[TowerTalk] Phillystran Tension Gage

[Steve Maki]

You're overthinking this. 10% of breaking strength pretension 
recommendation is not critical in most ham cases. It's a very general 
ballpark figure. On towers that are heavily loaded, pretensions can be a 
little more important. I see anything from 8% to 15% specs for 
engineered towers at 60°F. Depends on many factors.

BTW, SS guy wire is generally rated for slightly *less* breaking 
strength than galvanized EHS of similar construction.

Just figure 400 lbs pretension in either case for 3/16".

73, Steve K8LX.



On 7/25/2021 4:04 PM, Ken Alker wrote:
> If my conclusions are correct, the chart appears to be based upon the 
> breaking strength of a different type of wire than one would use for a 
> tower.  The chart appears to be based upon stainless steel cable (for 
> sailboats) rather than zinc coated cable (for towers).  The SS cable has 
> a higher breaking strength, hence, using the Loos would mean one would 
> over-tention the guys on a tower if using the % scale, rather than the 
> LBS scale.
> 
> --On Sunday, July 25, 2021 3:49 PM -0400 john at kk9a.com wrote:
> 
>> Why are you concerned with the Loos gauge's breaking strength chart?  I
>> just use the table to set the guy wires to the recommended tension
>> (usually 10% of its breaking strength).
>>
>> John KK9A
>>
>>
>>
>> Ken Alker ka6ken wrote:
>>
>> I'm new to this, but did a lot of research and found that the Loos PT2
>> appears to be calibrated for wire with a breaking strength of 4545-5000
>> lbs, while the Rohn 3/16EHS500 wire has a breaking strength of 3990 lbs.
>> I  assume, based on specs on various types of wire rope found at
>> <http://www.wcwr.com/catalog/webcat.pdf>, that the Loos PT2 is calibrated
>> more for 1x19 Stainless Steel type 304 wire rope used for sailboat
>> rigging  (4700 lbs) rather than zinc coated 3/16EHS500 (3990 lbs).  Here
>> is my math  based upon the chart found on the Loos gauge (from the web
>> site quoted by  Tim, below):
>>
>>  LBS   %  LBS/%
>> ----  --  -----
>>  240   5  4800
>>  300   6  5000
>>  420   9  4666
>>  500  11  4545
>>  640  14  4571
>>  840  18  4666
>> 1030  22  4681
>> 1240  26  4769
>>
>> In conclusion, perhaps one should pay more attention to the "LBS TENSION"
>> portion of the Loos chart than the "% BREAK STRENGTH" if using the Loos
>> for  3/16" EHS (assuming it deflects in the same way that the sailboat
>> wire rope  deflects), or one may overtension their guys.  (Although,
>> perhaps the error  when tensioning to 10% of breaking strength when
>> tensioning to 400lbs, or  600lbs in the case of Phillstran, isn't big
>> enough to worry about?)
>>
>> Even then, however, I'm very curious as to why the Loos numbers are all
>> over the map (4545-5000) rather than consistent at one breaking strength;
>> it is not just rounding error since their "LBS TENSION" appears to be
>> +-10  lbs.
>>
>> Ken, KA6KEN
>>
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