Mike: I have been using a modified prop pitch motor to turn first a large 20m
4 el and later a full size 2 el 40 with no windmilling. I use a heavy duty wall
switch triac w rotary knob feeding a step down xfmr and bridge rectifier. I
always turn the triac switch down when I start rotating and move it up slowly
as I watch the direction indicator. When I approach the correct direction I
turn the triac knob down to coast to a gentle stop. Apparently some others have
had problem w windmilling but not I. This setup was used for 20 plus years in
Tulsa and Dallas.
Re the selsyns, I used them for about a year in Tulsa but moisture got in the
bearing and the rotator one froze up. Since that time I have used 5K pot driven
by very small stainless cable w pulleys. Some people make a toothed gear out of
sheet metal to drive either a selsyn or a pot. This mates w the bevel gear on
the prop pitch and mounts in tilted fashion to be at 90 deg to bevel gear teeth
surface. It can be either a large one and a single turn pot or a small one and
a multiturn pot. At the station end I use a simple LM 324 op amp driving a 1 ma
meter. I have a large 7 inch one. The scale was flipped over and hand lettered
w degree scale. I haven't seen selsyns in flea market for years so no idea what
they might cost. 73, and GL. Dan, N5AR
Mike Nash, NO6X wrote:
> Well I did the inevitable. I have a tower to rotate, and think I have
> figured out how to do it. By means of a prop pitch that I purchased this
> evening.
> I know there was just a big thread on this and I do not mean to re-open
> that by any means.
> This prop pitch has been(cover your eyers) modified.
> In hooking it up to 12 volts, it draws in the neighborhood of 10 amps while
> rotating and takes about 40 seconds to to make one complete revolution.
> Please forgive the stupid question, but will it hurt anything to run this
> at say 7 or 8 volts to slow it down?By basic principles it is only a DC
> motor and should NOT, but I thought I would ask before I did it.
> Now selsyns...
> Where to get them and how much do they normally run?
>
> For all those wondering... the Prop pitch will turn a small tower with two
> 10 meter yagis, spaced approx 1/2 wave apart.
>
> Good use for it???
> Please advise of pit falls if you know of them.
> Thanks
> Mike...NO6X
>
> A Keyring, what a handy gadget. It allows me to lose all of my keys at one
> time.
>
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