I've not used Nylon rope for a tram line but "way back when" I did use it
for some temporary guys on a small vertical. The stuff is like a rubber
I do use Poly rope for hauling things up the tower, but for a tram line I'd
go with something that doesn't stretch and is rugged.
I have no worry about Phyllistran as a tram line if using good pulleys, not
cheap ones. My preference would be galvanized wire rope over EHS just
because it's much easier to handle. I'd still be looking at 1/4" or 5/16"
though and that is as expensive as the various Kevlar lines. I use 3/16"
wire rope for temporary guys, but I'd go larger for a tram line.
I'd also use the stuff the way Dennis does with the tower at the apex of a
triangle so it would not be taking all the side force from the tram line.
When you add the tension, weight, and then throw on a good size antenna the
side force can be considerable and much more than expected.
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
>I don't want to be contrarian, but has anyone seen a tram line made of
> reasonably strong rope break? Has anyone calculated the actual forces on
> tram line? For example, the breaking strength of 7/16" nylon rope is about
> 4,500 lbs, with a safe working load between 450 lbs and 900 lbs (some
> references say no more that 1/5 breaking strength, others say no more than
> 1/10 breaking strength.) Would the forces exerted by a 100 lb antenna on a
> tensioned tram line exceed that? Also, the haul rope supports some of the
> weight of the antenna. Doesn't that figure into the equation as well?
> I ask this question because yesterday I successfully trammed a 44 lb
> Cushcraft 40-2CD to 110 feet using 7/16" 3-strand nylon rope. The next
> antenna to be trammed is an 81 lb SteppIR. Is there really a chance that
> tram line will break?
> 73, Dick WC1M
>> -----Original Message-----
>> From: Dennis OConnor [mailto:firstname.lastname@example.org]
>> Sent: Monday, December 18, 2006 7:27 AM
>> To: email@example.com
>> Subject: [TowerTalk] Tram rope
>> Let me second Dave's comment... Using rope for a tram line,
>> or small diameter cable is asking for a crash... I also use
>> only 1/4" EHS... Because the tram line is pulled into a
>> caternary shape the total forces on it are far greater than
>> just the weight of the beam...
>> The other thing I do is that the tram line is run up to the
>> top of the tower, through a pulley, and back down to a ground
>> anchor on the opposite side... This way the side thrust is
>> not transferred to the tower... Because of having to fly the
>> beam over the woods, etc., my tram line is 600 feet overall
>> and is kept on a drum and used only for that purpose.....
>> denny / k8do
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