A N Thompson wrote:
>
> Hi. Does anyone here have any suggestions on
> dismantling a tower with use of a crane? Obviously
> the crane operator is going to have a major vote in
> how he takes the tower down, but I would appreciate
> input from others on the best way to do this. We're
> talking about a large tower (4 ft. on a face, 200 ft.
> high), by the way.
>
> [Oh, and why would a ham buy something that size?
> If you have to ask, you wouldn't understand. Besides,
> the price was right. And too much is never enough,
> etc.]
>
> Thanks & 73,
>
> Arliss
> W7XU
>
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Depends on the tower.
We are looking at taking down a 150' of 32" face tower. I got the tower
specs and figured that if we hook on at the 100' level with a crane, and
cut the guys, we could just lay it down gently onto preleveled blocking
support every 50' and unbolt the sections on the ground. This is a
rolled angle tower so we do not have to worry about internal corrosion
on round legs.
This way we are taking down a 150' tower using a 110' crane. Total tower
weight on the pick will be about 7000 lbs. including guy wires - don't
forget them.
To do this type of thing, you have to have good specs on the tower.
The trick in taking down large pieces of tower with a crane (more than
one section at a time) is in knowing what the condition of the tower is
from a corrosion stand point, what the yield specs are on the tower
material, the weight per section including anything that has gotten
attached to the tower, and the maximum tensile and compressive loads
each tower leg can handle.
You also have to pay a lot of attention to how the crane is going to
attach to the tower sections, how they are going to react as the load
transitions from the tower with the section vertical to the crane
holding it with the sections at a slight angle. You have to understand
and track where the center of gravity for reach part of each pick of the
tear down. You have to consider what happens if a section hangs up after
it is unbolted and won't separate from a tower.
All connections to the tower have to be positive, i.e. no chains into
open hooks. Working with stuff this large, you can get crushed by a
swinging load. If you drop something large, it will probably shear of
the remaining guy wires and dump the rest of the tower and the workers.
Usually this requires professionals with experience guided by competent
angineering analysis. I am not saying you can't do it, just that it is
darn trickey when you wind up with 7000 to 10,000 pounds hanging on a
crane and it isn't doing what you expected.
de n0yvy steve
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: K7LXC@contesting.com
Sponsored by Akorn Access, Inc & KM9P
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