On 11/3/2012 10:51 AM, Kenneth Grimm wrote:
While not taking issue with any of the comments made about the Tailtwister,
I feel that I need to point out that while "overkill" in the form of the
high priced worm gear rotors is fine, it isn't always necessary. For
example, I used a Tailtwister to turn a stack of a HyGain 204BA, Wilson
4-15 and Wilson 4-10 for about 15 years without failure.
I used to run a 5L KLM 20, 6L KLM 15, and a 7L Wilson on 10. Each on its
own tower and turned by the Tailtwister's early ancestors. The Tail
twister wasn't even available back then and I had nary a problem. This
was out in open flatland with absolutely no protection from the winds.
I never had a problem with a brake, motor, gears, or bearings.
When I moved here I put up the big array. It tore apart the rotator in
a matter of days. I picked up to HDR 300's. The HDR rotators were
plenty strong enough, but the motors offered too little resistance to
turning. One day which was kinda windy I tried to turn the system, but
as soon as I released the brake the array spun around before I could
stop it with the motor. It took the rotator right past the stops.
A few days later it did the same thing with a second HDR. That was when
I ordered the double worm gear rotator and swore I'd never use a rotator
with a wedge brake on anything larger than a small tribander.
As these rotators were 20 feet down from the top of a 100 foot 45G they
were a royal PITA to repair which required raising the mast a few inches
with all that load and locking it in place to keep it from turning with
the rotator out.
As I was working alone most of the time it took numerous trips up the
tower and I'm now too old for that much climbing. Once or twice is OK,
but I no longer have the stamina to spend all afternoon up there.
It's basically "the luck of the draw". I had those large antennas on
small rotators for quite a few years, moved to a new location and lost
them in short order. If I do the math the torque from that bit array is
no more than the big KLMs I had up. Yes, the lateral force is much more,
but that was supposedly taken care of by two TB-3 thrust bearings. The
wind load was well within the capabilities of the HDRs.
After moving to a new location and a complete tower and antenna
replacement, I decided to upgrade to a more powerful Yaesu G2800DXA. After
2 years, the failure (mechanical/electrical) of the Yaesu led me to put my
trusty old Tailtwister back up to turn a 4 element SteppIR and a Force 12
Delta 230/240. It has now survived a derecho earlier this year that
produced 80 mph gusts plus the much milder winds (40-60 mph) from Sandy.
Obviously, I didn't try turning the antennas in 80 mph winds, but the
brake held and the ring gear and case survived intact.
That's where we differ. If I want to operate, I don't care what the
weather is, other than thunderstorms. <:-))
I'm still scratching my head about what to use to replace the Tailtwister
to give me that added feeling of security that you get with a little
"overkill". My original idea was the M2 2800, but the bad reports on
eHam.net give me pause. That is still my first choice....I think. 8*) Is
there another, better, made in America, rotor?
I may build my own next time with a gear reduction with external motor
and use a commercial controller.
Now here's a rotator and antenna system.
http://www.rogerhalstead.com/ham_files/skyhook.htm
73
Roger (K8RI)
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