[TowerTalk] Tensioning guys

[Chris R. Burger]

1.  How does one tension a guy cable if there is insufficient travel 
    in the turnbuckle?  

    I have a long-link chain to which I can attach the turnbuckle, so 
    it's merely a matter of putting the shackle through a different 
    link.  However, I will have to keep something like 1 kN (or 225 
    lbs, if you really must) of tension in the cable while moving 
    the shackle.


2.  A second, albeit more subtle, question:  I have pretensioning 
    specifications for 8 mm (rougly .4") cable.  However, I'm using 
    insulators with dead-ends, adding rougly 1 kg to the cable every 
    4,5 m (or 2 lbs every 15').  My logic says that the larger 
    distributed mass will cause more sag in the lines.  If the same 
    amount of motion is to be allowed, more pre-tension will have to 
    be used.  Is this correct?  If so, how can I estimate the 
    required amount of pre-tension?

    To put some figures to it:  The upper guys are at the 33 m (109') 
    level.  The manufacturer specifies a maximum of 65mm (2.6") of 
    motion at the top.  The maximum wind load with the full antenna 
    complement will cause 10 kN (2250 lbs) of tension in the cable.  
    Recommended pre-tension is 1 kN (225 lbs).

Chris R. Burger
ZS6EZ

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