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Author Topic: mast comparisons  (Read 397 times)
N4UE
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Posts: 291




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« on: August 21, 2002, 04:18:11 PM »

I know this topic has probably been run into the ground, but I havn't seen any of it.

I have had some experiences with stacking large VHF antennas and would like your comments.
I tried Schedule 40 water pipe. In addition to being real heavy, it bent (45 degrees)(both towers). Now, I understand that it is not designed for side loading but we all know we are cheap.
I replaced said pipe with 6061-T6 aluminum. I have to say, that I was very skeptical!. Those beams swayed in the wind, but never, ever bent. I still have a 10' and 20' section (1 1/2" o/s, .250" wall).
I am going to erect an even bigger array at the new house and found a supplier of the al mast. Although it's $, I only want to do this once. A really (really) stout piece of 6061 (2" o/s, .375" wall, 24' lond) is $400 without shipping.......
I am not braging, but I'm an acomplished TIG welder with the necessary tools. I have built a lot of race car suspension parts with chrome moly but have never used it for masting. Anyone have any comments?
I guess I'm concerned about the mast weight/cost. I would have no problems splicing either, but would rather not!

thanks,

ron
N4UE
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WB2WIK
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Posts: 20547




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« Reply #1 on: August 22, 2002, 11:07:36 AM »

Chromolysteel alloy is extremely strong, as you know, but also heavy and expensive.  And, surprisingly, for an antenna mast application, it's only marginally better than high carbon steel, which costs less.

I've used 2.00" OD (1.50" I.D., .250" wall) 6061T6 alloy Aluminum "hollowbar" extruded tubing for many years with great success.  Never bent one, regardless of what was on it, and I've loaded them very heavily with stacked arrays, etc.  As you noted, the 6061T6 will bend and sway but not permanently -- it snaps back vertical again, amazingly enough.  And the only problem with it, as you also noted, is its cost!

I've heard stories of people finding strong stainless steel pipe at metal scrapyards and using it for antenna mast.  Sounds like a good idea, but I've never tried it, nor found it, myself.

WB2WIK/6
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N4UE
Member

Posts: 291




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« Reply #2 on: August 22, 2002, 03:38:20 PM »

Thanks Steve. I remember being at Dayton and 'running' into a fellow with a small display, selling al mast. I had just experienced the double failure at the old QTH.

Metal and Cable, Inc, Twinsburg Ohio. They have ads in QST.

I used a smaller size than I should have (1.5" od), but it worked great and has been on several towers. The only failure I experienced was my fault. I accidently dropped it from the 100' level, and true to my luck, instead of doing a javalin impression, it hit paralled to the 'er, rather uneven ground. Still have that piece, makes a cool template for big rocks.....

I remember the truck that delivered the two 24' masts. a 53' 18 wheeler. I lived in the boonies and boy, that trucker could cuss almost as good as I can......

tnx

ron
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