Date: Thu, 1 Aug 2013 16:26:11 -0700 (PDT)
From: Steve Dyer <w1srd@yahoo.com>
To: Patrick Greenlee <patrick_g@windstream.net>,
"towertalk@contesting.com" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Crankup Danger
I think crank-ups with positive pull-down are never fully "lowered" and are
still supported by their lift cable.
I know this is the case with my LM-470.
73,
Steve
## That is the case with my old style HDX-689. All 5 x sections are 21 ft
long. When fully nested,
it is 26 ft tall, and not 21 ft. ALL cables are under full tension when nested.
If you plan on stuffing steel
in there, and then gently lower the tower onto the steel, to take the stress
and weight off the main lift cable,
watch out. You want the bottom of the 2nd section to either just barely touch
the inserted steel, or sit
.1 to .2 inch above it. Lower it down too much, and the lift cables etc will
not only go slack, they
could easily jump the pulleys and get wedged between the outsides of the
pulleys.
## On mu HDX-689, the upper sections all have 3 cables per section, one per
face. There is no mech
advantage to them. For an upper section to come crashing down would require
that all 3 x cables for
that section to break.... which is extremely unlikely. However the very top
section only has a single cable,
so the very top section is a concern.
## If the main lift cable from the drum every broke, the tower comes crashing
down, end of story....
and ditto if the chain ever broke. Back in the mid 90s, I read a few horror
stories where folks had
foolishly climbed a crank up tower, and had not inserted extra steel 1st. In
one case, the fellow lost
both hands and both feet. In another case, it was both feet and one hand.
Ever see a ^pile driver
hammering 14 inch steel tubes into the ground ? They drop a 1000 lb weight 7
feet above the steel
piling tube, then lift it back up 7 feet. That racket goes on all day long,
as the steel tube eventually
gets hammered into the ground. Now imagine 3500 lbs dropping from 90 ft up.
No wonder these crankups
make one helluva mess to the base when they come crashing down.. Mine weighs
5000 lbs, not including the
mast and ants.
## The plan is to insert rectangular steel tubing to support the bottom of
section #2, when required.
6 inch wide x 2 inch tall x .25 inch thick. Treat any crank up with a lot of
respect. I don’t
trust the gear boxes used on the UST towers. They were never designed to be
used as a hoist.
The gear box, aka..speed reducer, made by hub city, is a gear reduction device,
typ used for
stuff like conveyor belts etc. If the gear box ever seized up, you are in a
real mess. Then
you cant extend or retract the tower.
Jim VE7RF
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|