<\/a><\/noindex><\/p>\n1. The history of the pneumatic brake.<\/h1>\n \nThe task of managing any mode of transportation involves regulating its speed. Railway transport is no exception; moreover, its structural characteristics add significant nuances to this process. A train consists of a large number of interconnected carriages, and the resulting system is considerable in length and weight while maintaining a fairly high speed.<\/p>\n
By definition, brakes are a set of devices designed to create artificial, adjustable resistance forces used for controlled deceleration of the vehicle's speed.<\/i><\/p>\n
The most obvious and straightforward method of generating braking force is through friction. From the very beginning until today, the block friction brake has been used. Special devices\u2014brake pads made from high-friction material\u2014are mechanically pressed against the wheel's running surface (or against special discs mounted on the axle of the wheel pair). Frictional force occurs between the pads and the wheel, creating a braking moment.<\/p>\n
the braking pressure.<\/i>The question is only which mechanism is used for pressing the pads, and, the history of brakes is partly the history of the development of this mechanism.<\/p>\n
The first railway brakes were mechanical and were operated manually by special individuals \u2014 brakemen or conductors, separately for each car. Conductors were located on the so-called brake platforms equipped on each car and operated the brakes at the engineer's signal. Communication between the engineer and conductors was conducted via a special signaling rope stretched along the entire train, which activated a special whistle.<\/p>\n
An old two-axle freight car with a braking platform. The handbrake handle is visible.<\/i>
The further development of brakes required, firstly, an increase in braking force, and secondly, the ability to control them remotely from the engineer's workplace on all cars.<\/p>\n
The hydraulic drive, used in automobile brakes, gained widespread adoption because it provides high pressure while keeping the actuating devices compact. However, when such a system is applied in a train, its main drawback becomes apparent: the necessity for a special working medium \u2014 brake fluid, the leakage of which is unacceptable. The long length of hydraulic brake lines in a train, combined with high demands for their tightness, makes the creation of a hydraulic railway brake impossible and impractical.<\/p>\n
Pneumatic drive is a different matter. Using high-pressure air allows for high braking forces with acceptable dimensions of the actuating devices \u2014 brake cylinders. There is no shortage of the working medium \u2014 air is all around us, and even if a leakage occurs in the braking system (which is inevitable), it can be relatively easily replenished.<\/p>\n
The simplest braking system that uses compressed air energy is a direct-acting non-automatic brake<\/i><\/p>\n
The diagram of a direct-acting non-automatic brake: 1 \u2014 compressor; 2 \u2014 main reservoir; 3 \u2014 supply line; 4 \u2014 driver's brake valve; 5 \u2014 brake line; 6 \u2014 brake cylinder; 7 \u2014 release spring; 8, 9 \u2014 mechanical brake transmission; 10 \u2014 brake pad.<\/i>the main reservoir<\/i> (2). The pumping of air into the main reservoir and maintaining constant pressure is performed by the compressor<\/i> (1), which is powered by the locomotive's energy unit. The supply of compressed air to the brake control devices is carried out through a special pipeline called the supply line (PL)<\/i> or the pressure<\/i> line (3). <\/p>\n
The control of the car brakes and the supply of compressed air to them is carried out via a long pipeline running throughout the train, known as the brake line (BL)<\/i> (5). When compressed air is supplied through the BL, it fills the brake cylinders (BC)<\/i> (6) directly connected to the BL. Compressed air pushes on the piston, pressing brake pads 10 against the wheels, both on the locomotive and on the cars. Braking occurs. <\/p>\n
To stop braking, that is, release<\/i> the brakes, it is necessary to vent the air from the brake line to the atmosphere, which will return the brake mechanisms to their original position due to the force of the release springs installed in the BC.<\/p>\n
To enable braking, it is necessary to connect the brake line (BL) with the supply line (PL). To release \u2014 connect the brake line to the atmosphere. These functions are performed by a special device \u2014 the driver's brake valve<\/i> (4) \u2014 when braking, it connects the PL and BL; when releasing, it disconnects these pipelines while simultaneously venting air from the BL to the atmosphere.<\/p>\n
In such a system, there is also a third, intermediate position of the driver's valve \u2014 the cutoff<\/i> When the PM and TM are separated, but air is not released from the TM into the atmosphere, the engineer's valve completely isolates it. The pressure built up in the TM and TC is maintained, and the time for maintaining it at the set level is determined by the amount of air leaks through various gaps, as well as the thermal stability of the brake pads, which heat up due to friction against the wheel tires. The application of the crossover during both braking and release allows for the regulation of braking force in stages. This brake provides both stepwise braking and stepwise release.<\/p>\n
Despite the simplicity of such a brake system, it has a fatal flaw \u2014 when separating a train, the brake line breaks, air escapes from it, and the train is left without brakes. It is for this reason that such a brake cannot be used in railway transport, as the cost of its failure is too high. Even without a train separation, the effectiveness of the brake will be reduced in the presence of a significant air leak. <\/p>\n
