Hi Steve, one solution to the set screw limitations is use of a shaft
collar. They are made in three flavors, solid with a single allen head set
screw (often 3/8" or 1/2"), single slot with one or two allen head screws to
pull the slot closed and tightly grip the shaft and with two slots and four
allen head screws that allow installation without removing the shaft from the
bearing.
You can get them from Graingers, McMaster Carr or most any bearing house.
They are available made from steel (they will rust), cad plated steel
(takes longer to rust), nickel plated steel (takes much longer to rust and also
aluminum.
For added security, two collars (or more) can be stacked.
The weight will be transferred to the bearing bore sleeve and the bearing
set screw or locking collar only keeps the mast centered. That is about all
they are good for anyway.
The issue of a rusting bearing set screw can be eliminated by using a
stainless steel set screw which are available at the same firms as above as
well
as Home Depot, Lowes and better hardware stores.
I have used this solution on some very large and heavy EME antennas
weighing as much as 2000 pounds. I have substituted the allen head set screws
with short stainless steel bolts on some to allow use of a box end wrench to
get the set screws really tight and more easily removed if need be.
Bearings are available with nickel plating but the cost is way more than I
want to pay. As someone suggested earlier, some paint and a rain shield
will work quite well to preserve the bearing. I think the main precaution is
keeping rain from washing out the grease which could allow the bearing to
rust.
73,
Gerald K5GW
In a message dated 4/17/2015 4:56:23 P.M. Central Daylight Time,
towertalk@contesting.com writes:
> 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.
That's pretty SOP for a mature TB3. What are you using the tb for? If
you've got all of your mast and antenna on it taking the weight off of
the
rotator, that's one thing. If you're just using it as a bushing to help
with horizontal forces, that's another.
With case 1, another bearing might be the way to go. The rough races
will only get rougher (steel ball bearings in an aluminum race will only
take so much abuse).
With case 2, it's probably FB since you're not asking it to do much.
> 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.
I haven't seen a decent bearing like you're describing that'll work
outdoors. US Tower uses a pillow bearing that's designed for indoor use.
There's an Allen screw that holds everything and over time the Allen
screw
rusts terminally and you have to drill it out to do anything with the
bearing
or mast. Not recommended.
> Array Solutions has their model TB2 which is this type of bearing but
it only has a two hole flange for mounting.
Again, even if you have the bearing holding the weight, you're still
not asking it to do much. I don't see any way to secure the mast from the
picture. If it's got the aforementioned Allen screw, you could be screwed
as
well.
IMO thrust bearings are only marginally useful since you want some/all
of the mast/antenna weight on the rotator or just have it act as a
bushing
so you might rethink the TB issue and whether you even need one.
Cheers,
Steve K7LXC
TOWER TECH
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|