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Kingsbury Thrust Bearing
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The predominant
thrust bearing used in hydroelectric generators is the Kingsbury thrust bearing.
It was invented by Professor Albert Kingsbury of WPI, the much revered Worcester
Polytechnic Institute. It consist of a annular arrangement of babbit covered, pie shaped, stationary,
shoes. The shoes form a circle around the rotating shaft. A cylindrical thrust
block with a highly polished end is pressed onto the shaft and held to the shaft
with half moon collars. The polished end of the shaft rests on the surfaces of
the babbitted, stationary shoes. The shoes are mounted on spherical studs that
allows them to tilt. As the hydraulic turbine spins the shaft, the collar turns
on the shoes. A wedge of oil is driven between the shoe surface and the surface
of the thrust collar. The thin film supports the weight of the turbine runner,
the runner shaft, the generator rotor, the generator rotor shaft and the
hydraulic thrust of the water column.
Many
years ago, I purchased a salesman's model of a Kingsbury bearing. It came in an
oak box with a hinged cover. Inside is a model bearing. The salesman would take
the model out. There was a battery with a light bulb and electrodes to attach to
the runner and the shoes. You put a drop of oil on the bearings. When the
bearing is stopped the light bulb turns on. As you spin the runner, the runner
rises up on the oil film, the connection is broken and the light goes out.
Kingsbury Bearing,
salesman's model, circa early 1900s. Note light bulb in front of the aluminum
housing and small bottle of lubricating oil.
Kingsbury Bearing model
taken apart to view the three pie shaped tilting shoes.
Kingsbury is still in business today in Philadelphia,
Pennsylvania. You can contact them at:
Kingsbury, Inc. • 10385
Drummond Road • Philadelphia, PA 19154
Tel: 215-824-4000 • Fax: 215-824-4999 • www.kingsbury.com
The
following photographs show a Kingsbury style bearing from the No. 2 unit at
Pepperell, Massachusetts. A copy of an older Kingsbury Catalouge follows the
photos.
Typical Kingsbury style tilting shoe
bearing. This is before we sent the shoes out to be refinished. Note the RTDs
embedded directly in the end of the shoe. The PLC uses the RTDs to measure the
instantaneous temperature of the bearing surface.
Kingsbury thrust collar with annular
thrust collar bolted to its bottom. Note the 5 micron finish on its bottom
surface. It is so shiny it looks like it is chrome plated!
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