Based on the above, there arises a requirement that train braking should be initiated not by an increase, but by a decrease in pressure in the TM. But how then do we fill the brake cylinders? This leads to a second requirement \u2014 each moving unit in the train must store a reserve of compressed air, which needs to be replenished promptly after each braking.<\/p>\n
Similar conclusions were reached by engineering thought in the late 19th century, which resulted in the creation of the first automatic railway brake by George Westinghouse in 1872.<\/p>\n
The structure of the Westinghouse brake: 1 \u2014 compressor; 2 \u2014 main reservoir; 3 \u2014 supply line; 4 \u2014 train engineer's valve; 5 \u2014 brake line; 6 \u2014 air distributor (triple valve) of the Westinghouse system; 7 \u2014 brake cylinder; 8 \u2014 auxiliary reservoir; 9 \u2014 stop valve.<\/i>
The figure shows the design of this brake (figure a \u2014 operation of the brake during release; b \u2014 operation of the brake during braking). The main element of the Westinghouse brake became the brake air distributor<\/i> or, as it is sometimes referred to, a triple valve<\/i>This air distributor (6) has a sensitive element \u2014 a piston that operates based on the pressure difference between the brake line (TM) and the reserve tank (ZK). If the pressure in the TM drops below that in the ZK, the piston shifts to the left, opening the path for air from the ZK to the TC. If the pressure in the TM exceeds the pressure in the ZK, the piston shifts to the right, connecting the TC with the atmosphere while simultaneously connecting the TM and ZK, allowing the latter to fill with compressed air from the TM.<\/p>\n
Thus, in the event of a drop in pressure in the TM for any reason, whether due to the actions of the engineer, excessive air leakage from the TM, or a train break \u2014 the brakes will engage. This means that such brakes have automatic operation<\/i>. This characteristic of the brake has allowed for an additional way to control the train's brakes, which is still used on passenger trains today \u2014 emergency stopping of the train by a passenger through connecting the brake line to the atmosphere via a special valve \u2014 the emergency brake<\/i> (9). <\/p>\n
. For those familiar with this feature of the train's braking system, it is amusing to watch movies where cowboy thieves deftly uncouple a gold-laden car from a train. For such an act to be accomplished, the cowboys must have first closed the end valves on the brake line that separate the brake line from the connecting hoses between the cars. But they never do this. On the other hand, closed end valves have often caused terrible disasters related to brake failure, both here (Kamensk in 1987, Yeral-Simskaya in 2011) and abroad.<\/p>\n
Because the filling of the brake cylinders occurs from a secondary source of compressed air (the reserve tank), without the possibility of constant replenishment, this brake is called non-direct acting<\/i>. The charging of the ZK with compressed air occurs only when the brake is released, which leads to the situation where, with frequent braking followed by release, if insufficient time is allowed after release, the ZK does not have enough time to charge to the necessary pressure. This can lead to complete brake depletion and loss of control over the train's brakes.<\/p>\n
The pneumatic brake has another drawback, related to the fact that a drop in pressure in the brake line, like any disturbance, propagates in the air medium at a high but still finite speed \u2014 no more than 340 m\/s. Why no more? Because the speed of sound is the ideal case. However, in the pneumatic system of the train, there are several obstacles that reduce the speed of propagation of the pressure drop, related to air flow resistance. Therefore, if no special measures are taken, the speed of pressure drop in the brake system will be lower the further the car is from the locomotive. In the case of the Westinghouse brake, the speed of the so-called brake wave<\/i> does not exceed 180 \u2014 200 m\/s.<\/p>\n
Nevertheless, the emergence of the pneumatic brake allowed for an increase in both brake power and operational control directly from the engineer's workplace. This served as a powerful impetus for the development of railway transportation, increasing travel speeds and weights of trains, and consequently, a colossal increase in freight turnover on the railways, along with the expansion of railway lines worldwide.<\/p>\n
George Westinghouse was not only an inventor but also an enterprising businessman. He patented his invention as early as 1869, which allowed him to launch mass production of braking equipment. Quite quickly, the Westinghouse brake gained widespread use in the USA, Western Europe, and the Russian Empire.<\/p>\n
In Russia, the Westinghouse brake reigned supreme until the October Revolution, and even for quite some time after it. The \"Westinghouse\" company built its brake factory in St. Petersburg and skillfully drove out competitors from the Russian market. However, the Westinghouse brake had several fundamental drawbacks. <\/p>\n
Firstly, this brake only provided two modes of operation: braking<\/i> to fully fill the brake cylinders, and release<\/i> \u2014 emptying the brake cylinders. It was impossible to create an intermediate brake pressure value with prolonged maintenance, meaning that the Westinghouse brake lacked a holding mode<\/i>. This did not allow for precise speed control of the train.<\/p>\n
Secondly, the Westinghouse brake performed poorly on long trains, and while this could be somewhat tolerated in passenger traffic, it created issues in freight. Remember the braking wave? The Westinghouse brake lacked the means to increase its speed, so in a long train, the pressure drop in the brake systems on the last car could start too late and at a pace significantly lower than at the front of the train, resulting in a wild unevenness in the activation of the braking systems throughout the entire composition.<\/p>\n
It should be noted that the entire activity of the Westinghouse company, both in Russia at that time and around the world, was permeated with the capitalist stink of patent wars and unfair competition. This is what ensured such an imperfect system's long life, at least during that historical period.<\/p>\n
