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Take a generator and a couple of motors (one at each wheel), and you've got an electric bike with all-(or should that be both-)wheel-drive. For gearing, a simple switching system could switch on or off different coils in the generator, effectively changing the gear ratio.
I know this would be more
inefficient (at least I'm pretty sure) than a regular bike, but it would offer a few things otherwise outside regular bikes' territory: all-wheel-drive, maximum torque at zero RPM, and a serious cool factor (look, ma, no chain!).
(?) chainless bicycles
http://customer.man...~worldscape/se2.htm
"originally invented before the turn of the 19th century" [FarmerJohn, Oct 04 2004, last modified Oct 05 2004]
regenerative brake bike
http://www.halfbake...tive_20Brake_20Bike
some annotations here are duplicating the discussion over there... [badgers, Oct 04 2004, last modified Oct 05 2004]
Rokon Trail-Breaker
http://www.rokonron.com/
Two wheel drive off road motorcycle. [gzuckier, Oct 04 2004, last modified Oct 05 2004]
Attempting to bake something very similar
http://www.angelfir...etesCafe/ebike.html
This is an interesteing set of pages about trying to build somthing like this. It includes some discussion about the pros and cons f this approach. [scad mientist, Oct 04 2004, last modified Oct 05 2004]
Mando Footloose
http://www.gizmag.c...e-alternator/24330/
new e-bike trades the chain for an alternator [xaviergisz, Oct 12 2012]
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One motor for each wheel? Wouldn't you need to synchronize them so one doesn't turn faster than the other? |
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Not if each motor has its own connection to the generator, and both motors are identical. Besides, I tend to think the pavement would keep that from happening. |
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Beautiful. Simple, elegant, and cool. I think motor mass may be too high for comfort, but overall it may be nearly as efficient as a chain system. |
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Especially after high-temp superconductors become available. |
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Ok, you're right. Did a bit of research - bicycles lose between 0.5% to 15% of power to friction depending on the bike. A generator and motor on this scale will probably lose 10% each. So, market it as a weight-loss device and you're set. |
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Of course, there's no law that says there must be two motors. Front-wheel-drive bikes, anyone? |
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Don't limit yourelf based on the 10% loss each thing. If you have two motors that are each losing 10% of 1/2 the load, that's the same loss as one motor losing 10% of all of it. |
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add a LiIon battery, so you can store up energy when you have it, and coast on it when you are running low. |
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better yet. store the energy in flywheels! have a big flywheel which you add energy too by pedalling. current is drawn off a generator attached to it as needed. this has the added advantage that the spinning flywheel keeps your bike upright when standing still! |
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plus, you are missing the best feature of your setup. regenerative breaking! motors are generators too. when you brake, pull the energy off the wheels and feed it back into the flywheel. hmm.. I want to build one of these now. |
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The only reason I want a battery is so people will give me goofy stares as I sit at the light, pedalling madly and going nowhere. At the change of the light, engage - and the front wheel lays rubber all the way across the intersection. |
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[johnmeacham]'s got a point about regenerative braking; there's a lot of hills where I ride and it would help a lot. |
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I wouldn't limit myself to battery or flywheels, though. There's many ways to store energy on a bicycle: |
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Batteries (& other chemical storage, e.g. fuel cell) - are heavy, require maintainance, inefficient to charge and discharge but offer high torque and suitable hub motors exist to be adapted; |
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Magnetic induction (including superconducting coils) - is interesting, but has all the problems of batteries and may require larger sizes and heavier equipment; |
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Flywheels (& other kinetic storage) - are heavy, of large size, lossy, noisy and require complicated continuous gearing mechanisms to spin up/down, but offer tremendous torque and avoid transduction; |
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Compressed air (and other compression storage) - are light-weight, offer easy transduction (piston) and high initial torque, but are noisy, and have a difficult power delivery profile; |
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Elastomers (and springs) are efficient in some configurations and easy to implement for the home builder. However, they lack the smooth delivery of electrical systems and you have to be careful not to overload them. |
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I can't say for sure which system is going to be the best. |
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There are regenerative braking electric cars and Aprilia have made a rather sexy fuel cell bike, and electric (battery) bikes abound. However, these are typically pre-charged/ fueled systems with a pedal assist, so I don't know if a purely regenerative application is viable; |
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I've never heard of an induction storage bike, so maybe it's too complicated and heavy; |
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Flywheel powered toy cars were pretty common when I was a kid, but I never saw a system that powered anything bigger than a shoe; |
