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motobike from old drill Answered

Does anyone know how to motorize a bike, when the motor is from an old drill? I have been trying to do this for weeks, and I couldn't figure it out. This is what I have so far:

I am trying to put the motor on the frame of the bike, and attach a sprocket to the end of it. The sprocket will be linked with the bike chain, coming from the rear wheel and leading to the petals (actually, the axle where the pedals used to connect). I will most certainly need a bike chain extension, so I would also like links to sites where I can get some.

Also, I would like my bike to go fast AND have moderate torque, so I need a gearbox assembly.

I know this is a lot of requests, so take your time. Thanks.


i strapped on a drill on my bike rear rack using hose clamps. i used a rear cog that i got off of an old bmx bike. i took a 3/8 inch bolt, fed on a fender washer, then the cog and then another fender washer and then a nut. although i sandwiched the cog in tight, i used a liberal amount of lock-tite on it after trying to get rid of most of the wobble. at first i tried to use a cheap dril (20 bucks/18 volt) that i got at an auto parts store. it didn't have variable speed and it performed like a 20 dollar drill should when used to power a bike - not well. i then used a ryobi 18 volt drill - it did pretty well. by running the chain to the large ring on the front cranks, i was able to get a decent amount of torque, but had to worry about my shins because the pedals would crank around and around. i will try to post some photos of it. hope you are able to build your bike/motorbike. -tmherrin

Has anyone ever seen a bicycle with a generator in the crank shaft. The generator could power the lights at night and be a self contained unit.

Argh, my last comment disappeared. Generators in the pedals are not generally used because generators prefer higher RPMs than your pedals normally turn at, putting one in the bottom bracket would unnecessarily increase mechanical complexity, and it wouldn't generate while freewheeling. There are hub dynamos that fit in the rear wheel hub that address the above issues without the drawbacks to bottle-type dynamos that rub on the wheel.

When I said generators I meant it in the most generic terms. Also to clear up confusion I didn't mean to run a drill motor I meant to charge a battery that would supply power to lights etc. Thanks for the info on rear wheel hub dynamos, I didn't know that.

Or one that snaps on to the rear fork, it acts as a chainstay and the sprocket powers the generator, zero bike mods needed... I may have to go build that now, I see a beaten to death derailleur in my garage...

Hmm not quite but an interesting idea for reclaiming energy when pedalling to be used for electrical locomotion...

You mean, while it's not using the motor the pedals are turning a generator, charging a capacitor, which powers the motor. Okay, that obeys the laws of physics :P.

Yeah well, it can do it all the time, helping you charge the battery for a hub motor, if the motor ran the front wheel it would still be efficient I think, not wasteful, well either way the motor's giving locomotion, the generator adds power to the system allowing for more locomotion...


10 years ago

Your plan sounds entirely plausible but I agree that I don't think a drill motor is the best option- cordless drills are usually only a few hundred watts, which just isn't enough power to make your bike particularly fast at any gearing (your legs can probably put out over a thousand watts when pedalling hard), and corded drills will require 110 or 240V, so to power one from a battery would require an inverter, adding weight and reducing efficiency. If you are set on using your drill motor, however, your plan is valid- figure out where to attach your motor, how it will mount, and where the battery will fit. How to attach a sprocket to the motor will depend on the precise motor but a competent welder would be able to do that step for you, and you can buy chain and a chain link tool from any bike shop for not very many local currency units :) If you have more specific queries I'm sure one of the experienced E-bike builders will be able to help you.

yeah i think u need to specify the size of drill, my whipper snipper motor powered my bike comfortably, but it wasnt fast and definatley didnt have moderate torque lol, if ur thinking of a hand drill i think you have no chance. If you had one from a bench drill or sumthin it wld go but wld be 240V AC, my suggestion is a starter motor, check out "electric bar stool racer" on google

Umm I would suggest using a motor from something else, like an old E-scooter or wheelchair...

All I have is a drill and a few assorted low-torque electric motors that wouldn't move my bike at all.

Well it probably wouldn't do much better to be honest, unless it's fairly powerful, you do get drills that would power a bike but they're not all that cheap...