Here's a few things I learned about basic and home built e-things

Discussion in 'Electric Bicycles' started by professor, Apr 24, 2010.

  1. professor

    professor Active Member

    Batteries are the closest thing to a mystery black box, they can show good voltage and be bad. I put a meter on and then hook up a load- like a car headlight, then watch the voltmeter. If it really dives and keeps dropping. The battery is toast. If it drops a little and stablizes it may be good. I went 'round and 'round with batteries until I figured out a load test.
    V belt drive works well. I used a 20 inch bike rim attached to the spokes and a 1 1/2" pulley ( 1/2 inch bore 4L size - this means 4 one eighths across the V) and a 3L belt. The belt fits down into the groove farther than the wider (designed for) 4L belt - to get the motor to have a better gear ratio. The thing flies- I would like a lower ratio. Maybe using a 20 inch back wheel (smaller bike), this would slow it down and could use a bigger motor pulley (which would grip better- needing less force on the belt from the clutch/ tensioner arm). I am not wild about my rim / hoop attachment method, but for a test, it is fine.
    When I say it flies, I mean at full throttle I am pedaling fast in highest gear. Probably 20 mph or so. When I had the 2" motor pulley I could not keep up with the bike without it being annoying.
    The motor is a 450 w. Unite motor from Allelectronics in Cal. The shaft is .475, so I used a 12 thousandths shim between it and the pulley- no problem.
    I had wanted to make a range comparison between the former chain/jackshaft deal (which was a real drag to pedal) and the new belt drive, but I bounced a battery out of it's little holder and it went bad. I forgot to tie the kangaroo down mate.
    Anyway, there is no doubt in my mind the belt is more efficient. Spinning the motor over (belt engaged) is about equal in pedal effort as just spinning the chains/ jackshaft and idlers like before. That 450w spins over a lot harder than the 250w I have- stronger magnets?
    With a better gear ratio, the 250w would be OK.
    I bought pulleys and belt from McMaster Carr online. The 250w had just over a 5/16 shaft, so I ran the motor and hit the shaft with a die grinder cut off wheel until it was a slip fit.
    The ratio with a 2" motor pulley was 7.5 or so. 14 to one would be good (or close to it). this would increase the motor's effective power, probably give it longer life and drop the speed down to pedal bike range.
     

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