Problem with mount turret on vehicle

function Hummer::onAdd(%this,%obj)
{   
   $HummerCount ++;

   for (%i = %obj.getWheelCount() - 1; %i >= 0; %i--) {
      %obj.setWheelTire(%i,HummerTire);
      %obj.setWheelSpring(%i,DefaultSpring);
      %obj.setWheelPowered(%i,false);
   }

   // mount turret
   %turret = new Turret()
    {
       dataBlock = GenericTurret;
    };
    // mount turret at whatever mount point
    %obj.mountObject(%turret,1);	

   %obj.mountedTurret = %turret;
   
   // Steer front tires
   %obj.setWheelSteering(0,1);

   // Only power the two rear wheels...
   %obj.setWheelPowered(0,true);
   %obj.setWheelPowered(1,true);

   %obj.mountable = true;
   %obj.setEnergyLevel(%this.MaxEnergy);
   %obj.setRechargeRate(%this.rechargeRate);
   %obj.playThread(0,"ambient");
}