The spring attempts to reach a target angle by adding spring and damping forces.

The /spring.spring/ force attempts to reach the target angle. A larger value makes the spring reach the target position faster.

The /spring.damper/ force dampens the angular velocity. A larger value makes the spring reach the goal slower.

The spring reaches for the /spring.targetPosition/ angle in degrees relative to the rest angle. The rest angle between the bodies is always zero at the beginning of the simulation.

	// Make the spring reach shoot for a 70 degree angle.
	// This could be used to fire off a catapult.
	hingeJoint.spring.spring = 10;
	hingeJoint.spring.damper = 3;
	hingeJoint.spring.targetPosition = 70;

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Example() {
        hingeJoint.spring.spring = 10;
        hingeJoint.spring.damper = 3;
        hingeJoint.spring.targetPosition = 70;
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Example() as void:
		hingeJoint.spring.spring = 10
		hingeJoint.spring.damper = 3
		hingeJoint.spring.targetPosition = 70

Modifying the spring automatically enables it.