Thrust bearing (designed to take a load axially) or a bearing to take side
loads (e.g. wind loads) - Especially indoors, a sheet of High Density
Polyethylene with an appropriate sized hole will work great. A cutting board
drilled, then sawed in half across the hole so you can fit it around the mast,
would work well. You're looking at a very low rotation rate and an even lower
duty cycle. HDPE is very "slippery" (almost as good as PTFE).
On Tue, 21 Apr 2026 13:58:49 -0400, Dave WB2PJH via TowerTalk
<towertalk@contesting.com> wrote:
Thanks to all for the suggestions.
After some investigation, it will be much less expensive to make my own
supports from some 3/4" or 1" pipe with flanges and use some steel plate
for the rotator plate bottom and top plate. If I lived closer to Jon I'd
purchase a cutoff section and plates, but my current plan is to out up some
sturdy (2x6) stringrers across the roof joists, sister them and likewise
reinforce the base so there will be minimal pressure on the roof structure
and distribute the weight or the ceiling joists below. I can cut and
thread 3/4" pipe which should, given the short distance, support the
rotator and thrust bearing. Yaesu has a handy formula and table in the
manual and HRO sells a G-2800 motor (but not the connector) which will work
with my RT-21 controller and a G-065 thrust bearing which should more than
handle the TA-33 with the WARC mods. I have a 2 inch by 15 ft 6061
aluminum mast so half will be inside and the rest outside, and a stock vent
pipe collar should keep the water out. When it's time to move, I can
unbolt everything and cover the hole with one of the extra shingles. If
anyone sees a problem with this plan, feel free to correct me.
If anyone has or know of anyone selling a serviceable rotator and/or thrust
bearing at a reasonable price, I'm interested, otherwise I'll buy them new.
I've always had good luck with Yaesu rotators, but would consider any
heavy duty model that's not a repairman's special.
73,
Dave WB2PJH
On Tue, Apr 21, 2026 at 1:31 PM Mickey Baker wrote:
> This seems like a waste of a tower section unless the structure of your
> attic specifically matches structurally.
>
> Pressures on the mast are primarily vertical, so the bottom surface must
> bear the static weight of the antenna, mast and rotor unless you devise
> another rotating scheme.
>
> Lateral pressures on the opening are a function of the wind on the antenna
> and mast that allow calculated wind load. This and should be calculated,
> and a solution created that fits the space and will support the wind load
> and weight.
>
> You can then should be able permit for the combined structure that will be
> safe. You can actually design and document a decommissioning process so
> that a potential buyer won't run away from you or your family down the road.
>
> Mickey N4MB
>
> “Ends and beginnings—there are no such things. There are only middles.”
> Robert Frost
>
>
> On Tue, Apr 21, 2026 at 11:29 AM Jon Zaimes, AA1K via TowerTalk <
> towertalk@contesting.com> wrote:
>
>> Hi Dave,
>> Back in the 1960's my best friend's dad was W3ANO in Allentown, PA. He
>> had a mast going through the peak of the roof as you propose, with a TA33
>> or similar trapped tribander on it. No rotor though. The mast went through
>> the ceiling on the 2nd floor and he had fashioned a brake of some sort and
>> a steering wheel on the bottom of the mast in the hallway next to the radio
>> room. He would reach up to turn the steering wheel to adjust the beam
>> heading, then lock it down!
>> You will need a rubber boot where the mast enters the roof to keep water
>> out.
>> Rohn does have a couple of short top sections:
>> https://www.3starinc.com/rohn_25g_antenna_rotor_and_bearing_accessory_shelf_r-bas25g
>> or
>> https://www.3starinc.com/rohn_25g_top_cap_thrust_bearing_plate_r-bpl25g
>> Maybe a bit pricey for your purposes. Any cut-off straight section with
>> two accessory shelves would serve the same purpose.
>> I have a couple of used top sections with rotor plates in my stockpile if
>> you are interested.
>> 73/Jon
>>
>> Jon P. Zaimes, AA1K
>> Tower climber for hire
>> Felton, Delaware
>> http://www.aa1k.us/
>> Cell: 302-632-2353
>>
>> Reviews of AA1K tower work on eham website:
>> http://www.eham.net/reviews/detail/12922
>>
>> Hug your favorite tower every day, and always stay connected to it.
>>
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
--
Dave WB2PJH
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