In the video above, the character has a Furnace attached to their back that was not animated with the character's movement (initially shown without the Spring Controller connected).
We then connect the nodes to include the Spring Controller that is targeting the Furnace Bone and adjust the Spring Stiffness and Spring Damping settings to generate the movement.
Name of the bone to apply the spring solver to.
If enabled, the spring solver is applied.
The maximum distance the bone can stretch.
A multiplier for the amount of force applied by the spring. Larger values require more bone velocity to displace the bone and result in a larger applied force.
The amount of the bone's velocity removed by the spring.
Error Reset Thresh
A threshold displacement - if the spring stretches more than this amount, it resets in order to avoid errors introduced by sudden, large displacements such as those caused by teleporting Actors.
If enabled, the displacement in the Z axis is ignored by the spring and is always correct.
Spring Controller nodes are also affected by the LOD Threshold system introduced in 4.11. You can find the setting for this in the Details Panel for the Spring Controller node.