The tram line needs to be somewhat tighter as the beam approaches the
tower, other wise you'll get fouled up with the last set of guys. My
approach is to tighten the tram reasonably tight to start with so by the
time the beam gets halfway up the stretch makes it quite loose. That's if
I'm using 1/2 inch rope. On bigger stuff 5/16 ehs is used, stretch isn't
an issue then. Regardless, too much tension when the beam is in the middle
2/3rds certainly does cause a lot of side pull on the mast. A back guy
is always a good plan, a bent mast is a real hassle. We use those
4000 lb rated cable pullers to tension the tram, and once the beam gets
near the tower we just tighten the tram, the beam is lifted away and you
can the tram the beam right to its' resting place.
On bigger beams (like 3 el 40 fullsize 400 lbers) the tram is usually
attached the tower, not the mast. Once the beam is trammed up next to the
tower, a chain fall type of hoist is used to pull the antenna vertically
up into place.
73 Don
VE6JY is Don Moman email: ve6jy@freenet.edmonton.ab.ca
Box 127 Lamont, Alberta
T0B 2R0 (403) 895-2925
On Thu, 9 Jan 1997, Tony Brock-Fisher wrote:
> 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.
etc
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