What is a connecting rod (con rod)?
The connecting rod (con rod, or conrod) connects a piston to the crankshaft. The rods are made from drop-forged, heat-treated steel to provide the required strength. Each end of the rod is bored, with the smaller top bore connecting to the piston pin (wrist pin) in the piston. The large bore end of the rod is split in half and bolted to allow the rod to be attached to the crankshaft. Some diesel engine connecting rods are drilled down the centre to allow lubrication oil to travel up from the crankshaft and into the piston pin and piston (see below).
Connecting Rod with Bored Oil Passage
A variation found in V-type engines that affects the connecting rods, is to position the cylinders in the left and right banks directly opposite each other instead of staggered (most common configuration). This arrangement requires that the connecting rods of two opposing cylinders share the same main journal bearing on the crankshaft. To allow this configuration, one of the connecting rods must be split or forked around the other.
Tip
Many people often refer to the piston rod and connecting rod as if they are the same thing, but this is not true. A piston rod is a separate piece that is connected to a crosshead, whereas a connecting rod connects directly to the crankshaft. Piston rods are still found on large marine engines, but not within modern automobile engines.
Marine Diesel Two Stroke Engine
Additional Resources
https://en.wikipedia.org/wiki/Connecting_rod
https://www.flight-mechanic.com/connecting-rods
https://www.sciencedirect.com/topics/engineering/connecting-rods