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front derailleur on old Dahon: get misfit clamp FD, cut clamp to stub, use hose clamp

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front derailleur on old Dahon: get misfit clamp FD, cut clamp to stub, use hose clamp

Old 07-05-22, 02:50 AM
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Antifriction
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front derailleur on old Dahon: get misfit clamp FD, cut clamp to stub, use hose clamp

Thought I'd mention this in case others are wondering if it's worth trying.

Folks have come up with a few ways to attach FDs to thicker-than-the-market-is-motivated-to-serve downtubes. Starting from a two-piece commercial solution of "braze-on" FDs* and adaptor clamps**, tomtomtom123 figured out the flaws in market adaptors and had a non-flawed one 3d-printed in alumnum. Falconista went old-school, and just forced the FD and the adaptor to mate using a hand file. Meanwhile, starting from a band FD with a too-small band, Celika cold-formed it to the needed radius using a vise and a cylinder.

Being more of a Dremel guy, I just succeeded by the method stated in the thread title. It wasn't totally straightforward. A gusset on the 2009 Eco3 prevented FD from being placed at height where chain would clear cage crossbars in all gears; to deal with that I had to amputate part of the FD, specifically the flange which houses the limit screws. I also needed to trim the FD cage a little, because at the viable height it interfered with the large chainring. But now I have a 28/48 double, and a 16.5" low gear, and can ride up the scenic route to my place - with its 15% grade - to the amazement of neighbours.

* relic term, confusing for two reason: the things actually brazed on were never the FDs, but frame features they screwed on to; and those features aren't really brazed on any more; "screw-on FDs" would nail it
** screw-on bands (from Litepro; haven't heard of others) with alleged equivalents of those frame features, that sometimes don't quite work

Last edited by Antifriction; 07-05-22 at 12:32 PM. Reason: clarity
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Old 07-05-22, 06:53 AM
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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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Old 07-05-22, 11:23 AM
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Ugly in some eyes, but it shifts the chain: my criterion for success. I think Celika too would argue there is no angle problem, or that it has been dealt with, if the thing works. As Thoreau puts it in Walden, "To be a philosopher is not merely to have subtle thoughts... It is to solve some of the problems of life, not only theoretically, but practically."

Last edited by Antifriction; 07-05-22 at 02:25 PM. Reason: typo
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Old 08-07-22, 12:34 PM
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Regarding how precise FD profiles have to be, I just cut right side of this FD cage to a 52t profile to fit over a chainguard I picked up, & it still works fine with 48t ring. Knocking the chain off to the left is after all a pretty simple task.
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