We are stymied in our work to bring the Jamesburg 30 meter dish back into
operation. The dish is currently in the "stowed" position, pointing
straight up. It is locked in that position by a 3" diameter stainless steel
"pin" that is electrically driven up a cylinder, into a hole in the heavy
steel elevation motion system.
The pin's close fitting cylinder-housing has zerk fittings for heavy grease
liube that probably had not been attended to in years, possibly decades.
The dish probably had not been the stow position for decades, if ever, as,
it sat pointed at an Intelsat geosynchronous satellte, low to the horizon,
over the Pacific since 1968. Two years ago, someone moved the dish to stow
position. We, wanting to do moonbounce with the dish, have tried the two
ways to retract the pin to unlock the vertical motion, using the locking pin
motor drive, and the manual crank, with no luck. We have hand cranked the
vertical motion support so as to remove any shear forces on the pin; That
is, the pin is precisely centered in the close fitting hole. The pin is
so solidly stuck, it may as well have been epoxied into place. Moderately
powerful forces have been used to try to push the pin down out of the locked
postion. to no avail.
Some of us think there may be wear ridges inside the cylinder preventing pin
movement downward. The pin is in some ways similar to a piston, has a
connecting rod and wrist pin-like connection in its bottom for motorized
We are going to investigate that for possible cylinder interference, in
detail our next visit.
Others think that the 30 year old grease has fossilized to something akin to
epoxy, or coax seal, and is keeping the pin from moving.
My question is what does thick bearing grease evolve to in, say 30 years, if
untouched? Stone? Epoxy? Grit?
A parallel to normal towers might be a tower in decades long storage, that
had heavy greased cable pulleys. Has anyone found 30 year old pulleys to be
jammed up hard with what used to be lube grease?
73, DX, de Pat AA6EG email@example.com;
Moon or Bust!--Jamesburg Gang Rides Again!
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