A countersteam brake is a brake on a

steam locomotive A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, oil or, rarely, wood) to heat water in the locomot ...

that uses the engine (specifically the cylinders) to help brake the locomotive. It uses the working principle of steam cylinders fitted with

slide Slide or Slides may refer to: Places * Slide, California, former name of Fortuna, California Arts, entertainment, and media Music Albums * ''Slide'' (Lisa Germano album), 1998 * ''Slide'' (George Clanton album), 2018 *''Slide'', by Patrick Glees ...

piston valve A "piston valve" is a device used to control the motion of a fluid along a tube or pipe by means of the linear motion of a piston within a chamber or cylinder. Examples of piston valves are: * The valves used in many brass instruments * The va ...

s such that, by changing the configuration of the

valve gear The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle. It can also serve as a reversing g ...

, the motion of the valves is also altered such that they work in opposition to the movement of the pistons. Because of the inertia of a steam locomotive in its initial direction of travel, changing the direction in which the steam cylinders have to work acts first to brake the movement of the

connecting rod A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the cranksh ...

, which in turn slows the transmission of power to the drive of the locomotive until it stops. The countersteam brake is often confused with the counterpressure brake, which works with air, not steam, and acts as a dynamic brake. Unlike the countersteam brake, the counterpressure brake is permitted to be used as an independent braking system in its own right.

Operation

The countersteam brake is actually not a brake in the true sense; but simply a way of using the working principle of a

steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...

to produce a braking effect. It is therefore not a separate component of a steam locomotive. Countersteam braking is however only achievable with piston valves. On simple slide valves, no opposing steam admission is possible due to the way they are constructed. Using the countersteam brake, experienced locomotive drivers can reverse the running direction of a steam locomotive almost as if it hasn't been brought to a stop, because the actual changeover point occurs whilst the locomotive is still moving in the initial direction of travel. This technique requires detailed knowledge and experience because if it is not carried out correctly, damage to the locomotive engine may result. On steam locomotives without a second independent brake system (like e.g. a

compressed-air brake A railway air brake is a railway brake power braking system with compressed air as the operating medium. Modern trains rely upon a fail-safe air brake system that is based upon a design patented by George Westinghouse on April 13, 1869. The We ...

vacuum brake The vacuum brake is a braking system employed on trains and introduced in the mid-1860s. A variant, the automatic vacuum brake system, became almost universal in British train equipment and in countries influenced by British practice. Vacuum bra ...

or steam brake) for the engine, in addition to the usual counterweight or fixed brake, the countersteam brake was used as a braking system. Today, steam locomotives generally have to have two independent brake systems in order to be licensed, so that the countersteam brake is not viewed as a braking system, but is nevertheless still used.

Sources

* Heym, Rudolf: ''Wie funktioniert sie eigentlich, die Dampflok?'', Bruckmann, 2004, {{Railway brakes Railway brakes Steam locomotive technologies