ada12

I would like to make an electric bicikl.Ne should be quick to 25 km / h.Now I have for engine wiper motor 100w and a small battery of 7.2 ah.Now I wonder whether the engine can power the bike and to transfer that attitude. The motor has a 65 rpm.Something like this.

turbo1889

Brushed DC gear motor builds built off of automobile type motors (such as wiper blade motors) has been done before. The main problem with such builds is that the continuous duty rated motors (such as the wiper motors) are usually low wattage in the 100watt range for even the heavier duty ones and the high wattage automobile motors are usually not continuous duty rated (such as the engine starter motors).

That combined with the inefficiency and comparatively short life span of brushed motors as well as the high amperage and heavy wiring needed to take the wattage levels at the lower voltage levels make such self done builds an occasional anomaly in the e-bike world presently.


Not that I think there is anything wrong with such builds personally, in fact I think if done correctly they do fill an important nitch that is not currently being filled in the commercial e-bike market. Namely a hill helper only motor for a bike that is intended to be primarily human power driven on flat ground but does have a low wattage helper motor that is geared low for higher torque at lower speeds. If geared correctly even a mere 100watt motor can be a big help when pedaling up hill if the motor is geared low to match the low end of the pedaling gears when ascending a hill.

ada12

Does anyone have any suggestions for the transfer. I have imagined such a transfer of 32/22 * 42/14 * = 283.63 65rpm rpm.Gear of 32 he went to the engine and it would look like this in the picture:

turbo1889

That's a cyclone set-up in the picture you included in your last post. A whole lot depends on the RPM's of the motor you use and your normal pedaling RPM that is comfortable for you. For example if your comfort zone is 60-90 RPM for your pedaling speed on the cranks and intend to build a crank drive with a motor with a 210 RPM motor speed then you need to set up your gearing accordingly. Since the RPM ratings on a motor are usually free wheeling under no load then its usually best to gear it for the top end of your comfortable pedaling RPM range. So in the above example you would want to set up a gear down ratio between the example motor and your crank of 2.333/1 so that when the motor was at the top of its RPM range of 210 RPM under little or no load then your pedaling speed would also be at its top end of 90 RPM and as the motor loaded down your pedaling speed would load down as well so that your pedaling and motor would be synchronized and working together and will load down together.


The closest I have come to doing what you are suggesting is when I used a 250watt 24V cheap geared front hub motor and rigged it up to the right of the rear wheel to drive the big 34-tooth granny gear on my rear 7-cog freewheel off of a 16-tooth drive sprocket on the hub-motor attached to the six disk brake mount bolts on the left side of the motor hub so it was a 2.125/1 gear down ratio on a second chain running up to the hub-motor mounted in a home built rack on the right side of the rear wheel inside the right side pannier bag with its back side cut out so it was just a cover over the motor, controller, and small 24V battery pack all together in a tight package under the pannier used as a cover and then just used only five of the seven rear gears for the main pedal drive chain (not using the #1 granny gear on the rear because it has the second chain on it for the hill helper motor or the #2 gear, its just a clearance spacer between the two chains). In that case I was setting up my gearing such that the motor would be in its peak power output at a little less then half the normal speed so its peak power output would be at the speed I'm climbing a hill at rather then at full speed on the flat which is how hub-motors are usually set-up.


It works fine for my needs as a hill helper motor that is "stealth" and very few people ever notice the second chain going up into the right side rear pannier and I still have the left side pannier empty for carrying cargo. Actually balances better with a little cargo in the left bag to equal out the weight of the hill helper motor and battery pack under the right side pannier.


You could build something very similar with a low voltage automobile type motor. Rigging up something to the rear drive cogs with a second chain was the option I chose instead of using a crank drive-setup for that bike. For not just a hill helper motor but a constant use drive motor I agree that a crank drive is best. It’s all up to the builder though of course.

ada12

My engine has the 65th highest rpm I do not know if you could put a voltage of 24V to the motor ga damage. So you could get a higher speed. For now I try this transfer. The engine has a very strong transmission on it and are unlikely to come under load. I tried coming up out of the shaft to turn but I could not even run a little.

turbo1889

Use the voltage your motor is intended for or just slightly more or less. A lot of guys with hub motors designed to run off of 36V have over-volted them up to run on 48V and gotten away with it but if you try to go too far to one side or the other of the intended voltage then you can end up burning things up. Long story short if your motor is intended to run off of 12V then you could probably get away with over-volting it a little bit. I wouldn't hesitate to run a twelve cell NiMH pack (14.4V) or a 5 cell LiFePO4 pack (16V) on a motor originally designed for 12V but I would be cautious about anything getting much above 18V or so. I certainly wouldn't use anything less then 12V since lower then design voltage under load can often do more damage to an electric motor then over-volting (that why "brown outs" hurt stuff with electric motors in them like freezers, fridges, and AC units in household electric problems). And 12V may be your best bet anyway for ease of charging and the fact that you then have so many automobile accessories which will run of that voltage no problem like a full set of tail lights and a horn.

Now I'm not sure if I understood your last post correctly but are you saying the motor you have is a 65-RPM free load speed motor? If so then you actually want to gear it up a little instead of down. If you have a standard mountain type triple chain-ring on your crank then your "granny gear chain ring" up front should be anywhere from a 22 to a 28 tooth count and you could probably hook the motor up to that and just use to two larger chain-rings for the main chain and use the bottom end adjustment on your front derailer to lock out your granny gear chain-ring up front. Obviously a triple ring freewheeling crank set-up would be preferred for non-driven pedals but with a low-wattage motor and thumb throttle on the motor driven pedals aren't too bad. You would use anywhere from a 28 to a 34 tooth freewheeling sprocket on your motor depending on the tooth count of your granny chain-ring which could be hard to rig up in a left hand freewheel unit but not impossible by any means. You will need to transplant an appropriately sized big #1 low position sprocket from a right side multi-sprocket right hand side freewheel spool into a left hand freewheel body and then make or have made an adapter for your motors output shaft to thread into the left hand threads of a left hand side BMX freewheel body (it will be on the right hand side of the bike but using a left side freewheel on the right side makes it a driving freewheel rather then a driven freewheel and vic-a-versa).

Maddy Lighter

i think buying one would be more cheaper ...