Page 80 - The Tribology Handbook

Plain bearing form and installation A12

Dynamic loads Rotating loads
Dynamic loads may result in flexing of the housing if this High rotating loads (in excess of 4-6 MN/m2) such as
is not designed to have sufficient rigidity. Housing flexure occur in the planet wheels of epicyclic gearboxes may result
can result in fretting between bearing back and housing, in bushes very slowly creeping round in their housings and
and in severe cases, in fatigue of the housing. Increase working out of the end. Location features such as dowels
of interference fit with a corresponding increase in bolt- are unable to restrain the bush and it is normal practice
ing load, may give some alleviation of fretting but in these circumstances to cast the lining material on the
stiffening the housing is generally more effective. Poor pin.
bore contour and other machining errors of the housing
can lead to fretting or loss of clearance. Surface finish of
housing bore should be 1 to 1.5 fim cla. Oil distribution
grooves in the bore of the housing should be avoided for
all except thick-wall half bearings.

PRECAUTIONS WHEN FITTING PLAfN B EAR1 NGS

Ha If bear i ngs Bushes
(1 ) Ensure cleanliness: between bearing and housing, be- (1) For insertion: use oil or other suitable lubricant to
tween bearing bore and joint face of bearing and facilitate pressingin and prevent scoring of bush
housing, and in oil-ways and oil system. outside diameter. Use a 15" lead in chamfer in housing,
(2) Check free spread: bearing should be in contact with and press in square.
housing in region of joint face. (2) Check assembled bore size: with comparator or plug gauge.
(3) Check nip: tighten bolts, slacken one side to hand tight, (3) Remove burrs and sharp edges from sha) : to avoid damage
use feeler gauge on housing joint. Tighten bolts and to bush bore during assembly.
repeat on other side. (4) Check cleanliness: in bush bore, at bush ends and in
(4) Tighten bolts: to specified stretch or torque. lubricant supply drillings.
(5) Check clearance: between journal and assembled bore
with leads or similar, particularly checking for distor-
tions (IocaI loss of clearance) near oil grooves or
bearing joint face. (For new design of housing conduct
fitting test: measure bore diameter with shaft re-
moved.)
(6) Oil suplface: before turning shaft.

AI 2.6