What are the functions of the crankshaft?
4 Answers
The functions of the crankshaft include converting the thrust transmitted from the piston connecting rod into rotational torque, transforming the reciprocating linear motion of the piston into the circular rotational motion of the crankshaft, and then delivering the engine torque to the transmission system through the flywheel. The crankshaft is the most important component in the engine. During the engine operation, the piston is driven to perform linear motion by the combustion of the compressed air-fuel mixture, and the force is transmitted to the crankshaft through the connecting rod, which converts the linear motion into rotational motion. The crankshaft is mainly composed of the crankshaft front end (or free end), connecting rod journal, main journal, crank, counterweight, and crankshaft rear end flange (or power output end).
As a master mechanic with 20 years of experience, the crankshaft serves as the core converter in an engine. When a car starts, the pistons move up and down, and this linear force must be converted into rotational power by the crankshaft to drive the wheels. It's similar to how bicycle pedals drive the chain to turn the rear wheel—without the crankshaft, the entire engine would be useless. It also drives other critical components, such as the camshaft to control valve timing and the alternator to power the vehicle. I've seen many cases where poor-quality oil caused crankshaft bearing failures, so I remind car owners to change their oil regularly to protect this vital component.
With over a decade of experience in racing modifications, I've particularly focused on crankshaft performance. When increasing engine power, piston impact forces surge dramatically, and the crankshaft must convert these violent strokes into smooth rotational power. After upgrading to a forged crankshaft, it can withstand higher RPMs without deformation or fracture. During a recent track day, I witnessed the disastrous consequences of a broken crankshaft—engine bay parts scattered everywhere. A high-quality crankshaft also optimizes rotational balance, reducing engine vibrations for more linear acceleration. Additionally, the front end of the crankshaft typically connects to the timing chain, directly affecting valve timing precision. If you're planning to tune the ECU for more power, remember to reinforce the crankshaft system first.
Daily drivers may not understand engine mechanics, but crankshaft failures show obvious symptoms. When cold starts produce loud knocking sounds, there's an 80% chance it's due to worn crankshaft bearings creating gaps. It's like how an old wooden chair wobbles when its joints loosen. During my engine overhaul last year, I saw the crankshaft body riddled with oil passages - the mechanic said these holes function like blood vessels delivering lubricant to the bearings. That repair bill cost over 7,000 yuan, so now I religiously check the dipstick monthly. After all, fixing a crankshaft requires complete engine disassembly - it's literally a bone-deep operation.