Despite all this, it must be acknowledged that the Westinghouse brake laid the foundations of braking science, and its principle of operation remains unchanged in modern rolling stock brakes.<\/p>\n
2. From the Westinghouse brake to the Matrosov brake \u2014 the emergence of domestic braking science.<\/h1>\n Almost immediately after the appearance of the Westinghouse brake and the realization of its shortcomings, attempts were made to enhance this system or create a fundamentally new one. Our country was no exception. By the early 20th century, Russia had a developed network of railways that played a significant role in ensuring the economic development and defense capability of the country. Improving transport efficiency is linked to increasing the speed of movement and the mass of cargo transported at once, making the issues of improving braking systems particularly urgent. <\/p>\n
A significant impetus for the development of braking science in the RSFSR and later the USSR was the reduction of the influence of large Western capital, particularly from the Westinghouse company, on the development of the domestic railway industry after October 1917. <\/p>\n
F.P. Kazantsev (left) and I.K. Matrosov (right) \u2014 creators of the domestic railway brake<\/i>direct acting automatic brake<\/i>. The diagram below outlines all the key concepts introduced not only by Kazantsev, and its aim is to explain the fundamental principles of the improved automatic brake operation<\/p>\n
Direct acting automatic brake: 1 \u2014 compressor; 2 \u2014 main reservoir; 3 \u2014 supply line; 4 \u2014 engineer's brake valve; 5 \u2014 leakage feed device for the brake line; 6 \u2014 brake line; 7 \u2014 connecting brake hoses; 8 \u2014 end valve; 9 \u2014 stop valve; 10 \u2014 check valve; 11 \u2014 auxiliary reservoir; 12 \u2014 air distributor; 13 \u2014 brake cylinder; 14 \u2014 brake lever transmission.<\/i>equalizing reservoir<\/i> (ER). It is shown in the diagram to the right of the engineer's valve (4) and above the leakage feed device from the brake line (5). The density of this reservoir is technically much easier to maintain than the density of the brake line \u2014 a pipe that can stretch for kilometers throughout the train. The relative stability of pressure in the ER allows maintaining pressure in the brake line, using the pressure in the ER as a reference. Indeed, the piston in the device (5) drops down when the pressure in the brake line decreases, opening a valve that fills the brake line from the supply line, thereby maintaining pressure in the brake line equal to that in the ER. This idea had a long way to develop, but now the pressure in the brake line did not depend on the presence of external leaks (within known limits). Device 5 made its way into the engineer's valve and remains in it, in a modified form, to this day.<\/p>\n
Another important idea underlying the design of this type of brake is the feeding of the auxiliary reservoir from the brake line through check valve 10. When the pressure in the brake line exceeds the pressure in the auxiliary reservoir, this valve opens, filling the auxiliary reservoir from the brake line. This ensures continuous replenishment of leaks from the auxiliary reservoir and guarantees the brake's sustainability.<\/p>\n
The third important idea proposed by Kazantsev is the design of an air distributor that operates based on the difference of not two pressures, but three \u2014 the pressure in the brake line, the pressure in the brake cylinder, and the pressure in a special working chamber (WC), which is supplied with pressure from the brake line when released, along with a spare reservoir. During braking, the WC is disconnected from the spare reservoir and the brake line, preserving the initial charging pressure. This feature is widely used in the brakes of rolling stock to provide stepwise release and to manage the uniform filling of the brake cylinders along the train in freight trains, as the working chamber serves as a reference for the initial charging pressure. Based on its value, both stepwise release and earlier filling of the brake cylinders in the rear cars can be ensured. I will leave a detailed description of these aspects for other articles on this topic, but for now, I will say that Kazantsev's work stimulated the development of a scientific school in our country, leading to the creation of original brake systems for rolling stock.<\/p>\n
Another Soviet inventor who significantly influenced the development of domestic brakes for rolling stock was Ivan Konstantinovich Matrosov. His ideas were fundamentally similar to those of Kazantsev; however, subsequent operational tests of the brake systems designed by Kazantsev and Matrosov (together with other brake systems) showed a significant superiority of the latter system in terms of operational characteristics, especially in freight trains. Thus, Matrosov's brake with the air distributor No. 320 became the basis for further development and design of brake equipment for railways with a gauge of 1520 millimeters. The modern automatic brake used in Russia and the CIS countries rightfully bears Matrosov's name, as it absorbed, at the initial stage of its development, the ideas and design solutions of Ivan Konstantinovich.<\/p>\n
In conclusion<\/h1>\n \nSo what is the conclusion? Working on this article convinced me that the topic deserves a series of articles. In this pilot article, we touched upon the history of the development of train brakes. In the following articles, we will delve into intriguing details, addressing not only domestic brakes but also the developments of our colleagues from Western Europe, highlighting the designs of various types and service roles of train brakes. Therefore, I hope the topic will be interesting, and see you again on Habr! <\/p>\n
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