Dual Mass Flywheel

Dual-Mass Flywheel (DMF) — Operating Principles

Jump to:
1. Overview
2. How It Works – Step by Step
3. Key Components Involved
4. Common Misconceptions
5. Why This Matters

Anchor 1

Plain-English summary: what the system does

A dual-mass flywheel (DMF) is a drivetrain component designed to reduce torsional vibrations generated by the engine before they reach the clutch and transmission. It achieves this by splitting the flywheel into two independently rotating masses connected by a damping system. By smoothing torque fluctuations, the DMF improves driveline refinement, reduces noise and vibration, and protects transmission components from excessive cyclic loading.

How it Works - Step by Step

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Torque generation at the engine
Internal combustion engines deliver torque in pulses rather than as a perfectly smooth output. These pulses are more pronounced in high-torque, low-speed engines.
Primary mass rotation
The primary mass of the dual-mass flywheel is bolted directly to the engine crankshaft and rotates with it, receiving the raw torque output.
Torsional damping
The primary and secondary masses are connected by a system of arc springs and friction elements. As torque pulses occur, the springs compress and extend, absorbing rotational irregularities.
Relative movement between masses
A bearing between the two masses allows controlled angular movement. This decoupling prevents sudden torque changes from being transmitted directly downstream.
Torque transfer to the drivetrain
Smoothed torque is delivered from the secondary mass to the clutch assembly and then into the transmission input shaft.
Continuous vibration control
During normal operation, the damping system repeatedly absorbs and releases energy, reducing drivetrain vibration across a wide range of engine speeds and loads.

Key Components Involved

Anchor 3

Primary mass
Attached to the crankshaft and exposed directly to engine torque pulses.
Secondary mass
Provides the friction surface for the clutch and delivers smoothed torque to the transmission.
Arc spring damper system
A set of curved compression springs that absorb and moderate torsional vibrations.
Centre flange and spring carrier
Transfers torque between the two masses through the spring system.
Internal bearing
Allows controlled relative rotation between the primary and secondary masses.
Friction and damping elements
Provide additional energy dissipation and stabilise spring motion.

Common Misconceptions

Anchor 4

“A dual-mass flywheel increases engine power”
A DMF does not alter engine output; it only smooths torque delivery.
“It replaces the clutch damper springs”
A DMF complements clutch damping and often allows simpler clutch disc designs.
“Dual-mass flywheels are only for diesel engines”
While common in diesels, DMFs are also used in petrol engines with high torque output.
“The flywheel eliminates vibration completely”
The DMF reduces torsional vibration but does not remove all engine-generated irregularities.

Why This Matters

Anchor 5

Modern engines produce high torque at low engine speeds, increasing torsional stress on the drivetrain. Without effective damping, these stresses can lead to noise, harshness, reduced comfort, and accelerated wear of transmission components. The dual-mass flywheel plays a critical role in maintaining driveline durability, refinement, and predictable clutch operation.

Quick Reference

Primary function: Torsional vibration damping
Operating principle: Spring-based rotational decoupling
Location: Between crankshaft and clutch
Key benefit: Reduced vibration and drivetrain stress