Page 14 The Lever and Elbow Linkage

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The Stirling engine is rather too tall for a boat.

The pumped beta diagram is something like 5
times taller than it is wide.

Boats need a low profile, low centre of gravity engine.

The lever elbow linkage shortens the engine by “bending” the con rods through 90

The displacer
rod is connected to the end of a lever. This means that the big end of the
con rod traces out an arc. The longer the lever, which is near horizontal, the gentler the arc. This reduces side forces and friction.

The centre of an “elbow” is pivoted at the mid point of the lever.
One end of the elbow is fixed
to the pin on the crank disc.

The piston con rod is connected to the other end of the elbow.

When the piston is pushed by the gas, the con rod swings the elbow and, in turn,
this pushes on the crank disc pin and turns the shaft.

This is horrendous to describe.

Have a look at an animation opposite.

Why bother with this linkage?

It shortens the height of the engine whilst preserving near straight line motion of the con rods.

There are absolutely perfectly straight line linkages. (No side forces)
Roelf Meijers 1960’s rhombic drive is rightly world famous.
But it keeps the engine tall. (And takes some skill to make)

The lever elbow linkage is just levers – much simpler.