Lo buck belt drive report and pics

[professor]

My reasoning for the belt drive is the chain set-up I had was a bear to pedal without power and I thought that the motor was having to fight all the drag of the idlers, chains and jackshaft- thus sucking up power and range.
I also considered a roller drive but thought the belt was easier to do.

I used a 20 inch bike rim for a wheel "Pulley", 450 watt scooter motor with a 1.5 inch OD v-belt pulley with a 1/2" bore (the pulley is for a half inch belt- called "4L"). I'm using a 3/8 drive belt (this combo makes the belt ride as low as possible in the pulley- to get the drive ratio as low as I can). Had to wrap a twelve thousandths shim between the motor shaft and pulley to take up the difference between the metric shaft and the SAE pulley.

The controller is a 500watt 24v from TNC scooter along with a thumb throttle.
Batteries are 9ah 12v - definitely on the small side but I don't go very far. They are in a rack covered with a plastic bag.

The good- awsomely quiet, the only sound is a very high pitch faint hum from the controller and a slightly noisy idler brg in my belt "clutch"- actuated by a HT clutch lever.
Power is OK, maybe goes 20 mph.

I just went 5 miles and it did loose some power but still good- a lot better than the chain set-up I had.

In the event of any failure, the drive belt can be slipped off eliminating drag- the belt just rolls along next to the wheel.

Very inexpensive to do but I did do quite a bit of fabrication.

The bad- drive belt slips on full throttle when the batteries are full- belt spray (grip) would probably end this. The slippage is on the motor pulley.

The thumb throttle is like a bear trap after a while, I am thinking about putting a counter-operating spring on it to make it lighter.

I had to modify the frame a little to allow for the drive pulley's extra width.

Pics-

 

[professor]

I thought to add this bit of info- I have 2 motors, a 250 watt (that I used last yr) and a 450 (currently on bike). When you spin the motors over by hand the, 250 has light resistance from the magnets but the 450 is much harder to turn over- you can feel it kind of flip between the magnet sections. So I am thinking the stronger magnets should give more power from the same input when the motor is engerized.
Does this sound right?

 

[moondog]

I like it. There are a lot of different motors you could try with that setup.

It's kinda like an electric golden eagle setup except heavy duty.

I am not sure a golden eagle setup would handle the instant torque of an electric motor.

 

[professor]

Gebe would have to test it, I used some belt spray and still get some slippage at full throttle. It does have some kick to it.
Today, I actually sent an e-mail to BMP with the idea that there is a market for one of their rack set-ups for a motor like I am using. Really, a friction drive with electric should work OK.

 

[moondog]

Gebe would have to test it, I used some belt spray and still get some slippage at full throttle. It does have some kick to it.
Today, I actually sent an e-mail to BMP with the idea that there is a market for one of their rack set-ups for a motor like I am using. Really, a friction drive with electric should work OK.

Did they answer ? A friction drive kit for an electric motor would get me to click on their pay pal button !

P.S. I am one of their early customers ! Years ago they sold plans on eBay showing how to build a friction drive. Still have them.

 

[james65]

friction drive

I have built two electric drives. I have stayed away from friction drives, it was a gut feeling that there would be a lot of energey losses. I realize that I coulde be all wet. How does a friction drive compare to a electric that runs through the multi speed dereliure?

Jim

 

[professor]

Yes, I did get a reply from BMP. The fellow who contacted me said they were very busy right now but he would convey my thoughts to the other guys. I think they need to get a feel if there is sufficient market for it.

James, very interesting set- up there. With that, I would not even consider a friction drive. Looks bullet-proof to me. + you transmit into gears.
I mentioned the friction drive because it is so simple and an inexpensive start to motor assist. Can't comment on efficiency, depends on the set-up, there are losses with any drive.

 

[kjparker]

Any chance of a pic of how you fitted that rim to the wheel?

 

[Luka]

Any chance of a pic of how you fitted that rim to the wheel?

I'll second that request.

 

[professor]

Oh boy. I disassembled the whole thing when I didn't want to buy new batteries.
Here is what I did-
24 inch bike rim attached to the 26 inch wheel spokes, I used a wooden "Cradle" to lay the wheel in so it would lay flat. Actually it was a riser I made to hold an amplifier over the top of a cassette player and I couldn't throw it out - used it for a step stool occasionally. But flipped over, it is great to set on a table to work on bike wheels.

Anyway, I centered the 24 rim onto the 26 by measuring with a dial caliper to the 26 inch rim- NOTE- whatever run out the 26 inch rim has will be duplicated into the 24 using this method, so it would be best to align the 26 incher first.
I had about a 1/16 of runout but it didn't seem to bother anything- I just didn't like it.

After getting the rim centered, I carefully clipped clothes pins onto the set-up to hold it in place. Now, I had to decide how to attach the rim to the spokes. I chose to make tabs to braze onto the rim which would lock it (between the spokes)from spinning radially. then drilled tiny holes for wire to capture each spoke.
If I did it again, I would not use the wire- they had to be JB welded to eliminate creeping around. I would make locking tabs which would go across two spokes and clamp them.

One other thing- I had used a pulley on the motor for a 1/2 inch belt and it would slip, because the 3/8 belt would ride too far down. I used a hack saw on the pulley as I ran the motor, deepening the groove (making the place where the belt rode narrower) and the slip went away.