Re: [TowerTalk] Noob question re: Thrust Bearings

[Grant Saviers <grants2@pacbell.net>]

Rich,

I posted the picture from last year's maintenance checkup on dropbox
https://www.dropbox.com/s/3u7mjsz8kjrgef0/Rohn%2065%20UHMW%20bearing%208-2019.jpg?dl=0

The collar is not handling any load, it is there for servicing and 
backup in case there is a prop pitch failure.  It is made from 6061 
heavy wall tubing plus a load ring.  This diameter is held to the six 
1/2-13 IIRC SS grub screws tube part with 3 flat head machine screws.  I 
machined the mating ring in the UHMW so debris wouldn't accumulate.
The mast is 3" dia 0.25 wall x 20ft.  15ft up is a JK 2L 80 yagi. Four 
galvanized bolts hold the bearing to the custom waterjet cut Rohn 45 top 
plate.
Extruded UHMW is a bit wavy so a light milling cut was done on both top 
and bottom surfaces.  Probably overkill.
I borrowed this idea from Brad K7ZSD when he sold me the other yagis on 
my tower.  He was using the design for top and bottom swing arm bearings 
on an R45 tower.  The white UHMW he used was showing significant UV damage.
Grant KZ1W

On 5/10/2020 09:26, Richard Smith wrote:
>   Peter,
> Thanks for sharing the PI4CC photos and info. Lots of good engineering.
> I am also interested to see Grant's design of a radial top bearing with 4" 
> thick UHMW.
> 73, Rich, N6KT   PJ4K
>      On Sunday, May 10, 2020, 07:45:17 AM PDT, Peter <pc2a@pi4cc.nl> wrote:
>   
>   Rich,
> Have look at https://www.pi4cc.nl/album/rotor%2040M/slides/07.html for
> some ideas.
> Here is a rotor bearing that carried all the load for a 2 el full size
> 40 meter beam
>
> Have also a look at the rotor build and breakout rotor pipe if the
> torque is too high for the rotor.
> Yes the beam can spin free but it willsave a broken rotor :-)
>
> https://www.pi4cc.nl/tech-info/ is also a nice source for our way to
> explain "How do they do it?"
>
> Peter
> PC2A
>
> Op 10-5-2020 om 16:18 schreef Richard Smith:
> >    Hi Grant,
> > I am also interested in your concept of a UV resistant UHMW radial top bearing. 
> > I am part of a team that is building a station in the Caribbean, and am 
> > considering trying a non-metal bearing approach. Do you have a sketch or 
> > drawing that you might share?
> > 73, Rich, N6KT   PJ4K
> >        On Sunday, May 10, 2020, 06:01:51 AM PDT, Art Greenberg <art@artg.tv> 
> > wrote:
> >    
> >    > My choice is a UV resistant UHMW radial top bearings for low cost, no
> > > maintenance, long life, and low friction.  A 6x6x4" thick block ($47) is
> > > what I made for the 3" mast radial bearing with 500# loading.  In
> > > perfect condition after 6 years.
> > Grant,
> >
> > I'm curious about this. Some questions:
> >
> > - How did you drill the hole for the mast?
> >
> > - How much oversize? I imagine its not very critical, is that true?
> >
> > - Is any particular color better with respect to UV and other environmental 
> > exposures?
> >
> > Thanks, and 73.
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