[TowerTalk] Prop Pitch Speed Up

[dan hearn]

My friend, Jack Kennedy, W5DJ has analyzed the small prop pitch motor gear
train. He found that the output gear train ratio (eliminated with this mod )
is 9 1/3 .He has a Curtis Wright manual for the rotator which says the
unmodified unit has a torque output of 1350 ft-lbs and draws 11 amps at 24 v
d.c. This is about 1/3 horsepower. Output shaft speed is about 2/3 rpm. To get
this, the motor is turning at about 15000 rpm and is rather noisy. Brush wear
at this speed is significant. as is wear on the motor shaft oil seal.There is
some incentive to slow this thing down, Hi. 73, Dan, N5AR

Paul Nyland wrote:

> Hello All,
>
> I have been told by Rush W7RM, and others, that if you make this
> modification you lose a lot of the braking power of the gear reduction. I
> had one prop pitch that was modified like this and luckily Rush gave me
> another gear for it so I could convert it back to stock. Once you machine
> the teeth off the output gear you can't go back unless you can get another
> gear.
>
> 73,
> Paul
>
> At 01:45 AM 1/15/99 -0800, you wrote:
> >
> >
> >Hi All
> >
> >Here's something I found in the 1949 June QST that might
> >be of some interest to the guys with prop pitch motors.
> >The article was "Speeding up prop pitch beam rotors"
> >
> >Here's a way to speed up the rotation of a prop pitch without
> >external speed up gears, V-belts or speeding up the motor
> >until it burns out.  Here's how it's done--remove:
> >
> >     1)  the bevel gear;
> >     2) its thrust bearing plate;
> >     3) the upper case of the speed reduction unit housing;
> >     4) the large ring gear with the spline on it;
> >
> >This last item is the first thing you will see upon removing Item
> >3.
> >
> >Grind the teeth off the hardened splined ring gear. (Not off the
> >splined portion, but off the inside of the ring!)  Next drill and
> >tap
> >four holes in the gear carrier over which the ring gear was
> >placed.
> >Line up the holes with the holes that already exist in the face
> >of
> >ring gear, and bolt the two together.  Reassemble the whole thing
> >and fill it with oil.  You can now turn your beam at 4 or 5 RPM.
> >To reduce this to a more-comfortable 2 RPM, it is only necessary
> >to reduce the voltage to the motor.  Don't worry about the slight
> >reduction in power caused by "short circuiting" one of the
> >several
> >planetary gear sets.  It will still have enough steam to "rotate
> >the
> >house should the beam get stuck."
> >
> >This original article appeared in "Hints and Kinks" in the
> >magazine
> >and was written by W2VLL
> >
> >73
> >Tom W7WHY
> >
> >--
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> >
> >
> K7PN/5V7PN
> paulnyl@teleport.com
> http://www.custommetalworks.com
>
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