My Electric Bicycle Project

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  this is v1.0, with a single drive belt and a smaller 80 amp controller. Great for flat terrain at 30 mph.

V1.0  had just one long vee-belt from the motor to the rear wheel. It had a top speed of around 30 which was great but slowed to about 12 mph on the steep hill near my house. However, other people building their own have asked about using the single vee-belt because it is easier to put together without machine tools, and it works pretty well on the flat.

The goals were these:

The single belt reduction runs from a 1.75" drive wheel on the motor directly to a 16" driven pulley mounted to the left side of the rear wheel. This is actually a 20" bicycle rim mounted to the wheel hub using half of the rim's spokes through additional spoke holes drilled into the wheel hub. This setup gives a reduction of about 8 to 1.

 ^ The vee-belt setup, giving a reduction ratio of 8:1


V1.3   After using the single vee-belt reduction for a while, it seemed  that I needed to gear the bike down some more. At full throttle the belt would slip on really steep hills off-road. Also it was overheating on my hill and ended up burning out my 80 amp controller. So after some thought I added an idler shaft or "jackshaft" for an initial belt reduction. I have a metal lathe and fabricated a bearing housing for a 1/2" shaft running on ball bearings. This is mounted on a pivoting system in order to get the belt tensioned correctly.  With the pulley combination pictured below I have an overall reduction of 17 to 1. This translates into a top speed of 13 mph and good hill climbing ability.

The most critical thing on a setup like this is to mount the jackshaft very solidly so that it stays parallel to the motor shaft under belt tension and during high power loads. This required a lot of reinforcement of the mounting bracket, as the whole thing mounts to the motor  face using two bolts, and flex was a problem.

 ^ Double reduction using toothed belt to a jackshaft running on ball bearings

I suspected the ideal gear ratio for my needs lies somewhere in the middle. I will probably settle on a top speed of about 20 mph. The good thing about this setup is that I can change the gearing fairly easily with just a couple of different toothed belt wheels and possibly a slightly different length belt.

The primary belt I added is a Gates Powergrip XL belt. I actually had a bunch of belts and wheels lying around from other motorization projects but these are available from ball bearing and rubber belt industrial suppliers. This belt is really way too small and narrow for a motor this size at full throttle, but hey it was free.


 ^ Controller with added heat sink mounted to the top tube

This is the previous Eagle 80 amp controller from 4QD. It melted down from driving over 100 amps for extended lenths of time. It is really to small for the Scott 1hp motor but worked surprisingly well for quite a while. Like the Scoota 120, it has adjustable acceleration and deceleration curves, but no regenerative function.

V1.4   had a single long timing belt. After experimenting with a single vee-belt and an ealrier two stage belt reduction, I tried to simplify in the name of efficiency. I especially wanted to get rid of the vee-belt completely, which would slip on really steep hills and also is less efficient than a timing belt. This setup was less than ideal because the belt is so long. There was not enough rooom for a wider belt and this belt was simply not strong enough for the amount of power being delivered. Also, this Type L timing belt was noisier than I had expected. The trapezoidal tooth shape is noisy, and the idler tensioning wheel added a surprising amount of racket even though it was ruuning on the "flat" side of the belt.

v1.4 motor and belt drive

1. Current Version      2. Design Details      3. Early Versions      Electric Bicycle FAQ      Eric Peltzer Sculpture     My BookGem book holder