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[TowerTalk] M2 2800 rotator mast clamps

To: <>, <>
Subject: [TowerTalk] M2 2800 rotator mast clamps
From: "Al Williams" <>
Date: Fri, 28 Apr 2006 09:08:00 -0700
List-post: <>
----- Original Message ----- 
From: <>
Sent: Friday, April 28, 2006 7:37 AM

> It's becoming clear that  while there are sometimes problems with the 
> rotator (M2 2800)
> itself, the emerging  reliability culprit is the mast clamp. The Orion one
> has so little actual  clamp-to-mast surface area that it is unable to hold 
> any
> large sized array. The  mast clamp on the BigBoys seem to have their 
> limits as
> well.
>        BTW I'm having some more  suitable clamps for the Orion fabricated
> and they'll be available for sale in  the near future. If you're going to 
> have
> an Orion/MonstIR installation, you'll  need one of these.
The problem with the mast clamps furnished by M2 for the 2800 rotator has 
been discussed on Towertalk before, however not fully enough to provide 
solutions or explanation of the problem.

The M2 literature includes "Ductile iron, massive, toothed mast clamps".  As 
Steve mentions the 'toothed" clamp has little area in actual contact with 
the mast.  Further, the massiveness may actually be detrimental because the 
"ductile" iron cannot conform much to the mast?  Mechanical 
engineers--comment please.

The M2 specification claims "Wind Area Capacity.......35 sq. ft.".  Sounds 
great but no wind speed is included so that the specification is useless?

The M2 specification claims "Braking Torque.......17000 in. lbs.".  That is 
about 5 times the starting and rotating torque specification which would 
also seem great.  But how does one determine the torque that is being 
applied to the rotator from the wind and/or the moving antenna load?  I can 
see quite a bit of movement at the tips of the MonstIR in light winds 
indicating some play in the gearing which can allow a "shock" load to the 
clamp.  Again, Mechanical engineers--comment please.

The M2 literature includes " DO NOT "PIN" THE MAST TO THEIR POSITIONER. 
PINNING THE MAST WILL VOID THE OR-2800 WARRANTY.".  The literature also 
discusses that slip may even be desirable.  What happens to the warranty if 
a stronger mast clamp (not of M2 design) is used?

The M2 literature also includes the proper bolt tightening sequence.  How 
important is this and could improper sequence be the cause that some our 
mast/clamps have slipped?  However, the literature does not include the 
proper bolt torque to apply for tightening.

I have two M2 2800 rotators so would like to get answers and solution to 
this problem. I hope M2 will contribute.



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