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[TowerTalk] Prop Pitch seals

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Subject: [TowerTalk] Prop Pitch seals
From: (James Hurt)
Date: Wed, 7 May 1997 19:56:07 -0400 (EDT)
Mike & Frank:

While generally agreeing with Frank's comments, I have rebuilt a few
prop-pitches, and may be able to offer some suggestions.

The upper planetary of the prop-pitch is running at very high speeds.
It was originally designed to run horizontally, as opposed to the vertical
method you find most of them used today. The original seal was designed
as Frank says, and will not hold the oil in the vertical plane. It would
make sense, to run lubricant of some type, whether it be grease or oil.

As a suggestion, the seal is a standard part, even today. It is available
in a number of configurations.  I am not an Engineer, or a seal expert,
but there is a seal available from CR that is a double seal, with a small
tension spring on it, that will work better than a single seal. Also,
if you use a double-sealed bearing as the bearing next to the seal, this
will help hold lubricant in the prop-pitch.

I have used this method on a number of prop-pitches here, and this method
has held transmission fluid as a lubricant. All of this assumes that the
shaft that protrudes thru the seal is in good condition. The seal has a
range of diameters that it is rated to work with, and if necessary, you
can turn down the shaft some, and still stay in spec with the seal.

You should also carefully inspect the seal at the low-speed shaft as well.
The construction of the prop-pitch mounted in the vertical, makes this
an excellent avenue for water ingress.

While I do not have the information in front of me, I can probably find
part numbers, if that would be any help.

73, Jim
K8MK, ex-KC8MK

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