[TowerTalk] My 48' Delhi Self Supporter folded over :-(

[Jim Thomson]

Date: Sat, 8 May 2010 07:01:16 -0500
From: "Gary \"Joe\" Mayfield" <gary_mayfield at hotmail.com>
Subject: Re: [TowerTalk] My 48' Delhi Self Supporter folded over :-(
lost itsbolts!



What are folks' opinions on nuts with nylon inserts in the cap?  We
refurbished a Jontz tower, and used them.  They seem to be doing very well
after 5 years.

Joe kk0sd

##  Funny u mentioned that.   I just came back from  711... and  looked at the embedded anchor rods
used for the lamps in the parking lot.  All 4 x bolts  were double nutted.  They used the same size nuts
for both top and bottom nuts.   The top one however, is furled on top portion, and looks to me exactly
like a Ny-lock nut... aka  aircraft nuts, and various other names.     I did not see any leveling nuts below
the steel plate.... so dunno how they level the things.    I also notice that USTower also
uses em on all their pulleys'.  Single nut  per  pulley.  These are galvanized.. and look like  G5 or G8 bolts. 

## Most traffic lights. and 100' tall light poles at local university playing fields etc.. all use anchor bolts...
but with leveling nuts below.    Most have protective covers over top, so you can't see  the nuts, excess
thread on top etc. 

##  I didn't know you could get high strength galvanized nylock nuts... so will purse this further  with my
local anchor rod sales guy on Monday.    The new spec for anchor bolts is called  ASTM-1554... and
the rods come in 36/55/105 ksi.  I need a doz of em.  USTower sez the correct anchor rod for my 
DXX-689 is  1.125"  diam  by  28"  long... with 6"  thread on top  [ 6"  sticks above concrete] 
That only leaves 22"  embedded into the  9' deep block of cement.   Both L bolts and J bolts are out
of vogue these days...in lieu of steel plates on the bottom's of anchor rods. [bottom 6" is then threaded]
Local eng sez the 28"  long, 55 ksi  rods, with no plates on the bottom.. as speced by ust is fubar..esp.
in a 9' deep block of cement.  

##  He wants the embedment depth of the rods to be at least  1/2 of the 9' deep  block of cement. 
In my case their is 4 x rods, on 5" C to C square spacing..for the anchor rods... 12 x rods in total,
4 per corner.    We will install the 9"  square plate at the bottom of the 4 x rods... so 3 x plates have 
to be made up.  The new rods will be 60" long.. with  4.5' embedded.  Rods will have 6" threads top
and bottom.. and be 105 ksi  variety.   Concrete  will be some where between  4350 and 6000 psi.

## This  HDX-68 that's stitting in my driveway  weighs 5000 lbs.. including the small 48 lb
prop pitch.  Stick 400-600 lbs on top... and with the 3/8" thick chromolly mast sticking 14' 4"
above the tower... it tops out at  103' 4".   The only thing holding the tower to the 6' x 6' x 9'
concrete base is those 12 x anchors rods.   A  1.125"  diam anchor rod only has a  3.5"  circumference,
which is not much contact with concrete imo.   Heck, even my trylon concrete  stubs have a full 18"
in contact with the concrete. ... = 4 x 1.125" rods.    By putting a 9"  square plate on the bottom of
each grp of 4 x rods.. the increase in pull out capacity increases  by a whole bunch. 

## The next trick is... the underside of the UStower  540 lb,  1"  thick steel base plate is 2"  above
the concrete.  [1.2" tall leveling nuts below the plate].  If the base plate is raised up any higher
than 2"  above concrete, you are now stressing the anchor rods... IE: they will want to fold over....
another reason to use 105 ksi  rods. 

Tower legs mounted to base plate  via  6 x 1"  bolts... per leg.... via 5" wide x 19" tall steel plates.
All mine had rusted nuts. [ on the threads only] .   Mine were G-5..[ G-5 is identical strength as a 
ASTM-A325 bolt]. New ones will be either G-8 or ASTM-A490  or ASTM 354... all 3 x of those are
identical strength. 

Later......... Jim   VE7RF