Need some "guy"dance on a freestanding steel mast for wire antenna support

[VE7 Kilohertz]

Hi Gang,

I am getting ready to re-erect my 80M Double Ex. Zepp and want to put up a steel mast on one end. I have a concrete block, 24"x24" at the base, 18"x18" at the top, 3'6" deep with a 5" hole down the center. It is made for railway signal masts and guessing it weighs about 1500lbs, the way it handles in the bucket of my Bobcat. I have a collection of steel pipe, all sch. 40, starting at 5" and have various 15-25' lengths all the way down to 2".  I would like to make this about 60-65' tall, and freestanding. I was planning on 1 section of 25' 5" start, then another 15' section of 4", then bushing it down to 3.5", then finally top it with 3" for a total length/height of 65', with 5' in the ground inside the concrete block.  I'm planning to weld up the complete mast in front of the shop, then drag it to the hole with the Bobcat, get it into the concrete block, then slide/lift the whole works into the hole until it goes upright, then fill and tamp around the base, hopefully while not getting clobbered by the mast if it's at all unstable. 

My question is, once buried in the ground, and tamped, will this be stable? Should I start with just a short length of the 5" then step right down to smaller dia. pipe to keep weight down? I don't want guy wires if possible, as I would only be able to get 3 in the ground, as it is close to my fence line. I'm out in the country with no buildings or neighbors close by.

Your thoughts? Anyone with first hand experience with something similar?

Thanks in advance.

Looking forward to getting back on the air.

Paul
VE7KHz

[Bill, KD0HG]

How windy does it get in your area?

I would seriously consider three steel guys perhaps at the 40 foot level. At least one "counter guy" opposite the side of the wire antenna. And install a pulley! Even one on two sides.

You are going to have your hands full raising that thing as you describe. I would strongly suggest a brace or gin pole to help support it as it is raised. Even that 5" Sked 40 can buckle. Maybe use 20 feet of that big pipe to support it as it is raised.. If you have access to a tall loader, that would help.

Another idea might be to weld up an "A" frame with two smaller pipe masts. 3" pipe all the way. Might be lighter and easier to manage. Weld a cross brace or two in the middle and across the bottom.

Just some ideas.

Be careful.

Bill

[Ed/KB1HYS]

It should work, take your time, make quality joints and fittings, and be careful!  That mast will be heavy.

Go with Bill's advice above, check the wind loading for your area. You could be ok for a wire antenna, but a backside guide wire may be a good idea in any case to counter act the tension from the ant, especially the ant with an ice and wind load, always think worst case.  Packing the base in some 1" crushed stone would not be a bad idea.

The schedule 40 is strong, but butt welding two ends could seriously weaken the structure.  

You will need to make inserts to reinforce the butt joints, or make the whole mast of telescoping sizes.
If the pipes aren't a reasonably good fit (or to make inserts), weld beads around the smaller pipe, grind to a good slip fit inside the larger. Then either rosette weld or use through bolts & weld the seam.  As a rule of thumb the overlap should be at least 2x the circumference of the larger pipe (for a 5 inch diameter pipe, this means about 30 inches of overlap). This will spread the joint stress over a reasonably large area.

Make sure the welded joints were done well. Probably not something for a 'hobby' welder. No offense meant to your skills there, just be safe.
 
The length of mast is going to be heavy.  When you lift it you could be putting a LOT of bending stress on the pipe. Like Bill says, you are going to need to use an A-frame or gin pole with multiple lifting lines (top, 3/4, and 1/2 way up) and a few extra hands to keep the whole thing fairly straight.   Although if you have equipment (you mentioned a Bobcat) you could secure multiple lines and come-a-longs to keep pulling even along it's length. Don't forget something on the back side to keep it from going over once its up.  Ask me how I know this...  

A challenging project, but no reason it won't work.   Just be safe and over engineer it a bit, and after you're gone, someone will have a Heck of a Flag pole!

[K5UJ]

You say you are out in the sticks i.e. no one nearby.  That's good.  So, if anything keels over you don't have to worry about damaging anything right?  Other than the mast of course, and getting it off someone else's property if it is near a line like you said.

I wouldn't do any of this.  First of all, if it is free standing and holding one end of a long span like I think you are going to use it for, and it is unguyed, the top will have a lot of tension pull on it.  I know it is steel and pretty wide at the top but you have to think about the tension plus wind whip and ice load.  Take a look at structures holding power lines and how they are done even though they are much heavier gauge.   A long span of even no. 10 wire if it hasn't much sag has a lot of pounds of pull on it.

