[TowerTalk] Self Supporting Tower Install

[Patrick Greenlee]

I was given the option of a rectangular rebar cage intended for a 4x4x8 
ft hole or a rebar cage intended for a round 5 ft diameter hole 8 ft 
deep.  I found 2 sources for the round hole drilling. The less expensive 
one wanted over $2000 to drill the hole and I would be responsible for 
replacing any teeth on his tool if any were damaged and if he got stuck 
at my tower site I was responsible for paying to get him out.

An experienced local operator dug my rectangular hole with a back hoe 
for $85.

The round hole may have been more perfect but after struggling through 
about a millisecond of internal debate  I chose the backhoe.

Patrick        NJ5G



On 5/11/2017 11:00 PM, jimlux wrote:
> On 5/11/17 8:33 PM, Lee K. Brown MD via TowerTalk wrote:
>> I recently moved my US Tower crank-up from my old QTH to my new QTH,
>> While the tower had been originally installed with the usual
>> rectangular concrete base specified by the P.E. that US Tower used to
>> wet stamp the plans for me, the P.E. that I engaged for the
>> re-install locally specified a cylinder of concrete. Apparently not
>> unusual at all.
>>
> there's a well developed process for drilling round holes (caissons) for
> supports for things like traffic lights, etc. A machine comes out and
> drills a 3-4 foot diameter hole, you drop the rebar cage in, fill with
> concrete, etc.
>
> Works nicely in places without a lot of room (e.g. a sidewalk), if you 
> make the column deep, it can support an enormous moment (there's 
> several traffic signals spanning 3-4 lanes near my house doing this, 
> the cantilever loads must be huge with a fairly heavy left turn signal 
> hanging out 4 lanes in)
>
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