A steam whistle is a device used to produce sound in the form of a whistle using pressurized steam, which creates, projects, and amplifies its sound by acting as a vibrating system.
Operation
The whistle consists of the following main parts, as seen on the drawing: the whistle bell (1), the steam orifice or aperture (2), and the valve (9). When the lever (10) is actuated (usually via a pull cord), the valve opens and lets the steam escape through the orifice. The steam will alternately compress and rarefy in the bell, creating the sound. The pitch, or tone, is dependent on the length of the bell and how far the operator has opened the valve. Some locomotive engineers invented their own distinctive style of whistling.
Uses of steam whistles Steam whistles are often used on buildings such as factories, universities, and similar places to signal the start or end of a work shift, etc. Steam railway locomotives, traction engines, and steam ships have traditionally been fitted with a steam whistle for warning and communication purposes. Large diameter, low-pitched steam whistles were used on light houses, likely beginning in the 1850s. The earliest use of steam whistles was as boiler low-water alarms in the 18th century and early 19th century. During the 1830s, whistles were adopted by railroads and steamship companies.
Gallery
Railway whistles
Steam warning devices have been used on trains since 1833, when George Stephenson invented and patented a steam trumpet for use on the Leicester and Swannington Railway. Period literature makes a distinction between a steam trumpet and a steam whistle. A copy of the trumpet drawing signed May 1833 shows a device about eighteen inches high with an ever-widening trumpet shape with a six-inch diameter at its top or mouth. It is said that George Stephenson invented his trumpet after an accident on the Leicester and Swannington Railway where a train hit either a cart, or a herd of cows, on a level crossing and there were calls for a better way of giving a warning. Although no-one was injured, the accident was deemed serious enough to warrant Stephenson's personal intervention. One account states that [driver] Weatherburn had 'mouthblown his horn' at the crossing in an attempt to prevent the accident, but that no attention had been paid to this audible warning, perhaps because it had not been heard. Stephenson subsequently called a meeting of directors and accepted the suggestion of the company manager, Ashlin Bagster, that a horn or whistle which could be activated by steam should be constructed and fixed to the locomotives. Stephenson later visited a musical instrument maker on Duke Street in Leicester, who on Stephenson's instructions constructed a 'Steam Trumpet' which was tried out in the presence of the board of Directors ten days later. Stephenson mounted the trumpet on the top of the boiler's steam dome, which delivers dry steam to the cylinders. The company went on to mount the device on its other locomotives Locomotive steam trumpets were soon replaced by steam whistles. Air whistles were used on some diesel and electric locomotives, but these mostly employ air horns.
Music An array of steam whistles arranged to play music is referred to as a calliope. In York, Pennsylvania, a variable pitch steam whistle at the New York Wire Company has been played annually on Christmas Eve since 1925 (except in 1986 and 2005) in what has come to be known as "York's Annual Steam Whistle Christmas Concert". On windy nights, area residents report hearing the concert as far as 12 to 15 miles away. The whistle, which is in the Guinness Book of World Records, was powered by an air compressor during the 2010 concert due to the costs of maintaining and running the boiler.
Lighthouse fog signals
Beginning in 1869, steam whistles began being installed at lighthouse stations as a way of warning mariners in periods of fog, when the lighthouse is not visible. 10" diameter whistles were used as fog signals throughout the United States for many years, until they were later replaced by other compressed air diaphragm or diaphone horns.
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