Braking type

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Representation of the changeover device of a passenger coach

The type of braking distinguishes the brakes of railway vehicles according to their braking effect , which they can apply, their response time and their energy source. For this purpose, a distinction is made between the fast-acting passenger train brakes and the slow-acting freight train brake, depending on the braking position , with the most common type of braking, the automatic compressed air brake .

History and basics

The distinction between different types of brakes has to do directly with the development of brakes in railways. The initially existing handbrake as the main or only type of brake was later supplemented and finally replaced entirely by other types of brakes such as the direct-acting vapor barrier or indirectly-acting types of brakes , which also enabled automatic braking when the train was separated. Pneumatic systems that work either with underpressure ( suction air brake ) or overpressure (compressed air brake) have established themselves .

The automatic compressed air brake was able to prevail on mainline railways because it is the most powerful and the necessary control valve can be built in such a way that it works in more than one type of braking (thus it can have different braking and release times).

In contrast, the automatic suction air brake or vacuum brake has a simpler construction, but always requires an additional control valve for an improved braking effect. With a really powerful suction air brake, the actual source of the braking force is no longer the ambient air, but compressed air. This is why this type of braking is also called a vacuum-controlled compressed air brake , since only the control command is transmitted via the suction air line.

Today, depending on the braking position, a distinction is made between passenger train brakes (formerly part of type I braking for the DR and its successors) and freight train brakes (formerly part of type II braking system for the DR), because of the allowable length and maximum speed of the trains, corresponding requirements are placed on the brakes.

The changeover device for compressed air brakes enables the brake to be adapted to the braking position of the train. Locomotives are equipped with a G P , GP R or GR change, wagons mainly with a GP or P / R, P / R + Mg or P / R / R + Mg change. But there are also vehicles that are equipped with only one type of brake, this is the case especially with multiple units that can only run according to type. But if it is also found on wagons, the EW I and EW II of the SBB only have an R brake. Initially, it was also common practice for freight wagons to only equip them with the freight train brake, but then the maximum speed was limited to 80 to 90 km / h. In the case of high-speed freight wagons up to 100 [S] or 120 [SS] km / h, it is mandatory to equip them with two types of braking - and thus a GP change.

The changeover between the braking positions is carried out by hand, and must be carried out separately for each vehicle on the train. In the case of wagons with manual load change , this must be brought into the "empty", "loaded" or possibly "partially loaded" position depending on whether the total weight of the wagon reaches the changeover weight specified on the changeover device.

Passenger train brakes

Changeover device for selecting the braking position on a DB AG double-decker car
The brake cylinder filling times depend on the braking position. In P the air passages in the control valve are less restricted than in the slower acting braking position G.

Because fast moving trains need a longer braking distance, they need a correspondingly fast acting brake.

Passenger brake, P brake or UIC brake

The P brake (braking position P or RIC brake) is a fast-acting type of braking that is used for light to medium-weight trains. The brake cylinder filling time is about three to five seconds and the release time about 10 to 20 seconds. These short pressure development times require that all brakes on the vehicle material work equally and that the vehicles are tightly coupled . A braking ratio of approx. 110% can be achieved with the P brake . This type of braking is designed so that it can apply its braking power without monitoring. In contrast to the high-performance brake, it works on a purely pneumatic basis without additional components (anti-slip protection).

High performance brake, R brake

The high-performance brake or rapid brake (formerly S [fast] or SS [very fast], brake position R) is a further development of the P brake. At higher speeds of up to 160 km / h, the necessary braking distances can only be maintained if the brakes of the vehicles, which are equipped with brake pads made of gray cast iron , have a stronger effect in the upper speed range. So that the braking forces remain as constant as possible despite the changing friction value, the brake pad pressure is increased at speeds above a certain value (e.g. 80 km / h). When the speed drops below a certain value (e.g. 50 km / h), the brake pad pressure is reduced to the normal value again, which prevents the wheels from locking.

