A Journey by Bike… refining the design

Posted: September 7, 2015 in Uncategorized

After realizing that the gear segments had to be able to change radial position during the quarter of each revolution when they are not engaged in the chain, I also saw that I still had to work out the mechanics of how the gear segments would move. And this required framing the problem in a new way yet again.  Now the problem was: how can the gear segments change radial position when they are free from the chain, yet maintain their new position (and not slide inward) when they do engage the chain?  The problem was how to make the gear segments move when the bicycle’s rider wanted them to, yet remain fixed so as to serve as an effective power transmission.


CABT drawing

My next bright idea was to use long bolts radiating out from the center of a base plate, and affixing on them specialized nuts which would slide in a groove of the gear segments.  As the bolts turned, the nuts would be driven inward or outward, and the gear segments would expand or contract.  The turning of the bolts would occur as wheels on their outer end rubbed against control plates suspended next to the bolts as they pass the plates on each rotation of the crank.  Thus, depending on which side of the bolt rubbed against the control plate, the bolt would turn clockwise or counterclockwise, and the gear segment would pivot outward or inward.

Original CABT working model

Combining these ideas, I designed a device called the Continually Adjustable Bike Transmission (CABT) and set about trying to build and test the design.  After even more effort and many trips to hardware stores, I built a working model of that design.  I was quite pleased and excited that the CABT worked.  I even filed a provisional patent application and tried to interest various bicycle component manufacturers in licensing it. Unfortunately, I found no takers.  An engineer directed me toward Frank Berto’s book, The Dancing Chain, and becoming familiar with the history of the bicycle transmission, I realized that the CABT was too heavy and complicated to be marketable.

Back to the drawing board again. All of us have had to start over at some point, right?

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