A steam whistle is a device used to produce sound with the aid of live steam. Unlike a horn, the sounding mechanism of a whistle contains no moving parts (compare to train horn). 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 pulled, 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 also how far the operator has opened the valve. Some locomotive engineers invented their own style of whistling.
A train whistle or air whistle, (originally referred to as a steam trumpet), is an audible signaling device on a steam locomotive used to warn that the train is approaching, and to communicate with rail workers.
The older steam whistleswere almost always actuated with a pull cord (or sometimes a lever) that permitted proportional (tracker) action, so that some form of "expression" could be put into the sound. Many locomotive operators would have their own style of blowing the whistle, and it was often apparent who was operating the locomotive by the sound. Modern locomotives often make use of a pushbutton switch, which takes away the fine control over the way the whistle is sounded.
Because trains generally have extremely high mass and relatively low braking friction, they are inherently difficult to stop at normal speeds. Since train whistles were extremely inexpensive to institute compared to other more effective warning devices, the use of loud and distinct train whistles had become the preferred safety fallback for railroad operators.
Locomotives used bells and steam whistles from earliest days. In the United States, India and Canada bells warned of a train in motion. In Britain, where all lines are by law fenced throughout, bells were only a requirement on railways running on a road (i.e. not fenced off), for example a tramway along the side of the road or in a dockyard. Consequently only a minority of locomotives in the UK carried bells. Whistles are used to signal personnel and give warnings. Depending on the terrain the locomotive was being used in the whistle could be designed for long distance warning of impending arrival, or more for localised use.
Early bells and whistles were sounded through pull-string cords and levers. As the steam era approached the 1950s, automatic air-operated bells were made use of on locomotives such as the Challenger (steam locomotive) and Big Boy.
History:American steam locomotive whistles are legendary for their different sounds. They came in many forms, from tiny little single-note shriekers (Called Banshees on the old PRR) to larger plain whistles with deeper tones (a famous deep, plain train whistle is the "hooter" of the Norfolk & Western, used on their A and Y class Mallets). Even more well known were the wonderful multi-chime train whistles. Nathan of New York copied and improved Casey Jones's boiler-tube chime whistle by casting the six chambers into a single bell, with open "steps" on top to save on casting. This incredible whistle is still considered the "King of train whistles", and it's musical chord is wonderful to hear! This whistle is the most copied train whistle in the USA, and many railroad's shops cast their own version of it, the old Southern Pacific having one of the finest copies. Another very popular American train whistle, was again, a Nathan product. This was a five-note whistle, with much shorter bell, and therefore, much higher in pitch. This whistle sang a bright G-major 6th chord (GBDEG) and again, was heavily imitated, copies being made by many different railroads. Even the Chinese copied American five-chime whistles for their own locomotives. The final most popular American chime train whistle was the three-note version. These were either commercially made (Crosby, Lunkenheimer, Star Brass, Hancock Inspirator CO. among others) or shop-made by the railroads, themselves. Some famous and very melodious shop-made train whistles were Pennsy's passenger chimes and the old B&O's step-top three chimes. But the most beloved of all three-chime train whistles to the public and railroaders alike were the deep-chorded "steamboat minor" long-bell's. A well know commerially made chime was Hancock Inspirator Company's three note step top. These found use on almost every American railroad, and their deep, melodic sound is legend. Some railroads copied these also, examples being found on the old Frisco and Illinois Central. Perhaps the most famous of the three-chime train whistles were those home-made ones on the old Southern Railway. These were all distinctive as having top-mounted levers. They had sweet sounding short-bell three-chimes as well as their (highly copied) long-bell three-chimes of passenger engine fame, especially their PS4 engines, one of which resides today in the Smithsonian Institution. Two-note and four-note train whistles never caught on with North American railroads with one exception: Canadian National Railway created a large four-chime step top whistle for limited use on some of their locomotives. These were not common and only a few survive today in the hands of collectors. Otherwise American train whistles were in single-note, three-note, five-note and six-note combinations.
A few very well known American railroads, famous for their whistles: Southern Pacific for their wonderful six-chimes. Union Pacific for their Hancock "steamboat" chimes. Reading Railroad for their unusual high-pitched passenger six-chimes. CB&Q RR for their melodious five-chimes, and very unusual three-chimes. B&O RR for their wonderful three-chime steptops and very different sounding six-chimes. Grand Trunk for their pretty shop-made six-chimes (Nathan copies). New York Central for their wonderful shop-made six-chimes.
What the whistle of the train stands for
- One short: Stop or stopping; apply the brakes