NZFMM 1993 Auckland Convention page 4 of 17

Beam Engine by the late Lindsay Bond

A freelance model of a Cornish "pumping" or beam engine by Lindsay Bond.  The building that housed these engines formed the frame of the engine and supported the beam.  The power stroke was not produced by the expansion of the steam, as in normal steam engines, but the condensation caused by spraying water into the cylinder full of steam.  Thermodynamically therefore they were very inefficient and operated very slowly and with a characteristic hesitation before the condensation stroke - despite the flywheel it was noticeable.