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Chele

join:2003-07-23
kudos:1

Tower concrete base

We 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



WHT

join:2010-03-26
Rosston, TX
kudos:5

www.rohnnet.com would be a good starting place



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6
reply 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.
--
Nothing makes an American want to do something more than telling them they can’t.


Chele

join:2003-07-23
kudos:1

1 edit

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



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6

Need to know two items in particular...

- estimated maximum winds and risk of icing

- estimated square footage of the antennas
--
Nothing makes an American want to do something more than telling them they can't.



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6
reply to Chele

Here is the Rohn catalog. It should offer you some general guidance on how to proceed.

»www.rohnnet.com/resourcesmodule/···e/id/681

One of the other issues that you will need to address is the soil bearing capacity.
--
Nothing makes an American want to do something more than telling them they can't.



WHT

join:2010-03-26
Rosston, TX
kudos:5
reply 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.

bburley

join:2010-04-30
Cold Lake, AB
reply 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.


Chele

join:2003-07-23
kudos:1
reply to Chele

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.



DaDawgs
Premium
join:2010-08-02
Deltaville, VA
reply 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



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6

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.
--
Nothing makes an American want to do something more than telling them they can't.



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6
reply 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.
--
Nothing makes an American want to do something more than telling them they can't.


bburley

join:2010-04-30
Cold Lake, AB

said by John Galt:

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?


WHT

join:2010-03-26
Rosston, TX
kudos:5
reply 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.


John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6
reply 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...