[TowerTalk] TowerTalk Digest, Vol 81, Issue 32

[Dick Green WC1M]

We've been through this discussion before, but when I did a similar test to
Steve's -- i.e., comparing the Loos readings with a Dillon Dynamometer -- I
found that the Loos calibration was not correct for EHS. It was as follows:

Loos       Loos      Dillon
Reading    Chart     Reading

  26       450        300
  27       500        400
  30       660        450
  31       720        500
  32       780        600
  33       840        660
  34       900        700
  35      1000        765
  36      1100        850
  37      1200       1000

Quite a bit more than a couple percent difference. It's possible that either
Steve's or my Dillon wasn't properly calibrated, or our Loos gauges weren't
functioning the same (the slider has to be well lubed with silicone, and the
spring has to be in good shape.)

Others have done this test. My recollection is that W8JI disputes Steve's
assertion that the guy material becomes more "rod-like" as more tension is
applied, thus eliminating or smoothing out the differences in bending
potential of different materials. I agree with Tom. The Loos gauge is
clearly designed to mention the degree of cable bending, so it seems quite
reasonable that the type of material matters a lot, and that this doesn't
magically fade away as tension is applied. The gauge is calibrated for
stainless-steel wire rope, which is considerably softer than EHS, so it
seems reasonable to expect more than 2% difference.

All that said, the differences in tension shown in my chart for the area of
interest, say 10% of breaking strength or 660 lbs for 6700# Phillystran,
isn't enough to worry me: I don't lose any sleep wondering if my guys are
tensioned closer to 800 lbs than 700 lbs.

Whichever way you come down on this, a Loos gauge is invaluable for setting
and checking guy tension. Regardless of accuracy, it's close enough to let
you set the tension to the right ballpark, and ensure that all the guys are
at the same tension.

73, Dick WC1M



 
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