If you want to assemble it on the ground, I'd seriously look into treating it like a tall length of R25 tower and get a small crane with a multi-point sling to pick it up and erect it.  But, for the end of the wire antenna, I'd go with a solid wood telephone pole--that won't pull any, but even then you'll need to guy it 180 degrees opposite the wire antenna direction about half way up the pole.  use marine pulleys and counter weights so you can raise and lower the wire.
out where you are, it should not be hard to get a phone pole brought in--get a 75 footer; an auger will dig a 10 foot hole and it just plunks into the hole with the hydraulic lifters used by power companies.

For your nice 65 foot steel mast, I'd start looking for a big ceramic base insulator and use it in the future for a quarter wave 80 meter vertical.  You'll have to guy it but you'll have a nice signal at night from VE7 with 60 or more radials on the ground  

If you still want to go with the mast as is, keep in mind that if the wire antenna is intended to be balanced and fed with balanced line, the steel mast will unbalance it somewhat, if the other supports are insulators like trees.

One last suggestion--clamp a couple of arms sticking out 2 or 3 feet at the top 180 degrees opposite each other; use one to hold a drop wire that you can feed at the base for 80 meters (if you don't want to insulate the mast) and use the other to hold a drop wire that's bonded to the mast to make a 160 m. shunt fed vertical.  Put down a nice big ground system, the aforementioned 60 + radials quarter wave on 160.  You'll have to mess around getting a match to your feedline but it shouldn't be too hard to do and like I said, they'll be great at night.

Rob

[KB2WIG]

R,

I've toyed with this idea for a while. You may want to think about this method ,

http://wiki.radioreference.com/index.php/Tilt-Over_Mast

 for some design ideas.  I like the 'pivot' point.  I've seen the base idea in several flag pole designs.


klc

[VE7 Kilohertz]

Hi guys,

Just got back inside from a wet dreary day of outside work. Mostly digging my tr-ibanders out of the grass and getting my tower sections ready to raise. It's best to wait until winter to do antenna work, right? 

Well, thank you for the very thoughtful replies. I knew this group would have some excellent ideas. Yes, I am planning to telescope the sections with about 1.5' overlap and weld each joint, starting at 5" at the base and ending up at 3" at the top. I may back down on the length, maybe 50'? The location is kind of hard to get to for a crane or boom truck. I would like this to be something I can raise myself and know it will support one end of an 80M EX. Double Zepp, which is almost 300' of #12 wire in my case, with a new piece of ladder line to still be made. I used to keep it up with a 12V car battery counterweight and a pulley up in a tree. I would imagine the lateral pull to be equal to the weight of the battery. We don't get icing here and the pole will be well protected from the wind by the neighbors trees. (Don't ask why I just can't use the trees  )

I will consider the guys, at least up and down the hill which is 90 deg to the wire, as I can't guy onto the neighbors property.

What sort of unbalance will the steel pipe create? Would I need to shorten the wire on that side? I use a homebrew balanced tuner, 2 roller inductors, one vacuum variable and one broadcast cap on the choke input side. I think it's one that was discussed here a number of years ago.

Anyway, appreciate your help.

73
Paul
Kilohertz

[KA2DZT]

60ft of heavy steel pipe, you'll need a crane to stand it up.  That base you pictured is unlikely to hold it up.  You'll need some guying.  I've made a number of pipe poles and it's very difficult to get up 45ft of pipe with smaller and much lighter diameters.

What happens when the rope or cable holding up the antenna breaks and you then need to lower the pipe to replace it, or the pulley fails.  These things do happen, so you need a system that allows you to lower the pipe to fix things.

Fred

[K5UJ]

What sort of unbalance will the steel pipe create? Would I need to shorten the wire on that side?

Hard to say but I wouldn't fool around with changing the length of one side of the CF Zepp (why don't you just put up a regular 1/2 wave dipole?) because that would guarantee you have a balance problem and probably not fix anything.

I don't have the ability to do any modeling but in your case the balance problem might not be that much.  It depends on proximity I think.  In my case, I have one end of my 80 m. dipole being held up by an aluminum mast that's 50 feet high (BTW it tilts over with a wench and nylon strap) and when the mast is grounded as yours will be, there is a difference in currents of about 30% between one side and the other of the feedline, i.e. the side going to the mast will have 100 ma; the side held up by a tree, 70 ma.  If I float the mast so it is insulated from ground, the difference between the sides drops to 10% or less. 

BUT a few key things:  My dipole is too big for my property so 20 feet on each end has to hang down.  That probably means there is more than normal coupling to the mast on that end, because of that 20 feet there hanging down, even though I angle it out away from the mast.  If your Zepp, ends at the mast and doesn't hang down, there may be much less coupling.  Further, if you put up a regular dipole 1/2 wave (I don't know what the hell a "Zepp" is off hand, in terms of wave length, can't remember) so you have say 60 feet of rope between its end and the mast, there may be no unbalance at all.

