getting ready to put in a tower... have a few questions

[Captain Kilowatt]

Enough concrete to counteract wind loads. I have 2 1/2 cu. yrds of concrete that my 31' tower with an additional 7' mast and antenna array totaling 53' in height. It's overkill but it held up in Hurricane Floyd and numerous T-storms. I think that my tower may have the capacity to extend the tower an additional 20'. All of the weight is straight down unless it exoeriences side loading. There are websites that you can go on and find out what size footing is needed as well as on this forum. Footing shape is crucial too. I delivered concrete to cell tower footings. Cell towers have a wide footprint in order to counteract wind load forces acting on cell towers. And average cell tower footing may have over 132,000 lbs. of concrete.

Safety ,safety,safety. You got to think about what if you built a shoddy erected tower and if it were to fall on someone.

2 1/2 cubic yards is WAAAY overkill for a guyed tower. Half that is a bit of an overkill.

 

[Captain Kilowatt]

An inverse pyramid would work well for dispersing the load while saving weight. I've seen people dig back the walls trying to in effect make a pyramid, but I think and upside down pyramid is stronger if the concrete is up to the task. You don't have to think as much about the direction to load is heading to as much as the direction the load is pulling from.

A right side up pyramid is far better than an inverted one. Think about those "Bigfoot" deck foundation forms. They are bigger at the bottom than at the top. The weight of the ground is on top of them holding them down. Also think about a traffic cone buried. Which way is harder to pull out? Point up or point down?

 

[GnG8d]

A right side up pyramid is far better than an inverted one. Think about those "Bigfoot" deck foundation forms. They are bigger at the bottom than at the top. The weight of the ground is on top of them holding them down. Also think about a traffic cone buried. Which way is harder to pull out? Point up or point down?

I know what you're saying about a pyramid having to pull more dirt up, but an inverse pyramid would exert force lateral to downward. The question would be the strength of the concrete with lesser volume. Reinforcing is a must.

 

[Lil'Yeshua]

2 1/2 cubic yards is WAAAY overkill for a guyed tower. Half that is a bit of an overkill.

Actually,mine is free standing. It only took me 2 1/2 hours to dig the hole. It's all big grain sand but compacted enough that the hole's Wall's are straight down. I used the flat shovel to hoist myself out by putting it crossways in one of the corners. The only steel reinforcement I used is three three foot long,one inch diameter galvanized threaded rods. I have big washers at the bottom end secured by galvanized nuts. The tower base section is adjustable for tilt correction.

 

[Captain Kilowatt]

I know what you're saying about a pyramid having to pull more dirt up, but an inverse pyramid would exert force lateral to downward. The question would be the strength of the concrete with lesser volume. Reinforcing is a must.

I see what you are saying but a simple straight base would do the same. It would resist sideways movement that would be exerted as it tried to rotate. With the regular pyramid shape the weight of the ground bearing down prevents one side of the base from rotating by having weight above from the ground as well as the opposite side of the base bearing downward into the soil with it's much larger footprint.

 

[Captain Kilowatt]

Actually,mine is free standing. It only took me 2 1/2 hours to dig the hole. It's all big grain sand but compacted enough that the hole's Wall's are straight down. I used the flat shovel to hoist myself out by putting it crossways in one of the corners. The only steel reinforcement I used is three three foot long,one inch diameter galvanized threaded rods. I have big washers at the bottom end secured by galvanized nuts. The tower base section is adjustable for tilt correction.

OK I thought you had a guyed tower or it was bracketed to the house or something like that. must have confused you with someone else. I just went back and saw you have a 31 ft. tower with a 7 ft. mast. What kind of tower is it? Not many freestanding towers have the ability to add height unless it is a heavy duty version and you can get smaller top sections.

Wait a minute................................I just thought................did you make your own tower or was that someone else? 2 1/2 cu.yards is ok for something like you have as it is not that tall but I would not want to add another 20 feet to it and stand downwind during a storm.

 

[GnG8d]

I see what you are saying but a simple straight base would do the same. It would resist sideways movement that would be exerted as it tried to rotate. With the regular pyramid shape the weight of the ground bearing down prevents one side of the base from rotating by having weight above from the ground as well as the opposite side of the base bearing downward into the soil with it's much larger footprint.

I get it, I think I've even had this debate before ..... maybe with you. When I sit and try to visualize it the inverse pyramid has certain qualities, especially if done in a cone with no flat sides. The tower tries to rotate the base up and out from the surface side with no force.

After doing the "block" method I'll do the "pier" method next time for sure just to save weight. Of course next time I might be in a position the get a concrete truck in too

But like I said in post #2, do what the manufacturer says unless you want to do some bench top engineering.

 

[Lil'Yeshua]

OK I thought you had a guyed tower or it was bracketed to the house or something like that. must have confused you with someone else. I just went back and saw you have a 31 ft. tower with a 7 ft. mast. What kind of tower is it? Not many freestanding towers have the ability to add height unless it is a heavy duty version and you can get smaller top sections.

Wait a minute................................I just thought................did you make your own tower or was that someone else? 2 1/2 cu.yards is ok for something like you have as it is not that tall but I would not want to add another 20 feet to it and stand downwind during a storm.

Ok,20 more feet is a tad bit stretching things. I used a jig and wire welded 3/4&1/2" rigid electrical galvanized conduit into three ten foot tower sections with angle iron end caps and a one foot base section. All section are joined together with 9 galvanized bolts at each junction. The base and first section are joined with a homebrew hinge and final securing with 9 more bolts. A 13' gin pole attaches to a steel pipe sunk down into the footing next to the tower.

 

[Lil'Yeshua]

I did research and made rough calculations of what type of footing I needed and how much concrete I would need before I even dug the hole.

 

[Captain Kilowatt]

I get it, I think I've even had this debate before ..... maybe with you. When I sit and try to visualize it the inverse pyramid has certain qualities, especially if done in a cone with no flat sides. The tower tries to rotate the base up and out from the surface side with no force.

After doing the "block" method I'll do the "pier" method next time for sure just to save weight. Of course next time I might be in a position the get a concrete truck in too

But like I said in post #2, do what the manufacturer says unless you want to do some bench top engineering.

Nothing wrong with a round pier type base either. In fact we installed a 220 foot guyed AM broadcast tower on a round pier about three feet in diameter and about 6 or 7 feet into the ground. It extended about another 4 feet above ground where the HEAVY 24 inch faced steel tower sat on a pin atop a huge ceramic base insulator. There's the difference in a guyed tower and a free standing tower. The 220 footer had a smaller below grade foundation than my 64 foot free standing tower. All it has to due is support the weight bearing straight down.

 

[GnG8d]

I understand that part, lol.