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The rhombic drive is a specific method of transferring mechanical energy, or
In its simplest form, the drive utilizes a jointed rhomboid to convert linear work from a reciprocating
Mechanical Drives for Stirling Engines
Dr. Siegfried "Zig" Herzog, Assistant Professor of Mechanical Engineering, Penn State University at Mont Alto. 06/01/05 Accessed August 2007
{{Piston engine configurations, state=uncollapsed Piston engines Engine technology Linkages (mechanical)
work
Work may refer to:
* Work (human activity), intentional activity people perform to support themselves, others, or the community
** Manual labour, physical work done by humans
** House work, housework, or homemaking
** Working animal, an animal t ...
, used when a single cylinder is used for two separately oscillating pistons.
History
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 engine
A Stirling engine is a heat engine that is operated by the cyclic compression and expansion of air or other gas (the ''working fluid'') between different temperatures, resulting in a net conversion of heat energy to mechanical work.
More specif ...
s; the drive's complexity and tight tolerances, causing a high cost of manufacture, is a hurdle for the widespread usage of this drive.
Operation
In its simplest form, the drive utilizes a jointed rhomboid to convert linear work from a reciprocating piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-t ...
to rotational work. The connecting rod
A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the crank ...
of the piston is rigid as opposed to a common reciprocating engine which directly connects the piston to the crankshaft
A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecti ...
with a flexible joint in the piston. Instead, the rod connects to one corner of a rhombus
In plane Euclidean geometry, a rhombus (plural rhombi or rhombuses) is a quadrilateral whose four sides all have the same length. Another name is equilateral quadrilateral, since equilateral means that all of its sides are equal in length. The ...
. When force is applied to the piston, it pushes down; at the same time, the outer corners of the rhomboid push out. They push on two cranks/flywheels which cause them to rotate, each in opposite directions. 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
In a reciprocating engine, the dead centre is the position of a piston in which it is either farthest from, or nearest to, the crankshaft. The former is known as Top Dead Centre (TDC) while the latter is known as Bottom Dead Centre (BDC).
...
to being flattened in the perpendicular direction to the piston axis at bottom dead centre
In a reciprocating engine, the dead centre is the position of a piston in which it is either farthest from, or nearest to, the crankshaft. The former is known as Top Dead Centre (TDC) while the latter is known as Bottom Dead Centre (BDC).
...
.
In the pictured example the left crank/flywheel turns clockwise and the right crank/flywheel anticlockwise. They turn at the same angular velocity and this can be reinforced by intermeshing them as gear wheels.
References
Mechanical Drives for Stirling Engines
Dr. Siegfried "Zig" Herzog, Assistant Professor of Mechanical Engineering, Penn State University at Mont Alto. 06/01/05 Accessed August 2007
See also
{{Piston engine configurations, state=uncollapsed Piston engines Engine technology Linkages (mechanical)