The _connecting rod_, as you can guess from its name, forms the
_connecting link_ between the piston and crank shaft, _transferring_
the _energy_ of the explosive gas, acting behind the piston, to the
crank shaft and fly wheel, from which it can be transmitted to the
driving wheels of the automobile. It is made up in some such form as
shown in Fig. 18 and is made of steel or bronze. It has a bearing at
each end, the smaller one fitting around the piston pin, the larger
one surrounding a portion of the crank shaft called the _crank pin_.
Both of these bearings are lubricated by oil which splashes up from the
bottom of the crank case when the engine is running. You will notice
that one of the bearings is cut in two and bolted together so that you
can take it off from the crank shaft, should you wish to examine it.
[Illustration: Fig. 18--A typical Connecting Rod.]
[Illustration: Fig. 19--The two halves of the Connecting Rod Bearing.]