Crankshaft

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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

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

Crank mechanism

1 Pistons
2 Connecting rods
3 Fly wheel
4 Crankshaft

Product range

Forged crankshafts for:

  • Truck engines
  • Industrial engines
  • Gas engines
  • Engines for agricultural and forestry machines

Crankshaft accessories:

  • Toothed wheels
  • Bearing rings
  • Counterweight bolts