[TowerTalk] Aluminum mast

Bruce Ferratt uglyatc at msn.com
Wed Mar 15 15:47:09 EST 2006

My mast is 1 1/4" OD.   It is solid, round.  It states on the side ASTM 
6061-T6511.  It is 12ft long and will be mounted 4-5ft inside my Rohn 25g 
tower to the rotor plate with a thrust bearing at the top open section 
(Thrust bearing is the TB3).  I am looking to mount a Mosely TM-33A 
Tribander and stack a Diamond 2m/440 vertical. The aluminum mast weighs less 
than the old 6' steel mast that came with the tower!
I purchased this mast because there is a bushing inside the top of the 25g 
top section that limits me to 1 1/4" OD.  I welded a sleeve on the bottom of 
the mast so that my HD-73 rotor will clamp down on the mast.  Alliance 
HD-73's will tighten only down to 1 3/8" OD so the mast was too small.  I 
like the bushing in the top section to stay there as it will keep everything 
nice and snug but will be free enough to rotate the beam with some grease 
applied to it.  I think the bushing is plastic but there was some rust 
around the old 6 ft steel pipe/mast that I am replacing.  I can't believe 
that Rohn designed this tower to have a rotor mounted just below the top 
section!  It makes multiple accessory shelves worthless unless you don't use 
a thrust bearing!
Thanks for your email.

>From: "Bob Good" <k4bg at planters.net>
>To: "Bruce Ferratt" <uglyatc at msn.com>
>Subject: Re: [TowerTalk] Aluminum mast
>Date: Wed, 15 Mar 2006 14:35:48 -0500
>Bruce, I have used 2" and 2 1/4" rigid thick wall aluminum conduit for
>probably 15 or so years.  I have had my Mosley PRO-57A on it with about 3 
>above the top of 25g tower for about 8 years.  I have encountered wind
>gusts, probably 50 mph and never a problem.  It is much easier to work with
>than the heavy steel masts.  I would not use anything else.  (((73)))  Bob
>----- Original Message -----
>From: "Bruce Ferratt" <uglyatc at msn.com>
>To: <towertalk at contesting.com>
>Sent: Tuesday, March 14, 2006 10:56 PM
>Subject: [TowerTalk] Aluminum mast
> > Hello and thanks for letting me post a question.
> > How strong is a solid aluminum mast compared with a walled/hollow mast?
> > I secured a solid, round 12' aluminum mast 6061-T6511 grade.  What is 
>likelihood of bending when loaded with a TM-33A and VHF 2m/440 vertical at 
>rated 70mph wind load in Northern Virginia?  8ft of mast will be exposed
>above the point of the tower peak (Rohn 25G), with about 4 ft inside the
>tower to rotor plate.
> > Thanks
> > Bruce
> > K4BOF
> > _______________________________________________
> >
> >
> >
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