I think you have some major engineering job in front of you. You can
probably use your truck to erect it if you add a "falling derrick",
something used in many cases raising a tower. I used one myself.
Regarding all the adds-on you definitely will need some engineering
inputs. I also strongly suggest you get recommendations regarding the
tower base. Just dig something down does not necessary guaranteeing a
proper support. I imagine you will get some lifting forces on the
legs when you add structures to the top of the tower. Most towers
take care of these forces by the guy wires but I imaging you should
be able to use some nice size anchors at the tower legs for the
self-supporting tower.
You might check out my tower and its erection here.
https://www.facebook.com/media/set/?set=a.10150198503693539.328964.579753538&type=1&l=1c649b80ab
Good luck with your project and keep us updated what's happening.
Hans - N2JFS
-----Original Message-----
From: Patrick Greenlee <patrick_g@windstream.net>
To: towertalk <towertalk@contesting.com>
Sent: Mon, Mar 4, 2013 12:09 pm
Subject: [TowerTalk] Relatively large tower base install questions.
Background:
I have recently purchased the remnants of a failed tower from a
friend of
mine. The tower was originally 100 ft tall, of triangular
construction and
the legs were on a little over 14 ft centers (that is right over 14
feet not
inches) where they were attached to 18 inch diameter concrete piers 7 ft
deep into the ground. The tower held a wind generator and it failed
due to
gyroscopic forces applied by the rotating mass changing directions
due to
variable wind directions. A witness described the event as quite
spectacular. Anyway the bottom two sections are in great shape, just a
little surface rust. The legs are about 4 1/2 inches OD pipe and are
joined
at the 20 ft level by pipe flanges that are multiply through bolted.
Ditto
the connection to the pipe sections embedded in the 18 inch diameter
piers.
The cross braces are angle iron bolted together where they cross and
attached at their ends to pad eyes welded to the steel legs. One leg has
welded on ladder rungs alternating on either side of that leg. Two of
the
legs have hinged bases where they attach to the piers so the tower
can be
tilted up and down.
Over the years since installation lots of trees and brush has grown up
around and through the lower of the two sections making tilting down for
disassembly a real AXE MEN challenge ( hours of chainsaw work.) I
have the
chainsaws up to one with a 32 inch bar and a motor the size of a
small dirt
bike but it might be easier to just climb the tower and disassemble
it from
the top down. I have a friend who also has tower climbing experience
and
personal safety gear (harness etc.) We expect to get it taken apart and
hauled off with a two day weekend effort. I have a welding trailer with
17.5 KW genset and air compressor to support the use of air driven
impact
tools for taking the rusty fasteners apart (or twisting them off if
required.)
So far so good (just like the guy who fell from a 40 story building
and as
he passed the 20th floor he shouted out so far so good) Then comes the
re-erection at my site.
Questions:
I am open for suggestions. Lacking credible objections from this
august body
I will try to assemble this 40 ft tower on the ground and tilt it up
into
place. I will have 360 degree access and freedom all around the site. I
have a truck with a front mounted winch of 12,000 pound capacity. I
have a
good stock of 2 3/8 oil field pipe,k drill stem, etc and full welding,
cutting, bending, whatever capacity in my shop.
Since in its new life this tower base is not holding up a 100 ft
heavy duty
tower what is a reasonable pier size and depth? I can auger up to 12
inch
diameter holes up to nearly 6 ft deep with my equipment, Alternatively I
have a ride on trencher (like a backhoe but self propelled not on the
back
of a tractor) that can dig a 13 inch wide trench down to 7 ft or so.
I could
block off part of the trench and back fill prior to the pour and have
a more
or less rectangular pier about 13 by xx inches up to about 7 ft deep but
this is more effort and pending your input may not be required.
I intend to add a spiral (triangular) staircase around the outside of
the
tower to access the observation/work platform that I will install at
the 40
ft level. This deck will be larger than the tower's triangle
dimensions at
the top (40 ft level) and so will be cantilevered. I will not extend
this
deck so wide as to extend beyond a vertical projection of the piers
thus not
risk a tip-over event due to any load of sightseers. I want to
install an
automated crank-up tower inside this tower such that when fully
lowered you
can stand on the platform and access the lowest antenna on the tube
coming
out of the center of the top of the crank-up tower.
Any thoughts?
How much pier diameter and depth into the ground is enough?
Gin pole recommendations for tilting up after reassembly?
I assume I would install the crank-up tower inside the 40 footer
prior to
tilting the tower upright but will entertain alternative suggestions.
TIA for any help
Patrick AF5CK
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