Engine Crankshaft
The heart of internal combustion engines; a monolithic power transmission component designed to examine the conversion of linear piston motion into rotary torque, hydrodynamic bearing, and dynamic balancing principles.
Visualizing complex assemblies in 3D reduces error rates during maintenance operations and accelerates the learning curve for new technicians.
Interactive 3D Model
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Use Case
This structure is used for automotive engineering training, engine rebuild procedures, hydrodynamic lubrication analysis, and torsional vibration simulations.
Linear to Rotary Conversion
Explains how the combustion force transmitted from the connecting rods is converted into a rotational moment (Torque) around the crank axis.
Hydrodynamic Lubrication
Demonstrates the bearing system where there is zero metal-to-metal contact, and the shaft floats on a thin film of pressurized oil (hydrodynamic wedge).
Dynamic Balance and Vibration
Highlights how the crank webs (counterweights) balance the reciprocating mass forces created by the pistons, preventing the engine from tearing itself apart.
Engine Crankshaft - Detailed Specifications
Below is the comprehensive engineering breakdown of each component within the assembly. This data includes standard material selections, ISO tolerances, surface finishes, and critical engineering notes required for manufacturing and assembly.
Main Journals
Axial Bearing Region
The primary support points where the crankshaft rests on the main bearings in the engine block and rotates around its own axis. Cross-drilled oil galleries for lubrication run through them.
These journals do not physically rub against the bearings; they "float" hydrodynamically on a micron-level film of pressurized engine oil supplied through cross-drilled galleries. Surface hardness of 58-62 HRC and Ra ≤ 0.15 µm roughness are essential to maintain the oil film. Any out-of-roundness exceeding 0.003 mm will tear the film and cause a spun bearing. Main journal diameters are held to IT5 tolerance.
Crankpins / Rod Journals
Force Transmission Region
The offset journals where the connecting rods from the pistons attach, positioned away from the main axis by the half-stroke distance. This is the first point of contact where the combustion force is transferred to the crankshaft.
Combustion force is transmitted to the crankshaft through this journal. Its distance from the main axis (offset = stroke / 2) determines the total stroke volume of the engine. Cross-drilled oil galleries run from the main journals to the crankpins for lubrication. Angular phase error affects ignition timing; therefore a tolerance of ≤ ±0.25° is critical.
Crank Webs & Counterweights
Dynamic Balancing Region
The arms connecting the main journals to the crankpins, and the heavy counterweights added opposite to the crankpins. They balance the massive centrifugal forces created by the reciprocating motion of pistons and connecting rods.
Without these counterweights, the engine would shake itself to pieces in seconds. On the production line, precision dynamic balancing is achieved by drilling small holes into the edges of these counterweights. Balance quality conforms to ISO 21940-11, typically G6.3 for passenger cars and G2.5 for racing engines.
Crank Nose / Snout
Accessory and Timing Drive Region
The front end of the crankshaft that protrudes from the engine block, transmitting power for the timing mechanism and accessories. Features a keyway slot or spline profile.
The timing gear (which drives the camshaft), the oil pump rotor, and the crank pulley (Harmonic Balancer) are typically mounted to this end. The explosions in the cylinders momentarily twist the shaft; the harmonic balancer absorbs these torsional vibrations to prevent fatigue failure of the crank nose. h6 fit tolerance and JS9 keyway standard are used for assembly.
Flywheel Flange
Main Torque Output Region
The rear mounting flange where all the mechanical power produced by the engine is transferred to the flywheel to be sent to the transmission. It also serves as the contact surface for the rear main seal.
The slightest warp or runout on this flange face (exceeding 0.015 mm), combined with the massive mass of the flywheel, causes clutch judder and damages the transmission input bearing. The mounting bolts are usually Torque-to-Yield (TTY) type, meaning they are single-use and must not be re-tightened. The rear seal contact surface is polished to Ra ≤ 0.2 µm to prevent oil leakage.