Crankshafts

Crankshafts in Focus Setup Constituents Versions Crank mechanism Product range Catalog Download

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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

Setup

1 Control side or drive end

2 Counterweights

3 Main bearing journal

4 Conrod journal

5 Flywheel side/force transfer

6 Oil bore

Constituents

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.

Conrod journal

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.

Flywheel side

Support for the flywheel side

Control side or drive end

Support for the vibration damper/pulley.
Camshaft drive gear

Oil bores

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.

Crankshaft counterweights

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.

Hardening zones

In order to reduce wear and increase the resilience of the crankshaft, main and conrod journals are hardened and polished.

Versions

Forged counterweights
• e. g. OM 611 4-cylinder in-line engine

Bolted-on counterweights
• e. g. OM 335 6-cylinder in-line engine

Crankshaft, Offset connecting rod journals

Offset connecting rod journals
• e.g. OM 501 6-cylinder V engine

Crankshaft, Twisted connecting rod journals

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