Prop-pitch rotor help needed

[Stan Griffiths]

>I hope this is not repetitive.  I sent this request ealier this morning
>but since it han't shown up on the reflect yet I suspect something went
>wrong.
>
>I am in the process of putting up a beam for 40M and have recent
>acquired a prop-pitch rotor that I would like to use as the antenna
>rotator.  I have one small problem - I know nothing about the electrical
>requirements of a prop-pitch.  The unit had been previously used as
>an antenna rotator so most of the hardware is there, antenna clamp,
>tower plate, and AC syncronous tX/rx for the direction indicator.
>
>My main questions at this time are:
>
>1) What voltage does the prop-pitch opperate at? is it AC or DC?

Unmodified prop pitch motors were designed to run off of the normal aircraft
DC supply of 28 volts.  However, they will also run off of 35 volts AC at 60
Hz.  They take about 10 amps or so.  I understand that running them off of
AC wears the brushes a little more than DC.

There were several ways to modify prop pitch motors and several different
models as well.  Without seeing the prop pitch myself, it would be hard to
advise you any further.  Can you find a local expert to look over your shoulder?

>2) What can I do to give it a good check out before putting it up on the
>   tower?  Short of tearing the whole thing apart and rebuilding it.

You darn sure don't want to consider rebuilding it.  They contain lots of
precision bearings and if they are bad, I suspect replacements (if you can
find any) will cost an arm an a leg.

>3) How does one wire the AC syncronous tx/rx pair?  Each has screw
>   terminals marked - "X", "Y", "1", "2", and "3".  Also each unit
>   has on it that they are 115V 60hz type syncros.

Run five wires connecting the "X" of one to the "X" of the other, the "Y" of
one to the "Y" of the other, etc for "1", "2", and "3".  Then connect 110
VAC across the "X" and "Y" wires.  I would do this very carefully with a
Variac set very low and crank it up slowly.  Nothing should happen until you
turn one of the shafts manually and the other one should follow it.

>4) I noticed that the output shaft of the prop-pitch has essentially no
>   backlash.  Should I be woried that the unit is ceased and will need
>   some serious overhauling? or is this normal for a prop-pitch?

This is normal for a prop pitch since it uses what is known as a "planetary
drive" with a gear reduction of about 10,000 to 1.  Just a very little
friction in the motor itself acts as an excellent brake.  You will need no
brake on a prop pitch.

If you suspect your prop pitch may have been modified, I can tell you what
to look for, for at least one modification that I know about.

Good luck and BTW, I use a prop pitch on my 5el 20 on a 48 foot boom.  Been
there since 1975 with no problems.

Stan  w7ni@teleport.com