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Compressed air cars exist as experimental prototypes, and I've seen toys that use this principle. Using a compressed air vessel as the drive train with output matched with a flow comparator would be very special (think bagpipes), but I suspect you'd need to use a direct pedal drive in case there's not enough system pressure to power the drive train; |
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You've seen wind-up rubber-band aeroplanes and coil spring driven walking Godzilla toys, so you can imagine a ratchet system that allowed it to be wound up as it wound down (imagine riding a 15ft Godzilla while you turned the spring key to keep him going). |
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Personally, I like the simplicity of the elastomer or spring, but I expect I'll be riding a commercially available regenerative electric bike before I get round to building a spring powered one. |
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I've just thought of another problem for non-electrical storage systems (flywheel, compressed air and spring). You will need to install (and control while riding) two independent sets of gear trains. One for the drive train and one for the pedal input, because it will get more and more difficult to pedal as the system reaches capacity. This is independent of the timing of the up/down hill path of the bicycle. |
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Electrical systems can be electronically balanced to allow a constant pedal resistance, while the drive train would have conventional variable gearing to cope with changes in slope. |
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One solution for the mechanical systems would be to only use the system for regenerative braking, to supply power as a pedal supplement only. You could use a bi-directional ratchet (like you have in torque wrenches) to set charge vs. discharge, but that's getting away from [galukalock]'s concept. |
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From an engineering standpoint, has anyone considered the many conversions of energy required here, and the losses undertaken with each and every one of them? |
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Fat bottomed girls make the rockin' world go 'round, don't they? |
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[X2Entendre] Do they have to? |
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At any rate, there's energy loss in *any*thing you do (see [Worldgineer]'s comments earlier), so it's just a matter of limiting them. |
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And yes, y'all have strayed a bit from the original concept, but I thought along many of the same lines while working tonight, so keep it up; I don't mind. A regenerative-braking thingy would be nice indeed. |
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In that case let's take it a step further. Seat heater? Stereo system? Built in refrigerator? Adding electricity to the biking experience allows for oh so much invention and convienence. Saddened I have but one croissant to give to this idea. |
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Hyundai, in one of their hybrids (at least in the prototype) used an "ultracapacitor" instead of a battery. |
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The general idea is that batteries have a much better energy/weight ratio than capacitors, but most capacitors have a much better power/weight ratio than batteries ("supercaps" being a notable exception, since they trade power capacity for energy storage). In battery-based hybrid cars, a set of batteries which has enough power for the application will be able to store much more energy than is really needed. |
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The flywheel discussion on this idea sounds oddly similar to a competitor at "ideas happen"... |
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I will discard the flywheel. Probably will unbalance you if you want to turn... and worst of all, it will add a nasty weight... If all troubles are supprased, I would love to have one. |
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Hey! What about a nice dairreus eolical generator? |
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this idea has been trippin around my head for a while the main stumble is cost of decent motors, from tests etc I know a fastnut like moi can peak at about 1500W ( for a few secs ) so to gain anything need 2 1500W motors. but. how do yer balance for maybe 50 secs at the lights so I thought about a tricycle so 3 2HP motors... People stare at me already, so seeing me pedal furiously whilst still won't make any differnce. wot battery can charge/discharge with hi efficency about a KWh? |
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Nah, just a regular generator or alternator attached to the pedals. You can switch the circuits around with a switch and the motors will do the regen braking. |
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I really like the hill flattening possibilities of this bike + |
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Hmm. Very nice for recumbent - I hear started from stop is a bitch. Plus heavy so uphill rough. But faster downhill. Ergo really could USE the juice. Plus torque - oomph - pull stuff? Could use just normal non-deepcycle if just for extra at stopsign, like not-dual-mode hybrid car. Plus, regenerative braking worthwhile for the wet-weather use. Could always house battery in pipe lengths, too. Hmm... Roll your own batteries... |
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See the link I added about someone trying to bake this. |
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Just buy a electric bike conversion kit and a hyper capacitor and your good to go. |
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//A generator and motor on this scale will probably lose
10% each//plus storage losses |
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//Just buy a electric bike conversion kit and a hyper capacitor and your good to go.// (sic) [travbm] You meant to say: Just buy aN electric bike conversion kit and a hyper capacitor and you'RE good to go. |
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"If you keep correcting them, they will learn". |
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