This triple expansion engine was built by the Herreshoff Manufacturing Company in Bristol, RI in 1904 as internal job number 3207B. It has three cylinders with bores of 12 1/2″, 18″, 25 and a 13 1/2″ stroke. It produces 385 HP at 300 RPM on superheated steam.
Originally designed during the Spanish-American war to power torpedo boats, it was one of four used to power low voltage DC generators at the Phelps Dodge Company copper refinery in Maspeth, Long Island, NY. It exhibits many ingenious techniques to reduce weight and size, for example, the split connecting rods and the side mounted valves. In the triple expansion engine thermal loss is reduced by expanding the steam in three stages from boiler pressure to condenser pressure. The total temperature drop is divided into three parts so that the temperature difference across any cylinder is one third that of a single cylinder engine. Heat loss is correspondingly reduced.
Donated in 1982 by the Phelps Dodge Company. The engine was rigged and delivered from Brooklyn to the museum by Dave Smith and Paul Merriam.