Topics:
Function:
The connecting rod is a link between the piston and the crankshaft and converts the translating movement of the piston into a rotating movement of the crankshaft (translating means moving up and down). When the piston is pushed down, the connecting rod ensures that this force is transmitted to the crankshaft, causing the crankshaft to rotate. After the crankshaft has turned 180 degrees, the connecting rod is pushed back up in a smooth motion so that the piston returns to TDC.
The connecting rod is connected to the crankshaft at the big end (the bottom) by means of bearing shells, and at the top it is mounted to the piston by means of a gudgeon pin.
The large hole (the connection to the crankshaft) is also called the “big end”. In order to withstand the high forces that are released during combustion in modern engines, the connecting rod and big end are not just separate parts bolted together. A connecting rod is manufactured from one piece of steel. The big end is then broken off the connecting rod itself. Because the broken parts have a very rough surface, this provides extra strength after assembly. If both parts were smooth, friction could arise between them. Therefore, the components must absolutely not be interchanged.
Lubrication:
The big end of the connecting rod is lubricated by oil coming from the drilled crankshaft. The small end is lubricated by oil pressure in the oil passages and splash oil from the crankshaft or oil sprayers. The splash oil also cools the underside of the piston (piston crown).
