>I recently acquired a TB3 thrust bearing that had been in service for
>several years. When I removed it from the tower it was not turning smoothly;
>seemed like there was either serious dirt in there or perhaps busted bearings.
>
>I'll try a simple cleaning first, of course, but if there is internal damage
>I was wondering if these can be rebuilt?
>
>73/Jon AA1K
If you take a close look at your TB3, you will see a set screw inside which,
when removed, allows the bearings to come out. There is really nothing that
keeps this set screw in the right place. It can't back out since it will
hit the mast. It could work its way in too far, however, and cause the
bearings to bind as they pass the end of the set screw. It could also work
its way out too far (limited by running into the mast) such that a bearing
can drop into the hole that is supposed to be filled by the set screw. The
set screw is free to move within its threads for a few turns. There is an
optimum place for that set screw to be and that is when it just fills the
hole such that the bearings run smoothly passed the end of it and there is
no space for a single bearing to drop into.
I always recommend that buyers of TB3s modify them by adding another set
screw to hold the one discussed above in exactly the right place. This
means drilling and tapping a small hole for the new set screw which I have
done from the bottom of the bearing. The new small set screw hole is
parallel to the mast and it does not take much of a set screw to keep the
other one from moving.
I have never heard of anyone rebuilding a TB3. I suggest you experiment by
moving the original set screw in and out some to see how this affects the
smoothness of the bearings.
Stan w7ni@teleport.com
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