Abstract: A pneumatic system includes a pneumatic motor, which may take the form of a vibrationless paving breaker utilizing a blow-striking member or hammer that is propelled to and from its force-transmitting or blow-striking position by a compressed gas. A valving arrangement provides for relatively large-ratio expansion of the compressed gas in the space under the hammer between its infeed thereinto and its exhaustion therefrom, in order to significantly utilize heat energy in the compressed gas to assist in energizing the propulsion of the hammer. Such heat energy is usually invested in the compressed gas by and during substantially adiabatic compression thereof at a gas-volume transformer, or compressor, included in the pneumatic system. It may be noted that the process of substantially adiabatic compression in the compressor is to a significant degree reversely duplicated in energizing the propulsion of the hammer.