A steam brake is a type of brake for steam locomotives and their tenders, whereby a steam

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infin ...

works directly on the brake linkages. Steam brakes were primarily used on

railways Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...

where vacuum brakes were used to brake the train, but where there was no vacuum brake on the steam locomotive itself, as for example in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...

, or where there was only a cable-operated brake (e.g. a

Heberlein brake A Heberlein brake is a continuous railway brake used in Germany that is applied by means of a mechanical cable. Train braking is therefore initiated centrally from the locomotive using a winder. This causes the brake clips to be applied on individu ...

) running along the train, like for example in

Saxony Saxony (german: Sachsen ; Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a landlocked state of ...

on the

narrow gauge A narrow-gauge railway (narrow-gauge railroad in the US) is a railway with a track gauge narrower than standard . Most narrow-gauge railways are between and . Since narrow-gauge railways are usually built with tighter curves, smaller structu ...

railways. Steam brakes are usually found today on heritage steam locomotives.

Operation

Steam is supplied to the steam brake cylinders from the locomotive

boiler A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, centr ...

via a valve (the brake valve) which may have several fixed settings or be infinitely variable. The piston in the steam cylinder is set in motion by the steam admitted, the

piston rod In a piston engine, a piston rod joins a piston to the crosshead and thus to the connecting rod that drives the crankshaft or (for steam locomotives) the driving wheels. Internal combustion engines, and in particular all current automobile engin ...

transfers the brake force via a system of rods to the

brake block A brake shoe is the part of a braking system which carries the brake lining in the drum brakes used on automobiles, or the brake block in train brakes and bicycle brakes. A device that is put on a track to slow down railroad cars is also called b ...

s of the vehicle, thus achieving the braking effect. A return spring returns the piston to its rest position as soon as the steam supply is interrupted. The expanded and condensed steam is drained from the steam cylinder through a drain valve (''Entwässerungsventil'').

Direct steam brake

A steam brake acts directly and immediately; the sudden opening of the brake valve can easily result in overbraking by locking the wheels. The operation of a steam brake therefore requires a great deal of experience from the

engine driver A train driver, engine driver, engineman or locomotive driver, commonly known as an engineer or railroad engineer in the United States and Canada, and also as a locomotive handler, locomotive operator, train operator, or motorman, is a pers ...

Vacuum controlled steam brake

A steam brake can be operated directly by a lever (valve) and also indirectly together with the vacuum brake. In the latter case, a control valve linked to the vacuum system controls the admission of steam to the brake cylinder, so that the steam brake can be activated automatically in an emergency or if the train separates (the so-called 'automatic steam brake').

Literature

* Hodgson, Lake: ''Locomotive Management (9th Edition, 1948)''. The St Margaret's Technical Press Ltd {{Railway brakes Railway brakes Steam locomotive technologies