Building the simplest electric bike possible.....
First thing you have to understand is that when I say simple I mean simple. This is an electric bike for those of us mechanically challenged.
I began with the desire to build a bike that would allow me to pedal most of the time but help me up that hills that kicks my butt on even a good day. So I started with the premise that I just needed some help not a full blown motor scooter. It would be a bike with an electric assist not an electric scooter with pedals for emergencies.
From all I could find there was a great deal of math and mechanical knowledge needed for gear ratios ect. Not so with the friction drive assist. What I read told me that friction drive was the most logical for me. Mostly because it was the easiest.
So now I had decided what kind of drive. I then needed to know what kind of motor. I went looking around not really for the best possible motor but the easiest and cheapest one that would do. I stumbled onto a man on ebay who had a bunch of schwinn scooter motors for sale.
The first one I bought was 250 amps for about 20bucks. When it came it had a sprocket on the drive.
Okay I had the engine and I needed a drive wheel. I messed and messed wasted time and money till I came up with the easiest of all drive mechanisms. Below is the one that works.
My neighbor has a welder and loves to play with it. What I did was get a few 5/16 bolts of different lengths. I also got three nuts. I put all three nuts on one of the bolts and made sure they were lined up so that all could be taken off at once. Then my neighbor welded them together. He did a great job for me.
Then he welded the three nut package to the sprocket. As close to the center as possible. I ran a long 1/4 in bolt with washers through the sprocket (after it was off the motor or course) and then through the three nut package. I lined them up centered as much as i could and Mike welded them.
So to make the drive wheel I just bolt any kind of wheel to the nut package on the sprocket which I put back on the motor. I have used caster wheels and they work fine, i have made wheels from pvc water pipe joints of varying size. Those work just as well.
Okay at this point you have the motor and the drive wheel. Now you have to attach it to the bike somehow. This is where your ingenuity comes in. I have used a hinge on a flat bar then bolted the flat bar to the bike right behind the seat. Usually where there is a cross bar at the junction of the two rods that hold the wheel on....
Okay now you have the motor, the drive wheel, and you have it on the bike.
Next you need a power source. If you want the bike to be self contained you need small batteries. Sealed lead acid are the least expensive. I ran 8amp hour.
The way that is supposed to work is, your engine is rated in watts. To get the amp draw of the engine at full throttle, the only way i run mine, You divide the watt rating of the engine by the voltage required to run it. Mine was 250 amps divided by 24 volts equals about ten amps.
So you are looking at something under an hour of battery life. If your bike averages 15mph which isn't too far off. On a new full charged battery on fairly level ground you should bet about ten miles. However it never worked that way for me. I would guess more like half that amount due to hills ect.
If you don't mind lugging your power source on a trailer behind you, and I don't. You can get a little more bang for your buck with flooded cell batteries. Ie marine or auto batteries. Marine would be best.
Okay so now you have a motor, an attachment plan, a drive wheel, and a power source. How about all those fancy controls you hear about. Well yeah you can get an electric throttle, and a controller to help control the motor. I chose not to go that route. If you have a motor with brushes, which all mine are so they are not hard to find, and you are looking for an economical, and easy to find switch, which I was, It's home depot for a house switch. I use 15amp on the 250 watt motor and 30 amp on the 350 watt motor. I don't have any that are bigger.
Now you wire it up as the diagram below shows. It give me an on off switch which I use like a pulse jet engine. Flip it on when I need an assist and off when I no longer need it. If you want, you can use it all the time but it will eat up your batteries. I have done it both ways.
So here is how you wire it.
Okay Norm here is my contribution this is my 24 volt system
cheapo electric bike assist system 
Linear Mode
