Help with an electric motor question

red devil

red devil

AC Members
Jan 7, 2003
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Shenzhen, China
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I am amazed at the brilliance and resources that are represented on this forum, so I will take keyboard in hand and pose a question to you.

I live in China and need to get from one end of the city to another in as short a time as possible. The solution to this is to ride an electric bicycle but all of the bikes I have looked at have really weak brakes and are not designed to do any serious pedaling.

I want to do my own conversion but i am having trouble finding a suitable electric motor. I don't want a hub motor. Instead I am going to install a hub gear box in the fork and anchor a motor on top of the wheel and use a chain to drive it.

I want the motor to be about 350 watts at 48 volts but capable of using 96 volts at a later date. I need a motor that is more the shape of an alternator as opposed to the disk shape of a hub motor. Low torque would be nice, if not essential. Brushless or brushed? I think at the speed I will be going there will be no noticeable difference. Can someone help me with:

a. terminology - what kind of electric motor am I looking for? which kind is most useful? How do you decide if a motor is durable or not?

b. Where can I find this kind of motor? I have heard of people having their own built.

Thanks for any help you can give.
 
Schwinn makes an electric bike, which i have found to be a very nice ride :)

why would you want a motor with low torque? more torque means it will get you up to speed faster with more power to move you from a dead stop.
 
Ooopss! Yes, I mean more torque at the low end. The reason why I am thinking about going to all this trouble...all of the options I have here are designed to be ridden, and pedaled only occasionally when the going gets tough..but what i want is a bicycle with gears to pedal most of the time...and use the electric motor to assist me occasionally, or to help me travel long distances, farther than the battery will allow me.
 
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the schwinn bike i seen, was a sweet bike man, im pretty sure it was an 18 speed, as well as having a sweet electric motor for those rough patches :)

I have no idea of the model, but i know its schwinn that makes it. you might want to look into it.
 
Electric motors always have max torque at 0 rpms. Basically torque lowers when rpm's increase because of counterelectromotive force (I think thats what its called).
 
That would depend on the type of electric motors. For example the comon shaded pole motor found in things like ceiling fans (and aquarium pumps I beleive) has a very low starting torque.

BTW I have been toying with the idea of building my own electric 'chopper', one that can travel at highway speeds... but just strapped for time right now with all the projects and 1 yr old... would be great though to not have to buy gas for the daily commute, and even completely free if I invested in a big enough solar charger and second batterey pack.
 
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