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Loos Tension Guage Calibration

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Subject: Loos Tension Guage Calibration
From: k2wk@crystal.palace.net (Walt Kornienko)
Date: Wed, 25 Sep 1996 01:30:59 -0400 (EDT)
> I just got one from Steve and it works fine for 1/4 inch EHS. The scale is 
> included which goes down below 400#.....I have the smaller gauge from Loos.
> 
> Jay
> 
> 
> 
Hi Jay,

Thanx for the info on your Loos Tension Guage.  I take it you have 
the PT-1?  I have the PT-2 which has the following calibration chart.

------------------------------------
SCALE   | 3/16"  | 7/32"  | 1/4"   |
-----------------------------------|
13      | 300/6% |        |        |
18      | 500/11%|        |        |
21      | 640/14%|        |        |
24      | 840/18%|500/8%  |        |
28      |1240/26%|740/12% |        |
32      |        |1060/17%| 780/9% |
34      |        |1300/21%| 900/11%|
36      |        |1680/27%|1100/13"|
38      |        |        |1300/16%|
40      |        |        |2000/24%|
------------------------------------

I have a really neat public domain program called DPLOTW. One
of its nifttier features is the ability to extrapolate, or
perform curve fitting.   I entered the data points for all
3 cable sizes and using a log scale for the X-axis (pounds) 
I get a fairly straight line for the 3/16" and 7/32" cable sizes.
The 1/4" scale still has a slight curve to it.  Another
feature this program has is the ability to fit the curve
to the data using a 2nd order polynomial equation.
I now have an extrapolated curve that gives me values
for lower values of tension that do not appear on the Loos' 
calibration scale. Using this graph I can read values to below 
300#.  The expanded scale is shown below:


------------------------------------
SCALE   | 3/16"  | 7/32"  | 1/4"   |
-----------------------------------|
13      |   ---  |        | 315    |
18      |   ---  |        | 385    |
21      |   ---  |        | 438    |
24      |   ---  |  ---   | 500    |
28      |   ---  |  ---   | 615    |
32      |        |  ---   | 780/9% |
34      |        |  ---   | 900/11%|
36      |        |  ---   |1100/13"|
38      |        |        |1300/16%|
40      |        |        |2000/24%|
------------------------------------

Some one on here performed a test to determine
how close the Loos Guage calibration scale is 
to actual weight.  They hung known weights off
a work bench and noted the actual -vs- shown
tension.  The conclusion was that the Loos Guage
is accurate to within 2% to 8%.  The actual tension 
is 2% - 8% higher than shown. 

Based on the above emperical data and the extrapolated 
data I derived, a reading of 28 corresponds to a tension
between 627# and 664#.  This is close enough to the
recommended tension of 650#, or 10% of the 6500# breaking
strength of 1/4" EHS.  As long as all the guy wires are
at the same tension the small margin of error should be
negligible.


*****************************************************************
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*                73 de Walt Kornienko - K2WK (FRC)              *
*                                                               *
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