At 3/28/2007 04:55 PM -0500, mercian531@bellsouth.net wrote:
>I recently picked up a used Huret Duopar Eco model derailleur. Very
>interesting design! According to the archives it wasn't exactly
>the most robust derailleur ever made. Rolling a bike backwards
>could cause it to self destruct! That could definitely be a problem
>with a tandem.
>[snip]
>Did these late models prove to be any stronger? Thanks for any feedback.
Jim, The backwards destruct problem wasn't due to a lack of strength, but a very simple, and easily fixed, design flaw. (which they never fixed.) The inner plate did not come up high enough to prevent the chain coming off the jockey wheel if you back pedalled while the derailleur was misadjusted, usually due to bumping the shifter. This was aggravated by the fact the inner plate was a bit too far inboard of the jockey wheel, allowing the chain to jam between the plate and the jockey. I assume this will be even more of a problem now, with today's narrower chains.
Back when I started Bikesmith, my main business was modifying DuoPars. Changing cable leverage to make them more compatible with SunTour BarCons, modifying the jockey pivot to accept Bullseye Pulleys, adding a 2nd idler wheel to wrap up more chain and of course modifying inner cage plates.
The rightmost image in http://bikesmithdesign.com/
With the raised inner plate DupPars were reliable, even on tandems. I sold a couple to Lon Haldeman for his tandem record runs. As problematic as they were, nothing else shifted big jumps as well, in the pre-Hyperglide days. If you didn't mangle them, the pivots in the Ti ones would never wear out. I'm still running a few.
If you want your inner plate modified, contact me off list.
BTW I've never seen that strengthened arm before, even on Sachs/Huret branded ones. Must have been a very late modification.
Mark Stonich;
Minneapolis Minnesota
http://mnhpva.org
http://bikesmithdesign.com