50' tall Rohn 25G, bracketed.

johndjmix

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Jun 16, 2014
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Hey Guys, so, until recently, i had a 39' tower i put up about 8 years ago on the side of this building. Its attached via 1/4" steel wall brackets i fabricated. The brackets secure to the building go with 1/2" galvanized threaded rod that goes through the blocks then through steel plates on the backside welded to a vertical I Beam. Each bracket has 1/2" threaded rods holding it. In other words, the building will fall down before the brackets come off the wall =). The tower consisted of 3 sections plus the top (9') section. I have a steel mast pipe coming out of the top section thats about 8' with a super light VHF antenna on it. Thats it.

We took the tower down to facilitate work that had to be performed on the side of the building. It was super easy, we hinged it down off a bolt on the bottom bracket.

Now im ready to put it back up. Now the question, i have one more section i would like to add in there. That would make 2 sections plus the top section above the roof line shown in this picture. I would say about 35' above the top bracket not including mast pipe. Is this doable without guy's? I wouldn't mind guying but as you can see one guy would have to go on the other side of that fence that is not my property.

(Picture shows the first 2 sections going up, not securly fastened yet...., it was in progress when i took pic)
IMG_0151-s.jpg
 

mmckenna

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The Rohn 25G will do self supporting up to 40 feet with proper mounting/base. Since it looks like your brackets are above the 10 feet mark, you ~should~ be OK at 50 feet.

However, Rohn specs are ONLY if you are using all Rohn parts. While it sounds like your custom brackets are properly anchored, you'd really need an engineer to look at the whole setup and pass judgement.

 

prcguy

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I would also get a PEs comment just to make sure. If you guy it to your own building, that will take care of wind in most directions and will protect your neighbors property. Wind blowing into the building and tower from the left side of your picture will have the building height's worth of anchoring and protection. Winds blowing toward your neighbor or from right to left on your picture will be handled by the guys and also to either side to some extent which would be toward and away from the viewer of your picture.

I
 

Wally46

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I have a 50 foot Rohn 25 tower bracketed at the 20 foot mark with an 11 meter Mr.Coily. It's been up for years and even made it through the Derecho storm we had.
 

johndjmix

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Good call PRC, i was thinking the same. I can guy to the walls on both sides lengthwise then across the roof of the building.

Not going to lie, ive seen a 70' 25G only anchored by the "set 3 feet in concrete" method thats been up 10+ years. My friend asked me to climb it to install a wifi bridge. Ummmm.....no.

I would also get a PEs comment just to make sure. If you guy it to your own building, that will take care of wind in most directions and will protect your neighbors property. Wind blowing into the building and tower from the left side of your picture will have the building height's worth of anchoring and protection. Winds blowing toward your neighbor or from right to left on your picture will be handled by the guys and also to either side to some extent which would be toward and away from the viewer of your picture.

I
 

N5XPM

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It could work or not, but if you put too many antennas on it with too great of a flat plate wind load it will come down sooner or later.
 

n5ims

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It's hard to tell on the picture, but is the tower being supported simply by the brackets or is it also supported by the ground on a concrete pad. While with just a single, small wind load antenna it shouldn't make much difference, this will add stress to the mounts when a human is on the tower working (or the antennas grow to many, as often happens). With just the brackets, they must handle both the vertical and horizontal load. With the addition of a good concrete base, the base will take nearly all the vertical load so the brackets will only need to handle the horizontal loads.
 

prcguy

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I would guy it with only two cables 120 deg apart and centered out to the right of the picture, which would be the spacing if you had three and the missing one was off to the left of your picture. You would have to anchor the cables out in the middle of the roof somehow and I don't see any benefit of adding more wires unless you can get permission from the neighbor off to the left for one final guy cable.

Good call PRC, i was thinking the same. I can guy to the walls on both sides lengthwise then across the roof of the building.

Not going to lie, ive seen a 70' 25G only anchored by the "set 3 feet in concrete" method thats been up 10+ years. My friend asked me to climb it to install a wifi bridge. Ummmm.....no.
 
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