Ride, Wrench, Swap, Race
Join Date: Jan 2010
Location: Northern California
Posts: 9,194
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
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[QUOTE=MillieTheCat;21954844]I guess the inevitable happened...
Chain must’ve got caught either on the front derailleur itself or the chainring, snapped the chain and then destroyed the front derailleur...
back to the drawing board, and probably eBay.../QUOTE]
That looks symptomatic of the chain partially losing a sideplate off of a leading-side rivet head, which then caught on the outer plate of the front derailer, leaving the sharp bend there and forcing the derailer to rotate on the tube.
On occasion, I've come across same situation but before any real force was applied by pedaling hard, so fixing only the chain was still tenable.
On your derailer, both plates need to be restored to flat and parallel, which appears to still be quite possible with some judicious cold-working of the cage.
Beware that modern chain should never be re-riveted without using special pins or a proper connecting link. Modern chain's pins are peened flat against the outside of the outer side plates, and this narrow/thin ring of peening shears off completely when the pin is pushed out. So a pin is toast after breaking the chain there.
Last edited by dddd; 03-07-21 at 02:36 PM.