What keeps the grease from running down the tower when it gets warm?
----- Original Message -----
From: "Dick Green" <firstname.lastname@example.org>
To: "Tower" <email@example.com>; <firstname.lastname@example.org>;
Sent: Wednesday, February 27, 2002 6:37 PM
Subject: Re: [Towertalk] US Tower MA-Series Maintenance
> MARB owners:
> I use plain-old automotive grease on the inside surface of the upper
> on the rotating base. That's what U.S. Tower told me to use. It's OK to
> it on thick. I use a grease gun to squirt more grease between the collar
> tube when the old grease layer gets thin or rubs off (sometimes I spread
> around with a popsicle stick.) The grease is important for preventing
> hangups and also prevents abrasion of the tube. It's conceivable that
> rotating the tower against an unlubed collar could eventually cut right
> through the steel and compromise the tube. U.S. Tower hinted about this
> possibility. As mentioned, don't forget to lube the lower thrust bearing.
> I've found that the single most important factor for preventing hangup
> (besides greasing the collar) is making sure the pipe section that
> the tower drive shaft with the rotor can move freely. It's a poor-man's
> u-joint. It's there because it's not possible for the mast to be perfectly
> concentric with the rotor -- it moves around too much in the upper collar
> and the very long bottom tube isn't perfectly round and straight.
> a flexible joint is needed between the tower and rotor. The short pipe
> section serves this purpose. If the rotor jaws are too high on the pipe
> section (say, as high as the bolt connecting the pipe to the drive shaft),
> then the pipe can't move far enough to provide the needed flex. There
> be two inches or more clearance between the bolt and the top of the rotor
> jaws, more if possible. The same thing can happen if you tighten the
> aircraft nut on the bolt too tight -- the pipe can't move. Just tighten
> nut until it rests against the pipe.
> 73, Dick WC1M
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