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@windstream.net <mailto:patrick_g@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@contesting.com <mailto:TowerTalk@contesting.com>
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com <mailto:TowerTalk@contesting.com>
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|