Rohn has once again, about a year or so ago, discontinued
the torque arms for the GA25GD
as well as the ones for use with the 45G and 55G towers.
The torque arms have always
been sold separately from the guy attachment hardware, as
far as I can recall. I don't
ever recall them saying they were not effective for taking
care of some of the torque we
hams feel when stopping and starting long boom Yagis . . .
but then they say a LOT of
stuff I don't hear . . .
What I DO KNOW is that Rohn is FAR more interested in the
problems of the commercial
uses of their towers than they are for ham uses. I also
know that in order for a GA25GD
with torque bars to resist any significant amount of torque,
the tower actually has to
twist enough for the guy wires to tighten up and prevent
further twisting. A little
twisting does not bother any ham applications that I know
of, but even a couple of
degrees of twist in a tower will throw a sidemounted
microwave dish WAY off so a GA25GD
with torque arms has little or no benefit for the commercial
dish user. For fixing the
torquing problem for the commercial customers, Rohn
recommends the TA25 Torque Arm
Stabilizer which, you may recall, needs 6 guy wires at one
level where it is installed.
This REALLY takes care of tower torquing but not too many
hams use that method since it
requires 3 extra guys.
It would be interesting to make some twisting measurements
on a tower with and without
torque arms installed when starting and stopping a big beam
with about a 50 foot boom.
I have to believe there would be some difference but
probably not enough to satisfy any
commercial application problems. I also believe that would
be enough to convince Rohn
to discontinue making them . . . Hey, they discontinued
fold-overs and BX . . . who do
you think the major customers are for those towers . . . ?
I think K7PN is going to make some "after market" torque
arms for 25, 45, and 55 when I
can get him to take the time to do it. If it happens, I
will announce it here and watch
my web site:
Kurt Andress wrote:
> K7LXC@aol.com wrote:
> > In a message dated 6/22/01 8:45:52 PM Pacific Daylight Time,
> > K7NV@contesting.com writes:
> > > This bracket doesn't do anything for torque.
> > You sure about this? I talked to the Rohn factory about this when they
> > discontinued and then started up again production of the long revered
> > 'torque
> > arms'.
> > Hams had been using the torque arms for years and "knew" intuitively
> > that
> > they contributed "something" to the torque resisitance of the tower. When
> > Rohn upgraded to a new TIA-222 rev (this was awhile ago so it might have
> > been
> > Rev. C or D) and they ran the calcs, they found that the standard torque
> > arms
> > didn't really contribute anything to tower torque resistance. They
> > determined
> > that they were primarily useful for when the tower was climbed; hence the
> > "psychological help" they provided with little or no actual usefullness.
> > Rohn
> > decided to convert over to the new design with the oval rings.
> > Well, hams hit the roof because "we've always used them, therefore they
> > must be useful" and Rohn resumed production of the old TA's in spite of
> > their
> > marginal usefulness.
> > Cheers, Steve K7LXC
> Here's what I read in the posts I responded to Steve,
> Steve/n0tu wrote:
> > I see Rohn recommends their guy assembly (GA25GD) accessory for attaching
> > guys to the tower.
> Richard Thorne wrote:
> > Steve:
> > Either will work, I've done it both ways. I like the GA25GD attach method
> > though.
> The Rohn catalogue I bought from you says:
> Guy Bracket
> Mounts to tower at any tower at any horizontal brace.
> Torque bars
> TB25D (not shown)
> Optional for use with GA25GD
> Did either of those posts say anything about torque bars? Rohn is pretty
> clear that
> they aren't included in the GA25GD.
> I simply assumed those fellows meant what they said. I know I did.
> Now, that torque bars are part of the discussion, you seem to have covered it.
> 73, Kurt, K7NV
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