For vehicles with disc brakes or plastic - brake blocks can be dispensed with the speed-dependent R brake because the coefficient of friction over the entire speed range remains unchanged. Here, with the high-performance brake, only the brake pressure is increased compared to that of the P brake.

The R-brake can apply significantly more than 100% braking ratio. In order to prevent the wheels from locking, the R-brake requires anti-skid protection that is controlled mechanically in older vehicles and electronically in modern vehicles.

If the braking force is to be increased even further than is usually applied with the high-performance brake, new braking application points are necessary. This is simply for the reason that at around 170 braking hundredths with the high-performance brake, the physical limits are exhausted and there is no longer any adhesion between the rail and the wheel. These additional brakes are designed as rail brakes which, like the magnetic rail brake, touch the rail in the active position or, like the eddy current brake, work without contact.

Freight train brake

Changeover device for the compressed air brake (yellow) of a freight wagon. Above in white letters the type of brake. There is an O erlikon -Bremse with the brake positions G and P . The manual load change is set on the right with the red crank handle.

The freight train brake or G-brake (braking position G), internationally occasionally M for marchandises ( French goods ), is a slow-acting type of braking that results in longer braking distances. It is used for heavy, non-uniform wagon material or for extremely long trains. The different rolling stock and the loading conditions cause a different braking of individual cars and thus strong compressions and strains in the train, to buffer overlapping elements and at break of clutches for train separation could result. The G-brake is designed in such a way that the individual brakes respond as quickly as possible during braking and the braking force is then built up relatively slowly. The tensile and impact forces occurring in the couplings and buffers can thus gradually balance each other out. For the same reasons, the braking force must slowly decrease when the brake is released.

The brake cylinder filling time is about 18 to 30 seconds, depending on the length of the train, in order to reduce the longitudinal force differences that occur. The dissolving time is around 45 to 60 seconds. The breakdown time must be added to the brake cylinder filling time because it takes a certain amount of time for the air pressure drop through the air line to arrive at the end of the train. The breakthrough speed of modern trains is 250 to 280 m / s, with old control valves without a quick brake accelerator it is 90 to 180 m / s.

The braking ratio of the freight train brake is a maximum of around 80% and the maximum speed of the freight trains around 90 km / h.

Trains with G and P brakes

In the case of freight trains with non-uniform wagon material, a mixture of G- and P-braked vehicles can be used to prevent the train from buckling. When driving through tight arches and especially in tight opposing arches, there is a risk that the wheel flanges will rise on the rail head flank and cause a derailment . On freight trains with more than 600 (Switzerland) or over 800 (Germany) tonnes up to 1200 tonnes of trailer load , the locomotives at the head of the train run in braking position G. If the train weight is over 1200 tonnes, the first 5 wagons must also be set to G so that their brakes respond slowly. The brakes of the cars arranged further back, on the other hand, are in braking position P and thus respond faster than those of the vehicles in front. However, because of the air pressure difference moving backwards through the train set when braking at a speed of up to approx. 280 m / s, braking in the rear vehicles only begins with a certain time delay. The interaction of the delayed application of the brake with a faster response time distributes the braking force evenly in the train. As a result of the implementation of the TSI Operation, this procedure is no longer included in network access-relevant regulations and is the responsibility of the transport company.

Supplementary brakes

The braking capacity of the compressed air brake can be increased or supplemented with additional braking devices:

  • In the braking positions R + Mg and P + Mg, a magnetic rail brake is used in addition to the R or P brake during rapid braking . Their brake shoes under the chassis are lowered and pressed onto the rail head by magnetic force . As a result, the frictional force is exerted directly on the rail independently of the wheel / rail friction, which means that braking ratios of up to 200% are possible without any problems.
  • In the R + WB braking position, the pneumatic brake is supported by an eddy current brake during rapid braking and on suitable routes during service braking , which generates a magnetic field along the rail that induces eddy currents in the rail . These eddy currents create opposing magnetic fields that slow the train down.
  • In locomotives and multiple units , the electrodynamic brake ( recuperation brakes and resistance brakes ) (brake position P + E, R + E or R + E 160 ) supports the train's air brakes.
  • Diesel-hydraulically driven vehicles are often equipped with a hydrodynamic brake (brake position R + H).
  • Locomotives and control cars are usually equipped with an additional brake that does not act automatically and only on this vehicle.
  • The electro-pneumatic brake is an additional device for controlling the compressed air brake, which enables the simultaneous braking or releasing of all vehicles regardless of the length of the train. The locomotive is equipped with a control unit that controls the electropneumatic valves of the individual cars via an electrical control line . This achieves uniform braking with the lowest longitudinal compressive forces in the train.

