The Janney/MCB/ARA/AAR/APTA coupler, also commonly known as a Alliance, BuckEye, or Knuckle coupler, Master Car Builders Association and AAR coupler (for the Association of American Railroads) is a semi-automatic coupler patented by Eli H. Janney in 1873 (U.S. Patent 138,405). It is also known as a « buckeye coupler », notably in the United Kingdom, where some rolling stock (mostly for passenger trains) is fitted with it. The AAR/APTA TypeE, TypeF, and TypeH couplers are all compatible Janney couplers, but used for different rail cars (general freight, tank cars, rotary hoppers, passenger, etc.).
The purpose of couplers is to join the cars or locomotives to each other so they all are « coupled » together. Major Eli Janney, a Confederate veteran of the Civil War, invented the semi-automatic knuckle coupler in 1868. This coupler is unlocked manually and automatically locks upon the couplers on cars or locomotives closing together without the rail worker getting between the cars. This replaces the « link and pin » coupler, which was a major cause of injuries to railroad workers. The locking pin that locks the coupler together can be withdrawn by the « cut lever » which is built to be accessible from either side of the railroad car and does not require the worker to go between the cars. The only time the worker has to go between the cars is to hook up the air lines for the pneumatic brakes and the head end power cables in the case of passenger cars.
Diagram of the top view of Janney’s coupler design as published in his patent application in 1873.
Janney was a dry goods clerk and former Confederate Army officer from Alexandria, Virginia, who used his lunch hours to whittle from wood an alternative to the link and pin coupler. The term Buckeye comes from the nickname of the US state of Ohio, the « Buckeye state » and the Ohio Brass Company which originally marketed the coupling.
In 1893, satisfied that an automatic coupler could meet the demands of commercial railroad operations and, at the same time, be manipulated safely, the United States Congress passed the Safety Appliance Act. Its success in promoting switchyard safety was stunning. Between 1877 and 1887, approximately 38% of all railworker accidents involved coupling. That percentage fell as the railroads began to replace link and pin couplers with automatic couplers. By 1902, only two years after the SAA’s effective date, coupling accidents constituted only 4% of all employee accidents. Coupler-related accidents dropped from nearly 11,000 in 1892 to just over 2,000 in 1902, even though the number of railroad employees steadily increased during that decade.
When the Janney coupling was chosen to be the American standard, there were 8,000 patented alternatives to choose from. The only significant disadvantage of using the AAR (Janney) design is that sometimes the drawheads need to be manually aligned.
The Janney coupler is used in Canada, the United States, Mexico, Japan, Australia, South Africa, Saudi Arabia, Cuba, Chile, Brazil, China and elsewhere. Among its features:
- Minimum ultimate tensile strength:
- Grade E knuckles:650,000 pounds-force (2.9 MN)
- Grade C or Grade E knuckles are required  for interchange service.
- Grade E coupler bodies:900,000 pounds-force (4.0 MN)
- Several Janney coupler types exist to accommodate various cars, but all are required to have certain common dimensions allowing for compatibility.
- Janney couplers are always right-handed.
- Required coupler heights
- Empty cars: 33.5 inches (850 mm) ± 1-inch (25 mm)
- Loaded cars: 32.5 inches (830 mm) in ± 1-inch (25 mm)
- Janney couplers are uncoupled by lifting the pin with a lever at the corner of the car. This pin is locked when the coupler is under tension, so the usual uncoupling steps are to compress the coupling with a locomotive, lift and hold up the pin, then pull the cars apart. Side operated variants are called the « Sharon » or « Buckeye » coupler.
- Most Janney couplers are now bottom operated.
- Trains fitted with Janney couplers can accommodate heavier loads than any other type of coupler. Thus the heaviest coal trains in New Zealand use Janney couplings even though the remainder of the fleet has the « meat chopper » kind. Also, long-distance freight trains in North America are commonly more than 1-mile (1.6 km) long, whereas this is not seen in Europe, where most freight trains still use English buffers and chain couplers.
Changes since 1873
Standard AAR Type E couplers performing their function in a freight train. The upper coupler is bottom-operated, while the near coupler (on the locomotive) is top-operated by the chain.
The Janney coupler has withstood the test of time since its invention, with only minor changes:
- The current AAR contour dates back to the 1888 Master Car Builders Association (MCBA) design, which, in turn is based on the 1879 Janney patent.
- Buckeye coupler, a side-operated version of the MCBA coupler
- TypeD coupler, adopted in 1916 by the MCBA (predecessor of ARA), had individual parts interchangeable, simplifying maintenance. Earlier designs had compatible profiles, but component parts differed between manufacturers, creating maintenance problems when cars were interchanged with other railroads.
- TypeE coupler, adopted in 1930 by the ARA (predecessor of AAR), also had individual parts interchangeable, though not with TypeD due to improvements. Still the most widely use design today.
- Tank cars carrying hazardous materials are equipped with TypeE double shelf couplers
- TypeF coupler, an « InterLock » variation to prevent accidents, derailments and wrecks from disconnecting the coupler. TypeF also include versions rotating shafts for hopper car rotary dumpers, such as on the Pilbara railways.
- TypeH coupler, a « TightLock » variation to reduce slack action and improve safety for passenger cars. Now under the supervision of the APTA (American Public Transportation Association).
- Improvements in metallurgy and casting techniques to increase maximum trailing load.
- Narrow gauge railways such as the Victorian Puffing Billy Railway use a 3/4 or 1/2 scale version of the Janney/MCB coupler.
Modern Janney/AAR TypeE Couplers, note that these are bottom operated
Regular Janney/AAR TypeE Couplers as seen from above. The left one is top operated and the other is bottom operated.
AAR Type « E » coupler serving as a tow hitch on a mobile crane
. Pulling up on the link at the rear releases the knuckle allowing uncoupling.