I agree that it's not ruined but it will need some
machine work. I was given a converted prop pitch many
years ago when I was in the process of putting up my
first tower. Since I was out of money, I decided to
use it for my rotator even though I knew nothing about
it. The conversion broke the first winter and thus
started an ongoing series of fixes and improvements.
I learned quite a lot about them in the process! I'm
still using my original prop pitch to turn a small
array (by todays standards) of a TH6 and 40-2CD.
The weakness in these units is in how the conversion
was made. One of the original ring gears was cut or
ground off of the large splined assembly the exits the
case (which drives/turns the mast). After this
conversion, this spline assembly was drilled and then
bolted to corrosponding holes drilled & tapped in the
aluminum planetary gear assembly. Therein lies the
problem. I've managed to make mine fairly
bullet-proof by doing the following:
(1) Machine a "donut" (I used brass) to fit under the
spline assembly to fill in the space where the bolts
pass thru. When bolted together, this creates a solid
"sandwich" of the spline/donut/gear case so that there
is no "slop" in this part of the drive train that will
eventually work loose. This can then shear the bolts
(it happened here).
(2) The holes that were drilled into the aluminum
planetary gear assembly should be drilled and tapped
to accept either HELICOIL or NYLOK steel threaded
inserts. Install the inserts and then the bolts with
some medium-hold locktite and you should have a really
good, reliable rotator.
Have said all this, I'd still never use a converted
prop pitch for a really big array. The one I have is
a "small" model prop pitch. We had some of the big
ones at W3GM but I've never had any of them apart but
understand that they are similar in construction.
I've also used the sylsen/bicycle chain indicator
system for years with very few problems.
Hope some of you will find this info useful
73, Stew K3ND
--- Stan or Patricia Griffiths <w7ni@teleport.com>
wrote:
> art unwin wrote:
>
> > Hello Marc,
> >
> > Prop pitch ruined ???? Not so !
> > There is a brake that originally came with the
> prop pitch
> > that many hams did not connect up. Mine handles
> the wind
> > with a 35 foot boom plus 13 elements with the
> brake supplied.
> > It did move a 80 foot boom into the wind which
> really didn,t
> > bother me otherwise I would have increased the
> brake power
> > ( There is an advantage to having the antenna turn
> into the wind
> > rather than it be battered to death )
> > Usually those that complain of wind rotation have
> not
> > connected the supplied brake or given thought to
> adding one
> > Of course a small beam (< 20 foot),does not
> require a brake.
>
> You are right on this point, Art. I never did try
> to hook up the
> brake or make any other effort to brake the rotator.
> Of course, the
> original brake may be missing and lost forever at
> this point in time .
> . .
>
> > If you use a variac ( or a speed control unit) you
> can
> > vary the voltage for any speed desired.( Together
> with
> > a controled start and stop if you really want to
> get fancy).
>
> I use a Variac without controlled start or stop.
>
> > I do not recomend the use of selsyns, they are a
> cause of
> > problems in inclement weather. I made a circular 1
> inch
> > wide band of aluminum with the points of the
> compass
> > marked on it and secured it to the mast.
> > I use a cheap miniature c.c.d. camera ($40 new
> )aimed permanently
> > at the band and can see the direction it is
> pointed at
> > on a c.c.d monitor or t.v.in the shack.( 40 odd
> years have
> > passed since that article was printed )
>
> I have had a set of selsyns in place since 1975
> using bycycle chain
> drive with no problems, so far . . .
>
> > If the rotor has been modified with securing
> screws
> > as shown in the original C.Q. magazine article I
> > would recommend that you weld 3 -1 inch dia by 1
> inch long
> > to the underside of the bell housing instead so
> they mesh
> > with the 3 tapered, weight saving, holes in the
> circular sun gear.
> > These are much stronger than the questionable
> securing method
> > (shear resistance)originally described and is more
> inline
> > with the rotors original design torque abilities.
> >
> > If the rotor is to be used only for turning an
> antenna then
> > there is no need for the oil as there is no danger
> of overheating
> > and the non weld additive in the oil does not come
> into play
> > As with all rotors use a mast bearing to support
> your antenna
> > leaving the rotor to deal only with rotation
> especially with
> > a prop pitch where the vertical load bearing
> system is not
> > the greatest
> > Good luck
> > Art Unwin
>
> I use a thrust bearing and no oil in the gear box
> with mine.
>
> Stan
> w7ni@teleport.com
>
>
>
>
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