I have been offered a 40' TV tower and need to find out how big I need to make the concrete base so this thing doesn't fall over the first time the wind blows.
This is one of those triangle type towers with 3 pieces of angle iron embedded in the concrete for mounting.
I can get the surface dimensions from the existing base, but how deep does this have to be to keep the tower upright?
Thanks in advance for any help.
Tom
Antenna tower base
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spareparts
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Re: Antenna tower base
Tom,topcat270 wrote:I have been offered a 40' TV tower and need to find out how big I need to make the concrete base so this thing doesn't fall over the first time the wind blows.
I helped put up 3 towers - The depth of the hole for for the rebar cage was at least 4 times the width. The most recent one had 2 yards of concrete.
Take a look at http://www.anwireless.com/padpier.html for an idea what you are in for
Please DO NOT use the AN Wireless dimensions with another companies tower. The figures shown are for their product & likley are not suitable for your exisitng tower.
Martin
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Dan562
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Antenna Tower Base
Hello Tom,
In your description, "This is one of those triangle type towers with 3 pieces of angle iron embedded in the concrete for mounting" made me think the tower wasn't the typical 3 legged tubular towers manufactured by Rohn or Universal.
If the mounting legs are angle iron, Are each leg of the tower also angle iron? Does this tower taper down from the top at a 10 to 15 degree angle towards the base making a 2 to 3 feet spread between legs at the base into the concrete? The way this tower is current mounted in concrete, Is it self supporting?
I've seen and worked on many towers in the past, Rohn, Universal, Spaulding (Rohn) BX, PiRod and Heights. Each one is a little bit different for mounting on or in concrete .... it's almost too band you don't have a picture of this tower. A lot of hams use older Rohn 20 TV towers, they have a tubular legs and formed strap that's welded around the three legs forming the triangle shape.
I believe the distance between the legs is roughly 10-12". Rohn 25, 35, 45 and 55 have tubular legs that have what is called "Z" bracing welded steel rod 9.5' of each 10' section on each side of the tower. Universal is similar but has a distinctive difference how the manufacture bolts the legs together vertically. All of these vertical towers require guy lines to support amateur or commercial antennas so they don't collapse in wind, ice or snow storm conditions.
Most true self supporting towers require much larger concrete re-inforced rebar pads or piers depending on the type of soil you're mounting tower footing in too. If the soil is sandy, you must use a solid rebar re-inforced concrete pad 4' x 4' x 3.5-4' D.
I've got a 120' Rohn SSV and the separation between all three legs is almost 9'. I have each leg mounted in it's own individual rebar re-inforced cage concrete pier 30' diameter and 10 feet deep. I've got 10 cubic feet of a 6 bag mix of concrete supporting the self support vertical tower and it's been up for many years.
One thing I can't stress enough is to check your zoning laws covering covents and restriction regarding towers. Submit all the paperwork for a Permit. It far less expensive up front than retainer a lawyer after the fact and still even having a lawyer may not prevent you from removing the tower you installed. City, County and State government agencies can be a real pain in your lower posterior if you don't follow their rules and regulations.
Dan
In your description, "This is one of those triangle type towers with 3 pieces of angle iron embedded in the concrete for mounting" made me think the tower wasn't the typical 3 legged tubular towers manufactured by Rohn or Universal.
If the mounting legs are angle iron, Are each leg of the tower also angle iron? Does this tower taper down from the top at a 10 to 15 degree angle towards the base making a 2 to 3 feet spread between legs at the base into the concrete? The way this tower is current mounted in concrete, Is it self supporting?
I've seen and worked on many towers in the past, Rohn, Universal, Spaulding (Rohn) BX, PiRod and Heights. Each one is a little bit different for mounting on or in concrete .... it's almost too band you don't have a picture of this tower. A lot of hams use older Rohn 20 TV towers, they have a tubular legs and formed strap that's welded around the three legs forming the triangle shape.
I believe the distance between the legs is roughly 10-12". Rohn 25, 35, 45 and 55 have tubular legs that have what is called "Z" bracing welded steel rod 9.5' of each 10' section on each side of the tower. Universal is similar but has a distinctive difference how the manufacture bolts the legs together vertically. All of these vertical towers require guy lines to support amateur or commercial antennas so they don't collapse in wind, ice or snow storm conditions.
