[TowerTalk] 10 inch tube 100ft wind load? NN7J

[Robert Chudek - KØRC]

Digging around in the archives I learned it was Telrex that manufactured the "Big Bertha" system in the 1950's ~ 70's. Rich, KE3Q, had a good write-up about this company and their product line. This link should take you there: http://lists.contesting.com/_towertalk/2005-03/msg00067.html

73 de Bob - K0RC in MN

  ----- Original Message ----- 
  From: Robert Chudek - KØRC 
  To: towertalk at contesting.com 
  Sent: Thursday, August 31, 2006 12:29 PM
  Subject: [TowerTalk] 10 inch tube 100ft wind load? NN7J


  Dan,

  You can put your numbers through the WD9P mast calculator and see what you get, Here's the URL:  http://www.math.niu.edu/KARC/mast/

  I put your numbers into the calculator, just out of my own curiosity...

  SF = 2
  WL = 0.004
  MS = 60,000
  OD = 10
  ID = 9.732
  TL = 100
  HAS = 100
  Ant1 = 1 + Area = 1
  Ant2 = 0 + Area = 0
  Ant3 = 0 + Area = 0

  It told me this:

  Survival velocity = 38.9 mph
  Failure velocity = 55.1 mph
  Mast Weight = 1,415.29 lbs

  But if you used 1/2 inch wall, 10 inch diameter steel,

  Survival velocity = 71.2 mph
  Failure velocity = 100.6 mph
  Mast Weight = 5,085.03 lbs

  And if you used 1 inch wall, 10 inch diameter steel,

  Survival velocity = 93.2 mph
  Failure velocity = 131.9 mph
  Mast Weight = 9,634.80 lbs


  Of course if you are serious about installing something like this, a qualified design engineer should be your first step. The calculator can give you an idea of what kind of forces you are dealing with but as it warns, it is for instructional use only.

  Note, these figures were with a 1 sq ft two-meter vertical at the top, not even a small yagi! You can plug in 8 to 20 sq feet of area for Antenna 1 and see what happens. The results surprised me (assuming the calculator is working correctly).

  Free standing rotating tower systems like this have been engineered by HyGain (I think) and were called "Big Berthas". I knew of 3 installations in Minnesota, but nothing more. I'm sure other TT members can jump in with facts, figures, and stories about these types of installations.

  73 de Bob - K0RC in MN


  Message: 7
  Date: Thu, 31 Aug 2006 06:34:26 -0700 (PDT)
  From: Dan D <yaesu4u at yahoo.com>
  Subject: [TowerTalk] 10 inch tube 100ft  wind load?  NN7J
  To: towertalk at contesting.com
  Message-ID: <20060831133426.27075.qmail at web58303.mail.re3.yahoo.com>
  Content-Type: text/plain; charset=iso-8859-1

  How do you calculate how much load  a steel tube 10 inch with .134 wall can handle with no guys 100 ft tall.
     
    Dan NN7J.