Why not hinge up the first couple/3 sections by muscle alone and then drop the
next sections down from above and roll from there.
Sent from my iPhone
Begin forwarded message:
> From: Kelly Taylor <ve4xt@mymts.net>
> Date: March 16, 2012 4:56:01 PM EDT
> To: <kip@kdream.com>, <towertalk@contesting.com>
> Subject: Re: [TowerTalk] Looking for a sanity check on a tower install
>
> Seems to me the question of where to tie the upper pull ropes depends on the
> position of the tower.
> If it's alongside the building, you should be good to tie it at the top and
> pull. If it's laid out extending away from the building, it becomes a
> question of enclosed angle vs. force required to lift.
>
> The tower is going to weigh at least 240 pounds (40lb per section x 6
> sections), and the effective weight will increase as the enclosed angle goes
> down. Even from directly above the top of the tower, you might find that to
> be more than even a few people can pull up.
>
> You might want to pull up the first 50 feet and then attach the last section
> from the roof.
>
> As for the ground rod: isn't the lightning just as likely to travel to the
> base of the tower, into the butterfly fasteners and then on into the
> concrete anyway?
>
> And hasn't it been shown that exploding concrete bases are a myth?
> Especially when you consider designs for concrete-encased ground rods?
>
> 73, kelly
> ve4xt
>
>
>
> On 3/16/12 2:19 PM, "Kipton Moravec" <kip@kdream.com> wrote:
>
>> I am supervising the installation of a 60 foot Rohn 25 tower. (This
>> means finding the people with knowledge and muscle.)
>>
>> It will be placed next to a 50 foot building with concrete walls, a flat
>> roof, and a 5 foot parapet (wall) around the roof. (Top of the parapet
>> is 50 feet above the ground.)
>>
>> It will have one wall bracket for each section of Rohn 25 along the
>> wall. I know this is probably overkill, but that is what they want, and
>> they have the money for it.
>>
>> The proposed plan is to bolt a tilt-over base to the large 6" concrete
>> driveway/parking lot by using butterfly expanders.
>>
>> Then they want to assemble it on the ground, and tie a couple of ropes
>> to it at 50 ft and have 6-8 people pull it up from the flat roof. (With
>> the same number on the ground to help get it started.)
>>
>> First question is this a good plan?
>> Do we need to also pull from the middle (25 feet) so there is not a
>> bow?
>>
>>
>>
>>
>> Second part. The ground is all 6" concrete driveway. They are worried
>> that we can not just drill a 5/8" or 3/4" hole through the concrete and
>> put ground rods in because we have to have a certain amount of air gap
>> between the ground rod and the concrete, or the concrete will explode
>> when lightning hits.
>>
>> That does not sound right to me, because the even though concrete is
>> somewhat conductive, the ground rod is going 10 feet into the earth. And
>> if I have three ground rods the lightning will be spread into the ground
>> and not as much through the concrete and the unknown places of rebar in
>> the concrete. And we already have the tilt over plate bolted to the
>> concrete driveway. So it is not like there is a point connection to the
>> concrete.
>>
>> Do we really need an large air gap between the ground rods and the
>> concrete driveway? If so how much?
>>
>> Kip
>>
>>
>>
>> _______________________________________________
>>
>>
>>
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>
>
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