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[TowerTalk] Mast Collars

To: <>
Subject: [TowerTalk] Mast Collars
From: (Bob Gates)
Date: Tue Aug 5 18:32:12 2003
You make a very good point, and I also forgot the most important element, the
weight of the mast itself.  Duh!!!  It will weigh more than the antennas
combined!  Thanks again.
Bob  KG7KW
  ----- Original Message ----- 
  To: Bob Gates ; Tower Talk
  Sent: Tuesday, August 05, 2003 5:18 PM
  Subject: Re: [TowerTalk] Mast Collars


       The URL that Larry K1UO sent the list leads to a tech spec page  .  You can see that these collars have a
  specification for axial loading.  I suspect that most ham installations do
  not exceed these figures, especially since the collars will be one of two or
  three devices on a mast that actually support the vertical load (dead
  weight) of the antennas and mast.

       However, the muffler clamps I used actually bite into the mast a bit.
  (I bought 1-7/8 inch clamps for my 2 inch diameter mast.)  Besides, their
  cost (< $3 each, even here in DC) is considerably less than that of the
  collars.  I believe they provide sufficient support for my purposes -
  supporting the antenna and mast loads.  (I don't plan on climbing the mast
  any time soon.)

       I believe the most important spec you have to analyze to determine a
  tower's ability to support the mast and antenna loads is the rating of the
  bearing and rotator plates.  My Trylon's three plates are rated at 300
  pounds each.  With my smallish HF antennas (about 90 pounds total) and the
  mast weight (120 pounds), I have plenty of margin using only two supports
  (the rotator shelf and the top bearing shelf - 600 pounds.)  I have one
  muffler clamp set right on top of the bearing collar.

       To your question:  Will muffler clamps support the 160 pounds of my
  antennas?  How much does your mast weigh?  Add that to the mix, then ask the
  question again.  The muffler clamps ought to work IF you're using a rotator
  and plate as the bottommost support.  Install the mast onto the rotator
  clamps, then install a muffler clamp assembly to sit on the top bearing
  collar.  Then install your HF antennas.  That will distribute your dead
  weight loads between the two plates.

  BOTTOM LINE:  Yes, the muffler clamps will work if you have a rotator and
  shelf supporting the bottom, and you distribute the weight between/among the
  plates.  (I'm assuming you aren't just supporting the antennas and mast in
  the muffler clamps on the tower.)

  73 de
  Gene Smar  AD3F
  P.S.  Don't rely on the bearing's setscrews to provide vertical support.
  They could slip!

  ----- Original Message ----- 
  From: "Bob Gates" <>
  To: "Tower Talk" <>
  Sent: Tuesday, August 05, 2003 2:07 PM
  Subject: Re: [TowerTalk] Mast Collars

  > I somehow missed the first posts on this subject.  But I am curious if any
  > the suggestions take into consideration the weight of the antennas.  I am
  > looking to install two yagis with a combined weight of about 160#.  The
  > clamps would not appear to be strong enough, but I wonder about the "split
  > collar" and the "scaffolding collar".  Your thoughts would be most
  > Regards,
  > Bob  KG7KW
  > _______________________________________________
  > See:  for "Self Supporting Towers", "Wireless
  Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
  questions and ask for Sherman, W2FLA.
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