Thanks for the dozen responses to my questions about ProSisTel/Big Boy and
prop pitch motors.
The two first-hand accounts of ProSisTel/Big Boy rotators were posted on
TowerTalk, and I needn't say anything more about them. The basic point is
that the rotators work, and some work is required to get them working (not
unexpected with a project of this nature). The previous delivery concerns
at least seem to have been addressed.
As for prop pitch motors, I've received some leads that I'm following up.
Some background is in order.
I now operate two OR2800P rotators, and have imported two OR2800 prop pitch
controllers for ZS4TX. All of them have had reliability issues. Factory
support has been difficult. While they have answered my questions and have
offered to repair the units (even after the warranty period), they have not
been prepared to give me troubleshooting info. As you can imagine, shipping
stuff halfway around the world is time consuming and expensive. I would
much prefer being able to find the bug myself.
ZS4TX's one box came without the pickup, which the factory sent without
problems (except, of course, for the transit wait). His other box was
incorrectly wired. Once he fixed the wiring, it worked flawlessly.
My one rotator's neck broke just above the casing, where the spline starts.
The sideways load, imposed by a cable drive, was well below what would have
been experienced with a point load of the rated area, at the top of the mast
clamp (the most favourable situation for the rotator). My contention is
that the rotator should have been able to withstand that side load, as it's
well within specified loads; Mike maintains that I abused the rotator. A
replacement shaft was almost $ 60, including postage. A metallurgist's
first opinion was that it was a casting fault, but I haven't had his final
report back yet.
Both my control boxes have developed intermittent faults. The faults come
mysteriously, and generally disappear as mysteriously some weeks or months
later. In some cases, the box loses the heading each time I turn off the
power. In other cases, the beams keep running after I release the button.
The display keeps running even after the beams hit the stop (i.e. the LED
digits keep rolling even though the beam is no longer turning). The display
goes way out of range (like 750 degrees). The lasest is that my one beam
refuses to turn in one direction, even though the relays sequence as they
should. I haven't found time to diagnose the problem properly. I'm hoping
it will also disappear mysteriously...
I now want to turn a guyed rotating tower. The 2800 in-lb of rated rotating
torque is dangerously close to the actual requirement, due to bearing drag
on the guy rings. I have to look for something heavier. The prop pitch
option would have been attractive if I didn't have this nagging fear of
Orion control boxes. The effort involved in making a selsyn-based indicator
system is beyond my available time right now.
K6NA used to supply a control box with prop pitch motors, but has indicated
that he doesn't have enough time to churn them out right now. They are also
pretty expensive, and don't offer an automatic rotation option (i.e.
hands-free).
Bottom line: If you want to turn really heavy stuff, and you don't have
lots of time, you can choose between ProSisTel, Giovannini
(http://www.antenna.it) and a prop pitch motor with an Orion box. None of
these constitute really simple options. Perhaps stamp collecting really
isn't such a bad hobby after all...
Chris R. Burger
ZS6EZ
http://zs6ez.za.org
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