Countersteam brake
Encyclopedia
A countersteam brake is a brake on a steam locomotive
that uses the engine (specifically the cylinders) to help brake the locomotive.
It uses the working principle of steam cylinders fitted with slide or piston valves such that, by changing the configuration of the valve gear
, 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
, 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.
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, vacuum brake
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.
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
that uses the engine (specifically the cylinders) to help brake the locomotive.
It uses the working principle of steam cylinders fitted with slide or piston valves such that, by changing the configuration of the valve gear
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...
, 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
Connecting rod
In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts linear motion into rotating motion....
, 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 engineSteam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
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, vacuum brake
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 those countries influenced by British practice. Vacuum brakes also enjoyed a brief period of adoption in...
or steam brake
Steam brake
A steam brake is a type of brake for steam locomotives and their tenders, whereby a steam cylinder works directly on the brake linkages.Steam brakes were primarily used on railways where vacuum brakes were used to brake the train, but where there was no vacuum brake on the steam locomotive itself,...
) 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, ISBN 3765472557