"Spring Joint is a Macro Script for applying and managing a script controller and a set of custom attributes to simulate procedural torsional spring motion. You can apply Spring Joint to any object that has a position/rotation/scale transform controller and unconstrained rotation.
You can think of Spring Joint as a spring - or rubber joint between an object and its parent - which only affects the objectâ€™s rotation.
Features include uniformly or non-uniformly limited Spring Joint motion - support for common forces - and speed increase through run-up - caching - and converting to keyframes. Most of the Spring Joint Attributes are animatable.
1.10 Update: now uses cache automatically if it exists - so it is easier and faster to work with.
View the Spring Joint Online Documentation"