Counter-pressure brake

The counter-pressure brake is dynamic brake for steam locomotives, the locomotive brakes through a combination of measures by compression work in the driving cylinders. With the counter-pressure brake wear and overheating of the tire and the brake pads can be avoided by braking and a consistently high braking force can be achieved without fading risk.

The counter-pressure brake must not be confused with the other vapor barrier, which utilizes only the possibility of braking efficiency of a steam engine with rotary valves and is not approved as an additional braking system.

History

The invention of the counter-pressure brake is usually attributed Niklaus Riggenbach, so this also Riggenbach counter-pressure brake is called. The braking system has been used in vehicles for which opened in 1871, Vitznau- Rigi -Bahn for the first time. The same principle has already been realized in 1851 by the Scottish engineer John working in Vienna Haswell in the locomotive Vindobona for the Semmering Railway.

Operation

In the counter-pressure brake is, simply put, the operation of the steam engine turned over by letting them condense as in a piston compressor air. Since the steam after work performance in the cylinders is ejected into the smoke chamber by the blower tube below the chimney, the cylinder would be as air compressors without a modified air intake suck the polluted with residues exhaust gases during operation via the blast tube. To avoid this, the blowpipe to the smoke box is running toward sealed. By using the counter-pressure brake, a separate intake opening is released for the purpose of supply of clean ambient air with the blower tube closure at the same time. The fresh air suction has no typical installation point, but is usually in the vicinity of the cylinder. Furthermore, the actual direction of travel by the train driver the control opposite designed and operates the Ausströmdrosselventile via the slide boxes. About the Ausströmdrosselventile escapes the compressed air, usually by a downstream silencer, in the open air. This can not be suppressed by the resulting pressure in the valve body and the exhaust bends between controller and valve body, the controller, the throttle valves are used at the same time regulating the back pressure. When equipped with counter-pressure brake locomotives of the German Reichsbahn (GDR), therefore, was the requirement that the valve body pressure 6 bar was not allowed to exceed.

The counter-pressure brake is operated by a linkage from the driver's cab, with a combined control is possible. In her counter-pressure brake effect automatically as soon as the control has a negative value, so would actually work with on forward control is laid out in reverse. Once the control has reached a negative position, intake and exhaust line should be released.

To prevent overheating of the cylinder by the heat generation at high compression work, must be given a possibility for the injection of (hot) water into the intake air. The water quantity is increased with the degree of compaction (usually directly related to the control). Without this water injection would be the danger that the oil film would be destroyed in the cylinders due to high temperatures.

Properties of locomotives with counter- pressure brake

With a counter-pressure brake it is not only possible to keep a set braking force depending on speed; the braking performance enhanced even at higher speed. In this respect it differs from friction brakes, which zuallermeist in speed increase in their effects wear off ( due to fading ). The actual braking effect is directly related to the number of revolutions of the wheel, that is, the more does the wheel turns at the same time, the more braking power may be applied. The locomotive can thus, in spite of varying gradient, are kept in a narrow speed range without necessarily something needs to be changed in the setting, and is therefore the ideal steady brake, a brake in which the rate - usually in the slope - held, but should not be reduced.

Today's engines are at the side on which the compressed air exits the cylinder, a muffler. The compressed air is discharged usually via the chimney to help prevent the train for the furnace is maintained and the auxiliary blower must not be used. The steam locomotive typical exhaust strokes sound so even with an active counter-pressure brake, a pitch and volume difference to the normal exhaust stroke is recognizable. The number of exhaust beats per revolution of the wheel is, however, not changed.

Areas of application

Riggenbach counter-pressure brake found particularly for steam locomotives that were used on long downhill stretches, and rack railway locomotives (eg the Vienna Kahlenberg web ) application. For operation on steep grades their presence was indispensable, as these dynamic brake is the prescribed third independent brake for steam locomotives.

Another application of the counter-pressure brake was found in the measurement and experimentation. An equipped with counter-pressure brake steam locomotive can be used by the possibility of steady, largely wear-free braking and brake locomotive, so bring a defined tensile load and thus in the subjects to be examined locomotives the terms of a journey in the steady state (a state of motion, in which the prime mover only the eradication driving resistances necessary work applies ) simulate. Some of these steam locomotives were therefore used in Germany until the mid- 1970s as a brake locomotives such as the series 19 / DR series 19 ( Reko ) and the 18 314 VES -M Halle or 18.3 of the BZA Minden.