As a rule, the handbrake is no longer used today to brake moving trains and is only used to secure stationary vehicles against rolling away or to slow down moving or repelling vehicles in shunting services. A handbrake attached to the side of the vehicle frame is only suitable for securing stationary vehicles, which is therefore referred to as a floor-operated parking brake .

Former braking type I and braking type II at DR

The German Reichsbahn differed since the general introduction of the air brake for freight trains fast and slow-acting brakes in two types of brakes. The fast-acting brakes were considered braking type I, the slow-acting brakes as braking type II. Both successor companies retained this division for several decades after the end of the Second World War.

Braking type I included:

  • All brakes (Knorr, Westinghouse, Kunze-Knorr, Hildebrand-Knorr and Knorr-Bremse with unitary effect) in the positions: P (B), S or SS, whereby S and SS were later combined to form the braking position R.

Braking type II included:

  • the Kkg, Hikg and KEg brakes (later Kk-G, Hik-G and KE-G) in the positions empty and loaded
  • All brakes with GP changes or train type change changeover devices in position G
  • Hand brakes (operated)

literature

Individual references, comments

  1. ↑ The steam locomotive in operation at the Deutsche Bundesbahn's railway library, Volume 144, 1st edition, p. 153.
  2. ↑ The Steam Locomotive in Operation Railway Library of the Deutsche Bundesbahn Volume 144, 1st edition, p. 154.
  3. ↑ Daniel Jobstfinke, Matthias Gülker, Markus Hecht: Freight trains with ep brakes: higher speeds, less wear . In: ZEVrail, Glaser's Annalen . tape 143 , no. 4 , April 2019, ISSN  1618-8330 , ZDB -ID 2072587-5 , p. 124-129 .
  4. ↑ Helmit Griesser: Brake problems on long trains . In: Swiss Railway Review . No. 7 . Minirex, 2020, ISSN  1022-7113 , p. 350-352 .
  5. ↑ FDV R 300.5 Appendix 1, Chapter 2.1.1
  6. ↑ DB-Ril 408.0721 Section 2 Paragraph 2 Point f (Announcement 8, valid from December 13, 2009 to December 11, 2011)
  7. ↑ Federal Office of Transport: Driving regulations . Bern, 2012. R 300.5, Section 2.1.1
  8. ↑ Frank Minde: Fundamentals of Railway Brake Technology (PDF; 144 kB). Minden (Westphalia), 2007.
  9. ↑ Matthias Kölling, DB Systemtechnik GmbH, specialist author of the guideline 915.01: Transfer of brake operating rules. (PDF; 2.0 MB) In: BahnPraxis B. Eisenbahn-Unfallkasse , December 2011, p. 4 , accessed on February 9, 2015 : “As part of the implementation of the Technical Specification for Interoperability (TSI) of the subsystem“ Traffic operation and traffic control “The responsibility at the interface between the railway infrastructure company (EIU) and the railway company (EVU) is clearly assigned. According to this, rules that describe internal EVU processes should be the responsibility of the EVU itself. The braking rules are a process of the RU. DB Netz AG will therefore largely outsource this from Ril 408. The driving regulations for non-federal railways (FV-NE) will also be adapted accordingly. "
  10. ↑ in Germany for the crediting of an additional deceleration ability when braking from 140 to 160 km / h
  11. ↑ The steam locomotive in operation. Railway library of the Deutsche Bundesbahn Volume 144 1st edition pp. 153–154.