Abstract: A piston and cylinder machine for use as a prime mover, pump or compressor in which there are at least two pairs of pistons and cylinders for each crankpin, the cylinders of each pair being disposed on opposite sides of the crankpin and rigidly connected to each other by a yoke. For each cylinder pair, there is rotatably and eccentrically mounted on the crankpin a disc rotatably received in a respective yoke and whose eccentricity relative to the crankpin is equal to that of the crankpin relative to the crankshaft whereby the piston stroke is twice the crankpin throw. The discs are integral with each other within their superimposed peripheries so that a short, stiff crankpin may be used, and they are out of phase by twice the angular separation of the pairs of cylinders.