Grant,.
I am disassembling my 146 ft Rohn 65 (20 ft sections) and one tapered base
that was converted
To a top section. When I installed it I used a crane in two lifts first lift @
60 ft. Then attached the guys to the anchors , then the last lift with the
attach point @120'.
I did not do the moment /math. But am concerned in removal the 130 ft in one
shot. Leaving 16 ft stub.
The anchoring it to the ground and the layover ???
I helped in removal of two towers one @ 110 and one @ 100 with24ft of 1/4
wall cromemolly tubing and yagi monobanders. One lift up and then we laid it
down and di assembled the antennas at ground level.
The trick in this process is to keep the tower anchored , the crane ooperator
keep the free bottom legs pined against raised concrete base as he turned and
lowered the boom.
But R 45 is 80 lb and R 65 for 20 ft is 298. And my concern
Wayne. W3EA
Sent from my iPad
On Mar 10, 2016, at 4:45 PM, "Grant Saviers" <grants2@pacbell.net> wrote:
> R25 is 41.1 #/section so your nude tower weighs in at 500# or so with bolts
> etc.
>
> A single 3/16" guy at max load of 2000lbs (50% of break strength) and a 45
> deg angle to the tower could put a perpendicular force of 1414# on a leg, at
> a Z brace. In a smooth lift that force would never happen even with the 120'
> of tower horizontal.
>
> You can be sure that W8JI "ran the numbers" before his removal. The sling
> around (and threaded through so it won't slip) the tower at 2/3 height
> insures it will stay vertical at the initial lift. I'd rig with two slings
> as chokers to the pair of legs opposite the lift cable and then crossed over
> on the third leg to the hook so the tower won't rotate in the slings. Your
> crane operator will likely have a good suggestion about how to rig.
>
> Once you clear the base, then laying down the tower is where there is risk on
> the two legs that are first on the ground and start taking the load. Those
> short stubs would be easy to bend. Done right you never have the tower in a
> full horizontal position with a point lifting load at the 2/3 of height.
> Some short blocking e.g. 6x6 could be used at the bottom Z brace as the place
> to take the load, that would be better and placed along the length would
> allow easier removal of the bolts. This takes some coordinated moving of the
> crane tip and hoist line to not have the base slide around while lowering,
> but it's done all the time. Don't lay the low end down on a saw horse, they
> are too unstable. You will need tag lines if there is a breeze.
>
> /For my new tower, using a crane for the erection, I had to lift Rohn 65 20'
> sections from saw super strong saw horses because the ring rotators were
> already installed. I hoisted the low end in a sling from a fork lift and
> maneuvered it forward as the crane operator did the lift. A section with two
> rings weighed about 1300#. You could use a mid size tractor or fork lift in
> your situation to hold the bottom end off the ground with slings while the
> crane lowers the entire tower. Then you could load it on to cheap saw horses
> for ease of disassembly.
>
> I'm assuming you are hiring a pro crane company, this is not a job for
> amateurs, sign hangers, etc..
>
> Grant KZ1W
>
> On 3/9/2016 17:12 PM, Steve wrote:
>> I am planning on taking a 120 ft 25g tower down with a crane ,any
>> suggestions ? can i take the whole tower down and lay it over or will it
>> buckle ? any thought s or tips welcome Thanks
>>
>>
>> Steve Flory W9KOP
>> sflory@mindspring.com
>> "I like climbing towers because people look up to me"
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