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Raising (Hell) Beams

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Subject: Raising (Hell) Beams
From: (Tony Brock-Fisher)
Date: Thu, 9 Jan 1997 11:14:26 -0500
What may have been missing from your description, Lee, was that the
tram line which supports the antenna on the way up should NOT be
very tight. Dave Robbins, K1TTT (ex KY1H) wrote an article for
the YCCC Scuttlebutt a few years back which analyzed the physics
of this arrangement. Among other things, he found that the lateral
force at the top support (tower/mast) GREATLY increases when the
tramline gets taught and straight. It is MUCH less stressful on the
whole affair to let the tramline have a bunch of sag in it.

If there is any question about the strength of the top support,
I'd recommend using a temporary back guy, from the top support
to a solid attachment on the ground, running 180 degrees around the
tower from the tramline bottom.

I can personally attest to these affects. I was using a schedule 80
water pipe as a mast, and put a slight bend in it while raising
a KT-34XA with too tight a tramline and no backguy.

Tramlines are cool. It takes all day to set them up properly and
another to take them down. But when they work right, I've been
able to install large antennas with no more ground crew than the XYL.

Think through your arrangement carefully, visualizing each step
in the process. This will help you remember details like 'the
lifting line goes OVER the boom' etc...

-Tony, K1KP,

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