Trey Garlough wrote:
> I'm a little short on usable space for a guyed tower at my hosue, so
> I'm considering a freestanding tower, however I am seriously down on
> crankups. Is there anything out there that has the approximate form
> factor and capacity of those hefty US Tower 72'/89' crankups, except
> with no moving parts?
>
Hi Trey! You might consider a "cell site pole" type of construction. I
have a tall version (120') here in Cincinnati that was made for me,
custom, by Power Structures in Belle Chase, LA. It uses a pier type
foundation that was drilled with a construction-footer style
pier-drilling rig (big and heavy ~ $1.5K for the hole) that is 5'
diameter and 20' deep. It took about 14 yards of concrete to fill the
hole.
The tower is formed on a giant sheet-metal brake (~50' long) that makes
12 successive bends in a trapizoidally shaped steel sheet to form a
closed, tapered pole. The sheet form is then robot penetration welded
up the seam inside and out. Any fittings are then welded on and the
whole assembly is hot dip galvanized as one piece in a 50' by 10' by 10'
galvanizing tank.
I have three 42' sections that make up my 120' tower that overlap 3' at
the nesting joints. The sections stack like sugar cones from an ice
cream store. There are attach points welded above and below each
overlap joint to which come-a-longs are attached to nest the sections
together and provide a saftey when the crane picks the whole thing up to
set it on the foundation in one piece.
Yours could be done with 2 sections and be lighter, less demanding of
the foundation, and half as expensive as the one they did for me.
Power Structures is a subsidiary of Lapp Insulator and has a New Orleans
telephone number: (504) 394-7433 (as of July, 1989). These guys also
make monopole power-company electrical transmission towers.
They had a PE working with them in their communication pole group named
Tim Gooding, who designed and quoted my job. His firm was called
Engineered Endeavors, in Concord, Ohio at that time. I tried calling
his old number, but it has been changed.
The resulting tower is rated for 30 sq-ft at the top in a 30 psf wind.
It weighs a total of 6200 pounds. It is 8" across the flats at the top
and 26" wide at the bottom. It is fastened to the foundation with 4 11'
long j-bolts installed during the pour.
Questions cheerfully answered,
Mike - W8MM - EM79sd
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