This may be already known but since I've been a stunt hermit for a few years I missed the news.
Anyway, building a new ship for 2020 and like most of you, I have boxes of stuff to pull from for parts. I have bag of the old PSP 4" bellcrank assemblies that have been laying around since the 90's so I grabbed one. It was seized solid to the shaft! Checked another one and the same thing. Went back into the hangar and pulled out a ship I had built back in the day that had one and low and behold, seized controls. I've also had an issue with tightening up controls on an older Bearcat stunter which has one too.
What I found was that it appears that when the brass washer/sleeves that position the bellcrank were soldered on flux was used and that seeped into the pivot area. Over time this has rusted the shaft where it passes through the bellcrank seizing it. BTW, the outside, visible parts are fine and everything looks normal. Good news is simply replacing the shaft fixes the problem.
I would neutralize the center pivot with baking soda and water - the flux stays in the bellcrank material and can rust anything it touches for a long time. I had something similar happen to one of mine, and some of the Windy bellcranks that I somehow came in possession of. On mine, it never had a chance to seize up, but it got rough as it corroded, and severely wore the pivot.
This is why you don't ever want to use Sta-Brite flux on a closed assembly that cannot be inspected/lubricated/repaired/replaced. And, making soda, lye, etc, will only slow it down. No matter how careful you are, it gets everywhere, and you can't get rid of it. I used some on when I was a kid (long before it was available to the public, it was sold industrially, and my father had it) to solder something, and it got on the surface of my dad's cast iron table saw. It rusted in a few minutes, I wiped it off, rusted again in a day or two, I used baking soda to "neutralize" it, happened again in a few days. My dad noticed and used emery paper and oil to polish it. Rusted again, kept doing it on and off, and last time I saw it, something like 50 years later, it had a rusty spot and a divot there. Of course, that was cast iron, and while it was an excellent casting job, it was porous.
It's OK if you absolutely have to use it, nothing else seems to work better as a flux, but unless you can clean it immediately and leave *no* voids for it to remain, on steel and non-porous materials, it will corrode everything it touches.
Brett
Topic: PSP Bellcrank Issues (Public Service Announcement?) (Read 1299 times)