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[TowerTalk] PP Can

To: <>
Subject: [TowerTalk] PP Can
From: (antipode)
Date: Thu, 04 Oct 2001 08:58:37 -0700
You might check out some older issues of Wings and Airpower magazines. 
About 20 years ago they had the definitive story of the P-47 and I
recall clearly seeing the full prop-pitch motor gearhead with the
pointed motor cover.  I believe the "medium" size P-P was constructed
slightly different from the "small" size as used on the P-38.  Anyway I
could be mistaken, but that's what I remember.

Keeping the water out of these when used as rotators is the key to long
life.  I designed a rotator installation using a P-P motor about 35+
years ago for a good friend of mine in Fort Worth, and kept in mind the
necessity of keeping the water out.  When the assembly was taken down
about 25 years later, it was still working with no evidence of any water
problems.  Like you said, the water ingress points have to be thoroughly
sealed and places where water can collect have to be provided with
drainage exits.

Now if I can just get that d**n ring loose!

W5IQJ wrote:
> In regard to a partial cover on the P-47 PP motor, I've never seen that in
> looking at every PP Motor in the movies and TV since about 47.  Without the
> full cover water can get in the holes in the gear housing and put pressure on
> the oil seal when flying in the rain.  I'd like to see a picture of a
> partical cover like just over the motor part.  These holes have to be sealed
> for the same reason in use as a rotator without any centrifual force.
> Likewise with just the cover over the motor water can get in there also.
> It's true that the centrifugal force on the water would keep it out of the
> center but that is a poor design.  Don't let it get in when not rotating
> either.  k7gco
> In a message dated 10/3/01 3:46:06 PM Pacific Daylight Time,
> write:<<
>     Actually it depended upon the airplane type as to the configuration of
>  the prop-pitch motor assembly.  The small version of the P-P motor was
>  typically used on fighters such as the P-38.  The P-47 used the "medium"
>  size P-P.  As for external appearances, usually when the small motor was
>  used, a cover with a slight point to it encased the motor and gearhead
>  assembly entirely (e.g. C-46).  There were some older planes where the
>  prop-pitch was indeed fully exposed i.e. the deep-drawn cover over the
>  motor portion only and the gearhead itself exposed with no overall
>  cover.  The P-47 P-P was exposed when the Curtiss electric Propeller was
>  used.  Only the actual motor cover was used and is typical of the
>  "pointy" cover seen on the medium size versions.  The larger planes such
>  as the B-36 used the "large" motor which was fully enclosed.
>  From what I've seen, the B-29 did not use an electric feathering
>  propeller, but a hydraulic type instead.  The hydraulic type is evident
>  by it's nice straight-sided rounded nose cover in the center of the
>  propeller hub.
>  Bill Sievers
>  W5IQJ
>  On many
> wrote:
>   >  In a message dated 10/2/01 9:14:09 PM Pacific Daylight Time,
>  >  writes: <<
>  >   In a message dated 10/2/01 7:09:26 PM Pacific Daylight Time,
>  > writes:
>  >   > Does anyone out there have a proven way to remove the threaded locking
>  >   >  ring which secures the electric motor to the lower gear housing on a
>  >   >  prop-pitch motor?  All of the previous P-P's I've had experience with
>  >   >  had the retaining ring secured by peripheral bolts and was obviously
>  >   >  very easy to remove.  This one has a threaded ring which has an
> ominous
>  >   >  decal nearby on the housing which says "tighten to 250 to 300 foot
>  >   >  lbs.!!  (They must have only had gorillas in the AAF to work on these
>  >   >  things!).
>  >   >
>  >   >  I've got a spanner wrench which I believe was recommended in a post a
>  >   >  long time ago, but this doesn't even begin to turn the ring.  Using a
>  >   >  drive punch with a hammer looks like it would destroy the key slots
>  >   >  which obviously I don't want to do.  It seems like the only way to
>  >   >  remove this ring is with the proper tool and a VERY large gorilla!
>  >   >
>  >       Well - YEAH!
>  >
>  >       The only method I've seen has been to use a small chisel or
> screwdriver
>  >   to tap the ring off. If you gouge the slots, just file them with a round
>  >   file.
>   >       These transmissions and motors were used to change the pitch of the
>  >   propellors of WW2 airplane engines; the B-29 version plentiful and
> popular
>  >  so there's a reason why their specs are BIG. I can't even imagine how much
>  >   torque they had to hold and change.
>  >
>  >       You know all those pictures of WW2 planes with their propellors
>  > turning? You know that can on the front of the propellor? That's the motor
> for the
>  >  PP.  If anyone's got one for sale, let me know - I'd be interested in it.
>  >    Cheers,   Steve     K7LXC
>  >   Tower Tech
>  >    >>
>  >  That's not quite correct. It's the can for the motor and gear box.  There
>  > was another full housing over the whole PP motor and gear box.  It matched
> a
>  >  ridge on the top mounting plate.  Without the full housing the water would
>  >  get into the gear box as some had holes in the side above the oil seal.
>  >  These need to be sealed without the full housing.  They also weren't
>  > designed to work in the vertical position and that is why water can get
> down by the oil seal unless proper precautions ar taken.  It's the greatest
> rotator ever
>  >  made when properly used.  Speeded up they work just fine also.  I have my
>  >  original also and it cost $15.  k7gco
>  >
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