The Steam Engine Indicator

| January/February 1980

Case showing reducing motion

Indicator on 9 x 10 Case showing reducing motion or sometimes called ''detente.''

106 South Elm Street, Newkirk, Oklahoma 74647

During the early part of the 20th Century, the piston steam engine was in almost universal use driving the machinery in factories and the generators in electric light plants; Corliss engines in the larger, 'Automatics' in the smaller plants.

The operating engineers who attended the engines were generally required to hold an operator's license. To obtain it he would need to have at least an elementary knowledge of a device called the steam engine indicator.

The indicator is not a very complicated instrument. James Watt invented it. It is just about impossible to set the valves on a Corliss engine without an indicator and it is a great help in getting the valve on an 'automatic' especially a piston valve.

The indicator shows the engineer how the steam is acting in the cylinder: the 'valve events'; admission; cut-off; and release on the power stroke and back pressure and compression on the return. Any mis adjustment of the valve gear and leakage will show. In fact, the indicator card shows the engineer the same things that a cardiogram shows your doctor. The horsepower being developed can be calculated.

An indicator is especially needed in adjusting the reversing gears on traction engines and locomotives. The builders of traction engines needed them very badly but some surely didn't use them.