Stan Griffiths wrote:
> Hi Greg,
>
> You did not say if this was a Rohn thrust bearing or not. If it is a TB3,
> there is a potential problem with these that can cause exactly what you are
> experiencing.
>
> If you had the bearing (Rohn TB3) in your hands, you could see the hex head
> (Allen) set screw on the inside that plugs up the hole where the ball
> bearings are insterted and removed during assembly and disassembly of the
> the thrust bearing. This hex set screw "floats" in the hole and is not
> tightened since doing that would clamp one ball tight in the race and cause
> the TB3 to lock up tight. When the mast is inserted in the TB3, it prevents
> the hex set screw from coming out and spilling bearings. The problem is
> that there is a range of one entire turn or so over which this hex set screw
> can turn freely from clamping down on a ball bearing and bumping up against
> the mast. If it gets too tight, it will catch the balls as they go by,
> which is what it sounds like yours might be doing. If it gets too loose, a
> ball can drop into the hole it leaves in the wall of the bearing race and
> this, too, causes rough operation of the TB3 and it can lock up.
>
> The cure for this is a little modification on the TB3 before installation.
> (I know this advice is a little late. Sorry, Greg, better late than never.)
> What I have done is drill and tap a hole in the aluminum cast TB3 part and
> install another small set screw to hold the large one in the right place
> such that the balls run smoothly in the race. If the large hex set screw
> can't get too tight or too loose, it should work just fine. Without this
> modification, nothing keeps the large hex set screw in the right spot except
> a little thread friction and a lot of luck. You may have run out of both of
> those.
>
Hi Stan,Very clever that you figured out this problem.
Sounds like a good application for some blue Loctite.
73, Kurt
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