Adding to what Mike said:
My UK made crank up/ fold over is rated by the manufacturer for 9.9 square feet
of antennas at 120mph when guyed. It is rated for 70mph with 9.2 square feet
when not guyed. It's carrying a T2X rotator and a 4 ele Steppir at 62 feet now
- it was loaded up with a 205BA at 62 feet and a 4ele for 15 interlaced with a
4 ele for 10 at 68 feet. It stays up except dor maintenance and the occasional
predicted very high winds, although it was up in the storms of 1987 and 1992,
both of which hit 120mph. When I have time, there's a very big heavy electric
winch to go on it to save the trouble of hand winding. When I last looked, the
manufacturer's electric winch was over $1100 - and that's a good ten tears ago.
Interestingly, the concrete base called for is 5.5 by 5.5 feet by 4 feet deep,
with no rebar. The tower has a base mount that folds the tower (retracted, of
course!) over from about 6 feet up, and the whole lot weighs 1160 lbs, so when
folded over, there's a fair bit of tension on the concrete, but apparently, not
enough to worry about. The bolts holding the base plate in the concrete are
24mm diameter, about 24 inches long, with 3 inch square wash plates on them:
this sort of installation is probably reasonably typical for those UK hams who
have towers. Having said that, a number of people use a ground post to hold the
tower, rather than a bigger base plate approach. I went for the base plate
because it's easier to get a flat level concrete surface than a 6 inch diameter
steel post exactly upright in the concrete!
At today's prices and exchange rate, it's also around the $5k mark, over rather
than under, I suspect.....it's been up 20 years this month. (Suddenly realised
that with inflation, it might be underinsured - need to look into that). I've
changed the wire ropes once, not because they needed it, but they looked like
they might. Similarly, the guys, which are prestretched UV resistant polyester
rated for a breaking strain of 4000lbs. New ropes of this quality cost about
$600, plus the effort in splicing the thimbles in. (I use Marlow brand marine
ropes - they are well prized apparently in US yachting circles) When up, the
first section sits on a hefty catch. Climbing has only been done in an
emergency and then with lengths of 1 inch diameter BMS bar inserted so that
each section is sitting on the BMS, not on a rope. (It needs about 10 tons to
shear that much BMS) I use a spray wire rope dressing from Rocol, and touch up
the galvanising when needed with spray on cold galvanising s
pray - not brilliant, but better than nothing.
I guess there's a lot of difference here between UK and US practice, while at
today's prices the conccrete base alone would be the best part of $750. All in
all, doing a tower installation isn't likely to be cheap, crank up or fixed.
73 es HNY
Peter G3RZP
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|