Manual Modules Dynamics Rigid Bodies Rigid Body Spring Tag
Elastic Tab
Rest Length
The Rest Length defines the normal length of the spring, that is the length at which the spring will exert no force. In the diagram below, the top spring is at its rest length and hence it is exerting no force on the objects.
If you were to attach two objects using a spring whose Rest Length value is less than the distance between the two objects, the spring will be stretched because of this and it will exert a force on the two bodies that will attempt to pull them towards the rest length. Conversely, if the Rest Length value is greater than the distance between the two attached objects, the spring will be compressed because of this and will exert a force on the two objects that attempts to push them away from one another and towards the rest length.
The Rest Length is decisive in determining whether the spring will push, pull or exert no force on its attached objects.
Limit Force
In some cases, the force exerted by a spring can become too great for the solver object to process. Hence under Limit Force you can specify the maximum force that the spring will be allowed to exert.
Below
The following settings are useful if a spring is stretched beyond its rest length.
Lock
If enabled, this option will lock the Below values to be the same as the Above values.
Stiffness
These two input boxes define the stiffness of the spring for the Below and Above options. The higher the value, the greater the force that will be exerted by the spring when it is stretched or compressed. A stiff spring will be much harder to compress or stretch than a weak spring.
The Stiffness value of the spring is indicated in the viewport. The stiffer the spring, the greater its diameter. The Stiffness also affects the spring’s rate of oscillation, with a stiff spring tending to oscillate faster than a weak spring because of the greater force that it exerts on the objects it is attached to. The time taken for an oscillation in such a spring-mass system will also depend on the mass of the attached objects.
A spring’s Stiffness affects its diameter in the viewport
Damp
Like Stiffness, there are two input boxes. The left-hand input box defines the damping for the Below option; the right-hand input box defines damping for the Above option. All real springs will experience damping while oscillating due to resistance within their material. Without damping, a spring would oscillate endlessly. For realistic damping, set a value from 0.1 to 0.5.
Above
Different settings can be defined for compressed springs as for the stretched springs. To do this, deactivate the Lock option. Stiffness and Damping will function the same as before. The lock function can be used to hide the spring in this area.