[TowerTalk] My 48' Delhi Self Supporter folded over

[Grant Saviers]

The torque tightening values for A325 or grade 5 galvanized bolts are 
sobering

see  
http://www.portlandbolt.com/technicalinformation/bolt-torque-chart.html  
(note the cautions)

some values that might be of interest for some bolts used on 
towers/tower bases:

1/2"  94 ft-lbs   ok for your Craftsman 1/2" drive torque wrench if 
you've got a good purchase

3/4"  333 ft-lbs  need a 2' long 3/4" drive torque wrench 

1"    805 ft-lbs  now into a torque multiplier connected wrench or a 4' 
torque wrench, 1" drive

1 1/4"   1400 ft-lbs  (want to borrow my two man 8'  2000 ft-lb torque 
wrench I use on my dozer?)

Some other thoughts - zinc is soft and slippery, I'm not sure that 
lubrication is needed or a good idea.  The familiar Loctite grades 
catalyze in the presence of iron (Fe) and absence of oxygen.  Special 
grades are made for other metals.  The Loctite container/package/tubes 
are oxygen permeable so don't ever transfer it to something different.  
I was told by a Loctite apps engineer that shelf life is indefinite if 
kept in factory packaging.

PS:  columns (generally L/D rations > 10) fail because of buckling, 
which has nothing to do with yield or tensile strength and is only about 
the modulus of elasticity of the material.  see wikipedia for an 
explanation of this http://en.wikipedia.org/wiki/Buckling   Masts aren't 
columns, they are beams in bending.

Grant
KZ1W

Jim Thomson wrote:
> Date: Thu, 6 May 2010 21:05:31 -0700
> From: "Mike" <noddy1211 at sbcglobal.net>
> Subject: Re: [TowerTalk] My 48' Delhi Self Supporter folded over :-(
> lost its bolts!
> Mike,
>
> It almost sounds like they were not tightened down to the correct torque to
> begin with because they should not have come loose with lock washers.  I
> would get new nuts, bolts and lock washers and torque them correctly and
> double nut the bolts.
>
> Mike, K6BR
>
> ##  I installed  22 x of those tower's in yrs gone by.. and never seen one
> of em do what you had happen.  There are doz's of em here on Vancouver island.
> They are not my 1st choice for a tower.  I currently have the 96' trylon.. and those bolts
> are super tight.. and that was 10 yrs ago.. and re-checked  15 mins ago. [excuse
> to try out my new 2' long torque wrench.]  
>
> ## You may well have defective bolts.  You should also check the bolts on all the
> upper sections.  Did you use the correct base  stubs  [ the stubs that get embedded
> into the concrete] ??   Every delhi I ever saw, including new ones, has 3 [THREE]  bolts
> per leg on the base stubs. 
>
> ## Don't ever put loctite on galvanized bolts, you will screw em up. All that's required
> is one bolt, one flatwasher, one split ring lockwasher, one nut.  I think the Delhi uses 3 x 
> 1/2"   G-5  bolts  for the stubs.. and also the 1st few sections.. then  down to TWO  1/2"
> bolts per leg.  IF you double nut them, then the bolts have to be way longer.  They make
> special nuts  for this purpose, thinner than a regular nut, called a pal nut, or jam nut. 
>
> ##  I'd call this an anomoly...    All galvanized nuts are slightly bigger, to handle the mating,
> galvanized bolts.  I suspect you may have had defective nuts.  Does delhi use galvanized bolts
> on the upper sections.. or electroplated hardware... like trylon ? 
>
> later... Jim  VE7RF   
>
>
>
>
>
>
> -----Original Message-----
>
> Hi Guys,
>
> Mike VE9AA here.
> My 48' Delhi Self Supporter folded over a couple days ago .....
>
> As far as I can tell, the reason this happened is 2 large bolts (with lock 
> washers) backed themselves out and there were only 2 remaining legs holding 
> it up.  We had some wicked wind up here on the hill the other night, and 
> poof, it's was over.
>
> Has anyone else heard tell of this happening to any other Delhi towers? (or 
> 'similar' self supporting flat-stock towers like a Titan, etc.)
>
> After the fact, I heard that VE1DX had the exact same thing happen to him.
> http://www.ve1dx.net/fall_down.html
>
> What can I do to prevent this in the future please? Red Loctite? Tighten 
> bolts yearly? Other?
>
> 73/TNX, Mike VE9AA
>
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