> The bottom bearings on the main shaft usually burn out every
 > third year...

There are a number of ways that bearings can fail, and a number of 
reasons they do.  Bearings fail from inappropriate use for the bearing 
type, overloading, misalignment, abrasion due to contamination or rust 
or lack of lubrication.

Careful examination of the bearing, especially before total destructive 
failure takes place and destroys the clues will usually reveal the cause.

The bottom bearing in vertical shaft extractors is subject to 
considerable thrust and a bearing not rated for that thrust load will 
fail repeatedly.

The thrust load is the total of the weight of the reel plus the weight 
of the frames being extracted, plus a safety factor

Each bearing has a specification which designates the maximum working 
thrust and radial loads it can bear in service.  Good bearing shops have 
this information and it is available on-line as well.

Usually for any given inner and outer diameter, a selection of bearings 
is available for differing loads, and for radial or thrust loads or a 
combination.

If repeated failures are being experienced and misalignment, dirt, honey 
in the bearing or inadequate lubrication is not apparent, and rust from 
pressure washing or bad storage is not the culprit, a talk with a good 
bearing shop may pay off in selecting a suitable bearing to replace the 
original design choice.

Sometimes minor modification of the bearing pad may be indicated to 
accommodate the proper bearing, but once the correct bearing is in place 
and assuming that it is kept dry and clean, the problem should be over 
for a decade or more.

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html

Guidelines for posting to BEE-L can be found at:
http://honeybeeworld.com/bee-l/guidelines.htm