h a l f b a k e r yIdea vs. Ego
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//very small small replacement wheel//
Do you have a pair of casters jacking the (still spinning) front wheel off the ground? |
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Not heavy but rather FAST. If the wheel goes up in the air, and thru some (other-half baking process) received the braking energy (ie. brake is a clutch on back wheel, with an axle or chain leading power to front wheel now in air, which then gains great speed. Wheel must be airodynamic (ie spikeless or filled). The speed is the main power of the flywheel, with weight coming in as a much smaller factor. |
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Edited for clarity and small small typo corrected. Thanks [rcarty, skegger and 21Qu]... |
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I think I like it, but wouldn't this make it impossible to brake while turning at all? |
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I have to think that if the front wheel were turning very very fast to compensate for its lack of weight, you would lay some serious rubber on touching it back to the road. |
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Perhaps instead of having the front wheel as a flywheel, you could have a flywheel inside of the frontwheel. |
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The flywheel and ground-touching wheel could be connected together via an infinitely variable transmission. Braking can be accomplished purely by changing the gear ratio. |
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I had the same thought as goldbb. The only way a flywheel of reasonable weight will hold any useful amount of energy is if it is spinning must faster than a typical bicycle wheel. If one could fit in the hub of a bicycle wheel a CVT that was efficient but lightweight and inexpensive, such a flywheel might be quite useful (though I think it would be better in the rear than in the front). From a practical standpoint, however, I think that a battery and motor/generator, along with electronics to simulate a CVT, would be more practical. |
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Yeah, I agree with bungs goldbb (and supercat). I'll give myself a [-] |
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But anyway thanks for the discussion... And now I have to buy a gyro to put in my wheel (back wheel's better - your right!) |
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Another vote for the flywheel within the wheel. |
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I'm picturing one compact electric motor/generator fixed to the bike frame/axle at the wheel hub. Another motor/generator is wrapped around the flywheel rim, like a linear accelerator/maglev train track, and driving the outer rim/tyre assembly. |
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Hitting the brakes switches the rim motor to brake/generator mode and allows the hub motor to freewheel. Forward momentum is translated into angular momentum in the flywheel, ie it spins up. |
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Precision design, precise pulse timing and feedback mechanisms should allow energy to be added to the wheel at higher and higher speeds, up to its design limit. |
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When it's time to pop the clutch, the hub motor would be set to brake (generator) mode, and the rim motor in the reverse of its previous polarity (driving the rim forward relative to the flywheel) |
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The hub motor slowly brakes the flywheel by extracting energy from it, and feeds the electric current thus created to the rim motor, where it is added to the forward motion of the actual outer rim and tyre. |
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I may be wrong, but I think it would be difficult to do all this with a single motor. I can imagine a single motor acting as both brake/generator and motor - perhaps by incredibly rapidly switching between the two modes - but I don't see how to transfer the energy between the flywheel and the bike/rider and road without two separate motors. |
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Whether these are actually mounted rim/hub, hub/hub or rim/rim is more of a design and efficiency question, I think. |
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For a Mech Drawing class many (many many) moons ago, I drew a bike with an added flywheel in the middle of the frame. The teacher gave me a hard time about it, how it would be difficult to steer what with the added angular momentum etc. I pointed out that the idea was to draw kinetic energy off the vehicle for stopping, and add it back for accelerating again via an added clutched drivetrain. |
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The front wheel of a bike doesn't have a lot of mass. And if you add mass, you're going to make the bike really hard to handle at speed. |
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I'd say give it a try, but I wouldn't want to be the one to test it. |
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Just from the physics standpoint, go with a fly-RING, not a wheel, with as large a diameter as possible. This is the optimal mass/energy storage balance as the angular momentum is largest per unit weight for a ring or balanced pair of weights, but a ring will lose less from drag than a pair of weights. |
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This suggests a second wheel with spokes outside the main wheel, rather than using the actual front wheel. In fact, the angular momentum effects of trying to turn the fly-ring (it will try to tip your bike over) would suggest putting the fly-ring on the back wheel as it turns less than the front wheel, particularly at rest when the fly-ring is spinning. |
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To improve on the CVT stuff, a more manual version would give you an additional brake between the fly-ring and the rear wheel; apply the brake to grip the fly-ring to the rear wheel, thus accelerating the rear wheel. Once moving, apply the brake to accelerate the fly-ring. Under braking, apply the brake to a highly-geared connector to the fly-ring, such that the fly-ring needs to move at 10:1 or so to match the back wheel. |
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Voila, friction gearing (known as a clutch!) to transfer energy from wheel to ring, and ring to wheel. |
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