Jim (et al), I intend to make my own locking mechanism and add it to the
customized tilt/crank-up tower I mentioned. It has only one moving section
(20 ft) but since I intend to use it at various degrees of extension I want
to be able to lock it at various heights. I'm just guessing but I don't
think I would gain much by having the ability to lock the antenna in
positions less than a foot apart so since the bracing on this tower is in
one foot increments I will go with that.
I'm thinking a piece of steel welded to a leg every foot on the movable
section and a single pivoting piece to engage any of those mounted to the
fixed section. I'll start with manual operation but I want to automate it
with a solenoid or other actuator. Ideally I will be able to automate it
such that I can just raise or lower the telescopic section remotely and the
"latch" would release and reengage automatically as required. To avoid
slack cable problems I won't try to back off the winch automatically to put
all the weight on the latch system but will make the latch system strong
enough to easily take a one foot drop if there is a cable failure.
I followed the link to the work platform web site and read that with
interest but $400 seems expensive to me since I have a relatively well
equipped welding shop and could make my own relatively fast at a much lower
cost. Not knocking the product and if you don't weld, buying it is a good
option. What luxury to be able to stand on a step large enough to be
comfortable instead of pain in the feet and ankles climbing and standing
on small or sloping tower braces. Although I have never owned a tower
before, I have climbed a significant number of them and I'd just as soon
forgo the adrenaline rush and sore feet for a sedate ladder episode.
Patrick AF5CK
-----Original Message-----
From: Jim Thomson
Sent: Friday, August 02, 2013 7:41 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Crankup tower safety question... (Crankup
Date: Thu, 1 Aug 2013 20:13:45 -0400
From: Mickey Baker <fishflorida@gmail.com>
To: "towertalk@contesting.com" <towertalk@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 didnb t put 3 cables
on the very top section is a mystery.
## Even with the safety plates, the military b 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 USTb 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. Itb 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 doesnb 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, itb 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
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