Crankshafts in Focus
- The crankshaft in the engine has the task of converting the up and down movement of the pistons into a rotary motion with the aid of the connecting rods. This torque is transmitted to the flywheel.
- Two types of crankshaft are produced, cast and forged, with integrated or bolted-on counterweights. The pistons, connecting rods and crankshaft together form the crank mechanism.
- To ensure high quality standards, most BF crankshafts are produced on own tools and are subject to stringent checks.
- Owing to the high levels of stress common in the utility vehicle sector, BF follows OE specifications and offers a range comprising almost entirely forged crankshafts.
- To preserve the durability of newly installed crankshafts, we recommended replacing the following parts at the same time:
- Main bearing shells
- Main bearing bolts
- Connecting rod bearing shells
- Connecting rod bearing bolts
- Gasket set
|1 Control side or drive end|
|3 Main bearing journal|
|4 Conrod journal|
|5 Flywheel side/force transfer|
|6 Oil bore|
Main bearing journal
- The number of main bearing journals is dependent on the engine version.
- The crankshaft is mounted on the main bearing journals in the engine block.
- The distance from the centre of the conrod journal to the centre of the main bearing journal defines the stroke (crank radius).
- The stroke, diameter and number of cylinders determine the displacement of the engine.
- Support for the flywheel side
Control side or drive end
- Support for the vibration damper/pulley.
- Camshaft drive gear
- The connecting rod and main bearing points are supplied with oil via the oil bores.
- The conrod journals are supplied with oil from the main bearing journal via an oil channel in the crankshaft.
- The weights of the pistons and connecting rods on one side are compensated for by counterweights on the crank webs. This compensates outer moments; minimises internal moments and thus reduces vibration amplitudes and bearing stresses.
- In order to reduce wear and increase the resilience of the crankshaft, main and conrod journals are hardened and polished.
• e. g. OM 611 4-cylinder in-line engine
• e. g. OM 335 6-cylinder in-line engine
Offset connecting rod journals
• e.g. OM 501 6-cylinder V engine
Twisted connecting rod journals
• To allow for other crankshaft angles at the connecting rod journals, the crankshaft is heated again after forging and twisted at the main bearing points.
• e. g. OM 906 6-cylinder in-line engine
Two connecting rods per connecting rod journal
• e.g. OM 422 8-cylinder V engine
|2 Connecting rods|
|3 Fly wheel|
Forged crankshafts for:
- Truck engines
- Industrial engines
- Gas engines
- Engines for agricultural and forestry machines
- Toothed wheels
- Bearing rings
- Counterweight bolts