The crankshaft is attached to the connecting rod in offset areas called throws - where the downward power pulses change into rotating motion.
Crankshafts must be strong enough to do this without bending or twisting. They are a one piece casting, or forging, of heat-treated alloy steel of great mechanical strength. Counterweights are formed to balance the throws, and also the big end of the connecting rod.
Fine balancing is done by drilling out or adding small weights.
The crankshaft rotates in the engine on journals which run in bearings called the main bearings.
The connecting rod with its big end bearings are attached to the crankshaft crank pins located on the throws.
Drilled passages carry lubricant under pressure from the main bearings to the adjacent big end bearings.
The rear of the crankshaft is drilled and tapped for flywheel attachment. Near the front of the crankshaft, a timing gear or sprocket is attached to drive the camshafts.
A drive pulley is mounted on front of the crankshaft. It drives many components including the alternator, the fan and water pump, and power steering.
Many in-line and V engines have a harmonic balancer attached to the crankshaft. The harmonic balancer is more correctly called the crankshaft torsional vibration damper. It prevents crankshaft vibration. In most cases the harmonic balancer incorporates the drive pulley.
