Multi-stage torsional damper

Torsional damper with multiple damping stages.

When clutches with permanent power take-off (PTO) are installed, there can often be misunderstandings because the springs on the torsional dampers are de-signed to lie loosely in the spring windows. Sebastian Motsch, who is in charge of technical documentation at ZF Services, explains why this is not a deficieny.

Oscillations and vibrations occurring in the powertrain and the assemblies driven by it (e.g. hydraulic pumps) cause noise and increase wear in the power-train’s components. In order to prevent resonance vibrations due to overlapping vibrations from the powertrain and an assembly that it drives, torsional dampers with multi-stage damping properties are used.

Spring window with spring.

Coil springs with different dimensions (length, material thickness, and number of coils) are installed in the torsional damper opposite each other in pairs. Due to their different dimensions, these springs show a corresponding degree of play in the spring window. The springs in the first stage fit snugly in the spring window; the springs for the next respective damping stages are somewhat shorter and thus have greater play. When the clutch is removed, the springs move in the spring window on the carrier disk, and can cause rattling noises due to the large degree of play. This is a constructional feature and not a deficieny. When the clutch is installed, the springs cannot rattle because they lie against one end of the spring window due to the rotational forces. Depending on the torsion angle between the torsional damper and the clutch disc, the pairs of springs successively handle the corresponding damping stages which yield the multi-stage damping effect.

This type of torsional dampers for PTO clutches ensures a high degree of noise and vibrational damping and high resilience at the same time.