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18+1 Speed Bike

Add an extra gear to bicycles for generating power
  (+15)(+15)
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I ride my bike around town a lot, and frequently would like to carry a laptop or similar with me, but worry about battery power, et cetera. I also find myself sitting and waiting upwards of 2 minutes for those stubborn "walk" lights or busy traffic, or stopping to talk to someone and not wanting to unclip my toes.
Thus, on to the idea. add a small generator as an extra gear, so when the bike is at rest or cruising downhill even, the rider can shift to the "power" gear and charge a battery, which can later be used to power small, low-wattage devices (read: laptop at the largest).
Perhaps there could also be other percentage-geared gears, in which 75% of the power is transferred to the wheel, and 25% to the battery.
I looked and couldn't find this as baked; if you find it, buy me one for christmas.
edit
In response to annotations, I didn't consider balance; I would just lean on something, or have a symmetrical, moped- or motorcycle-style bottom-mounted kickstand rather than incorporate a gyroscopic flywheel, simply for ease of manufacture.
roleohibachi, Nov 21 2005

Generator powered bike light http://www.aztlanbi...es-00123-lights.jpg
Start here. [Worldgineer, Nov 21 2005]

Touring with a bicycle and a laptop http://www.kenkifer.../touring/laptop.htm
Q: Why don't you use a bicycle generator (dynamo) for power instead of a solar panel? [jutta, Nov 22 2005]

Hub Dynamo http://en.wikipedia...ting#Dynamo_systems
[xenzag, Feb 06 2009]

Buy it here http://www.peterwhi...les.com/schmidt.asp
simple technology that's as old as dirt [xenzag, Feb 07 2009]

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       Sounds reasonable to me. They exist for bike lights, though the generator pulls power constantly rather than only in certain gears. I suppose you could have this always connected, but it only draws current (and therefore has significant friction) when you flip a switch.
Worldgineer, Nov 21 2005
  

       I'm not sure how this works... do you keep peddling when the bike is at a standstill? and if so, how does the bike stay upright? perhaps a gyroscope on the same axis as the wheel (with similar rotational inertia).
xaviergisz, Nov 21 2005
  

       What you're looking for here is a clutch, not a gear.
RayfordSteele, Nov 22 2005
  

       Just pedal backwards and attach the generator to the cog on the rear wheel.
Antegrity, Nov 22 2005
  

       I like the 'pedal backwards idea... that would allow you to have a regen brake by using the motion of the 'free-wheel'. You could have a variable dial (or possibly an extra 'brake' handle) to control the torque provided. As for balance, I think that's a tricky one, as you're going to have to unclip to trip a stand down unless you add another handle for when you're stopping?   

       I like it though.
Skrewloose, Feb 06 2009
  

       I like the idea, but am not sure about the hours you want to spend on this bike - 40 watts a laptop does draw, and 120 watts one can produce on a bike without being paid for it, so you'd end up in the +1 gear for 1 hour for every 3 hours of laptop usage - if that fits your time budget, thats cool.
loonquawl, Feb 06 2009
  

       Hub dynamos linked to storage batteries have been around for years... My dad used to ride a bike with a set of these. The dynamo charged a set of batteries carried in a tube attached to the frame, and when you stopped, they took over the running of the lights, so what's the new idea here? //I looked and couldn't find this as baked; if you find it, buy me one for christmas.// see link and put in your order.
xenzag, Feb 06 2009
  

       For daily commuting, least fiddly would probably be a medium-sized battery (say 1/4 the size of a car battery) mounted on your bike; recharge or run the laptop from that and recharge the big battery at home.   

       For larger or "greener" trips a hub-mounted CVT/clutch/motor-gen/brake system connected to the same medium-sized battery.
FlyingToaster, Feb 06 2009
  

       Another possibility is to have a wee gearbox attached to one of the break assemblies such that with braking pressure of 0-60% what actually happens is you drive a 1:200 gearbox attached to your dynamo. The heavy gearing means that you get high friction, sufficient for slowing you down. When you press the brake still harder (over 60%) - standard brake pads engage and although the dynamo will still turn it no longer bears the bulk of the braking load. End result is that you charge as you brake, e.g. whenever you go down hills, stop at junctions, etc. To me - it's much easier to charge by not peddling than to charge by peddling...
vincevincevince, Feb 07 2009
  

       //how does the bike stay upright? perhaps a gyroscope on the same axis as the wheel (with similar rotational inertia).// This reflects a common misconception about how bicycles balance; the main mechanism is small negative feedback movements of the front wheel/handlebars. Raw gyroscopic stability is a relatively tiny effect. Try riding with the steering fixed and you'll get the idea.
spidermother, Feb 07 2009
  

       this is a good idea but haven't figured out the amount of energy/crank etc. This could also be done with exercise bikes, I mean think of a health club? couls probably juice up a whole bank of batteries at the local Gold's Gym!! Also engage the generator going down hills. So two birds with one stone. Fitness and free(or otherwise wasted) energy.
porge, Feb 07 2009
  

       [porge] Why don't you post your energy generating gym as a separate idea? (Note - I am joking).
spidermother, Feb 07 2009
  

       So was I kinda. but it does make sense.
porge, Feb 07 2009
  

       giant hamsters.......the enargy of the future!
porge, Feb 07 2009
  


 

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