I'm about done tearing down a donor PX-10. I have the crank, bottom bracket, headset cups and rear derailleur remaining. Too early to make noise tapping out the headset cups, and I need to borrow some tools for the crank removal. That leaves the rear derailleur.

I've never worked on one of these Simplex beasties before, but I vaguely recall seeing admonitions about the process. Do you loosen the bolt from behind the dropout, or mess around in front? Does the upper pivot spring go "sproing" if you're not careful, or is it pretty well self-contained?

Thx...