Ken:
Thanks for your note. I agree that a BIG rotator can withstand and
survive many of the overloads that torque imbalances can place on it. I'm
not familiar with PP rotators, but I'll take your word on their robustness.
BUT, if the rotator survives, that means that the torque has to go
somewhere else. That's the tower itself. NOW I have the problem of
ensuring that my guys are strong enough, the tower material is beefy enough,
etc., etc., ad nauseum. All this co$t$. I'd rather not have those
headaches.
As I've been saying (writing), do your math, move things around on the
proper size mast, and sleep soundly each night.
73 de
Gene Smar AD3F
-----Original Message-----
From: K7GCO@aol.com <K7GCO@aol.com>
To: towertalk@contesting.com <towertalk@contesting.com>;
SPELUNK.SUENO@prodigy.net <SPELUNK.SUENO@prodigy.net>
To: <towertalk@contesting.com>
Date: Friday, June 08, 2001 6:52 AM
Subject: Re: [TowerTalk] Wind Loading redux, PP Motors
>In a message dated 6/7/01 9:20:40 PM Pacific Daylight Time,
>SPELUNK.SUENO@prodigy.net writes:
>
><< Kurt:
>
> With my planned antenna arrays, I won't have appreciable mast torque
> caused by off-center mounting of the boom on the mast. I'll have a small
> V/UHF vertical at the top, a D40 rotatable dipole (same length on either
> side of the boom bracket) below that, and the Bencher Skyhawk (purportedly
> torque balanced by the element and boom compensator pieces.) If and when
I
> install the 2M Yagi (KLM 144-148-13LBA), it will be mounted at the center
of
> its boom; there's not enough element aluminum to worry about finding the
> balance center of the boom.)
>
> I think what you're cautioning us about is the case where we have
large
> HF Yagi arrays in which the balance point (and mounting point) of the
array
> is not the center of the boom. In these cases, wind blowing broadside to
> the boom will want to turn the longer side of the boom away from the wind,
> creating torque on the mast/rotator/tower.
>
> Dick's papers on aerodynamic balancing discuss how to compensate for
> such imbalances, e.g., fixing a weight onto the boom so the balance point
is
> shifted to the center of the boom, or entending the shorter side of the
boom
> with a piece of aluminum tubing sleeved onto the main boom, or installing
> compensators.
>
> BOTTOM LINE: You have to do some "cypherin' " before you put up an
> antenna/tower system. Apparently, there's more to ham radio than Ohm's
Law.
>
> GL es V=IR de
> Gene Smar AD3F
> >>
>All these factors are certainly important. However there are ways to avoid
>all this concern and calculations for mechanical and wind unbalance that
can
>occur. Use a Prop Pitch Motor, it's far cheaper and trouble free if
properly
>converted and installed. In over 55 years of spinning many beams, the size
>of the beam and any wind unbalance and other factors have never ever been
>given the slightest consideration. The beam was balanced mechanically and
>that's it--end of story. I use friction aluminum bearings I make and no
>other "Band Aids." I've never had a rotator problem except water got in a
PP
>once and rusted some bearings. I overhauled the bearings and improved the
>rain protection. All this time I apply power the beams turns each and
every
>time at 2-6 rpm depending on the size of the beam. No other commercial
>rotator user can make that statement. I use other rotators all speeded up
>(even the small TV rotators) and just never overload them. A fast spinning
>TV antenna is a joy to see. My rotator budget has been a little over $200
>for PP motors and I just paid an all time high of $50 for a medium PP
motor.
>It was a mechanical joy converting one again after 55 years. I have
>purchased 4 of the typical $120 rotators at flee markets for a total of
$120.
>
>
>The 3 Big Fears of John Q Ham are:
>1. There's a big wind and he worries about all the TT Band Aids not holding
>up
>2. He's running over power and thinks the FCC may be checking power levels
>3. His gal friend tells him she missed her period
>
>If you have all 3 on the same night--it's almost unbearable. (Old K7GCO
>Axiom)
>
>
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>-----
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List Sponsor: Are you thinking about installing a tower this summer? Call us
for information on our fabulous Trylon Titan self-supporting towers - up to
96-feet for less than $2000! at 888-833-3104 <A
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