Mobile sandblasting apparatus

In a mobile, self-propelled machine apparatus for automatically progressively sandblasting over a surface comprising a platform, a swinging boom arm having a head at the end thereof supporting a sandblasting nozzle, the arm mounted on the platform for swinging movement about an axis through an arc in a plane between start and finish positions, swinging boom arm control and actuation means to drive the arm from start to finish position and return it from finish to start position, wheel means supporting the platform for movement along a supporting surface, and means to drive the wheel means a predetermined distance coordinated with the movement of the swinging boom arm, the improvement characterized by the swinging boom arm being mounted on a drive wheel driven by first pneumatic cylinder means for movement about the axis of pivoting of the arm, second pneumatic cylinder means associated with the means to drive the wheel means so that when the second pneumatic cylinder means is actuated, it rotates the wheel means a predetermined amount and thereby causes the platform to move a predetermined distance on the supporting surface, and pneumatic control means associated with the first and second pneumatic cylinder means so that the movement of the swinging boom arm is synchronized as desired with the rotation of the wheel means.