I am trying to use a multigear bike to make a pedal power bike. I am trying to add an extra cog to attach a chain to connect the motor to. See link.http://www.popularmechanics.com/technology/gadgets/how-to/a10245/pedal-power-how-to-build-a-bike-generator-16627209/ Is it possible with multigear or do I need a fixed gear?
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I can't see anything that would stop you attaching the generator to the largest (left most cog) of the cluster. With some clusters, it would even be possible to change that cog to get better gearing. Then any multispeed bike can be used with no modification. . You would loose the use of that cog and one, maybe two, beside it.– mattnzMar 16, 2016 at 3:01
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@mattnz normally the gearing requires a huge gear - I've seen some with 80-120 tooth cogs. If OP tried to use a 42 tooth the motor would likely not have the torque to take off. SECONDLY, the freewheel or freehub would be locked up, so the rider's pedals would be motor-driven... you could not coast ever. EDIT I've just realised its to power a generator, not motorise the bike.– Criggie ♦Mar 17, 2016 at 0:32
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It's fairly common to use one of the cogs on the cassette as the output, and in your case since you want to gera up you'd run the bike in the highest gear, and use the largest cog on the cassette to drive the generator. No need to modifying anything (I've done this with a water pump, I bought a cheap "drill pump" that goes on an electric drill and ran it this way).– NuіMar 21, 2016 at 7:31
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1 Answer
You need a rear hub that can have a cog on both sides.
Some fixed gear hubs have threads on both sides, or a fixed thread on one side and freewheel thread on the other. The author apparently has one of these.
The multi-gear option is to use a disc hub and cog that has been drilled to fit 6-bolt disc brake mount. This trick is usually used to make fixed gear hubs out of MTB front hubs, but could also work here.
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Sorry I am a bike noob. What is a disc hub and where could I find like a tutorial on how to do that. Thanks though! Mar 15, 2016 at 16:48
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Disc hub is a hub that can be used with disc brake. Googling for "fixed gear disc cog" will produce a lot of images of the setup and several shops that sell these cogs ready made.– ojsMar 15, 2016 at 16:53
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So I would put it on the other side of the wheel for a multi gear right? Mar 15, 2016 at 16:57
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It is held by the six bolts that are visible in the pictures. Google is your friend, search for bicycle disc brakes and you'll see where the disc usually goes. The cog can be mounted in its place - which of course leaves you without rear brake.– ojsMar 15, 2016 at 17:00