Towertalk
[Top] [All Lists]

[TowerTalk] Single Tram Line

To: towertalk@contesting.com, wa2fgk@yahoo.com
Subject: [TowerTalk] Single Tram Line
From: k7lxc--- via TowerTalk <towertalk@contesting.com>
Reply-to: k7lxc@aol.com
Date: Sun, 26 Aug 2018 11:32:11 -0400
List-post: <mailto:towertalk@contesting.com>
 
>  I have a 4 el 20 meter HyGain yagi, that I am going to tram to a 60 foot 
>Rohn 25.I bought 3/16 inch stranded stainless and will attach it to my garden 
>tractorI have a 2 inch diameter 1/4" wall aluminum mast on the towerNow my 
>question.The tower is guyed in two locations.Being the antenna only weighs 50 
>lbs, how important is it to back guy the mast ????
 
    The two factors to consider are the tension on the tram line and the height 
of the tram connection point (TCP) on the mast. At one foot, the tension factor 
will be a multiplier of 1. At 2 feet, the factor is 2, that is twice the 
bending moment and so forth. 
 
    I might try having the tram connection 2-3 feet and then put some tension 
on it. Slowly increase the tension and after each adjustment, look at the mast 
from the side to see if you can see any deflection. Some deflection is okay but 
obviously you don't want to over do it.  
 
    Your choices are either use a small distance up the mast for your TCP to 
get the antenna to the top of the tower and then heft the antenna to the mast 
manually. (An alternative is to hang the antenna from the tower once it reaches 
the top and then re-rig your haul line higher on the mast so your ground crew 
can pull it up into place and there's only a vertical pull on the mast.) The 
second way is to position the TCP high enough on the mast so that the antenna 
arrives at the top ready to be bolted to the mast. This is where you have more 
bending moment and may require back-guying. 
 
    Just proceed carefully and you should keep yourself out of trouble. You 
could always start out with the back-guying but of course it takes longer and 
you may not need it if you follow the aforementioned steps. And BTW a 50 pound 
antenna weight is not insignificant. Just ask the climber at the top of the 
tower as he's trying to heft the antenna into place!
 
Cheers & GL,
Steve      K7LXC
TOWER TECH 
    
_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
<Prev in Thread] Current Thread [Next in Thread>