hinge joint and spring not reacting to input

so the problem is, i added a spring to a object to make it act like a catapult and its scripted to turn with a input key, But its not working, the input is recognized, checked with debug.log, but the object not moving. also im new to unity, :)

 using UnityEngine;
 using System.Collections;
 
 
 public class Leftpaddle : MonoBehaviour {
     public float pressed ;
     public float unpressed ;
     public string leftpad;
 
     // Use this for initialization
     void Start() {
         HingeJoint hinge = GetComponent<HingeJoint>();
         JointSpring spring = hinge.spring;
         spring.spring = 1000;
         spring.damper = 10;
         hinge.useSpring = true;
     }
     void Update ()
     {
         HingeJoint hinge = GetComponent<HingeJoint> ();
         JointSpring springs = hinge.spring;
         hinge.useSpring = true;
         springs.spring = 1000;
         springs.damper = 10;
                 if (Input.GetButton (leftpad)) {
                         springs.targetPosition  = pressed;
                         Debug.Log (springs.targetPosition );
                 }
                 else {
                         springs.targetPosition = unpressed;
             Debug.Log (springs.targetPosition );
                 }
     }
 
 }