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Old 05-22-2009, 09:50 PM
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Earthman Earthman is offline
Motorized Bicycle Senior Member
Join Date: Mar 2009
Location: Pittsburgh, PA
Posts: 82
Default Re: thinking about buying a kit. i wont die will I?

The top speed of my 24” motorized bicycle is 23 MPH. I have no desire to go faster ‘cause it’s scary. However, I may make changes so I can use the gears on the back wheel and go up steeper grades, or ride slower off road. I've replaced the break cables with 2mm cables.

I too worry about the strength and reliability of bike frames – the tubing on most newer bikes is real thin for lightness. More expensive frames use butted tubing, which is thick at the joint ends and thin elsewhere along the member length (see photo). This may actually be a drawback for MBs. I’m using a cheap huffy frame, which I assume does not have butted tubing. I assume the tubing is strong enough in tension and compression, but clamping stuff to it (engine, chain tensioner, etc.) may weaken it. Also, higher speeds put higher impact loads on the joints of the frame. Bike frames do fail by joint fatigue from normal riding. In any case, bicycle frames were not designed for what we are doing to them. Use caution and inspect the frame and mounted hardware often. Finally, there must be zillions of these kits in use in China. I wonder how many bike frames have actually failed?

When I was a kid, I had an old, stripped-down, 24”, single speed Schwinn bike that I beat the crap out of for years by jumping off 8’ high hills, going up and down steps, etc. This was 20 years before there were mountain or BMX bikes. I dismounted my bike one day, and with no warning or load on it other than its own weight, the poor thing literally fell apart into a heap at my feet with me left holding nothing but the handle bars. It was like it just gave up and died. I was very sad.
Attached Images
File Type: jpg Butted Tubing.JPG (24.5 KB, 51 views)

Last edited by Earthman; 05-22-2009 at 09:54 PM.
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