The more I think about it the more I think in this arrangement pulling
toward the back stay anchor is the right thing to do. When I tram my back
stay has a hard attachment to the tower, yours doesn't. so if you pulled
straight down on the rope you will still have side force on the tower from
the hauling rope attachment to the antenna, the back stay can't compensate
for that since its not attached to the tower. If you pull back toward the
backstay with the rope then the force from the pulley will all be down the
mast instead of sideways toward the antenna.
David Robbins K1TTT
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: Al, N6TA [mailto:email@example.com]
> Sent: Sunday, November 23, 2008 04:54
> To: firstname.lastname@example.org
> Subject: [TowerTalk] Tramming help sought
> I won't bore the readers with the usual retread questions. Already did
> the reading etc. and lowered the old beam a month ago. This is one on how
> to rig the haul line to pull up the 110 lb SteppIr yagi.
> The tram line is to be rigged about 3 feet above the top on the Rohn 45
> tower which has a flat top plate. The boom will be mounted right above
> the top plate. The tram line is continuous in that it goes thru a pulley
> and down to a 'back stay point'. Trying to allow the tram line some
> ability to move but direct most of the force down the mast to the rotor.
> The beam will be hung from a sling that connects a pulley to the tram
> line. The boom will hang about 18 inches below the tram line. A
> tiller/torque arm will be attached 'behind' the boom, keeping the boom
> from rotating in two axes.
> The haul line is half inch polyester double braid and will be tied to the
> boom close to the CG point. The bracket that holds the tram line above
> the tower top has a place for a pulley to be mounted for the haul line,
> probably attached with a snap link or shackle. The question I have is how
> to rig the haul line's pulley such that I can pull straight down and not
> have interference with the tower's top plate. The bracket for the pulley
> is about 3 inches out from the mast and the tower needs about 9 inches
> clearance from the mast to go straight down without rubbing on the edge of
> the top plate. I fear way too much friction if I allow this. I lowered
> the prior beam this way and used the friction to advantage but do not want
> such issues when pulling up the new beam.
> If I rig the haul line pulley ( a CMI 2.375 inch 95% eff. rescue type)
> such that it is hanging out far enough to clear the top plate, I end up
> pulling sideways on the mast.
> There must be a standard practice here but I have not yet read any
> postings about this detail. I usually just 'go for it' and keep the
> fingers crossed. I have way too many PhDs in the School of Hard Knocks
> and prefer to not get another....
> If I can pull the beam up as far as it can get, to the haul line pulley, I
> plan to relax the tram line and let it settle the boom down where it will
> rest on the top plate until I can use other means to raise it the 6 inches
> to the boom to mast plate.
> Willing to call to talk about it.
> Tnx in advance.
> Yeah, I'm missing the CW test due to delay in getting this up.
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