[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:
>Greg --
>   Maybe you have some suggestions that will help these folks?
>-- Eric
>-------- 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.
>See: http://www.longandflatsociety.com/Default.aspx?tabid=474
>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 aa6eg at hotmail.com;
>Skype: Sparky599
>Moon or Bust!--Jamesburg Gang Rides Again!
>TowerTalk mailing list
>TowerTalk at contesting.com

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