[TowerTalk] [Bulk] Re: [Bulk] tower removal

Thu Mar 10 17:46:14 EST 2016

Wayne,

Yup, the bottom loose end of a 1 ton 130' (plus mast?) long battering 
ram swinging around is a scary thing!  A big jump from R25.

Rohn does have a spec sheet for the tower section mechanical properties, 
that would be best to find it for 65 and ask the question to a real 
ME/Structural Eng. if you want a single point lift.

You need a really big crane to hoist one ton plus plus the layover 
reach.  I think the crane ops don't like to see a chance of the load 
getting snagged on the crane boom, so that means the crane tip higher 
than the top of the mast.  The crane company here sent out the boss to 
scope out my job, that might be a good place to start.

We lifted each section individually after the first 40' pair for my 
tower, the crane was at max on the top section with one ring, prop 
pitch, 22' of 3" mast, 14' exposed, 1100#.  156' to mast top AGL.

Let us know what you learn.

Grant KZ1W

On 3/10/2016 13:16 PM, Wayne Kline wrote:
> 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 at 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 at mindspring.com
>>> "I like climbing towers because people look up to me"
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