black iron pipe for a mast?

[ClemsonSCJ]

Alright so I've done a little asking around in the past but I'm ready to get my shack finished up to at least get one radio up and running. I was planning on doing a roof tripod with a fence top rail mast but would prefer not to mount anything to my roof. Obviously wanting to get the antenna as high as possible, I had asked about possibly linking 2 fence top rails and most everyone agreed that the material just wouldn't lend itself to being sturdy enough under high winds without guying which is something I'm trying to avoid as well. While high winds aren't too much of an issue where I'm at, I still didn't want to risk it.

So a second idea I've come up with is getting 3 seconds of black iron pipe and using couplers to join them. This material seems as though it would be plenty sturdy enough to handle any amount of winds we would get here and also it's only holding a Diamond X50 antenna, so nothing of any weight or wind resistance. The plan would be to mount the base of the black iron pipe mast to the ground and then use one of those antenna mast mounting brackets that clamps the pole to support it approximately 10 ft up. With the 2 mounting points being about 10ft apart from one another I would think that should suffice to handle any leverage the wind might put on the mast. Does this sound like a feasible idea or would there still be an issue with 20ft of unsupported mast regardless of the material strength?

 

[KA9MGC]

I haven't done the exact thing, but the usual rule of thumb is 10' for each guy level. Schedule 80 pipe is heavier wall, and perhaps it would be more resistant to bending, but it's a lot heavier in weight as well.
1" pipe, Schedule 40 which is the most common found in hardware stores, is 1.7# per foot, S80 would be over 2# per foot.

I have considered this in the past, but never acted on it.

 

[SteveSimpkin]

I did something similar about 10 years ago. I bought three sections of 1-3/8 in x 10 ft. 6 in. 17-Gauge Galvanized Top Rail from Home Depot. These are tapered at one end so they lock together. I wet the ground below the apex of the roof on our single story home. I then used a fence post hammer to drive it about 5 ft into the ground. I attached the next 10 ft section to it which brought to top just above the apex of the roof. I used a eave mount bracket to attach to pole to the roof apex. I then mounted a 2M/440 J-Pole antenna and coax to the top of the third section and slid it over the two stacked poles. This gave me a J-Pole antenna on top of a 25 ft mast with no guy wires. It has withstood many 60 MPH+ windstorms over the years and still works great.

 

[KA9MGC]

That sounds good. I've often thought about it, but never tried it.

 

[AK9R]

Schedule 80 pipe is heavier wall, and perhaps it would be more resistant to bending...

Ah, my favorite subject in college...strength of materials.

When cylindrical objects bend along the long axis, the material along the outside of the bend is stressed in tension and the material along the inside of the bend is stressed in compression. The material in the inner part of the object sees less and less stress as you progress inside the object. That's one of the reasons why structural tubing, think roll bar tubing on a race car, is hollow. A solid bar doesn't have that much more bending strength and it weighs a lot more than a hollow bar.

So, assuming that Sch 80 and Sch 40 are made from the same material and assuming that Sch 80 has a larger diameter than Sch 40, the Sch 80 pipe will be stronger in bending.

BTW, I generally prefer rigid electrical conduit for these sorts of masts. It's finished better than water pipe and is usually galvanized.

 

[KO4RJX]

I used 2 sections of 10 foot black iron pipe and a 5 foot section to build a mast at my last house, worked great and survived through two inland hurricanes and numerous thunderstorms. Had a Davis Weather Station, GP9 antenna, and ADS-B Antenna at the top.

 

[900mhz]

Ah, my favorite subject in college...strength of materials.

When cylindrical objects bend along the long axis, the material along the outside of the bend is stressed in tension and the material along the inside of the bend is stressed in compression. The material in the inner part of the object sees less and less stress as you progress inside the object. That's one of the reasons why structural tubing, think roll bar tubing on a race car, is hollow. A solid bar doesn't have that much more bending strength and it weighs a lot more than a hollow bar.

So, assuming that Sch 80 and Sch 40 are made from the same material and assuming that Sch 80 has a larger diameter than Sch 40, the Sch 80 pipe will be stronger in bending.

BTW, I generally prefer rigid electrical conduit for these sorts of masts. It's finished better than water pipe and is usually galvanized.

I use 2 inch rigid. Its galvanized. Black pipe, in time, will rust.

