What is a crankshaft and why is it so important for the combustion engine?
The crankshaft is the heart of the car engine. Without it, it would be impossible to drive the classic combustion engine. Its main function is to convert the linear upward and downward movement of the pistons into a rotating movement. This process enables the transmission of power via the clutch and gearbox to the drive wheels. At the same time, the crankshaft acts as a buffer against irregularities in the engine’s work cycle by storing kinetic energy and ensuring smooth running.
It is also important that the crankshaft can withstand extreme mechanical loads. High-quality manufacturing and optimum material are therefore basic requirements for durability and efficiency. You can find an overview of our expertise in this area on the Bharat Forge CDP company page.
What is the structure of a crankshaft in a car?
The structure of the crankshaft is complex and follows a strict technical logic. Important elements are
- Shaft journals: They form the main bearing points in the crankcase and define the axis of rotation.
- Crank pins (connecting rod journals): They accommodate the connecting rods that transmit the piston movement.
- Crank webs: These connect the shaft and crank pins. Their arrangement determines the cranking and directly influences the firing order and engine running.
- Counterweights: They provide the necessary balancing and reduce vibrations.
- Bearing points: Highly stressed surfaces that must be specially hardened and lubricated to minimize wear.
The geometry depends on the number of cylinders and engine configuration. A four-cylinder engine has a different structure than a six- or eight-cylinder engine. Bharat Forge takes precisely these differences into account when developing high-performance crankshafts for passenger cars. You can also find an overview of other products in the section: Complex forging technology for commercial vehicle technology, cars & armor.
What function does the crankshaft perform in a car engine?
The function of the crankshaft can be reduced to one core task: It converts stroke movement into torque. However, this seemingly simple sentence only describes part of its significance. In practice, the crankshaft fulfills several indispensable functions:
- Conversion of the piston forces into a continuous rotary movement
- Storage of kinetic energy by the flywheel mass to compensate for the uneven operation of the four-stroke engine
- Transmission of the torque to the clutch, gearbox and ultimately to the drive wheels
- Reduction of vibrations and ensuring smooth engine running
- Basis for auxiliary drives such as camshaft, oil pump or engine cooling, which are driven by gears or chains
This makes it clear that the crankshaft is not just a connecting element, but a highly stressed precision component that determines the efficiency and durability of the engine. Technological details and manufacturing standards can be found on our page Crankshaft products.
Crankshaft task
The task of the crankshaft goes far beyond the mere conversion of movements. It is a multifunctional element that performs both mechanical and dynamic tasks. Every piston movement generates forces that are collected, distributed and transformed into a rotary movement in the crankshaft.
The tasks can be divided into three areas:
- Energy conversion – the linear upward and downward movement of the pistons is converted into torque
- Power transmission – the torque generated is transferred to the drive wheels via the clutch and gearbox
- Running stability – due to the mass of the flywheel, the crankshaft has a balancing effect and prevents jerking in the four-stroke process
The crankshaft is also crucial for synchronization in the engine. It drives the camshaft and therefore the entire valve control system via gears or chains.
The consistent fulfillment of these tasks is one reason why Bharat Forge CDP relies on particularly tight tolerances and state-of-the-art technologies in the production of crankshafts for passenger cars.
What material is used for a crankshaft?
The material of the crankshaft is a decisive factor for its performance and durability. Crankshafts in cars have to withstand enormous loads over millions of revolutions.
| Material type | Properties | Advantages in the car engine |
|---|---|---|
| Quenched and tempered steel | Heat-treated steel with high toughness and strength | Optimum ratio of weight to durability |
| Nitriding steel | Special steel with nitridable surface | Very high wear resistance at bearing points |
| Cast iron with spheroidal graphite | Inexpensive material with sufficient strength | Economical production with a lower load profile |
In addition to the choice of base material, surface treatment plays a decisive role. Bearing journals are nitrided or induction hardened, resulting in an extremely hard surface, while the core remains tough and can absorb impacts and bending forces.
This combination of tough core and hardened surface makes the crankshaft resistant and durable. This is essential for modern downsized engines with high specific torque. If you would like to delve deeper into the technological basis, you can find more background information in the Bharat Forge CDP company section. Information on the people behind this technology and possible career paths can also be found in the Careers section.
How does the crankshaft convert the upward and downward movement of the pistons into rotary motion?
The seemingly simple movement of the pistons in the cylinder is a highly dynamic process. Each power stroke in the combustion engine generates an upward or downward movement that is transmitted directly to the crankshaft via the connecting rod. This is where the decisive transformation takes place: the linear movement produces a continuous torque that supplies the entire drivetrain.
Cranking is therefore more than just a mechanical movement. It is the basis for power development in the engine. Without the precise geometry of the crank pins, crank webs and counterweights, the linear movement of the pistons would not result in smooth rotation. The crankshaft translates every single explosion in the combustion chamber into a harmonious rotation and thus forms the heart of the drive.
This transformation from linear work to rotating power shows how essential the crankshaft is for efficiency and smooth running. Bharat Forge CDP optimizes this process through precise manufacturing and the use of special materials to ensure stable and low-vibration cranking even at high speeds.
Conclusion on the crankshaft in the car
The crankshaft is far more than just a shaft in the combustion engine. It performs the central task of converting the linear movement of the pistons into a smooth rotary motion, thereby creating the basis for the entire power transmission in the car engine. The design, choice of material and precise production are decisive factors in the performance, smooth running and service life of the engine.
Whether for energy conversion, synchronization with the camshaft or stabilization through flywheel mass – the crankshaft is the irreplaceable heart of modern engine technology. Especially at a time when the focus is on efficiency and resilience, its quality remains a decisive factor for the success of every vehicle.
With the developments from Bharat Forge CDP, automobile manufacturers benefit from decades of experience, state-of-the-art production and the highest level of material expertise. You can find out more about the specific crankshafts for passenger cars and our product portfolio on our precision forged parts page.
FAQ about the crankshaft
What does a crankshaft do in a car?
The crankshaft converts the upward and downward movement of the pistons into a smooth rotary motion. It transmits the torque to the clutch and gearbox and ensures that the engine runs smoothly. It also drives auxiliary units such as the camshaft or oil pump via gears or chains.
What happens if the crankshaft breaks?
A defective crankshaft can cause serious engine damage. Typical signs are strong vibrations, knocking noises and loss of power. If the crankshaft breaks, the engine usually fails completely, as pistons, connecting rods and bearings are directly affected.
How much does it cost to change a crankshaft?
The cost of replacing a crankshaft varies considerably depending on the type of vehicle and the amount of work involved. In addition to the new crankshaft, bearings, seals and sometimes the flywheel also need to be replaced. Overall, the costs can amount to several thousand euros, which is why repairs should only be carried out by specialist companies.
What is the difference between a camshaft and a crankshaft?
The crankshaft converts the piston movement into torque and drives the entire drivetrain. The camshaft, on the other hand, controls the valves and determines when the intake and exhaust valves open and close. Both components are precisely connected to each other via a timing chain or toothed belt so that the combustion process is synchronized.