Old 07-05-22, 06:53 AM
  #2  
2_i 
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This sounds very interesting. Is there a chance for the photos? While you mention the diameter of the seat tube as a problem, in my perception there is more, if not way more depending on the bicycle and this is brought by the seat tube not pointing towards the center of the crank axle. Because of the latter you effectively need to adjust up to 3 degrees of freedom for the derailleur mount, horizontal and vertical positions and angle. On a regular bicycle you only adjust the vertical position and all else is taken care of. Your solution seems to adjust the vertical position, but all else is not taken care of and the angle problem can be painfully seen under the Celka link you post.
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