Steam Engine Specifications/Work Diagrams

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Design 5

50 PSI Boiler Pressure

Cutoff: 1/4
Bore: 4"
Stroke: 4"
Boiler Pressure: 50psi

Doing such diagrams is quite informative. Note that the expansion curve falls off below atmospheric pressure near the end of the stroke. Naturally, pressure in the cylinder cannot fall below atmospheric pressure, but it could fall to meet it. This is actually not desired. Some amount of back pressure in the cylinder softens the ends of the stroke cycle. This diagram also indicates how long the bump valve pins need to be in order to reach cutoff at 1/4 of the stroke length. Varying this will impact the amount of work produced in one cycle.

100 PSI Boiler Pressure

Cutoff: 1/4
Bore: 4"
Stroke: 4"
Boiler Pressure: 100psi

A more complete work diagram with an operating boiling pressure of 100 psi.