[Top] [All Lists]

Re: [TowerTalk] Tram rope

To:, Towertalk <>
Subject: Re: [TowerTalk] Tram rope
From: Eric Scace K3NA <>
Date: Tue, 19 Dec 2006 19:42:56 -0500
List-post: <>
Hi Dick --

   First, definitions... A capstan is not a winch.

   A "capstan", as you have, contains a drum around which several turns 
of rope are laid.  As the drum rotates, new turns are added to the drum 
and old ones are removed.  A capstan generally requires tending the dead 
end of the line, and attention so that turns do not get overlapped or 
become too slack.  Capstans are not man-rated in the occupational-safety 
world; i.e., they should never be used on a line that is supporting a 
person.  Capstans can handle an infinite length of line, since line is 
always exiting and entering the drum at the same time.

   A winch buries the dead end of the line at the bottom of the drum, 
and has a finite capacity to reel up line until it is full.

   A capstan (or winch) can be located away from the tower base; e.g., 
bolted to suitably anchored posts.  If you don't like having a line 
angling down from the top of the tower out to the capstan (or winch), 
you can run the line through a turning pulley near the base of the 
tower, and then horizontally over to the capstan/winch location.  Use a 
large diameter pulley with a sheave width that matches the rope diameter 
to minimize friction and to properly support the rope through the turn.  
(The later sentence is true of all pulleys used in tower work or any 
other application.)

   Wire clips of correct size, number, spacing and installation (nuts 
tensioned according to manufacturer's instructions) will have greater 
holding strength than the breaking strength of the wire cable.

   I didn't say, or mean to imply, that a Klein grip wasn't safe at the 
loads we were talking about... and I wouldn't object if someone left 
their Klein grip and come-along attached to the tram line and anchor 
point.  If I were doing the job, I'd probably secure the end of the tram 
line and get the excess hardware out of the way (having tripped over a 
few come-alongs in the past).  But that's just me.

   I'd feel comfortable using a guy grip on 7-strand steel cable tram 
line, since that's what it was designed for.  According to my 
understanding, one can't re-use the same guy grip over and over... so it 
would have to be tossed at the end of the job (unless you're saving the 
tram line with the guy grip for reuse at a future date).  I don't know 
how the manufacturer feels about using a guy grip designed for 7-strand 
cable on wire rope of the same diameter; the manufacturer's Prime 
Directive applies here.  Maybe there are grips designed specifically for 
wire rope.

-- Eric

on 06 Dec 19 Tue 18:34 Dick Green WC1M said the following:
>> Alternately, use an electric winch with a long cord to the 
>> control buttons, so the operator can stand well clear of the 
>> work zone.
> I have an electric capstan winch (the TowerJack model) bolted to the tower
> at the base. The capstan requires the operator to pull the excess rope off
> the drum in pretty much a straight line from the tower -- right under the
> tram. I guess the way around that would be to put a pulley on the tie-off
> post (I planted a 4x4 about 20' from the tower for that), and take the rope
> off at 90-degrees to the tram. I'd have to add about 30 feet of wire to the
> foot switch -- it only has a 10 foot cord now.
> Still have the problem of the person operating the tiller. You have to be
> under the antenna for that.
>> Properly installed wire rope clips are fine, as is a properly 
>> installed Nicropress compression fitting.
> Probably the subject of another thread, but my understanding is that there's
> no way to determine the load rating of a wire rope clip connection.
> Apparently, there are no published load ratings. Of course, the Rohn catalog
> shows wire rope clips as a method for terminating guy wires, so perhaps
> their engineers have the data. 
> A guy grip is a lot cheaper than a Nicopress tool. Any reason not to use a
> guy grip?
>> I would a wire rope clip at the bottom, rather than rely on 
>> the Klein grip during the job.  That reduces the number of 
>> potential failure points.
> I can't agree with that. Klein grips are designed for much heavier loads
> than we're talking about. My gosh, many of us routinely use them to tension
> our guy wires to 500-1000 lbs or more. If they're not safe for tramming,
> they're not safe for tensioning guys. Further, my feeling is that a Klein
> grip does a lot less damage to the wire rope than a clip.
> Now... Please don't flame me with a bunch of claims in defense of wire rope
> clips. I'm not saying they don't work. But I and concerned about the lack of
> published load ratings. Also, I've seen wire rope slip when the clips aren't
> tightened properly.
> 73, Dick WC1M

TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>