Rattleback

DCS Code: 1M40.90 Last Updated: March 27, 2026
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Purpose

A rattleback is an asymmetric spinning object with a preferred spin direction. When spun the "wrong" way, it rocks violently and reverses direction. Demonstrates coupling between rotational modes and the role of external torque from friction.

Two rattlebacks on a gray surface: a black elongated boat-shaped rattleback (left) and a shorter red oval rattleback with an adjustable black vane secured by a silver screw (right)
Figure 1: Standard black rattleback (left) and adjustable red rattleback with movable vane (right). The vane's displacement from the long axis determines the preferred spin direction.