Abstract: An engine is described having pistons and cylinder arranged in mutually orthogonal pairs. Each pair is driven by a respective crank, with the pairs of cranks rotating about a primary crank which in turn rotates about an axis orthogonal to the axes of the pairs of pistons and cylinders. The throw of the respective cranks about the primary crank is the same as the throw of the primary crank about its axis. A counter-balancing weight is provided opposite to the primary crank. The resulting engine is balanced and lateral forces on the cylinder wall are reduced allowing the use of ceramic materials for the cylinders.