[TowerTalk] Replacement Thrust Bearing

Sun Apr 19 13:58:05 EDT 2015

That is correct, George.  I reported the ID as nominal 2 inch and tube 
OD figures are often given nominal values.  If you read the fine print, 
if available, various supplier's actual OD on tubing varies as well.  It 
is easy to buy bearings and tubing and not be able to assemble them 
without a little sanding.  The "Other Ham" in our Zip Code got a very 
nice slip fit on the mast material he selected.  How I fare remains to 
be seen.

Luckily the RPM is so slow that a slightly undersized tube locked down 
by the bearing's set screws but not well centered will be just as smooth 
turning as a perfectly centered one if there is much distance between 
the rotator and the thrust bearing. In my instance the difference will 
be undetectable between a sloppy fit and a friction slip fit.  Worst 
case I would have to take a little metal off the ID of the bearing to be 
able to get the tube through the bearing.  Easily done by rotating the 
bearing and applying emery cloth carefully to the ID. I say carefully as 
the metal of the bearing ID is not particularly hard or difficult to 
sand in my experience.

My mast requirement is:
A 2.0" Dia x .250" wall 1026 DOM mast (yield = 85 Ksi) which will give 
me a safety factor of 2.57 for a DB42 antenna (38.9 SqFt Effective Area) 
mounted 2 feet above the tower top when the tower top is 94 feet above 
ground.
This is per ANSI/TIA-222-G, Exposure Zone C, on flat terrain in 
Pottawatomie County, OK which is a 90 Mph wind speed zone.

Although my crank-up/down tilt over Tash Tower is 54 ft tall it will be 
mounted on a steel structure 40Ft above grade (first choice) or a bit 
lower if my mech engineer friend/consultant doesn't approve the "full 
height (40 ft)" plan.

Patrick    NJ5G

On 4/19/2015 11:57 AM, George Dubovsky wrote:
> Towertalk,
>
> One thing to remember about real bearings is that they are precision 
> parts. A 2" bore bearing will be 2.00x ID, with x being a small number 
> like "1". A galvanized or painted real 2" tube mast will likely not 
> fit that bearing.
>
> 73,
>
> geo - n4ua
>
>
> On Sun, Apr 19, 2015 at 12:24 PM, Patrick Greenlee 
> <patrick_g at windstream.net <mailto:patrick_g at windstream.net>> wrote:
>
>     I have a NIB 2 inch ID bearing in a 4 mounting hole pillow block
>     with grease Zerk.  It is one HD unit rated for way more than
>     needed and cost about $20.  The box is labeled CJ Bearings and is
>     part number UCF210-31.  There are only two hams in our ZIP Code
>     and we went together and bought two. His is in use and doing fine
>     while mine awaits the arrival of my repurposed prop pitch motor,
>     SteppIR DB42, and Tash Tower HD LM354.
>
>     The box has this statement printed on a side panel, "Do not open
>     until ready to use, keep dry and clean."  I will be assessing the
>     methods/repurposed plumbing components mentioned here as used for
>     protection against the environmental hazards.  I have a hard time
>     understanding the rationale behind paying near or over $100 for a
>     bearing very similar to mine.  Maybe if I framed and displayed a
>     high dollar sales receipt from DXE or a tower company perhaps that
>     would help justify the price. ;) ;)
>
>     After all, a little frog that has been hand raised, dew picked,
>     and lightly killed is still just a crunchy little dead frog even
>     if related processes read like the menu of a high dollar French
>     restaurant.
>
>     Patrick   NJ5G
>
>
>
>
>     On 4/18/2015 11:04 PM, Roger (K8RI) on TT wrote:
>
>         All of the new TB-3s and 4s I've tried felt very rough. A real
>         bearing would be replaced if it were that rough, BUT the do
>         the job well. Gene's suggestion are much better bearings.  My
>         new (used, but new to me)LM470 has one of those mounted on
>         top.  I'd suggest a cover of some sort to protect it from the
>         rain.  They get rusty looking and look like crap, but continue
>         to work well.
>
>         73
>
>         Roger  (K8RI)
>
>         On 4/17/2015 12:49 PM, Robert Harmon wrote:
>
>             I am overhauling my rotator and thought it would be good
>             to replace my thrust bearing also.
>             I have the Rohn TB3 bearing now.  It has been in use for
>             18 years and feels pretty rough.
>             Im thinking of going with a different bearing this time
>             with a steel body and greased. (grease fitting)
>             Looked thru the archives on tower talk to find out what
>             others have used and can’t find much,
>             on this type of replacement and I know the bearing supply
>             houses have them, just haven’t
>             pursued searching with them yet.   I would like to know
>             what others have used.
>             If you have used a thrust bearing like this,  could you share
>             the number and supplier ?  Array Solutions has their model
>             TB2 which is this type
>             of bearing but it only has a two hole flange for
>             mounting.  They have a larger unit with a 4 hole
>             flange but it is for a larger diameter mast than 2 inch. I
>             want a 4 hole flange but for 2 inch.
>             Here is the info from their webpage:
>             https://www.arraysolutions.com/Products/thrustbearing.htm
>             Anyway, what say you ?
>
>
>             thanks,
>             Bob
>             K6UJ
>             _______________________________________________
>
>
>
>             _______________________________________________
>             TowerTalk mailing list
>             TowerTalk at contesting.com <mailto:TowerTalk at contesting.com>
>             http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
>
>     _______________________________________________
>
>
>
>     _______________________________________________
>     TowerTalk mailing list
>     TowerTalk at contesting.com <mailto:TowerTalk at contesting.com>
>     http://lists.contesting.com/mailman/listinfo/towertalk
>
>