Aar field manual pdf

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Unsourced material may be challenged and removed. The different types of coupling do not always have formal or official names, which makes descriptions of the couplings in use on any railway system problematic. This arrangement limits the slack in trains and lessens shocks. The earliest buffers were fixed extensions of the wagon frames, but later spring buffers were introduced.

The link-and-pin coupling was the original style of coupling used on North American railways. While simple in principle, the system suffered from a lack of standardisation regarding size and height of the links, and the size and height of the pockets. The link-and-pin coupler consisted of a tube-like body that received an oblong link. During coupling, a rail worker had to stand between the cars as they came together and guide the link into the coupler pocket. Once the cars were joined, the employee inserted a pin into a hole a few inches from the end of the tube to hold the link in place.

This procedure was exceptionally dangerous and many brakemen lost fingers or entire hands when they did not get them out of the way of the coupler pockets in time. Many more were killed as a result of being crushed between cars or dragged under cars that were coupled too quickly. Brakemen were issued with heavy clubs that could be used to hold the link in position, but many brakemen would not use the club, and risked injury. There was no standard design, and train crews often spent hours trying to match pins and links while coupling cars. Crew members had to go between moving cars during coupling, and were frequently injured and sometimes killed.

The links and pins were often pilfered due to their value as scrap metal, resulting in substantial replacement costs. Railroads progressively began to operate trains that were heavier than the link-and-pin system could cope with. Albert coupler during 1921, a key and slot coupler with two pins. Cars to be coupled were pushed together, both couplings moving to the same side. One pin was inserted, then the cars were pulled to straighten the coupling and the other pin inserted. This operation required less exact shunting.

Due to the single piece design, only minimal slack was possible. The system became quite popular with tram systems and narrow gauge lines. During the 1960s most cities replaced them with automatic couplers. But even in modern cars, Albert couplers get installed as emergency couplers for towing a faulty car. There may also be a U-shaped securing latch on the opposite buffer which is fastened over the top of the hook to secure it.

The Norwegian coupler allows sharper curves than the buffer-and-chain, which is an advantage on those railways. On railway lines where rolling stock always points the same way, the mechanical hook may be provided only on one end of each wagon. Similarly, the hand brake handles may also be on one side of the wagons only. Norwegian couplings are not particularly strong, and may be supplemented by auxiliary chains. Not all Norwegian couplings are compatible with one another as they vary in height, width, and may or may not be limited to one hook at a time. Two versions of radial coupler were used in South Africa.

CGR, those of the NGR also made use of Johnston couplers. Transition era AAR knuckle coupler. Coupling and uncoupling were done manually, which posed a high risk of serious injury or death to crew members, who had to go between moving vehicles to guide the link into the coupler pocket during coupling. 1927, but not on narrow gauge rolling stock.

Conversion of all older rolling stock was to take several years and both coupler types could still be seen on some vehicles into the late 1950s. During the transition period, knuckle couplers on many locomotives had a horizontal gap and a vertical hole in the knuckle itself to accommodate, respectively, a link and a pin, to enable it to couple to vehicles which were still equipped with the older Johnston couplers. In South Africa, these couplers were only used on the narrow gauge lines in the Cape of Good Hope. It is a radial coupler with a coupler pocket which is open at the top of the coupling face. Instead of a link and pins, it makes use of a drawhook which, upon coupling, slides over the drawhook pin in the coupler of the next vehicle in the train. To prevent the drawhook of the mating coupler from accidental uncoupling, the coupler bell is equipped with a drawhook guard, commonly known as a bridle, above the coupler pocket. Usual practice was to have a drawhook fitted to only one of the mating couplers and train crews therefore carried spare drawhooks and drawhook pins on the locomotive.