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Saturday, September 26, 2009

Electric Hub Motor Bicycle Prototype... not much to write about but pretty pictures included

A short time ago I had the opportunity to get a good deal on an electric wheel hub motor for a bicycle. These motors are built into the hub of a bicycle wheel where the spokes attach. At the time that I got it I didn't have a bicycle but I thought it would be something fun to have around the house. Well not really... right after I got the electric hub motor I went out to Target and bough a bicycle for $95.00. I don't know a whole lot about bicycles or what all the correct names are for the various parts in a bike, but I did build an electric bike and at the same time designed a rear dropout. Don't get upset if I don't know what I am talking about when it comes to bike stuff... just post something angry in the comments.  As I mentioned in the title of this post there isn't a whole lot to talk about but I do have some nice pictures!

The electric hub motor is made by a German electric motor company Heinzmann and is spoked into an Alexrims DM18 rim. I gather in talking to people that both the wheel and the rim are much better than the bike that I bought at Target. I don't feel too bad about this - having good expensive wheels on a crappy bike - because where I live almost everyone has a $900 piece of crap car with $3000 spinning chrome rims on it. At least I look super cool on the bike and they all look like idiots.
Anyway the aluminum box that I hose clamped into the frame holds the 12 volt SLA batteries (Sealed Lead Acid). There are three of them in there wired in series for a total of 36 volts. On the front of the aluminum box is a motor speed controller that is wired into the grip throttle on the handle bars. The grip throttle and the controller are both made by the same company and I got them with no documentation. I used a ohm meter to figure out which wire went where as far as the batteries and motor.

I got a small plastic box and added a couple of switches to switch a car battery charger to each SLA in succession. In other words I can charge each battery individually and then when the charger is disconnected they are all drained in series to run the bike. Mostly this project was just piecing together some parts. I had to get a single speed freewheeling sprocket for the Heinzmann Hub Motor to get it to fit into the bike. Other than some shimming and spacers the whole thing took less than a week to put together. With the rear single speed sprocket I just have the three front gears so the bike is a three speed + the motor.
Once fully charged I can make a round trip to the post office of the supermarket on one charge and just a little pedaling at an average speed of 20mph. I think if I got newer batteries instead of the used ones that I have it would get a bit more distance. As the price of gas has come back down a bit I'm not as eager to tinker with this but it is something that I will mess with. One thing I want to do is now that I know it works I'm going to make a cover for the aluminum box so it's sealed and I'm going to paint it blue like the bike.

During the construction of the bike I designed a rear dropout for another bike project that a friend of mine is doing. The CAD model of the dropout is in the picture above and he helped me get the parts for the electric bike. UPDATE: I made a post showing the bike this dropout is used in HERE Check it out!

Now I have told you everything that I know about bikes. When I get around to cleaning up the electric prototype pictured above I'll put up some more pictures...


  1. Hello Mr Belden, could you please send me the CAD file for that DROP OUT you made? I have a bike project going on that could use that exact part!
    Thank you already.

  2. Malk4vi4n,

    I'd be happy to help you design a dropout for you bike project. I can't send the CAD file for the one above because it's proprietary to my friends bike company. Let me know if I can help you!


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