Hm, On my way home from the store I had this flash of inspiration. It would be pretty easy to design a fairly generic electric bicycle conversion which could be a) documented as open source, b) designed to use low end parts and be real cheap to build.
I just checked on electricScooterParts.com and saw 24v200w controller for $30 or so, matching motor for $30 or so, hall effect throttle for $20 or so, 24v battery set for $70, etc ..
The individual parts seem cheap enough but you add it up and the total is at least $300. For a comparison I went on ebay to check electric bicycle conversion kits and found a 600w wilderness energy BL-36 kit for $375. That's including batteries and a 50A controller. The conversion would be a lot simpler to perform than the hack job I was pondering and give better performance.
Thoughts?
I use scooter motors on my bikes so I can use the bicycle gears to help. I think the hub motors are very limited in power below 1000 watts. When you get above 1000 watts then they seem to perform quit well but then the range suffers compared to a 400 to 600 watt motor. The reason I like the scooter motor is I can use about a 500 watt motor which gives good range and the gears gives me the advantage of both power and speed. The real problem with these "can" style motors is the mounting. I have figured a good way to mount mine but then they stick out from the side of the bike. I have a pair of saddle bags which I plan to use to hide the motor and batteries. The bike I really like is the Merida which uses a bottom bracket drive gearbox which allows you to motor, peddle, or both, while using the bicycle gears to drive the rear wheel. I have not found a hill I can not climb with just the 400 watt motor and top speed is just above 23 MPH which is fast enough for this bike.
I would say that is you want power it is easier to get from a bottom bracket motor and if you speed then a large over voltage hub motor may be the best choice. IMO the best of both worlds is to use the gears to help achieve the desired results.