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Author Topic: Mast material advice for mini beam?  (Read 883 times)
VA2FSQ
Member

Posts: 511




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« on: March 06, 2013, 04:47:54 PM »

Hi,
I'm relatively new to the beam scene but I'm about to take the plunge.  I plan on installing a mini beam like a TGM MQ36-SR, Cushcraft MA-5B or Mosley Mini-33A.  All of these have a wind loading of around 3.5 sf.  The mast will be installed in the top of a tower with a thrust bearing and a rotor.
The thrust bearing will be basically about a foot above the house and I would like the mast to extend 6 feet or more over the roof.
I am able to get any of the metal tubes for cheap (maybe free) through a friend.

Aluminum 6061T6 Schedule 40 pipe, 1.9" OD with a thickness of 0.145" (2" nominal pipe size)
Aluminum 6061T6 Schedule 80 pipe, 1.9" OD with a thickness of 0.2 " (2" nominal pipe size)

Aluminum 6061T6511 Holobar extruded aluminum tube 2" OD thickness 0.125, 0.25, or 0.375" thick (it's a friend, I can't overextend!!)

Which would be adequate?  And what if I want it 8 feet above the bearing.  We have winds that can reach 70mph here at times (rare) and there is a fair bit of icing possible.


Also, was thinking about a yaesu 1800sa rotor.
Thanks for advice...there's no one else I can ask!
Tom
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VA2FSQ
VA2FSQ
Member

Posts: 511




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« Reply #1 on: March 06, 2013, 06:52:36 PM »

Can also get DOM but ungalvanized
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VA2FSQ
WB6BYU
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Posts: 13341




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« Reply #2 on: March 07, 2013, 09:03:03 AM »

Pipe is designed for the flow of fluids.

Tubing is designed for other mechanical stresses where strength is important.

While there may be some specifications on the strength of pipe, it isn't typically
rated that way.

Unless I had specific information about the pipe, I'd go with the
tubing because it is designed for that application.
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AA4PB
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Posts: 12899




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« Reply #3 on: March 07, 2013, 10:10:21 AM »

I'd go with the 0.375" wall extruded aluminum. It probably comes in a 10-foot length. You'll probably need about 2-feet inside the tower leaving 8-feet above the tower. That should support your antenna at 8-feet above the tower with no problem.

Usually there is no difference is strength between tubing and pipe, given the same actual measured dimensions. The big difference is that pipe is defined by its inside dia. and tubing is defined outside dia.
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