Do you plan to support the feedpoint?  If you don't, the sag will be enough to put the feedpoint at only around 40 feet off the ground unless you have a hell of a lot of tension on the antenna.  I'd avoid regular copper house wire in that case and go with some kind of hard drawn or copper weld wire.  I'd also scratch the idea of a horizontal wire antenna on 160 except for receiving--it will be so low in wavelength that you won't get out well.  Go with an inverted L and 60 or more radials.  There are a lot of piss weak stations on 160 with low wire antennas and ops who can't deal with the cost and/or work of a ground system.

[Steve - K4HX]

Some ideas on a mast with guys at the link. I wasn't designed to hold up a wire but looks substantial.


http://www.bctonline.com/~skelly/4square/4square.html

[WBear2GCR]

I'm thinking that *if* the pipe mast will not bend and kink when horizontal and held at a point about 15ft - 20ft or so  up from the bottom section then I'd consider using the flagpole idea, where there is a vertical support/tilt point  and the mast has a counterweight at the base so that very little force can be used to pull it vertical... you'd need guys at least at the halfway point to keep it safe... the bottom can be clamped or pinned to the vertical supports... they may need short guys to keep them stable as well... that's how I would try to do it... plus you get the benefit of a mast that will flip down in a controlled way...

              _-_-bear

PS. the homebrew/DIY wind generator folks have been doing steel pole masts, and there are likely a lot of good pages on this...

[KL7OF]

"Marks standard handbook for mechanical engineers"  Its all in there...I don't see why you can't do somerthing good with the material that you have.....Good luck Paul...

[VE7 Kilohertz]

Well, she's all welded up and ready to raise. I played it safe and only went 50', 4" telescoping down to 2.5", lots of overlap at the joints. I picked it up at various points and she stayed really straight. I will add a bracket for a pulley at the top, and rings for 2 guys at about 40'. Should be able to get it raised tomorrow, if it's not pouring rain. It's been drizzly for about 3 weeks now. Forgot what the sun looks like. I want to borrow my neighbors excavator again, to make the hole a little deeper in the middle, so the pipe drops into it: I'm almost down to bedrock now.

As it was getting dark tonight, for grins, I stuck up a 21' 2" pipe strapped to my fence post, with a lean away from the antenna. Pulled up my Zepp and listened into our local AMers on 3885. It's only 20' off the ground but was good to hear the gang again, after 6 months of no radio.

Wish I had that Mark's book. Sounds like it would have all my answers. I'll start keeping my eyes open at the used stores.  Thanks Steve, and thanks to everyone for your help and ideas.

Here are a few pics of the finished product. I included one of my welds, for those who may be concerned.    I used 7014 at about 170A. Seemed to have good penetration.

Updates as I progress...hopefully tomorrow.

73
Paul
Kilohertz

[Ed/KB1HYS]

Looks like some good work.  Encouraging that it doesn't bend much when supported at one end.

[K5UJ]

I understand why you are in a rush to get back on the air but my experience with antennas is that if you take a breather you'll be glad in the long run.  the reason is you'll think of things to do that are a lot easier to do before the structure is up and in place.  Example:  Have you considered painting that thing?  Maybe you don't care if it rusts but a coat of primer and flat sky blue rust o leum or cold galvanizing paint won't hurt.  I've just learned that if I let a job sit on the back burner for a day or two I think of stuff that I would have missed in the mad dash to get the job done.

[VE7 Kilohertz]

Thanks for the compliments Ed. It took a few hours to get it all together, squared and aligned but it was worth it.

Well, I have been planning this for a couple of months now so it's not really a rush job, you are just seeing the end of the planning process and I needed some help with the forces at work here. I like the rusty colour as it blends into the background of the mountains and trees.

So, the sun is just coming up, it's going to be a nice sunny day here and I am heading out in a hour or so to mount the pulley support, guy rings and haul it into position. Decided to use the JD350 dozer to raise it...just has a little more mass and protection. 

Cheers

Paul

[VE7 Kilohertz]

Well, SHXT,

I finally got back to the project today and hauled everything up the hill to the hole. I spent 2 hours trying to get the bloody pipe into the base, but wouldn't ya know it, after all this, and measuring at least 3 times  , the hole got smaller 3" down the concrete block. Well at least I got to use the bulldozer..I got the Bobcat stuck in the mud and had to abort that machine.

So, as of today, it's mast and concrete block 1, Paul 0. Buggar me.

Tomorrow I cut off the bottom 4' of 5 inch pipe and go with the 4" with some slop. Oh well. At least I proved that the whole works will go upright without breaking, I had it up to a 30 deg angle trying to wiggle that damn pipe in.

