// Disable the spring on all HingeJoints 
// in this game object and all its child game objects
var hingeJoints : HingeJoint[];
hingeJoints = gameObject.GetComponentsInChildren(HingeJoint);
for (var joint : HingeJoint in hingeJoints) {
    joint.useSpring = false;
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public HingeJoint[] hingeJoints;
    void Example() {
        hingeJoints = gameObject.GetComponentsInChildren<HingeJoint>();
        foreach (HingeJoint joint in hingeJoints) {
            joint.useSpring = false;
        }
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public hingeJoints as (HingeJoint)

    def Example():
        hingeJoints = gameObject.GetComponentsInChildren[of HingeJoint]()
        for joint as HingeJoint in hingeJoints:
            joint.useSpring = false