Abstract: This disclosure concerns machines that convert rotating motion to reciprocation, and vice-versa, and more particularly, but not exclusively, to reciprocating piston machines. Some embodiments include a crankshaft defining a crankshaft-drive and at least one radially extending piston-journal spaced from the crankshaft-drive, and a piston configured to pivotally engage the piston-journal. The piston defines a cylindrical head and an elongate body. Some embodiments further include a drive-member defining a central-axis-of-rotation and being rotatably engageable with the crankshaft-drive. Some embodiments also include a block defining one or more cylinders for receiving one or more pistons. The drive-member rotates when the piston reciprocates, and vice-versa.