Campagnolo rear derailleur missing bit!!

Right, I have one of these...

and (I think ) I am missing a bit at the back where the fixing bolt is, which stops the derailleur from spinning round and round on the hanger.

Is there any fix for this other than sourcing another part, which will probably be like finding hens teeth..?

magnets?

Not quite sure I follow you...

i'm saying you'll need the thing that goes in the thing, the magnets idea...well it's only theoretical

reckon it would work though, but you'd have to be careful to do it right.

you mean because of the counter-intuitive inertial rotation?

yeah - that rings a bell, I read about it on sheldon brown. or a link from there I can't remember. It's so easy to F up though.

it's just a question of understanding how they work

You guys!

OP: you've got an '88-'91Athena derailleur and the missing piece adjusted it's maximum capacity:

It was notorious for going AWOL and being as you're also missing the cable adjuster, you'd be better off looking for another *complete *one.

If it's not for a period correct restoration, I've got a '95-'96 Athena RD you can have for £25.

Thanks for the help guys! I might shelve the idea of modifying it, and keep an eye out for any spare parts that might turn up, or just take it apart and use it for spares. It kills me to have to ditch a component just because of one silly little missing piece though!!