Wilson, to recap... The original installation was 100 ft tall with a large
wind generator on top. The three piers were 18 inches in diameter and 7 ft
deep. After spending a few minutes thinking about the situation and
comparing the means at hand, I have decided to dig the pier holes with my
backhoe-like ride on trencher rather than the 3PH mounted auger. I can get
whatever diameter I want and greater depth this way. An "L" shaped pier
will resist pull-out better than a cylindrical one will. I may exaggerate
the horizontal component of the "L" to accentuate the pull-out resistance.
Forming for a pour like this isn't very complicated. It is handy having a
3PH mounted cement mixer for the tractor. I may manually bell the "L" a
little in the opposite direction of the horizontal projection at its bottom
making for more of an inverted "T" configuration. When it comes to pull-out
resistance, more is better if you don't go crazy. I tend to over engineer
things, erring on the side of extra strength.
I'll be getting to start this project real soon but first I have a 3 hr
drive to a hamfest tomorrow (Saturday). I will start clearing the brush and
trees from around the tower base Monday. Ib ll take my safety harness and
climb the tower to apply penetrating oil to the fasteners. I'm not sure if
it will help much but it sure can't hurt. My mechanical engineer has
requested wall thickness measurements of the roughly 4 1/2 inch diameter
tubes so I'll take some digital calipers along.
Thanks for the kind words, Wilson. Maybe a little over done, but
appreciated. Everything is relative. For folks with little or no hands on
experience on the scale in question this project may seem "far out" and out
of control. I recall back when knowledge of Rogallo wing hang gliders was
uncommon and spectators used to say the darnedest things when they saw me
preparing to run off a high cliff strapped to one. Comparisons to Icarus
were not uncommon.
Patrick AF5CK
-----Original Message-----
From: Wilson Lamb
Sent: Wednesday, March 06, 2013 8:33 PM
To: towertalk
Subject: [TowerTalk] Large Tower Base
Lots of wasted bandwidth here!
Patrick is obviously one of the very few among us with knowhow and resources
to get outside the box!
Until you work in a few fab yards and around a few drilling derricks, you
donb t really understand possible!
With all his gear, raising this spindly little base will be a snap!
Ib d agree, however, that the proposed foundation piers sound a little small.
With all that gear, he should be able to just yank the old ones out by the
flanges and reuse them.
We know nothing of his soil, but drilling about 8b of 2-3b hole and planting
the old piers in them, surrounded by concrete, might just do it!
Positioning will be the hard part, so assembling the lower tower section and
using it to locate the piers seems a good idea.
I think sitting up there with a cool one and watching the sunset over the
Kansas plain will be a hoot...just be sure thereb s a handrail on that
staircase!
Please get those pictures out asap, Patrick!
Wilson
W4BOH
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