In my instance the tower in question will have the moving part of the
locking system near the top of the first (stationary) section which will be
reachable by extension ladder. The "distributed" part of the locking system
is composed of pieces of steel welded one per every foot of the movable
section (just have one movable section.) These steel pieces are pretty
simple and robust, just a chunk of steel welded to a tower leg to take the
force of resting on the movable portion of the locking system (think
deadbolt with multiple holes to secure it into.) These are spaced a foot
apart. Nothing special about the spacing, just didn't think I would need
more resolution regarding the antenna height. Spacing is more or less
arbitrary plus or minus interference with braces.
I realize mine is a trivial case and may not be the answer for "complicated"
installations but I don't think inapplicability regarding universal
application negatively impacts the utility in simpler cases with only one
movable section.
Patrick AF5CK
Message-----
From: Grant Saviers
Sent: Friday, August 02, 2013 11:10 PM
To: Jim Thomson
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Crankup tower safety question... (Crankup
My thinking about locks - every item has a failure mode and locks are no
exception. What if the lock won't disengage or worse snags with the
tower up or partially down? How does one safely disengage the lock with
the tower weight on it and perhaps the pull down cable also tensioned?
Would you climb that tower? Rent a bucket truck or boom lift and work
under the antennas that could come down on you? (boom lifts go to over
100' so removing all antennas first is probably an answer).
It seems to me that locks create another complex set of trade-offs. Well
maintained cables and winches are one answer, but stuff happens even
then. Maybe a simple redundant or "safety" cable would be a better
alternative. Then one more item to maintain and fail. An inertial lock
like safety belts if the tower descends to fast? (loop to the above issues).
OTOH, I think Luso and I know Will-Burt make locking mechanisms for
their towers and tallest pneumatic masts, respectively. Anyone know how
they work? How you get the tower/mast down if a lock fails?
Grant KZ1W
I own 4 crank ups & 2 Will-Burt masts
On 8/2/2013 5:41 AM, Jim Thomson wrote:
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?
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