[TowerTalk] Taking down a tri-ex LM354

[Roger (K8RI) on TT]

On 6/8/2014 9:48 PM, Richard (Rick) Karlquist wrote:
> On 6/8/2014 6:12 PM, Jim Lux wrote:
>>
>> If you don't have heavy lifting gear, then the next thing is a falling
>> derrick rig and a suitable winch/come along/tow vehicle, etc. The
>> falling derrick helps insure that as your tower comes down past the 45
>> degree point, the load is still reasonable.
>>
>> If you have 15-20 feet of suitable tower sections, you could probably
>> also rig up some sort of guyed vertical pole with a block and tackle
>> anchored at the top to help lay the other tower over.
>

The point on water pipe is well made, but pipe should never be used 
where strength is involved.  Yah, I know there's a lot of it in use, but 
pipe is soft and bends far, far easier than structural steel tube of the 
same size. It's also heavy for the strength.  Tower sections are by far 
the strongest for the weight, but you want the load on all legs, not 
just two..

It shouldn't be used for masting either, but probably over half the 
installations out there use it.
If pipe is used for a mast to give a big tribander a few more feet and 
it bends, how do you get the antenna down?

We let one down yesterday (40' steel, not terribly heavy) from the W end 
of my shop, with a novel  approach, (N8ERFs idea. Thanks Dennis) at 
least to me.  There was a pulley at the top of the tower. We ran a rope 
through a snatch block at the base, up through the pulley at the top and 
back about a 100' to the SE to an anchor. There were also two guys held 
by two hams.  The rope ran NW from the pulley at the base of the tower 
to three wraps snubbed around a 10" diameter Spruce tree. The guys at 
the tree just slowly let the rope out while those to the SE helped keep 
the load light.Other than a bit of a communications problem (the shop 
was between the two groups so they could not see each other.)

73

Roger (K8RI)

> A word of caution on the falling derrick method.
> If you build a falling derrick to put a tower UP, the
> first 6 inches are the most difficult.  So it is
> risk free to test the set up by raising the tower
> 6 inches and seeing if anything goes wrong.  I
> did this with my 50 ft Glen Martin tower and found
> out that the derrick was well on the way to buckling.
> Fortunately, I had the luxury of backing down and reinforcing the
> derrick before trying again.
>
> If you build a falling derrick to put a tower DOWN,
> and didn't use it to put the tower up in the first
> place, you have no way to test it.  You might have
> the tower within 10 feet of setting down and then
> the derrick buckles or something.  In your case,
> it might be a one time use derrick, where you don't
> want to waste money over designing it.  Cut corners
> at your own peril.  Be sure to side guy the falling derrick.
> Be careful.  Borrowed tower sections are greatly preferred
> over water pipe.


> Very hard to predict when a pipe is
> going to buckle.
>
> Rick N6RK
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