[TowerTalk] Re another w51

[Jim Thomson]

Date: Sat, 10 Jun 2017 10:12:39 -0700
From: "Don W7WLL" <w7wll at arrl.net>
Cc: <towertalk at contesting.com>
Subject: Re: [TowerTalk] Re another w51


<While I suspect there is no confusion in the ongoing current banter about 
<the Tri-Ex W-51, it might be well to remind all that the W-51, as I 
recollect, differs structurally from the later WT-51 (one of the crankups I 
have).  I don't have the specs for the W-51 but was there not a difference 
in the wall thickness of the vertical section tubing, the W-51 being 
thinner, thus reducing the load the tower could handle?? Seeing so many of 
these being up for sale or in use it might be useful if someone could post a 
chart that differentiates the important differences between the two, 
including whether the base mount dimensions also differ. This would be a 
useful tool when looking a load capability.

Don W7WLL

##  IF the wall thickness was increased, and everything else stayed the same, the 
tower would be heavier, weight wise. .   UST uses  46 ksi pipe for the vertical legs..and 36 ksi
for the zig zag solid rod bracing.  IF more bracing was used, the vertical distance where the solid bracing
meets the vertical legs,  would be reduced.    That alone would increase the overall strength of the tower. 
With more bracing, the angle of the braces would be shallower, which also makes it stronger. 

##  there is a lot of variables at play here.  Yield strength, and wall thickness of the legs  are just 2 items. 
Then you have the bracing.  The old style UST towers used Z bracing.  And also X bracing
on top of the Z bracing for the bottom and top 4 ft of each section.  The new style UST towers use W bracing  from
top to bottom of each section.  
And in both cases, the wider sections use less bracing.  The upper, narrower sections use more bracing, a lot more. 
The bottom section of the HDX-689 uses 10 W braces.  the top section uses 44 braces.   The narrower sections use
more bracing...to keep the brace angle the same. 

Jim  VE7RF