Lo buck belt drive report and pics

Discussion in 'Electric Bicycles' started by professor, May 22, 2010.

  1. professor

    professor Active Member

    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.


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  2. professor

    professor Active Member

    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?
  3. moondog

    moondog Member

    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.
  4. professor

    professor Active Member

    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.
  5. moondog

    moondog Member

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

    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.
    Last edited: Jun 2, 2010
  6. james65

    james65 Member

    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?


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  7. professor

    professor Active Member

    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.
  8. kjparker

    kjparker Member

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

    Luka Member

    I'll second that request.
  10. professor

    professor Active Member

    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.
    Last edited: Jul 1, 2010
  11. Luka

    Luka Member

    If a picture is worth a thousand words, you still have a few left to go.


    Thank you. Your description was pretty good.

    Probably would have taken at least a couple of pictures to show that.