So what are the kinds of drive systems on an electric bicycle?
http://visforvoltage.org/forum/7372-why-struggle-complicated-e-bike-kits .. talks about a GoPed designed friction drive system (http://www.goped.com/Products/GoBike/default.asp)
The drive systems I know of are: a) friction drive on front wheel, b) friction drive on rear wheel, c) hub motor in rear wheel, d) hub motor in front wheel, e) chain (or belt) drive to rear wheel, f) chain/belt to front wheel, g) trailer with its own motor pushing the bike ... any others?
And, uh, okay, if you're nutso enough you could mount a rocket engine ... but that's not gonna be electric so we'll ignore it.
The Electric Bicycle History shows patents for all those kinds of e-bicycles going back a hundred years. The earliest patent I saw was for a hub motor, in the 1890's. Friction drive systems go back to the same era.
BTW - my first electric bicycle, bought in 1995, had a friction drive. It was a ZAP DX kit. I daresay the GoPed kit is better designed than the ZAP DX kit ... One thing I've always heard about friction drives are they don't work when the wheel is wet. Something about friction not working too well when things are wet.
Someone on another forum had the video for a jet engine mounted on the rear.
But electric rocket engines are all the rage! Really. Anything else rocket is kind of out. Too inefficient, cannot carry enough fuel. The secret seems to be to eject very little mass, but close to the speed of light. Probably does not work too well inside a planets atmosphere, though!
But if you want real range, interstellar range, electric rockets are the way to go!
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There is always a way if there is no other way!
Or lithium crystal fueled warp drive. "Beam me up Scottie."
While Rockets are fun somehow they don't seem to be very good as a power source on a daily ride, unless you can calculate the size of the rocket to your commute distance, and hit all the lights green.
I think the best 2 ways to move a bike with an electric motor is the use of chain drive or hub motors. Both have advantages over each other. For example using a chain drive can be setup so you can take advantage of the gears of a bike so you can use a smaller motor than is needed using a hub motor. The advantage of the hub motor is it's simplicity. No gears, chains, pulleys, etc. to deal with.
My personal preference is chain drive.
Grandpa Chas S.
Somewhere in the video archives of early rockets there is one of a rocket bike. Did not work very well, but according to this link:
http://strangevehicles.greyfalcon.us/Richter%20Rocket%20Bicycle.htm
maybe the problems were never quite worked out.
Maybe electric start ?
Rockets were maybe a curious diversion but ...
At Interbike last week I found a company selling belt drives for bicycles. These are Gates belts, same as are used on Harley's. Their claim is the belt drive is lighter ..etc..
But the length of a belt is not adjustable like a chain is. That is, you can't add links to a belt. Their example on display was a fixie bike so obviously the chain length doesn't have to be adjustable making it possible to use a belt if you know ahead of time how long the belt must be.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
I've seen some discussion of belt drive on other EV lists. Apparently they are FAR lass forgiving of slack or misalignment than a chain, and, as you point out, can't be shortened either.
The are quieter and lighter, but they actually are less efficient.
In addition to chains and belts there are "chainless" designs using drive shafts or screw drives coupled to the gearing. I saw an electric bike design somewhere where the screw was actually routed within the bicycle frame. Very clean installation...not sure why they aren't mass produced. Maybe the weight is too great compared to a hub design?
Similar to trailers, I have heard of electric powered sidecars used as a type of pedicab. The driver would use the pedals to slowly drive around the city. Once a fare is found, the passenger sits in the sidecar and the electric motor is engaged. This increases the speed of travel. If I understand it correctly, the sidecars are owned by the taxi company while the drivers own the bikes. So at the end of the day the driver takes his bike home while the sidecar is either recharged then moved to another driver's bike for another shift.
There is electric-to-compressed-air with various means of converting the compressed air to turn the wheels. There also has been a lot of work on hydraulic bikes. But I haven't seen them coupled to electric yet.
I have heard of an e-bike with inflatable pontoons on the side and an electric propeller motor. The person would ride the bike to a lake, expand the pontoons and drop the propeller into the water. It would then act as a boat.
I have also seen a video of a bicycle converted to an electric hovercraft as a science fair demonstration. But it was actually plugged into the wall and run with a long extension cord. It will be really interesting when battery/capacitor weight drops to the point when hovercrafts become practical.
You can also always update the old propeller idea: http://blog.modernmechanix.com/2007/04/07/propeller-drives-novel-bicycle/ :)