salvaging the derailleur

It doesn't appear that Laura OLPH has written about it yet,but regulars on this blog might remember an earlier post where I mentioned her derailleur had locked up. She brought it to another mechanic, who apparently didn't know what to do with it; he recommended a soak in thick, viscous oil.

Well, no; what it wanted was a soak in thin oil so that the oil will seep into the doin's and break up whatever has concretized in there. I offered to give it a try, and soaked it in WD-40 for a couple days. I got some very fine particles out... but it still wasn't moving.

I loosened what I could, and attacked the pivot points with a selection of dentist picks. Then I bolted it up to a section of pipe and used screwdrivers to lever it, and got it to move a bit. It wouldn't retract, but it would respond to taps with a light mallet.

OK. Time to try some specialty stuff. I purchased a can of PB Blaster penetrating oil, gave the derailleur a dousing, and let it soak for over a day. More of those fine particles came out, and, after a bit of working it with the levers, it's back behaving again.

It's a bit the worse for wear; the levers left their marks.

I've filed them down a bit and had at them with steel wool, but the marks are still there. There's also a bit of a scar at the top of the clamp:

Nonetheless, it's alive again, which it was not last week at this time.

I have no idea how one might protect against such a thing: these lockups occur so seldom that I don't have a defense strategy (I don't have a big enough sample to hypothesize). Admitting ignorance on this. Any ideas?

Anyway, Laura, I'll get it to you the next time I see you.