Crank pin

In a reciprocating engine, the crankpins, also known as crank journals are the of the big end bearings, at the ends of the connecting rods opposite to the pistons.

If the engine has a crankshaft, then the crankpins are the journals of the off-centre bearings of the crankshaft. In a beam engine, the single crankpin is mounted on the flywheel; In a steam locomotive, the crankpins are often mounted directly on the driving wheels.

Big end bearings are commonly bushings or plain bearings, but less commonly may be roller bearings (see crankshaft).

In a multi-cylinder engine, a crankpin can serve one or many cylinders, for example:

There are three common configurations of big end bearing:

...
Wikipedia