1,038,136. Fluid pressure engines and motors. J. HANDLEY. July 18, 1963 [June 15, 1962], No. 23239/62. Headings F1M and F1P. In a piston engine comprising a cylinder and inlet and outlet ports for the entry and exhaust of operational fluid, an outlet port which communicates with the cylinder is provided with a valve which is directly responsive to cylinder pressure and which is arranged to adjust the cross-sectional area of the port in response to changes in fluid pressure in the cylinder volume. After the piston 7 has passed the sealing ring all fluid retained in the cylinder end must pass through the hole 11 in the damping piston 12. Pressure increases in the cylinder end 10 and this pressure forces piston 12 to more towards the tapered needle 15 further restricting the exhaust. The damping valve could alternatively be arranged to open in response to increased pressure in the cylinder. The device may be of gaseous pressure operated or liquid pressure operated type. Several engines of various lengths may be connected in tandem the piston rod of one to the cylinder of the next and may be mounted so that both pistons and cylinders can be moved in different directions.