Control rotation of a configurable joint

Hi everyone, I have been trying to control the rotation between two rigidbodies. I used for a long time hinge joints and their motors, but the results are not good enough. I want to be able to do the same with controllable joints but these seems really hard to master. Here's what I have been trying to do :

 private ConfigurableJoint conf;
 private float targetAngle;
 public float rotateSpeed;


 // Use this for initialization
 void Start () {
     conf = GetComponent<ConfigurableJoint>();
     targetAngle = 0;
     
 }
 
 // Update is called once per frame
 void Update () {
     
         targetAngle += Input.GetAxis("Horizontal") * Time.deltaTime * rotateSpeed;
         Quaternion targetRotation = Quaternion.AngleAxis(targetAngle, Vector3.right);
         conf.targetRotation = targetRotation;
     

 }

}

I applied this code to a basic cube with rigidbody linked to another cube with rb by a configurable joint. I set my axis to be around x axis and set every motion locked except the angular x one.

of course, this is not working :)

If everyone has the solution to control these configurable joints, I'd gladly take it. Thanks a lot