|The work presented involves the theoretical and experimental
studies of the kinematic and dynamic effects of bearing clearance in linkage
In the test mechanism developed a six-bar linkage, having a
test plain bearing, is oscillated at amplitude of 17.5 mm within the frequency
range 4-7 Hz. A transducer assembly is used to measure the impact
accelerations which are related to clearance size, mass distribution, spring
load and excitation configuration, ( the vibrators are independently phased ).
The motion-analysis of the test mechanism including clearance
at a bearing is described using Lagrangian mechanics. The behaviour of the
system is obtained by solving the coupled time-dependent equations using
Kutta-Merson integration procedure. The method proves to be lengthy in
computation time and not easily applied in design. Further, it is shown that
there is little difference, in a gross sense, between the results so found
and results obtained assuming no bearing clearance.
An empirical formula relating the three parameters, clearance
size, the rate of change of contact position and the corresponding minimum
reaction force is derived from the no-clearance analysis. The. variation
of this empirical relationship with excitation frequency is found to be
similar to that obtained for the experimental impact levels. Thus it may be
used to describe the impact accelerations and its numerical significance as
a design criterion is suggested.
The experimental work also demonstrates that the pattern of the
impact levels remains unchanged when the bearing is oil film lubricated.
Some simple design guides using the empirical relationship on
a four-bar chain are suggested and general application from a practical
point of view is discussed.