[TowerTalk] Crankup Danger

[Jim Thomson]

Date: Thu, 1 Aug 2013 16:26:11 -0700 (PDT)
From: Steve Dyer <w1srd at yahoo.com>
To: Patrick Greenlee <patrick_g at windstream.net>,
"towertalk at contesting.com" <towertalk at 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