Cheers

Paul

[Steve - K4HX]

That aggravation will add 10 dB to your signal once you get the antenna up!

[Ed/KB1HYS]

Oh man, that must have been a very bad feeling seeing that just hang there.

Keep us posted.

[VE7 Kilohertz]

End of the second inning...mast and concrete 2, Paul 0......

Well, I did make some progress. Cut the 5" sleeve off the 4" pipe and welded on some rebar strips to fill up some space to make it almost 5.5"..dragged it back up the hill and had it inserted in the block within 10 minutes. I then started to raise the whole works and plopped it in the hole..slowly with the dozer, until the mast was at 45 deg..then the rope and pulley got all wrapped up around the top so I dropped it and refastened it more securely to keep it from swinging....then the hole filled up with crap that got pushed in by the block...so I pulled out the whole works and dug out the hole again...then tried it again and ran out of lift on the dozer blade so I couldn't get the the thing properly centered..and it looked to dangerous to continue, after all, I have a pretty good understanding of the forces involved here and I just plain chickened out. Dropped the works back to horizontal and went to work on my water well system for a while..then came back to the mast project and had another go at it...was thinking all along if I just a add a few beers to the situation it would all be done by now. Well, I got it back up to about 75 deg. this time, and realized it was just NOT going to stable once at 90 deg. so again dropped the whole works...THEN had a beer and decided I am going to dig the hole deeper tomorrow, probably 6-8' if the backhoe can do it. I will be more comfortable if the concrete block is deeper in the earth.

I video taped the whole day in time lapse mode, and will post the erection once it's all up. Should be pretty funny.

Cheers....and on to inning 3 tomorrow.

Paul

[VE7 Kilohertz]

Grrrrrr! now it's snowing and blowing 30kph.......on to other projects for today...assembling a tribander to put up before winter really gets here and split some more firewood.

I'll keep you posted on the mast if the wind dies down later today...and I get the hole deeper.

Paul

[VE7 Kilohertz]

Hi guys,

Well today was a great day...-3C ground was solid, no mud...my son was with me and we got the mast erect!! I borrowed the excavator again and dug down a little more but just hit bedrock. So it's 4' deep and still strapped to the dozer blade for safety, until I get some big ragged rocks to dump in the hole to fill the space and get the guys secured. I have them tied to the big trees on my neighbours property for now, until I get the anchors in place. It sure looks good up there at 58'!! It's better than the trees I had the antenna in earlier this year. It was a bit nerve racking getting the thing straight up...as the brake doesn't hold on the dozer so everytime I had to jump off the dozer to re-rig the chains, my son threw a wood block under the tracks, then ran away.    That's one of the next projects..... fix the locking brake.

I'm also thinking of welding up a clamp on sort of tripod, to attach at 10-12' or so going down to some small concrete pads, just for a little extra support. Better safe.....

Relaxing now...making pizza and going for a hot tub later. So glad it's almost done. There should be much less horizontal tension on the tower once I change over my ladder line...see other post about open wire spreaders.  

Some pics of today's activities.

Cheers

Paul

[WQ9E]

Paul,

Congratulations!  I have been following your tale with interest.  In the old days this saga would have made a great QST article.  Now it wouldn't make QST unless you had an accident during installation requiring the local Emcomm types to grab their 2 meter rigs and rush to your rescue

Thanks for providing all of the photos.  It added a lot to your description.

[Ed/KB1HYS]

Great Job!  So the base is resting on solid rock?  I'd think that would be an ideal situation, you have a very large footer on that cement anchor!!

Here's hoping the work translates into a lot of dBs from your new antenna!

[VE7 Kilohertz]

Great Job!  So the base is resting on solid rock?  I'd think that would be an ideal situation, you have a very large footer on that cement anchor!!

Yes, solid big Axx rock. The bucket would only scratch it, I tried digging a couple of different places around that area and there is solid rock about 4-5' below the surface, which is also hard hard packed shale and almost cement like powder. Once I fill the empty spaces, it should be very solid. I'm also thinking of replacing the 5/16" rope I have for the pulley, with a small wire rope, maybe 1/8" or so. I would hate to have to drop this to change a broken support line.

Thanks all for your ideas and support.

73

Paul
VE7KHz

[K1JJ]

Good show, Paul.  Nothing like a strapping installation.

Yes, replace the rope with a flexible 3/16" wire stainless steel braided cable. Even galvanized is OK.  Hopefully the pulley is of high quality and designed to handle the wire cable, otherwise the cable could get caught in the pulley track.  

You could probably bring in a 60' bucket truck for future repairs or additions, but that would cost.

A lightweight boom hoisted to the top with pulleys on each end could even allow for a pair of phased driven inv V dipoles. Use the inv vees as guys.  Lots of options now.


Good luck with it. OM.

T