[TowerTalk] FW: Why preload guy lines?

[W2RU - Bud Hippisley]

> -----Original Message-----
> From: Tom Rauch
> 
> I've been thinking about this and I don't see how any tension gauge 
> that  requires scale compensation for wire diameter could be immune to 
> effects of wire stiffness.
 
I've been doing some thought experiments (it's too dark right now to do any
"real" experiments outside) since reading Tom's posting and after playing a
few minutes with my brand new Loos PT-2 gauge.

I think wire stiffness may affect readings or calibration at very low
longitudinal tensions.  However, I think it's also worthwhile to consider
the impact of wire "stretch", which K7NV has very kindly noted is a function
of guy wire diameter.  Thus, perhaps the difference in guy tension vs.
spring deflection numbers for 3/16-inch and 1/4-inch cables, as printed on
the Loos gauge, is related to the relative "stretchiness" of those two
cables.  (When thinking about this, I found it helpful to visualize a
comparison of strong but "limp" 3/16-inch "twine" with our standard 3/16"
guy cable.)  

FYI, from the Guy Cable tables in K7NV's "Notebook", for equal tension the
stretch in 1/4EHS is about 1/3 that of 3/16EHS (assuming the characteristics
of each are reasonably linear over their rated working load ranges).  On the
Loos gauge I have, the difference between the two is around 2.25 or 2.3 for
those tensions where Loos has provided data for both cable diameters.  That
is, it takes 2.25 times as much tension in 3/16-inch cable to obtain a given
spring deflection as it does with 1/4-inch cable.

To me, the value of the Loos gauge is at least partly in allowing me to
_equalize_ all my guy wire tensions quickly and simply.  Until we get to the
bottom of this issue, my guy tensions may all be low or they may all be high
relative to the 10% recommendation of Rohn, but by gar, they'll all be the
_same_ !!!!

Bud, W2RU