h a l f b a k e r yYeah, I wish it made more sense too.
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Elec. motors have relatively low torque, so to push a bike and rider, must be allowed to run fast and then geared down to achieve torque power. Noisy, frictonal.
Can't the large diameter bike wheel be treated like a (circular) linear motor, whose speed of rotation could be controlled electronically
rather than with a transmission of gears? Miniature elec. coils multiplied to 100 placed around the outside perimeter of the wheel. Instead of a two or four coiled motor, it would have 100, achieving a similar gearing down effect with more torque. The stator being an 60°arc of also multiplied magnets set like a fender close to the loaded wheel.
Maybe the whole thing multiplied exponentially using printed circuitry (exactly how?) to produce flat motors.
This must have been tried, if someone could just set me straight...
Homopolar generator
http://en.wikipedia...Homopolar_generator
Discovered by Mick Faraday, no less ... [8th of 7, Jan 20 2008]
Stepper motor
http://en.wikipedia.../wiki/Stepper_motor
A step motor can be viewed as a synchronous AC motor with the number of poles (on both rotor and stator) increased [baconbrain, Jan 20 2008]
Alternator on a similarish principle
http://www.otherpower.com/
Take a look at the alternators these guys make. Themselves. Out of wood. [Ned_Ludd, Jan 21 2008]
along these lines?
http://www.revopower.com/
[4whom, Jan 21 2008]
finally found it...
http://www.shelleys....co.uk/apr03mot.htm
the last I saw someone had developed this for police bicycles. [4whom, Jan 21 2008]
another, although for smaller operations
http://www.engr.psu...2003/flat_motor.htm
[4whom, Jan 21 2008]
[link]
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Yes it has been done. Will try and find link. |
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Sounds like a homopolar generator - low voltage, very high current. |
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Perhaps Less Friction, rather than Friction-Less? (in the title, I mean...) |
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we already have devices which sit close to the wheel... the handbrakes. Perhaps something along that line could be used as a linear motor, using the tire rim as the other component.
[+]'d |
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Easily damaged or destroyed. Difficulty in keeping close proximity of magnets/coils without touching. Water/dirt/sand/mud. Edge effect losses at ends of 60 degree arc of magnets. Otherwise, a great idea. |
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I imagine you'd put it on the mudshield so you'd have say a 1/3rd of the wheel covered.
//Difficulty in keeping close proximity of magnets/coils without touching// |
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no difficulty, just put a roller in front and behind the stationary magnet sections, so if you're wheel's a bit warped it compensates. |
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I think it would work, but the problem is the weight of the magnetic circuit. Each coil would need an iron core, and an effective circuit in the core routed across any air gap that you have and back round to the rear of the coil in some way. |
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It just so happens that I tried this on a bicycle wheel already. I didn't modify the wheel very much, as I didn't have any machining facilities (or much money!), but I did manage to put some iron core on the rim, and a set of 'C' shaped windings that went around the tyre (a sort of switched reluctance type motor). It was very heavy, and there was a tendency for the air gap to close on one side or the other. Rollers would add friction, so I decided not to use them from the beginning. |
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4whom, the revopower patent claims all sorts of things, some of which seem to be similar to the old Cyclemaster in the 50s. |
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Thanks mucho to all for the info. |
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Wouldn't it be just as effective to put the fixed magnets in the rim of the wheels? Then you'd be able to put the complicated electronic bits on the wheel frame, where they are somewhat less likely to get damaged or stolen. |
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