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[TowerTalk] torque stabilizers and a case history

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Subject: [TowerTalk] torque stabilizers and a case history
From: (Jim Henderson)
Date: Sun, 16 Mar 1997 16:43:35 +0000
Greetings Jeff and Reflectees:

        Regarding the query about torque bars/arms:

        I use the torque arms, not the "channel stock" torque type. I'm
sorry I cant quote you the Rohn ##s. But mine is the bolt-on bracket type
made from flat bar stock, with rigid arms at each corner. I remember the
other "channel" type being shown for 45G and bigger, and it bolts to the
tower legs with U-bolts. 

        Rod (W5HVV) says he uses what sounds like a similar HB arm approach,
and that likely works out the same in practice. 

        But I use them on the top 2 sets of guys on my 70' of 25G + 3'
bearing shelf; I have turned the same large Log Periodic for the past 10
years with it in our constant desert winds, with excellent success. The
antenna is heavy and has a 42' boom, so it developes a large inertia and is
less than optimum for symmetry in the wind. I tensioned the guys to about
15% of the rated strength, vice the standard 10%, and followed Rohn's
engineering data for wind zone-"C", which was deliberate overkill in this area.

        With these arms and the 15% tensioning, the tower is rock-solid when
stopping/starting the rotor, and in the stronger winds. January '96 saw an
unsusal 100+ mph wind storm here which took down some ham towers as well as
the county's main, commercially installed public service radio tower. (They
should have consulted K7LXC!) It was quite a mess. In any case, my LP and
25G stayed up, a fact which I delighted in mentioning to the county building
inspectors. Other than some rotor problems, the tower system stayed tight
and appears good as new as it enters it's 10th year. I have seen towers w/o
the torque bars twist like crazy with longer-boom antennas, so I think these
arm/bars were the saving grace.

        These bars are cheap, easy to install, and they WORK.

        Much good luck with your project.

73 de Jim, KF7E

Jim Henderson

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