[TowerTalk] Very Old Grease Characteristics
Eric Scace K3NA
eric at k3na.org
Fri Dec 22 16:27:34 EST 2006
Some suggestions from my brother, who is very good at mechanical stuff.
-- Eric K3NA
-------- Original Message --------
Subject: Re: Very Old Grease Characteristics
Date: Fri, 22 Dec 2006 15:47:46 -0500
From: Greg Scace <gregory.scace at nist.gov>
To: eric at k3na.org
References: <4589A097.3090500 at k3na.org>
Is there any way that they can try heating the assembly near the pin
to grow the hole? Heat, penetrating lube and a hammer and punch
often work pretty well.
At 03:44 PM 12/20/2006, you wrote:
> Maybe you have some suggestions that will help these folks?
>-------- Original Message --------
>Subject: [TowerTalk] Very Old Grease Characteristics
>Date: Wed, 20 Dec 2006 10:38:09 -0800
>From: Pat Barthelow <aa6eg at hotmail.com>
>To: towertalk at contesting.com
>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,
>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 aa6eg at hotmail.com;
>Moon or Bust!--Jamesburg Gang Rides Again!
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