Most true self supporting towers require much larger concrete re-inforced rebar pads or piers depending on the type of soil you're mounting tower footing in too. If the soil is sandy, you must use a solid rebar re-inforced concrete pad 4' x 4' x 3.5-4' D.
I've got a 120' Rohn SSV and the separation between all three legs is almost 9'. I have each leg mounted in it's own individual rebar re-inforced cage concrete pier 30' diameter and 10 feet deep. I've got 10 cubic feet of a 6 bag mix of concrete supporting the self support vertical tower and it's been up for many years.
One thing I can't stress enough is to check your zoning laws covering covents and restriction regarding towers. Submit all the paperwork for a Permit. It far less expensive up front than retainer a lawyer after the fact and still even having a lawyer may not prevent you from removing the tower you installed. City, County and State government agencies can be a real pain in your lower posterior if you don't follow their rules and regulations.
Dan
40 foot tower base
First of all, a 40 foot tower isn't worth all the hassel your going to be in for. It won't get you above the trees, if you have a 2 story house, it will get you above the roof line, but then what.
To make a long story short, a tower base is designed around several factors. It starts with the loading (antennas) that will go on the tower and how high up that loading will be. Then you take into account the spread between the legs on the tower.
Most of the towers I have built over the years are in the range of 100 to over 300 feet high. The base spread goes from about 12 feet to over 40 feet between the legs. The further apart the legs are, tha smaller the base can be. One 240 foot 4 leg tower had 4 H beam steel piles installed under each leg. The piles were 120 feet long. Then we added the pile cap cement foundation on top of the piles.
In sandy soil for a 150 foot tower, it was fairly common to pour a 30 foor square by 8 foot high rebared single concrete block. This became a big anchor for the tower. In order for the tower to tip, the whole dead weight of the base would have to be tilted.
You need to look at the soil where the tower is going to be installed. Is it soft and mushy, is it sandy, is it clay, is it hardpan, is it shale, is it rocky, is it a granite ledge just under the surface?
A tower base is designed to provide a safety margin of 2.5 times what would be required. This provides the safety factor to allow for unseen factors like high wind gusts and some dummy putting too much antenna too high up on the tower.
You also need to take into account just how much the tower weighs, and how the tower is constructed. Most tower bases are designed to just add weight to the bottom of the tower so they won't tip over. Picture it like a weighted punching bag with a mast sticking out of it. The kids use to have these toys where when you hit the bag, it would come back up to the upright position. A tower is the same, except you don't want it to move.
Hope this gives you something to think about.
Jim
To make a long story short, a tower base is designed around several factors. It starts with the loading (antennas) that will go on the tower and how high up that loading will be. Then you take into account the spread between the legs on the tower.
Most of the towers I have built over the years are in the range of 100 to over 300 feet high. The base spread goes from about 12 feet to over 40 feet between the legs. The further apart the legs are, tha smaller the base can be. One 240 foot 4 leg tower had 4 H beam steel piles installed under each leg. The piles were 120 feet long. Then we added the pile cap cement foundation on top of the piles.
In sandy soil for a 150 foot tower, it was fairly common to pour a 30 foor square by 8 foot high rebared single concrete block. This became a big anchor for the tower. In order for the tower to tip, the whole dead weight of the base would have to be tilted.
You need to look at the soil where the tower is going to be installed. Is it soft and mushy, is it sandy, is it clay, is it hardpan, is it shale, is it rocky, is it a granite ledge just under the surface?
A tower base is designed to provide a safety margin of 2.5 times what would be required. This provides the safety factor to allow for unseen factors like high wind gusts and some dummy putting too much antenna too high up on the tower.
You also need to take into account just how much the tower weighs, and how the tower is constructed. Most tower bases are designed to just add weight to the bottom of the tower so they won't tip over. Picture it like a weighted punching bag with a mast sticking out of it. The kids use to have these toys where when you hit the bag, it would come back up to the upright position. A tower is the same, except you don't want it to move.
Hope this gives you something to think about.
Jim