also has 3 mounting holes. I suspect someone mechanically inclined could perhaps connect this with 1:1 ratio to the crank/chainring assembly. The 125 RPMs would likely drop under load but under low load it should maintain close to that I would think. It would be fun to try it with some type of freewheel mechanism or centrifugal clutch so when the motor is turned off, it would not load the cranks. Since the rotational speed mimics a normal cadence (probably will drop to 60 to 100 RPMs under load), it can possibly be used to run a multispeed bike and if the rider pedals too, they would help each other out (like 100 watt motor plus 100 watt rider = 200 watts total).
So has anyone ever tried this and do you think it could work and if you think so, do you think it would work well? What about pitfalls?
UPDATE: I tried the motor with a 12V battery and a short crescent wrench and I was able to hold the wrench still but there was a fair amount of tug on it, meaning it might be ok as a helper motor but not strong enough to move the bike on its own. It would be interesting to see if after getting the bike going say 10 MPH, if this motor would at maintain that speed or at least help the bike to coast down longer.
Also since it spins at about 125 RPMs, it can be geared down even more such as thru a 16T drive sprocket and a 20T driven sprocket which is a a 4:5 reduction so then about 100 RPMs, giving it more torque. I think if this motor spun at half the speed, it would be harder for me to hold that wrench still. Maybe some other wiper motors spin slower like 60-100 RPMs.