[TowerTalk] Crankup tower safety question... (Crankup

[Jim Thomson]

Date: Thu, 1 Aug 2013 20:13:45 -0400
From: Mickey Baker <fishflorida at gmail.com>
To: "towertalk at contesting.com" <towertalk at contesting.com>
Subject: [TowerTalk] Crankup tower safety question... (Crankup
Danger!)

Patrick, AF5CK's thread on his tower raised an issue that I really don't
understand...

Why isn't there a "lock" mechanism on crank up towers?

We spend lots of money on these things, and, basically, they hang there
suspended by a single cable. We all have either known someone or have had
our own tower's cable (or winch) fail and the tower crashes, with great
damage to tower and antennas.

I could thing of a number of gadgets that could be made to work:

   - A solenoid locking bolt
   - A brake mechanism (Electronically controlled?)
   - Stops every few feet requiring a raise then lower like a safety ladder.

But here I am, about to step off into yet another $10k tower project with
another tower hanging by a cable. (I feel like Homer Simpson - Doh!)

I realize that the market is small and price sensitive for these towers,
but certainly this has been recognized as a problem.

Isn't there a better way? If there is, and I can implement it, I'd do so,
simply for the purpose of making the tower safer for me and my antennas.

Thoughts?

-- 
Mickey Baker, N4MB

##  UST already makes an ideal locking device....for their commercial-military versions of crank ups. 
So does one other manufacturer.  It consists of what appears to be 1 inch thick steel plates welded
to the tops of the legs...on the bottom section.  Mating  1 inch thick steel plates are bolted to the
fixed plates... but the mating plates swivel sideways.  All  3 are joined via horizontal rods, like a 
triangle at the top of the bottom section, aprx 20 feet above the ground.    Another rod  drops
down vertically from one corner..to aprx 4 ft above the concrete. 

##  When you pull down on the vert rod, the steel plates swivel around, and hook around the legs 
of the 2nd section from bottom.   2nd section from bottom is now captivated.  The 3 steel swivel
plates  sit below the horizontal bracing, and also diagonal bracing of the 2nd section. But the plates
cant be just engaged anywhere.  They have to be activated where there is a clear unobstructed
portion  on all 3 faces.    That still allows the tower to safely be locked just about anywhere from
fully nested to fully extended.   What is being captivated and locked is anywhere along
the lower 17 feet of the 2nd section from the bottom. 

##  On my old style  HDX-689, the upper sections, except the very top section, have a single cable 
on EACH face, 3 per section.    The only way that any upper section can come crashing down is
if ALL  3 cables for that section break.... which is extremely unlikely.   Why UST didn’t  put 3 cables
on the very top section is a mystery. 

##  Even with the safety plates, the military – commercial versions of UST  towers  can still
come crashing down IF the main lift cable off the drum breaks...but only with plates dis-engaged.
The only time the plates are dis-engaged of course, is while raising or lowering the tower.
Once the tower is raised or lowered to the desired height, the plates are engaged.  If you look
at UST’s  site,  you will see these devices...painted red. 

##  I forget the name of the 2nd crankup tower manufacturer who also had an identical plate
safety feature.  Array solutions was selling their towers for a few years, then stopped carrying them,
due to lack of sales.   So no solenoids. It’s  strictly a mech device.   Pull the rod down, and all 3 plates
engage. Push the rod up, and all 3 plates dis-engage.   Between the triple plates and redundant cables
on the upper sections means the tower can also be guyed if required. 

##  Why  UST doesn’t offer the triple plate safety feature on their ham towers is beyond me.  It should
come standard.  If you have ever seen pix of this device close up, it’s  not a big ticket item either. It
would not add much expense to the total cost, maybe $200- $300  tops. 

##  In my case, the PP rotor is 6 feet down inside the tower.   The tower has to be extended  to 52-53
ft level....just to gain access to the PP rotor, for removal, or install.  That requires stuffing  safety
steel tubing horizontally, 8 ft above the ground..just below the bottom of the 2nd section  from base.  
The rotor is then fully exposed at the  45 ft level.  The tower still has to be climbed to the 45 ft level.

Jim  VE7RF