Topics:
Function:
The connecting rod is a link between the piston and the crankshaft and converts the reciprocating motion of the piston into the rotary motion of the crankshaft (reciprocating means up and down movement). When the piston is pushed down, the connecting rod ensures that this force is transmitted to the crankshaft, causing it to rotate. After the crankshaft has rotated 180 degrees, the connecting rod is smoothly pushed back up so that the piston comes back to the Top Dead Center (TDC).
The connecting rod is connected at the big end (the bottom) to the crankshaft via bearing shells and at the top end it is mounted to the piston by means of a wrist pin.
The large hole (the connection with the crankshaft) is also known as the “big-end.” To withstand the high forces that occur in modern engines during combustion, the connecting rod and big end are not merely separate parts mounted together. A connecting rod is manufactured as one piece of steel. The big end is then broken off from the connecting rod itself. Because the broken surfaces are very rough, this provides extra strength after assembly. If both parts were smooth, friction could occur between them. Therefore, the parts must not be interchanged under any circumstances.
Lubrication:
The big end is lubricated by oil originating from the drilled crankshaft. The small end is lubricated by oil pressure in the lubrication holes and splash oil from the crankshaft or oil squirters. The splash oil also cools the underside of the piston (piston crown).
