On the TIC ring we use for the 15 meter Hemi 426 yagi, the truss is mounted
on a vertical pipe slightly off center.
The one thing I would do differently and will change when we have to lower
the beam....its been working fine so far....is to mount the pipe so it is on
the "outside" of the beam, we have it on the "inner" side of the boom so it
does come closer to the tower than is necesary. it don't hit nothin but is in
the way at times. By mounting the truss on a heavy duty pipe (i.e. sched 40
water pipe) and using a hefty truss to boom plate and u bolts you can use the
truss as a lifting point. We trammed the beam up and then dead a vertical
lift from the top of the truss pipe - it was a convenient place to snap a
carribeener on. the load was slightly off balance but close enough.
Someone suggested you use a piece of tv mast for the truss.....don't! It is
crap, check out your junk bin for some galv pipe. If necessary, go to the
hardware store and check out the bin where the guy has his cut pieces....he
is begging to sell them, not very popular once cut, the drop piece is pretty
much so already paid for stuff in the storeowners eyes, so anything he gets
is a relief. Check out what he wants per foot on a whole piece and offer him
less than half that for the drop piece, i.e. if it is selling that diameter
pipe for 2 bux a foot and there is a four foot piece in the drop bin offer
him (4 ft x 1 buck) "you take 3 bucks for that piece?" He will be relieved at
your offer.
RE: trusses, they DO give your beam that professional rigid look. If you
wanna go all the way you can order some Phillystran and guy grips, whether or
not it is necessary since the truss is at right angles to the radiators will
be debated by others, I used it on the last beam and it went on VERY easily.
Be sure and get the correct size for the grips, the smallest Phillystran
while duty wise is big enough for the job, does not have guy grips, you have
to go up to the next size.
73
zx k1zx@contesting.com
|