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Old guy from Ohio

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    Old guy from Ohio

    copied from Introductions area:

    Hi. I'm a 71 year old retiree who wants to convert my daughter's bike to electric. The bike is a nice 21 speed with a heavy-duty aluminum frame. It has 700 type wheels. I have good mechanical and electric skills. I plan on short rides no longer than three-four miles. No big hills, only minor changes in grade. I am a big guy, 260 pounds, so I am going to build a little on the heavy duty side. I have a 44 tooth rear sprocket that I can attach to the left side of the rear wheel. That way I'll still have all 21 speeds available to pedal. I want to mount a 36 volt motor above the rear wheel and drop the chain down vertically to the 44 toother. I plan on using three 12 volt, 18 amp/hour batteries wired in series. Do I need a gear-reduced motor (480 RPM) or just a 2600 RPM without gear reduction?
    I plan on ordering everything (motor, batteries, controller, etc...) from Motor Scooter Parts in California. Andrew there has been very helpful, but I am still not sure what type of motor to get. Thanks for any help or guidance.
    Fred from Ontario quickly replied:

    Originally posted by Fred
    Perhaps you have your reasons for building something that way, but if it were me I would be putting on a standard hub motor - either front or rear. There's a lot less that can go wrong with a hub motor setup. Also when you say 3 x 12 volt batteries, are you talking about SLA batteries? While they may be a little cheaper to buy, they will not last nearly as long as lithium and will weigh an awful lot. I would definitely go with lithium no matter what else you do with the motor.
    Also in your proposed design, you would have all the weight - batteries, motor, etc over the rear wheel. It will be quite unbalanced for riding.
    Just my humble opinion.
    And from me to Fred

    Thanks for your input and reply. I am going to mount the batteries low, only the motor will over the wheel height. Yes $LA - I am retired and Social Security doesn't give a rat's sprocket about my hobbies. ;-) My budget, daily, fairly short rides, my climate and my health are on which I based my decision(s). I've carried milk and groceries in a handle bar mounted basket and survived - well, at least I'm still here.
    Fred, I really want to know about the motor RPM. Thanks again for your thoughtful reply, Lee

    Can anyone else offer anything about motor speed? I am really at sea here about motor RPM. Can anyone recommend a site or book for a beginner? I shouldn't have any assembly problems once I know which motor to order.
    Thanks everyone.