My First Home Built Electric Bike

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I have always wanted to build an Electric Bike. No insurance, no license, but must have a helmet, lights, and be able to pedal using your own power.


The bike I found by a pile of garbage discarded by someone, looked like a real solid frame and was in good shape. This front wheel is the back wheel from another scrap bike I had found discarded a while ago.


I first mounted the controller from a mobility scooter to the handlebars to see how it looked. The forward reverse lever can easily be reached by my thumb.


I then built a frame from some scrap angle iron and mounted the motor to align with the sprocket on the front wheel.

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I had an 8 tooth #35 roller chain sprocket in my collectable stash and machined it to fit the electric motor. The sprocket on the wheel is a 72 tooth. The maximum RPM of the motor at 24 volts is 3300.


I didn't want to have the batteries mounted too high because it may make the bike top heavy and difficult to manage, so I built a frame which fit nicely under the cross bar.


With the batteries in place, I wanted to have the speed and charger controller mounted in a safe place because this is the brains. The black box just forward of the batteries is the battery charger, it was small and light and I wanted it to be with the bike all the time.


April 9 2016, a very cold day but the sun was bright so I went for a little test drive. The bike is easy to pedal and was originally an 18 speed, I removed the derailers from both the back wheel and the pedal sprocket and aligned the chain to a fixed ratio that would be comfortable to power the bike.

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The front wheel, actually the rear wheel from the other bike was also a multi speed bike but I removed the sprockets and the oneway clutch ratchet drive. The front wheel idles and dose not drive the motor when I pedal the bike. The bike pedals very easily and I only use the power when required like up a hill.


It is very easy to manage and balance the bike, I thought the batteries and motor would make it top heavy but that is not the case. I think a 12 year old would have no problem from using the bike.


When I picked the bike from the garbage pile it had an aluminum style kick stand that worked but I didn't think could be trusted, so I made the stand for the back wheel from half inch EMT electrical Metalic tubing, conduit, and brazed it together. It easily pivots up behind the seat when not in use and holds the bike upright and secure when down in place.


This is a close up of the drive sprocket on the motor. The motor was from a mobility scooter and was mounted to the transaxel with a self aligning coupling. The motor shaft is very short and I had to machine a drive pin into the sprocket through the motor shaft to add strength and prevent the sprocket from slipping. There is a flat on the motor shaft for a set screw but I want to be sure there is no slippage.


The 72 tooth sprocket from Princess Auto , $19.79 and a box of #35 chain $17.97 and the length of conduit were my only expenses. You can still see the original sprocket in front of the large sprocket, this was the rear wheel from another scrap bike. If I was to pick up the front of the bike I can spin the wheel in a forward rotation and not drive the motor, however, spinning the wheel in reverse will then turn the motor shaft.


This is the original speed controller from the mobility scooter. The knob missing from the speed controller at the upper left corner of the control box is to pre set the maximum speed no matter how far your thumb pushes the lever. I leave the dial at MAX fully on and control the speed with the lever. At the bottom there are 3 LED's indicating battery life and to the left a button I will connect to a small horn I found in my stash.


A close up of the charger. I wanted the charger to be with the bike at all times just in case. They usually advertize that a mobility scooter will carry the average person any where from 5 to 10 miles depending the terain, battery condition, speed, and so on. I believe my bike could go many times that distance for these reasons, I can pedal without the motor, coast down a hill, and I don't have to use the motor power at all if I don't want to, but when I need it, I want it to be there.


A close up of one of the two batteries, the mobility scooter uses 24 volts for the motor drive, lights and horn. I have some LED lights I intend to use but they are 12 volt so I will use one of the batteries for that. This has been a fun project and I enjoyed the many hours of planning and engineering all that goes into such a project. I plan on using the bike in the city but will somehow have to develope a hold down devise for the batteries, they bounce around while driving thorught the potholes and the uneven rough streets in Kitchener.

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