Abstract: The free piston vacuum producing apparatus is an internal combustion device with no piston rod or constraining mechanism attached to the free piston. After fuel ignition the piston is rapidly propelled toward the open end of a cylinder. As the combustion gases expand, the piston's momentum propels it past the point where the pressure is equal on both sides of the piston. A vacuum is created in the cylinder behind the piston. When the piston comes to a stop, the vacuum in the cylinder is secured. An air/gas/vapor entry port into the cylinder is then opened to allow outside air, gas, or vapors to enter the cylinder. The gases drawn into the cylinder's vacuum pass through a device, such as a turbine, in order to produce work or energy from the flowing gases. The cylinder's vacuum can thus be used as the basis for vacuum pumps, evaporators, or gas evacuation device.

Abstract: A lightweight backstop, equipment set, method of defining a playing field and method of playing a baseball related game is provided. The invention integrates a ball stopping backstop, attached strike zone, foul line ropes and base hit markers with methods and means for defining and marking a playing field scaled to the size and number of players. A separate strike zone is attached to the backstop by means allowing the players to quickly change the vertical position of the strike zone and acoustical responses generated by balls hitting the strike zone. Players may also adjust the sound generated by balls missing the strike zone, but striking the backstop net. One embodiment of the disclosed game eliminates base running and ball throwing near batters after the ball has been struck. The entire equipment set is light weight, easy to move, and simple to assemble.