In a message dated 1/20/01 6:37:31 PM Pacific Standard Time,
k0myw@worldnet.att.net writes:
> I am preparing to sprout some antennas from a recently erected U.S.
> Tower HDX-555 crank-up.
> While I am VERY PLEASED with all other aspects of the tower and
> associated U.S. Tower hardware, I have a slight reservation about the
> TB-2US thrust bearing. I'm no expert in such matters, but that thrust
> bearing just doesn't look "right" for rugged outdoor service, laying
> flat atop the tower...
> So I'm wondering:
> Should I consider substituting a thrust bearing that more obviously is
> purpose-built for tower-and-mast application, such as one from Rohn,
> Yaesu or the new Glen Martin TB-25?
Hi, Mike --
Since it looks like no one else has answered your question, I'll take a
run at it.
Generally, pillow-block type bearings (they're not galvanized and
typically have one Allen set screw) are intended for indoor applications and
aren't suitable in the longterm outdoors. What happens is that the Allen
screw rusts and you have to drill it out in order to remove the mast - not a
pleasant job. The US Tower ones I've seen seem to be better in that respect.
> Or should I just continue to follow LXC's Prime Directive and "do what
> the manufacturer recommends" (in this case, use the tower
> manufacturer's thrust bearing)?
In this case I'd go with the US Tower bearing. The top of the tower is
already drilled for it and they seem to be okay reliability-wise. I'm not too
excited about one little Allen screw holding the mast load but you don't have
much choice. You might want to consider not tightening the Allen screw and
having the rotator take the vertical load by just having the TB function as a
bushing that supports the mast for sideloads.
I use the Rohn TB-3 (2") and TB-4 (3") for just about everything else. I
think the GME one is cast aluminum and isn't as rugged as the Rohn. It also
looks like the Yaesu one so it might come from the same manufacturer.
Cheers, Steve K7LXC
Tower Tech
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