Hi Bruce, et al,
I suggest a two piece shaft collar be placed on the mast so as to
transfer the weight of the mast and antennas to the TB-3. The shaft
collar is designed for such, it will not mar the mast, and is
available in stainless steel from industrial supply and/or bearing
houses. This is the method I use and it has worked very well for several years.
Look up www.grainger.com or www.mcmaster.com and search for "shaft
collar", then narrow the search by inside diameter and desired material.
At 03:01 PM 3/15/2006, you wrote:
>Date: Wed, 15 Mar 2006 15:47:09 -0500
>From: "Bruce Ferratt" <firstname.lastname@example.org>
>Subject: Re: [TowerTalk] Aluminum mast
>Content-Type: text/plain; format=flowed
>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.
Robin Midgett K4IDC
615-322-5836 office - rolls to pager
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