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Re: [TowerTalk] guying a crank-up

To: "Its from Onion" <>, <>
Subject: Re: [TowerTalk] guying a crank-up
From: "WA3GIN" <>
Date: Thu, 8 May 2008 07:59:51 -0400
List-post: <">>
Interesting thread.

The Triex CT-100 is a 100ft crank-up tower. It is a guyed tower (at three 
locations). The tower sections are lifted by a single cable. Each section 
raises the next section by use of a pair of cables that run from the bottom 
of the preceeding section over a pulley at the top of that section and down 
to the bottom of the next section. When the tower is fully extended there is 
a locking pin (fashioned from a 2" x 2" x 1/4" piece of angle that is used 
as a pin under a welded piece of 2" x 1/4" bar that is welded on "one" tub 
of the second section from the bottom section.  So, the entire weight and 
stress of the 80ft of tower (rated at 40sq ft and 600lbs of dead antenna 
weight) is supported by the welded 2" x1/4" x 1/2" latch.

There are two amazing things about steel. Check out the ratings of 1/4" 
steel rope and 3/8" or 1/2" bolts.  It takes a lot of force (several 
thousands of lbs) to bring a fault.  These towers we use for our antennas 
are pretty amazing!

Have Fun,
----- Original Message ----- 
From: "Its from Onion" <>
To: <>
Sent: Thursday, May 08, 2008 2:59 AM
Subject: [TowerTalk] guying a crank-up

> Not to start a big discussion, but as long as you 'ONLY' guy the bottom 
> section of the tower It can be guyed.
> That is to say, not guy any of the 'cranked up' sections.
> Pinning the movable sections, like an extension ladder steps will only 
> transfer the stress to the rung, cross member, ect
> that is rests on.  Something that is surly NOT designed for that stress.
> Ya must remember its like building hot rod cars when we were kids:  big 
> motor, runs fast.  but who thinks about upgrading the brakes
> untill its time to  stop?  In other words, the tower companies spend a lot 
> of mony engineering the tower.
> UNLESS, you also do the same; what makes your design safe,  better, 
> strong???
> Just food for thought...  Have you ever SEEN a tower come down?  they 
> twist into the ground.
> Lee
>  Message: 1
>  Date: Wed, 07 May 2008 22:02:20 -0400
>  From: jim Jarvis 
> <<>>
>  Subject: Re: [TowerTalk] ma550 guying
>  To:<>
>  Message-ID: 
> <<">>>
>  Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>  Ignoring, for the moment, the prime directive,  let's look at what
>  you're doing if you
>  guy a crankup tower.
>  The lateral forces on the tower, which cause it to flex and shed
>  load, are transferred to
>  the guys, and to the vertical structure itself.   With a crankup,
>  that means to the hoist cable!
>  The cable is not specified for anything more than lifting the weight
>  of the tube, with some
>  safety margin.
>  Thus, adding guys to the ma550, or any similar light duty tower, will
>  NOT increase its load
>  capacity, or its safety, but will reduce it.
>  Now, if you upgraded the winch cable, carefully calculating the
>  downforce resulting from the
>  increased load area you plan, and the increased wind zone withstand
>  which the zoning requires,
>  you COULD add capacity to the structure.    But in that case, be
>  prepared to present an engineering
>  wet seal to your zoning people to justify the structural decisions.
>  It's a whole lot easier and cheaper to follow the prime directive,
>  don't you think?
>  N2EA
>  Jim Jarvis, MBA
>  President-Executive Coach
>  The Morse Group, LLC
>  732 548 5573 office
>  908 410 9130 cell
>  People-Process-Strategy
>  Achieving Results in a Changing World
> _______________________________________________
> _______________________________________________
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