Rhombic drive
The rhombic drive is a specific method of transferring mechanical energy, or work, used when a single cylinder is used for two separately oscillating pistons.
It was originally developed around 1900 for the twin-cylinder Lanchester car engine where it allowed perfect balancing of the inertial forces on both pistons.
A current example of its use is on beta type-Stirling engines; the drive's complexity and tight tolerances, causing a high cost of manufacture, is a hurdle for the widespread usage of this drive.
As the wheels rotate the rhombus progresses its change of shape from being flattened in the direction of the piston axis at top dead centre to being flattened in the perpendicular direction to the piston axis at bottom dead centre.
They turn at the same angular velocity and this can be reinforced by intermeshing them as gear wheels.
1 (Pink) - Hot cylinder wall, 2 (Dark grey) - Cold cylinder wall (with coolant inlet and outlet pipes marked 3 in Yellow), 4 (Dark Green) - Thermal insulation separating the two cylinder ends, 5 (Light Green) - Displacer piston, 6 (Dark Blue) - Power piston, 7 (Light Blue) - Flywheels,
Not Shown: external heat-source, and external heat-sinks. In this design the Displacer piston is used without a regenerator.
