[TowerTalk] Fwd: Relatively large tower base install questions.

[K8RI]

On 3/5/2013 10:45 AM, Patrick Greenlee wrote:
> My apology for using the term "pipe" loosely. Of course it is structural
> tubing with circular flanges welded to each end of each of the 12 ends.
> Multiple through bolts attach the 20 ft sections together at the flanges
> to make 40 ft.

Here's a tower with a similar stance although the base was not "tip up" 
it did use 3 separate concrete piers.
http://www.rogerhalstead.com/ham_files/skyhook.htm

Over all it was just shy of 200 feet with IIRC the top 120' rotating.
I took two men, (WD8RXP & WD8RZE) several years to complete. It even 
made the January 87 cover of QST

That's Ken (WD8RZE) working 120 feet above me in the cover shot.

They used square flanges with 4 bolts at the leg junction. The base was 
5" structural steel tubes.  I don't remember for sure, but IIRC the base 
alone weighed 4 tons.  There were several truck loads of concrete in 
those piers.


  I'm sure if the tower had been used to support an antenna
> it would still be in fine shape but the gyroscopic forces eventually
> work hardened the bolts and caused the failure.

It depends on the length, speed, and mass of the blades as well as the 
speed of direction change,  but the force from precession could have 
been tremendous. Every time it changed direction the top of the tower 
would have tried to tip up or down.

Like has already been mentioned this is one very large base compared to 
the size of the antennas and for only 49 feet

73 es good luck,

Roger (K8RI)


  I will be replacing the
> bolts. I intend to cut off the tops of the tubing embedded in the piers
> to be able to reuse the flanges. I will weld on telescoping tubing to
> replace that left behind in the piers.
>
> As regards "The Base", the installation didn't have one large "lump" of
> concrete for a base, just the 3 piers 18 inches in diameter and 7 ft
> into the ground with tubing embedded to provide flanges to mount the
> tower.  I think the width of the tower's "stance" at over 14 feet
> contributed greatly to its stability and lack of a requirement for a
> massive lump of concrete. Given its aspect ratio with the top 60 ft
> removed (over 14 ft wide at the bottom and only 40 ft high) erecting it
> on the ground and tilting it up should be relatively straight forward
> considering I have a tractor with a front end loader to let hydraulics
> assist muscle, a 12,000 pound pull winch on the front of a one ton
> dually diesel Dodge truck, and two of the tower base connections are
> very stout tilt over hinges.
>
> This may not be the first time something like this has been done but it
> is a first for me and I have never heard of nor seen anything like it. I
> haven't worked out the details of how to mount a crank-up free standing
> tower inside this 40 foot tower but it will not include concrete.  Even
> with a crank-up tower fully extended from inside it with a couple
> antennas on that the load on the tower base will still be significantly
> less than it had when the original full 100 ft were intact, and more so
> if you consider the load and drag of the wind generator which is
> considerable.
>
> I suppose I could take a few more progress snaps and post them as there
> might be some interest in seeing how this project goes.  Next Monday is
> the date of a brush clearing expedition to clear brush and trees that
> have grown up and are intertwined with the legs and braces of the first
> 20 ft section.
>
> The picture labeled Big Tower is a shot of one of the tilt over hinges.
> The misspelled Flangte and pier is a picture of one of the piers and
> flanges.
> Tower is a shot of the whole thing as it sits in the brush.
>
> The rust is light, superficial, and not flaky. It will clean up easily.
> I will paint it with Rustoleum brand hamertone paint intended to be put
> on rusty metal with no primer.  I have used it on rusty metal before on
> outdoor steel and after 10 years it still looks new.  This paint comes
> in spray cans or quarts at the big box stores. I have found it in colors
> in spray cans but only black and silver in quarts.  Silver can be tinted
> and gives a slightly pastel metallic look when I had it tinted as dark
> green as they could.
>
> 73,
>
> Patrick AF5CK
>
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