Bearings
Big End Bearings Big end bearings as shown in fig. 6 are commonly
known as shell bearings. They come into two evenly split
pieces with provision for oil passages and fit on the big end
of the connecting rod, one on the rod and the other piece on
the cap. They are lined with copper lead alloy and lead tin-plated.
This face of the bearing is very
delicate and soft and care should be taken not to scratch the same.
Any scoring on the face will affect the performance of the
bearing shell and may result in the leakage of oil pressure between
the crankshaft and the bearing.
Fig. 6 Bearing cap and bearing shell.
Always ensure that the bearing shell are matched pair and are not
scored or damaged. That the locks match correctly with the slots on
the connecting rod. Care should also be taken to ensure that a
proper torue is applied
after installing the bearing for operation. !efer figure ".
Small End Bearing)
The small end bearing is a phosphor bron#e bush, which is pressed
fit into the small end of the connecting rod.
Main Bearing)
The main bearings are similar to the large end bearings and are
fitted between each crank $ournal to support and centrali#e the
crankshaft. These bearings are manufactured to very fine tolerances
and are easily renewable. This is done if the clearances are found
to be e%cessive or at periodic recommended overhaul. Two halves are
dowelled together and located by the lugs formed on the outer
surface of the shells, which engage with notches machined in the
bearing housing and caps. &ifferent types of engine bearings
are shown in fig. '. The caps are numbered for the correct
replacement, as they are pre-machined for the correct bore and
aligned
with the other bores. (ismatching will cause the bearing distortion
and damage to the crankshaft.
Fig. 8. Different types of bearings used on engine.
*hr")t Bearing.
)t is of prime importance that the crankshaft must have end float
with the tolerable set limits. *teel backed copper-lead pads are
therefore fitted to both sides of one of the main bearings to avoid
the e%cessive a%ial
movement of the crankshaft.
