h a l f b a k e r yInexact change.
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(How come no category Vehicle:Bicycle:Electric?)
This idea is about fast and easy to attach/detach pedal assist device (electric bicycle kit) for any bicycle.
Its fast and easy. First time setup for the wheel takes 3 minutes. Then, for every ride, you come to the bike with a backpack, connect
the stators in less than a minute and your off. It is controlled with a remote on your thumb.
Details: An electric motor consists of a stator and rotor.
Instead of installing an electric motor inside the hub,
why not put the magnets ON the side of the external wheel rim. Wouldn't add much weight and could be controlled digitally so that no power is lost when there are no permamagnets in the area of the pulling/pushing electro magnets.
The stator would consist of one or more powerful electromagnets on the side of the wheel. Only part of the wheel would be 'covered'.
There can be a few sizes of pre-fabricated stators for different size wheels, or you can use the dynamic separated single stator devices.
"Under the hood": On the back wheel, you attach 12 magnets to the right-side rim of the bike. They are held tight by being in a lightweight plastic encasing that is tied tightly to the spikes, with a grip on the rim from the inside. You then connect three stators (electro magnets with each with a sensor): one to the seat pipe, one near the pedals, one suspended from a back rack. Or a attach a single stator device that has multiple magnets and reaches to the side of the wheel. This stator device would have a semi circle parallel to the wheel with electro magnets and a sensor on it. When a magnet on the wheel is in the vicinity of the electromagnet in the stator and the motor is on, it pulls and assists with the bike ride.
less friction bike generator/motor
less_20friction_20b...20generator_2fmotor
[xaviergisz, Feb 24 2010]
Linear Induction Motor
http://en.wikipedia.org/wiki/Linear_motor
"a piece of plate metal, that is placed in this field will have eddy currents induced in it thus creating an opposing magnetic field. The two opposing fields will repel each other, thus forcing the conductor away from the stator and carrying it along in the direction of the moving magnetic field." [BunsenHoneydew, Mar 21 2010]
Magnetic levitation
http://en.wikipedia...odynamic_suspension
".. naturally stable - minor narrowing in distance / create strong forces to repel the magnets back to their original position, while a slight increase in distance greatly reduces the force and again returns the vehicle to the right separation. No feedback control is needed." [BunsenHoneydew, Mar 21 2010]
Swtiched reluctance motor
http://en.wikipedia...ki/Reluctance_motor
Wot [Ling} referred to? [BunsenHoneydew, Mar 21 2010]
Variable frequency drive
http://en.wikipedia...ble_frequency_drive
[BunsenHoneydew, Mar 21 2010]
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Annotation:
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I think that you may be on to something. There is a weight/output problem and it must act on both sides of the wheel. |
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Don't pull: push. Otherwise the rim will bend over and stick. This is really difficult to implement because the air gap needs to be really small, and the wheel on a bike is normally all over the place. Weight is also a problem. I spent a year or so, fiddling with a similar solution, wasting my time on a switched reluctance drive that was finally pretty good at not much at all.
In terms of mechanical advantage, and potential low friction, the basic concept is a beauty. |
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Instead of magnets on the wheel, fit an aluminium segmented ring and feed AC to the coils, creating a synchronous motor. |
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The small air gaps may be maintained by mounting the coils on a pivot or slide, similar to brake calipers, with small rollers to run on the motor ring. This will maintain the air gaps even if the wheel is slightly buckled. |
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Nice concept, needs development. |
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It is an interesting idea in theory, but the reality would bring complications. As stated wheels are out of round and bearings are loose enough to cause issues at large moment arms. Magnets on the wheels would pick up metallic debris. To invert/build on [Twizz]s idea, I'd put the coils on the wheel and then connect them to power using one rolling contact on each side. The rolling contact would also act as a floater to keep the magnets from contacting the coils. |
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Would it help at all if the motor was only asked to turn the
wheel less than one full revolution, and only at very low
speed? I believe that would be genuinely useful, for people
who ride in a bike lane, and hate coming to a full stop at red
ligts because of the difficulty accellerating from a standing
start when the light changes. |
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of course you could regenerate electricity to the battery, from braking... I thought I mentioned that. |
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xavier thanks for the link. related, but very different. I propose much less use out of this motor, so a. don't need so much fine tuning (gap, quantity of coils, location etc) and b. mine should be easily assembled or removed from the bicycle. (At least parts of it should). |
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would be much easier to sell it as a replacement wheel with the motor built-in.
Standard wheels won't cut it strengthwise and have too many variations, and most people don't understand motor theory well enough to deal with non-obvious things to look for with the clip-on magnet approach.
Would be easy to make some torque with such a large diamter rotor though. |
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I am reading this as a kind of linear induction motor [link] which just happens to run around an arc of a circle. |
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Building it as such would have advantages: |
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The rotor/wheel could be a solid aluminium (thus: lightweight) disk, or a disk with most of the center removed, leaving a track around the edge like a drum brake disk. Machined as a single piece, the disk would have either integrated spokes (like a plastic BMX "tuff" wheel) or standard threaded spokes added later. |
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Permanent magnets would not be needed: induced eddy currents in the purely passive rotor provide the back EMF. |
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And the rotor would only be magnetic inside the accelerator section; the bit closest to the ground would not pick up ferrous or magnetic debris. |
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Magnetic levitation principles [link] could self-regulate the airgap. Mounted on both sides of the wheel, I imagine doubly so. In fact, it may regulate so well and so quickly that opposing pairs of coils could be free to slide (together) from side to side (left to right as the rider sits), and ride out any irregularities in the rotor. |
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Complex control systems would be reduced (I think) to a variable frequency AC inverter, where throttle setting = frequency. Either that or a PWM/PFM driver (pulse width modulation and/or pulse frequency modulation) |
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//solid aluminum disk// crosswind, gyroscopic moment. |
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// disk with most of the center removed // |
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I'm picturing between 10 and 50mm (0.5 to 2 inches) of flat disk remaining at the edge, sticking inwards towards the hub from the integrated wheelrim/tyre bead. |
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why not just use the rim ? |
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Good point. I guess I assumed more area and/or more mechanical strength would be needed for the torque required, but perhaps not. |
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but perhaps.
I assumed caliper-brakepad size'ish LM's: x4 is 3-4 sq.in area, which sounds like enough... but you'd also need room for the truck and cowcatcher. |
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