Couplers in some form have been an important part of railroading since the very first trains. The engineering and importance of these essential little parts is often overlooked and understated.
The first couplers were simple affairs. Often, a short length of chain was used to connect the small cars. This chain evolved into the “link and pin” coupler that came to symbolize the dangers of railroading in the Nineteenth Century.
The link and pin used a single heavy iron chain link and two iron pins to join the cars. A brakeman would stand between the cars, holding the link in one hand and the pin in the other. As the train backed together, he would drop the pin through the holes on one car and the link and then get his hands and body out from between the couplers and closing cars as quickly as possible. In most cases, this was all done completely out of the sight of the crew in the locomotive.
With tight tolerances and a high margin for error, the seemingly simple act of coupling cars claimed many lives and careers. These basic couplers had another flaw as well, with the safety of the entire train literally depending on the “weakest link.” As equipment continued to grow in size, weight and strength, the link and pin became a limiting factor to railroad operations.
European railroads opted to keep the link and pin arrangement. Large buffers were installed on the ends of cars to make the manual coupling more safe. North American railroads’ demand for larger and longer trains forced a new design.
Numerous patents were issued in the Nineteenth Century for new couplers. All faced the same glaring obstacle – the enormous cost of converting the national fleet of cars across multiple railroad lines. Passage of the Railway Safety Appliance Act in 1893 finally forced the railroads to come together on a single design and begin implementation.
Since the adoption of those standards couplers have continued to evolve and improve. But with critical dimensions remaining constant, a car from 1912 can couple to a car from 2012 without any problems. Today’s couplers are bigger, but still sit at the same height to the rails and have similar spacing in the moving parts of the “knuckle” itself.
Today’s couplers come in three types, E, F and H. Type E are the most common. Although larger than the old Type D, based on the Eli Janney patent, they are similar in design. Shelves can be added to the bottom or top of the standard coupler to prevent one car from lifting and sliding into the other. These “Double Shelf” couplers are required on all hazardous materials cars in the United States.
Type F couplers are larger and feature additional castings which prevent also prevent cars from uncoupling in the event of a derailment. These couplers have an extra tooth and socket on the side of the couplers. Type F couplers are found on many locomotives today as well as on the rotary couplers used in some unit trains. These couplers allow a train to remain coupled while cars are individually turned upside down in a rotary dumper.
Type H couplers are even more complex and are used on passenger cars. These couplers not only prevent the high/low problems like the type F, they also keep cars together in the event of a jackknife.
Amtrak uses these couplers on all of its equipment and requires them on any private cars it handles. The type H also reduces slack from conventional couplers, offering a more comfortable ride.
Despite all of these additions, the strength of the coupler is still limited to a pair of pins. One locks the knuckle in place and is found in the casting itself. This pin is lifted by the cut lever, also called a “pin lifter,” which is accessible from the side of the car. The second pin acts as a hinge for the face of the knuckle. Rough handling of a train can still cause a broken knuckle. Usually this is a failure of this pin or the pulling face itself. Locomotives typically have a space – usually on the rear pilot – to carry a spare type E and F knuckle face in the event of a failure en route.
Considering the millions of pounds of force these couplers endure year after year, their engineering is nothing short of amazing. Today’s couplers perform feats Ely Janney and his peers wouldn’t have dreamed – yet they can still shake hands with his first prototype. Give them a thought the next time you’re counting cars in a passing train.