[TowerTalk] Fwd: Fwd: Tower foundation and bedrock

[Hans Hammarquist]

 Pete,
I made a lot of simulations for various wind conditions and found out that my tower, unguyed, was going to safe sustain wind up to 85 mph with a surface area of 20 sqft. As the wind, frequently, reaches that value where I live, on a hilltop in Southern Vermont, I simulated the possibility of adding guy wires. That increased the safe sustained value to 135 mph. So, against all advice, I have a guyed tower that can be unguyed. I don't know where this misnomer comes from that a self-supported should be weaker if you added guy wires. Maybe somebody can tell me. I understand if the guy wires have a very steep angle the load on the tower will increase but that is not the case with mine.

Hans - N2JFS
 
 
-----Original Message-----
From: N4ZR <n4zr at comcast.net>
To: TowerTalk <TowerTalk at contesting.com>
Sent: Tue, Apr 9, 2019 11:21 am
Subject: Re: [TowerTalk] Fwd: Tower foundation and bedrock

Was your tower guyed or unguyed?  Makes a lot of difference in the 
loading on the base. I gather Chuck's would be unguyed, and that 
suggests to me that he needs to be very sure of the quality of the 
rock.  Limestone can be strong or weak (decomposed).  A weird example - 
50-some years ago, I lived in Hong Kong, right after they built a new 
cruise ship terminal.  It had two levels, independently supported on 
separate columns, and within months of its opening they discovered that 
the second level was driving its columns down into the stone at about 8 
inches a year.  In about 25 years there would have been 6 inches of 
headroom on the first floor.

73, Pete N4ZR
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On 4/9/2019 8:53 AM, Hans Hammarquist via TowerTalk wrote:
>  Hi Chuck,
> Bedrock is, I believe, the best to anchor a tower in. Just make 100% sure it is bedrock you have where you are erecting the tower. When I was planning for my tower a (big mouth) "friend" of mine told me where to find bedrock. He pointed out a spot that was 100% bedrock. He even "tested" it by kicking on it with his boot. Well, the "bedrock" turned out to be a relatively large rock, ~100 lb but there was no "bed-" with it. I'm just happy I checked before I spent the time to attach anything to the rock. I, instead, dug down 5 feet, placed a 6'x6' granite block (that just happened to lay around on my property), and attach my tower to that. As I also had a ton of scrap metal laying around, I placed that on top of the granite to add some extra weight.
> I used 6 galvanized angle irons attached to the granite block with 12 bolts-and-nuts. The bolts all go through the block. The angle irons are encased in concrete. I felt I didn't have to add any yards of concrete for this installation. It has been a few years now and nothing has moved.
> 73 de,
> Hans - N2JFS
>  
>  
> -----Original Message-----
> From: Charles Lind <cxl24 at case.edu>
> To: TowerTalk <TowerTalk at contesting.com>
> Sent: Sun, Apr 7, 2019 7:41 pm
> Subject: [TowerTalk] Tower foundation and bedrock
>
> I have the opportunity to put up a TX-455 tower on the property of my
> brother-in-law:  200+ acres and no zoning issues.  He says, however, that
> there is limestone bedrock about only three feet down.  Before I start
> Digging pilot holes, is there any advice a how to proceed with providing a
> solid foundation if this is the case.
>
> Tnx, Chuck, N8CL
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