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Motor Drive System

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Old 03-25-09, 05:52 PM
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jomac
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Motor Drive System

Hi,
Im very new on the forum, so appologies first if i mess up on etiquette. I found a while back an abandoned escooter with a smashed body. The motor, throttle, controller and batteries all turned out to be 100% OK, so they were put aside for a rainy day,recently i was given an 18 speed mountain bike (MTB?) and the two began to merge in my mind and the reason for joining this forum.

I have one or two questions, if you guys can help me out. Here in the UK the legal speed for one of these is 15mph so i would like to aim for that (unless a higher speed can be obtained without drastically reducing the range). The motor is an ungeared MY1018, ive seen different specs on the rated speed from 2400 to 2800 rpm, the motor says 2750, is this no load? and is the 2400 rpm on load?

The bike has 26" wheels so what would the ideal ratio be between the motor and wheel? The 2 batteries are 12Ah and on the flat with a 160 lb guy what sort of distance per charge could i expect?

And the last question (promise!) has anyone ever done a conversion using the gears and how? i realise there could be an issue with the pedals turning but i have access to some serious engineering kit and could worrk around most problems.

Any help and advice would be greatly welcome, and hopefully i can post my efforts here

John
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Old 03-25-09, 09:25 PM
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unime
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Originally Posted by jomac View Post
I have one or two questions, if you guys can help me out. Here in the UK the legal speed for one of these is 15mph so i would like to aim for that (unless a higher speed can be obtained without drastically reducing the range). The motor is an ungeared MY1018, ive seen different specs on the rated speed from 2400 to 2800 rpm, the motor says 2750, is this no load? and is the 2400 rpm on load?
You can find a lot of information through web searches. This page, for example, talks about modifying your motor. I haven't read it carefully, but it seems to say that 2400RPM is the top speed under load.

The bike has 26" wheels so what would the ideal ratio be between the motor and wheel
26" wheels going 15mph spin at 194 rpm, so you'll need 12:1 gearing, or so. You should try to understand the calculations before building the bike.

The 2 batteries are 12Ah and on the flat with a 160 lb guy what sort of distance per charge could i expect?
1-2 miler per amp hour? Of course it depends on how much pedaling your do.

And the last question (promise!) has anyone ever done a conversion using the gears and how? i realise there could be an issue with the pedals turning but i have access to some serious engineering kit and could worrk around most problems.
Yes. Conversions like this have been done. You should look into freewheel crank resources, among other things. Keep in mind that you may need a second freewheel for the motor, so you don't have to fight to turn it when using only human power.

Good luck!
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Old 03-26-09, 04:13 PM
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jomac
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Well, i got a load of information from your reply Unime, and i followed the link you gave, its answered a lot of questions and i have things clearer in my mind thanks to you. I had in mind trying to devise a method of using the 3 gears on the pedal crank to give me 3 speeds via the motor, i realised i had to devise a way of not only stopping the pedals from turning when under motor powerm but the motor from turning when under pedal power, i had the idea of using 2 freewheel sprockets with the teeth removed, one for the pedal chain and one for the motor, ive not fully thought it through though.

John
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Old 03-27-09, 11:32 AM
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unime
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Glad I could be of help, John. I'd love to hear about your progress, so keep us posted!

Good luck.
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