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National Advisory Committee for Aeronautics, Technical Notes - Tests of Several Bearing Materials Lubricated by Gasoline

This investigation on the relative wear of several bearing
materials lubricated by gasoline was conducted at the Langley
Memorial Aeronautical Laboratory; Langley Field, Virginia, as
part of a general research on fuel injection engines for air—
craft. The specific purpose of the work was to find a durable
bearing material for gear pumps to be used for the delivery of
gasoline and Diesel engine fuel oil at moderate pressures to I
the high pressure pumps of fuel injection engines.

The bearing surfaces were prepared for test by scraping,
and by wearing them in under load with the shafts. The bearings
were then baked and weighed to within 0.903 grain on analytical
balances. The bearings were held in rockers attached to the
bottom of a gasoline tank and to a lever, and the loads impased
by weighing the lever. The tests were made with 0.5 in. diame—
ter shafts turning at approximately lBOO R.P.M., the shafts
and bearings being immersed in gasoline. The wear was deter-
mined by baking and weighing the bearings after test.

Eighteen bearing materials were tested. These tests in-
eluded determinations of the wear of two bearing materials at
various loads with both machine steel and hardened tool steel
shafts; seizing load tests of 16 hearing materials; and wear
tests of 8 bearing materials, selected from the seizing load
tests, at a load of 250 lb. per sq.in. with hardened tool steel
shafts.

When a machine steel shaft was used, the seizing load
for a commercial hard bronze was about 65 lb. per sq.in., and
for another commercial, but softer more porous bronze, it was
about 80 lb. per sq.in. With a hardened tool steel shaft, the
seizing load for the hard bronze was about 115 lb. per sq.in.,
and for the soft bronze it was about 210 lb. per sq.in. Spe~
cial bearing brenzes, containing lead up to approximately 35
per cent or graphite up to approximately 50 per cent, carried
loads up to 500 lb. per sq.in. 'without seizing, though in all
cases considerable wear occurred above a load of about 300 lb.
per sq.in. The wear obtained in the tests on the 8 selected
bearing materials ranged from 0.55 to 21.55 grains per million
turns per square inch of bearing contact surface. The least
wear was obtained with a hard alloy of graphite and powdered
bronze pressed and,sintered at high temperature.