A pneumatic motor for rotating an axle including: a. a housing including: b. an air intake port; c. an air exhaust port; d. at least two cylinders; each cylinder being positioned radially from the axle; e. at least two air channels in communication with each cylinder; f. at least two pistons, each piston attached to the axle by a connecting rod, each piston and respective connecting rod being radially aligned, each piston to be received in one of said at least two cylinders; each connecting rod being attached centrally offset in relation to a central axis of the axle; wherein when one connecting rod and piston are in power stroke, the other connecting rod and piston are in exhaust stroke.

The invention provides a fluid working machine comprising: a cylinder block (1) having an axial bore (4); a crankshaft (2) which extends within the axial bore (4) and is rotatable about an axis of rotation (3); and first and second valve cylinder devices (13) provided in the cylinder block (1) arranged about and extending outwards with respect to the axial bore (4), the first and second valve cylinder devices (13) being axially offset from each other, the first and second valve cylinder devices (13) being offset from each other about the axis of rotation (3), and the first valve cylinder device having an axial extent which overlaps the axial extent of the second valve cylinder device, wherein the first and second valve cylinder devices (13) comprise first valves (14) having respective first working fluid ports (48, 49), the said respective first working fluid ports (48, 49) of the first valves (14) of the first and second valve cylinder devices (13) being in fluid communication with each other via a common conduit (50, 52) extending within the cylinder block (1).

The invention provides a fluid working machine comprising: a crankshaft (2) which is rotatable about an axis of rotation (3); adjacent first and second groups (5, 6, 8, 10) of valve cylinder devices (13) spaced from each other about the axis of rotation (3), one or each of the first and second groups (5, 6, 8, 10) of valve cylinder devices having first, second and third valve cylinder devices (13) arranged about and extending outwards with respect to the crankshaft (2), the first and third valve cylinder devices being axially offset from each other, the second valve cylinder device being axially offset from the first and third valve cylinder devices and the second valve cylinder device being offset from the first and third valve cylinder devices about the axis of rotation, wherein the second valve cylinder device has an axial extent which overlaps with the axial extent of one, or the axial extents of both, of the first and third valve cylinder devices.

A piston unit includes a piston which has a rolling element seat configured to rotatably support a rolling element. The rolling element seat has a bearing surface with a surface coating composed of a polymer compound or with a ceramic surface coating.

A pneumatic motor for rotating an axle including: a. a housing including: b. an air intake port; c. an air exhaust port; d. at least two cylinders; each cylinder being positioned radially from the axle; e. at least two air channels in communication with each cylinder; f. at least two pistons, each piston attached to the axle by a connecting rod, each piston and respective connecting rod being radially aligned, each piston to be received in one of said at least two cylinders; each connecting rod being attached centrally offset in relation to a central axis of the axle; wherein when one connecting rod and piston are in power stroke, the other connecting rod and piston are in exhaust stroke.