During Hurricane Katrina we received winds up to 125 mph on the east
coast of Florida. A tree blew over onto my guy wires taking out my guyed
and bracketed 50 ft of Rohn 25G and destroying my KT34XA. The four foot
of Plumbing Schedule 40 pipe extended from the top of the tower was just
fine.
Bill Marx W2CQ
On 3/9/2011 3:09 PM, Rick Scott wrote:
> What would that look like for 6061-76 its yield is 40,000 I believe.
>
>
>
>
>
> ----- Original Message ----
>> From: Dave Hachadorian<k6ll@arrl.net>
>> To: Rick Scott<w7psk@yahoo.com>; Towertalk reflector
>> <towertalk@contesting.com>
>> Sent: Wed, March 9, 2011 11:31:40 AM
>> 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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