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[TowerTalk] Very Old Grease Characteristics

Subject: [TowerTalk] Very Old Grease Characteristics
From: "Pat Barthelow" <>
Date: Wed, 20 Dec 2006 10:38:09 -0800
List-post: <>

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 
retractor/inserter drive.
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;
Skype: Sparky599
Moon or Bust!--Jamesburg Gang Rides Again!


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