[TowerTalk] Prop Pitch Speed Up

[dan hearn]

The prop pitch motor used by most hams has a gear reduction of 9576:1 .I
modified one per the QST article in 1950. I have used it to rotate first a 4
el 20 on a 42 ft boom. I later used it to rotate a KLM 5 el 20. This "Big
Stick" antenna , when mounted at the center of gravity, has very bad
unbalanced wind torque. In 40 + years of use I never saw any evidence of
windmilling. Even with the loss of one gear reduction in the train, I have
doubts that any ham antenna could turn it backwards. Has anyone out there
actually had a problem with this ? 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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