----- Original Message -----
From: <K7LXC@aol.com>
To: <w2rds@arrl.net>; <Towertalk@contesting.com>
Sent: Thursday, March 14, 2002 8:26 PM
Subject: Re: [Towertalk] CRANK UP TOWERS
> In a message dated 3/14/02 7:41:52 AM Pacific Standard Time,
w2rds@arrl.net
> writes:
>
> > I do not have any direct experience with this but I do not that some
towers
> > have a mechanism to provide support of the tower in the extended
position
> > other than relying on the cable.
>
> No they don't unfortunately.
Well, they DID, at least in the mid-70's. I have a TriEx catalog from that
period in time showing some manually installed "Safety Stops" that were to
be installed at the 20 foot level as each section of tower was raised. In
the THD Series, for example, the TOP section cranks out first, and when it
is fully extended, you climb a ladder leaning against the tower and install
the first set of Safety Stops so that section cannot retract. You then
continue cranking until the next section is fully extended and climb the
ladder again and install Safety Stops for that section, and so on. The THD
Series is GUYED crankup tower which means nothing but the bottom section is
really guyed until the tower is fully extended. Kinda scary and you do this
ONLY on a calm day . . .
Also, in the same old TriEx Catalog, is something called the "Guy As You
Erect" feature. In this case, the tower sections are locked together such
that all of the top sections are extended while still nested. When the
second section and it nested upper sections are extended to the full height
of the second section, that section is guyed and then the remaining upper
sections are unlocked from it but THEY remain locked together. They are
then cranked up, nested, to the height of the third section where it is
guyed, and so forth. The locking mechanisms are individually unlocked by
cables from the ground. It was not clear to me that the "GAYE" mechanism
had a feature that allowed the tension to be removed from the raising cable
after the tower was fully erected.
Also, in the same old TriEx Catalog, is something "new" called the "Safety
Lock Feature" which fits many then existing TriEx tower models. I believe
all of these towers use the cable stringing method ("telesopic cabling,
TriEx calls it) that extends all sections uniformly and at the same time.
The Safety Lock Feature allowed you to lock all sections of the tower at
almost any height (depending on the "W" bracing spacing of the sections)
from the ground with a single control cable. TriEx offered that as a
customer-installed add-on kit for TriEx and some unspecified towers from
other makers.
Once, when I was a TriEx dealer, a customer wanted to order a tower with a
feature to lock the sections in place while extended, and also, on the same
tower, they wanted a power winch and a positive pull-down feature. TriEx
REFUSED to take the order claiming the customer could inadvertently forget
to release the stops and engage the power winch with pull-down and something
would surely BREAK, causing a disastor. They did NOT want their name on it
. . . If you wanted positive pull-down . . . OK . . . but no stops. If you
wanted stops . . . OK . . . but no positive pull-down. This is one of those
"gotchas" that exist ONLY in crankups . . .
> > And I know that several of the guys in my
> > area are retrofitting these devices onto their towers that do not have
> > them, to prevent the scenario that Sherman descirbed.
>
> Ah, jeez - great. A bunch of amateurs making modifications to a
> well-designed structure that the manufacturer CERTAINLY WON'T endorse and
> might even make the situation worse and increase the risk to the owner.
Would
> you please talk these guys out of doing that?
Actually, believe it or not, there are SOME guys out there with the
capability of doing this with as much skill and safety as the real tower
makers. I would not try it, but then, since I will not ever own a crankup,
it will not ever be a problem to me . . . Just remember to not have stops
and positive pull-down on the same tower unless you have an absolutely
fool-proof memory. Yeah, right!
> > I would not want to
> > rely on the cable to hold the entire weight of the tower, mast,
rotator,
> > and antenna's for years on end.
>
> Why not? They're designed to do just that with a significant safety
> factor. I've seen several original Tristao crank-ups that were
installed
> by Lou himself with the original cables and they're in fine shape
considering
> their age.
Well, it appears the perhaps Tristao and TriEx had some differing ideas on
that subject . . . since TriEx offered several ways to relieve cable tension
on a cranked up tower. I am not sure about Tristao. I guess I will have to
search my archives and see if I have some old Tristao catalogs somehwere . .
.
> > I will be very interested to see the results that are compiled.
>
> Me too. I would suggest you only include first-person experiences.
> Getting a bunch of real anecdotal stories about a friend-of-a-friend type
> stuff you can't substantiate doesn't seem very useful. There won't be any
> useful details either (age, cable size, condition, load, failure mode,
etc.).
>
> Cheers,
> Steve K7LXC
> Tower Tech
For what its worth,
Stan
w7ni@easystreet.com
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