 

[mass-man]

the trick is the mounting to an eave...that gives it much needed support. That much pipe will have some sway, but hard to know how much. And don't fool yourself, the X50 has some wind load properties. I've got the very same problem, only with a metal roof I have no eave to attach to!

 

[Firekite]

This gave me a J-Pole antenna on top of a 25 ft mast with no guy wires.

the trick is the mounting to an eave...that gives it much needed support.

These are called bracketed installations vs guyed. For those who have it an option, it can be a good one, and they’re not mutually exclusive. You can use a bracketed installation up to a point, after which you add to it and guy it. Whether black iron pipe is necessarily a good choice or even the best choice, I’m not sure, but you can always try it and see. From an aesthetics standpoint I’d be concerned about rust forming after being out in the elements, but I’m sure it’d take many years in most environments for it to progress to the point where it’s structurally compromised.

 

[Duckford]

I run 1 inch schedule 40 black pipe, 10 foot long, and mounted on 3 foot tripods on the roof. supporting antennas like the big 2 meter G7 and Tramp 1498. Had some near record winds this last year and everything held up without a problem.

I'm thinking of ways to get my center fed dipoles up in the air, and not use my trees because I like my trees more than my radios. I think I'm just going to go with more schedule 40 pipe, galvenized, and think about what sizes to use for maximum strength. With some guying, I'm pretty certain they will take anything you throw at them (far better than cheaper chain link fence tops) up to the 30 feet I would like to go without a problem.

I'd say the bigger issue if you want to go higher is how you will get the heavy damned thing up and down when necessary.

 

[paulears]

Lots of folk here in the UK have access to our galvanised scaffolding tube, but it’s so heavy. Aluminium is far, far easier to mount. A ten foot length attached up on the air to a structure is an awful lot of weight to carry, even without wind load. However, you do what you have to do.

 

[iMONITOR]

I use 2 inch rigid. Its galvanized. Black pipe, in time, will rust.

Threaded black iron or galvanized pipe is not good to use. The threaded portion if very weak due to the threads cutting into almost half the thickness of the pipe. Thread cutting removes the galvanized plating at the joints where it's needed the most at the highest stress point.

 

[Firekite]

I'd say the bigger issue if you want to go higher is how you will get the heavy damned thing up and down when necessary.

I think that’s why telescoping push-up masts exist.

 

[Duckford]

I think that’s why telescoping push-up masts exist.

I can put up two 40 foot masts made out of 1 inch schedule 40 black iron pipe for the price of ONE telescoping mast to reach 44 feet. Not to mention that pipe can be cut up, welded, bolted, used for other purposes beyond just being a mast.

I've looked at that Rohn H50 several times. But there are advantages to simple pipe from the hardware store yet.

 

[clbsquared]

Black iron = rust. Unless you have it dipped in something or keep it clean and painted, its going to succumb to the elements in short order.

 

[iMONITOR]

Black iron = rust. Unless you have it dipped in something or keep it clean and painted, its going to succumb to the elements in short order.

Internally too!

 

[clbsquared]

Internally too!

Very true. Always seems to rust from the inside first. Condensation from Mother Nature on bare metal is never good.

 

[Firekite]

I've looked at that Rohn H50 several times. But there are advantages to simple pipe from the hardware store yet.

The only advantage I can think of is once you realize dealing with 40 feet of iron pipe is a painful and ineffective way to save a couple bucks over decades, then once you’ve replaced it with something more useful you can cut up the pitted and rusty pipe to make whimsical yard art to sell to folks who go for that kind of thing.

I can put up two 40 foot masts made out of 1 inch schedule 40 black iron pipe for the price of ONE telescoping mast to reach 44 feet.

how you will get the heavy damned thing up and down when necessary.

 

[iMONITOR]

Had anyone used schedule 80 PVC pipe as a mast and if so how does it rate and stand up to the elements?

 

[clbsquared]

Had anyone used schedule 80 PVC pipe as a mast and if so how does it rate and stand up to the elements?

Schedule 80 PVC, although twice the thickness of schedule 40, will initially be stronger. But again, unless it’s dipped or coated with something, the sunlight will degrade the oils in the plastic and cause it to become brittle over time. There’s a reason why it’s for direct burial only. I’ve even seen specialized plastic pipes that are rated for exterior applications above ground become weathered and brittle over time. Some people have luck with it and some don’t. YMMV.