Nice find!! Glad you rescued that, doesn't look too bad to me. I use AeroKroil for penetrating oil, expensive but good and one can lasts an eternity. Someday I gotta try Corrosion-X but it will be a long time before the Kroil runs out. Setscrews can be a PITA but yeah I also stay away from screw extractors like the plague. Heat and impact are your friends. For those ones in the pedestal cap, you've got a steel screw in an aluminum casting, so they aren't rusting into a blob but can still be tricky to get out. I usually just drill out setscrews carefully if they don't cooperate. The whole latitude adjustment is under-designed, no real party foul to just drill them out a bit and tap for a larger setscrew if you want. Sounds like you have that in hand already.
Counterweights are another story. Those things are deeply recessed and it's a steel screw in cast iron so they can rust to perdition. I think the suggestions above are good... For the main dec shaft weights I think retaining them with those smallish recessed setscrews is somewhat risky anyway...my 1975 8" deluxe mount came with retaining collars with their own setscrews that are much easier to maintain and secure. in your photos those aren't present. For my project I've additionally put in a big washer with a sturdy retaining screw in the end of the dec shaft to make absolutely sure the weight cannot fall off and cause the tube to drop. I know you want to avoid modifications, but it brings me a lot of peace of mind about protecting my OTA and irreplaceable mirror. Sadly I can't say whether the retaining collars aren't period correct for your mount or if they're just missing, but I bet there are folks here who can.
For de-rusting I'd just go with either Evaporust or electrolytic rust conversion. Results are fairly comparable, but electrolytic is way cheaper for big parts like the pier tube. You can do it with any old tub and a $30 import DC power supply. Five gallons of Evaporust will cost $100+.
Edited by Dave Cook, 05 February 2023 - 02:55 AM.
Then the creepy thought hit me that if I ever end up with another can, it just might be the last can I'll ever need. Close enough and it made me chuckle. I doubt I'll get any unless it shows up at an estate or garage sale. I don't do aviation stuff much anymore, haven't flown in over 2 years now, long expired all my ratings and registrations. It seems that every few years a few of us get together in the outback Rockies and sneak in some seat of the pants barn storming. This looks like a fun year.
