Refer to a parent Rigidbody

Hey

I would like to make a simple reference to my parent gameobject which has a Rigidbody. All time I would like to hadle with it I suck. Does not rly work at all. I hope you can help me there.

 using System.Collections;
 public class TankMoveBehaviour : MonoBehaviour {
     public Rigidbody daVoda;
     public string daVodaX;
     public Vector3 eulerAngleVelocity = new Vector3(0, 100, 0);
     public bool check = false;
     public bool forward = false;
     public bool backward = false;
     public bool rotateleft = false;
     public bool rotateright = false;
     // Use this for initialization
     void Start () {
     
         daVoda = null;
         //daVodaX = this.gameObject.transform.parent.name.ToString();
     }
     
     // Update is called once per frame
     void Update () {
         //daVodaX = this.gameObject.transform.parent.name.ToString();
         //Debug.Log(this.gameObject.transform.parent.name.ToString());
         if(check == true)
         {
             {
         daVoda = this.gameObject.transform.parent.rigidbody;
                 Debug.Log(daVoda.ToString());
         }
         if(Input.GetKeyDown(KeyCode.F))
         {
             forward = true;
         }
         else
         {
             forward = false;
         }
         if(Input.GetKeyDown(KeyCode.C))
         {
             backward = true;
         }
         else
         {
             backward = false;
         }
         if(Input.GetKeyDown(KeyCode.X))
         {
             rotateleft = true;
         }
         else
         {
             rotateleft = false;
         }
         if(Input.GetKeyDown(KeyCode.V))
         {
             rotateright = true;
         }
         else
         {
             rotateright = false;
         }
         if(forward == true)
         {
             daVoda.AddForce(transform.forward * 200);
         }
         if(backward == true)
         {
             daVoda.AddForce(-transform.forward * 200);
         }
         if(rotateleft == true)
         {
             Quaternion deltaRotatio = Quaternion.Euler(-eulerAngleVelocity * Time.deltaTime);
             daVoda.MoveRotation(rigidbody.rotation * deltaRotatio);
         }
         if(rotateright == true)
         {
             Quaternion deltaRotatio = Quaternion.Euler(-eulerAngleVelocity * Time.deltaTime);
             daVoda.MoveRotation(rigidbody.rotation * deltaRotatio);
         }
         }
     
     }
 }

That's all. I don't know why nothing happens....

Thank's for each answer ;)