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Chele
Member
2013-Jan-14 11:45 pm
Tower concrete baseWe just bought a used 30' guyed tower. It is hinged between the lowest and middle segments(no need to climb!). My question is: where can I find out what size the concrete base needs to be?
Thanks |
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WHT join:2010-03-26 Rosston, TX |
WHT
Member
2013-Jan-14 11:50 pm
www.rohnnet.com would be a good starting place |
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John Galt6Forward, March Premium Member join:2004-09-30 Happy Camp |
to Chele
The requirements for a 30 footer are rather modest. Generally speaking, the base size depends on the overturn moment and the soil conditions. Again, in this case...modest. |
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Chele
Member
2013-Jan-15 9:26 am
WHT I looked through the site and I couldn't find any info other than Rohn offering their professional services.
John I don't want to over-engineer the base because of the difficulty of getting the material to the site. And definitely don't want to under engineer it because of the risks. Any idea where I can find at least a starting point? Thanks |
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John Galt6Forward, March Premium Member join:2004-09-30 Happy Camp |
Need to know two items in particular...
- estimated maximum winds and risk of icing
- estimated square footage of the antennas |
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John Galt6 |
to Chele
Here is the Rohn catalog. It should offer you some general guidance on how to proceed. » www.rohnnet.com/resource ··· e/id/681One of the other issues that you will need to address is the soil bearing capacity. |
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WHT join:2010-03-26 Rosston, TX |
to Chele
said by Chele:WHT I looked through the site and I couldn't find any info other than Rohn offering their professional services. Look at specs for towers similar to yours and will give you an idea as a starting point. |
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bburley join:2010-04-30 Cold Lake, AB |
to Chele
The manual for a DMX-68 wants 4 cubic feet of concrete. Your tower is smaller, but it also has to tilt over. My uneducated guess is that the same amount of concrete should work for you.
I also met someone who was concerned about concrete + lightning. He said that a direct hit could split the concrete and his solution was a rubber insulator around the concrete and a separate ground rod. At only 30 feet, I don't know if that is a concern. |
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Chele
Member
2013-Jan-15 10:17 pm
THANK YOU Gents! I will start looking through the docs and see what I find out. In the mean time, I don't think we will need to install more than four 2' dishes, ice loading is not a factor(just light frost), and the ground is clay. The tower had had two very heavy cameras at the very top(80-100lbs).
Thanks again. |
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DaDawgs Premium Member join:2010-08-02 Deltaville, VA |
to Chele
Chele;
A thirty foot tower hinged near the middle needs you to set a concrete/cement base about 18" x 18" x 36"...
Dude, trust me on that.. unless you are putting really heavy stuff on the top that is all you need.
Take it to 24" x 24" by 48" if you feel nervous.
Mike |
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John Galt6Forward, March Premium Member join:2004-09-30 Happy Camp |
The tower is guyed, so the base can be smaller than a freestanding tower, provided the soil can bear the load (sounds like it can).
Also, the guy anchor blocks will need to be appropriately sized.
A 2'x2'x4' base will require 33 bags of concrete at 60 pounds per bag...plus water at 8 pounds per gallon. |
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John Galt6 |
to bburley
said by bburley:The manual for a DMX-68 wants 4 cubic feet of concrete. Your tower is smaller, but it also has to tilt over. My uneducated guess is that the same amount of concrete should work for you. Perhaps you mean yards...?? I also met someone who was concerned about concrete + lightning. He said that a direct hit could split the concrete and his solution was a rubber insulator around the concrete and a separate ground rod. At only 30 feet, I don't know if that is a concern. This demonstrates a complete lack of understanding of the issues involved (not you...the other person). The base needs a spot-welded rebar cage with a tail for a bonding jumper to the tower/grounding system. |
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bburley join:2010-04-30 Cold Lake, AB |
said by John Galt6:said by bburley:The manual for a DMX-68 wants 4 cubic feet of concrete. Perhaps you mean yards...?? I also met someone who was concerned about concrete + lightning. He said that a direct hit could split the concrete and his solution was a rubber insulator around the concrete and a separate ground rod. At only 30 feet, I don't know if that is a concern. This demonstrates a complete lack of understanding of the issues involved (not you...the other person). The base needs a spot-welded rebar cage with a tail for a bonding jumper to the tower/grounding system. That should have been 4^3 feet or 64 cubic feet. I was typing without thinking The rebar cage makes sense. Do you have a link to any page where I can read more on that? |
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WHT join:2010-03-26 Rosston, TX |
to bburley
Referring to what DaDawgs said, said by DaDawgs:A thirty foot tower hinged near the middle needs you to set a concrete/cement base about 18" x 18" x 36"... Look at Rohn's fold-over #55 tower uses. said by bburley:I also met someone who was concerned about concrete + lightning. He said that a direct hit could split the concrete and his solution was a rubber insulator around the concrete and a separate ground rod. That is so absurd, I'll let someone else have a laugh at that. |
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John Galt6Forward, March Premium Member join:2004-09-30 Happy Camp |
to bburley
said by bburley:The rebar cage makes sense. Do you have a link to any page where I can read more on that? Check out the Rohn link I posted above... |
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