[TowerTalk] Anchor bolt material

Roger (K8RI) on TT K8RI-on-TowerTalk at tm.net
Sun Oct 12 19:37:06 EDT 2014

I like the idea of a device that would get me to the top of the nested 
tower.  Mine is also a tilt over, but there are buildings, a fence, and 
a guy anchor with guy lines to the big tower that prevent the use of the 
tilting fixture on the antenna at the top of the tower.  My neighbor has 
a tilting fixture at the top of his, so when he tilts the tower over, 
the antenna stays level which is a very handy feature.

2 things about this bother me.  How deep are the holes?  You say you had 
to cut off the bolts as you could not go deep enough.

When you seal the bolts/nuts into the bottom of the holes with the 
proper epoxy for the proper strength, the weak point is the amount of 
concrete out and above the bottom of the holes in an upside down cone 
shape, which is likely less than the pull out strength of the potting 
material. (depending on depth)  If the holes are less deep than required 
the holding strength is reduced.  "I believe" it's to the square of the 
reduction in depth, but diameter also comes into play. I'm not a 
structural engineer so I'd seek the help of a qualified individual. Ask 
around.  Maybe one of the local hams is qualified, or knows someone who is.

In this case, a reduction in strength is a safety issue, so I'd 
certainly seek qualified advise.

As for the potting material, although there is a material for leveling 
concrete surfaces that is quite strong, I'd stick with the recommended 
epoxy, even if it is expensive. You can get killed falling from the 
height of a retracted td err on the side of safety, cost be damned.  If 
I can't afford it, I'd not do it.

73 and good luck,

Roger (K8RI)

On 10/12/2014 11:37 AM, Marvin Shelton wrote:
> Here’s a question for everyone. I’m installing a new T-base for my crank-up US Tower so that I can use the raising fixture and stop climbing it when it’s retracted. (getting too old for that) and I’ve got the holes prepared and am wondering about the anchoring material to use.
> I’ve drilled the holes 2.5” in diameter to account for the nuts at the base of the anchor bolts, which I’ve had to cut off because I couldn’t go deep enough. So now I have 2.5” diameter holes to install 1-1/8” anchor bolts in.
> My obvious choices are anchoring epoxy, which is expensive at over $20 per tube, Quikrete anchoring cement, and I just discovered something called Rockite- for anchoring and patching.  I’m hoping that any of these choices will work. I’d like to save a few $$ and use the Quikrete which will be much easier to use (mix like concrete and pour into the holes). It has a pull-out strength of 14,100 psi  after 24 hours and 21,000 psi after 28 days.
> Anyone have experience with any of these products. I’d like to do my pour today if possible.
> Thanks in advance.
> Marv
> wa2bfw at arrl.net
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Roger (K8RI)

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