Try Metal Supermarkets. Hopefully you have one in your area. They will sell
you anything in any length. Even cut it for you.
http://www.metalsupermarkets.com/
I buy all my amplifier building stock cut to size from them. Good folks.
73
Jim W7RY
--------------------------------------------------
From: "Dave Hachadorian" <k6ll@arrl.net>
Sent: Wednesday, March 09, 2011 11:31 AM
To: "Rick Scott" <w7psk@yahoo.com>; "Towertalk reflector"
<towertalk@contesting.com>
Subject: Re: [TowerTalk] Sorry to bring up an oldie - Mast Material
> Here is a neat mast calculator:
> http://www.math.niu.edu/KARC/mast/
>
> Plugging in some numbers for 1.5" schedule 20 water pipe:
> Safety factor f 2
> Wind loading factor k .004 lb/ft2/mph2
> Maximum stress S 30,000 psi
> Outside diameter D 1.9 in
> Inside diameter d 1.61 in
> Total length of mast 8 ft
> Height above support h 4 ft
> Antenna 1 height h1 4 ft area a1 6.1 ft2
> Antenna 2 height h2 ft area a2 ft2
> Antenna 3 height h3 ft area a1 ft2
>
> Survival velocity: 63.0 mph
> Failure velocity: 89.1 mph
> Weight of mast: 21.79 lbs
> ---------------------------------------
> As indicated above, I wouldn't be confident in using Sch 20 water
> pipe. That 30,000 psi yield strength for water pipe is hard to
> prove, because water pipe is not specified for structural
> purposes. Also, the last time I priced water pipe, I was amazed
> to see how expensive it had become.
>
> You are much better off using structural tubing, which has a
> specified yield strength. If you go to a metal supplier and ask
> for structural tubing, he should be able to quote you some prices
> on various strength material. You will probably have to buy a
> 20-footer though. Another thing you can do is to order some
> galvanized steel mast from Texas Towers. They will sell you a 10'
> piece for $139, and cut off a foot, which makes it UPS-shippable
> (at least the last time I did it, in 1978). Their material is
> 87,000 psi. Plugging that into the calculator:
> ---------------------------------------
>
> Safety factor f 2
> Wind loading factor k .004 lb/ft2/mph2
> Maximum stress S 87,000 psi
> Outside diameter D 2 in
> Inside diameter d 1.75 in
> Total length of mast 8 ft
> Height above support h 4 ft
> Antenna 1 height h1 4 ft area a1 6.1 ft2
>
> Survival velocity: 107.0 mph
> Failure velocity: 151.3 mph
> Weight of mast: 20.07 lbs
>
> That will definitely work.
>
>
>
> Dave Hachadorian, K6LL
> Yuma, AZ
>
>
>
>
>
>
> -----Original Message-----
> From: Rick Scott
> Sent: Wednesday, March 09, 2011 10:51 AM
> To: towertalk@contesting.com
> Subject: [TowerTalk] Sorry to bring up an oldie - Mast Material
>
> Im really confused. Id like to buy Local, because the mail order
> houses have
> Really high prices and high shipping
> plus they only do 5 or 10ft intervals.
>
> Ive seen all manor material from them from chrome molly to
> Aluminum and AES even
> has Fiberglass.
>
> I have a Glen Martin 9ft roof mount tower. Its just shy of 4ft
> from the rotor
> to the top of the tower. Right now I have
> a 2 1/2" Fence Post mast (really heavy wall) that I hold an A4S
> up with.
>
> A4 is going bad so I decided to get my dream antenna the standard
> SteppIR 3
> element beam and nothing else will go on the mast. I would
> like to get 8ft as that will give me 4ft above the tower, I can
> put the antenna
> at 2 - 3 feet and be ok.
>
>
>
> So I need 2" mast material,
>
> I would dearly like to buy local and we have a few metal shops
> but I need to
> know exactly what I have.
>
> I searched the forum and man there is a lot of material. K7XLC
> used to sell
> mast but his site doesnt.
>
> I posted on the local Snohmish County hams and I got a gazzilion
> answers.
>
> One guy swears by Home Depot stuff
> One says only buy Sched 40pipe nothing else needed
> Another says this and that.
> Another says 6061-T6 Extruded Tubing
>
>
> So not really wanting to open a can of worms, whats the best
> material to hold
> what I plan to put up
> for the best cost.
>
>
> Scotty W7PSK
>
>
>
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