Engineers use the resulting diagram to check the design and performance of the engine. This is a replica of the original steam indicator invented in the late 18th Century by James Watt of Scotland.

The valve ellipse, together with the Zeuner, Reuleaux, and Bilgram valve diagrams are described, and some typical single-valve problems are worked out.

Steam engines. For most of us, they conjure images of horseless buggies, paddle ships and classic locomotives, but soon they may be setting new speed records and hitting new benchmarks for ...