Editing Railway coupling (section)

==Link and pin==
[[File:Link and Pin.jpg|thumb|left|A link-and-pin coupler]]
[[File:Early Janney-type AAR coupler.JPG|thumb|Transition era AAR knuckle coupler. The gap in the knuckle accommodates the link of a [[#Link and pin|link and pin coupler]] and the vertical hole in the knuckle accommodates the pin.]]  
[[File:08-130 Esclusas de Miraflores (23).jpg|thumb|Link and pin coupler combined with side buffers on a [[Panama canal mule]].]] 
The link-and-pin coupling was the original style of coupling used on North American railways. After most railroads converted to semi-automatic [[Janney coupler]]s, the link-and-pin survived on [[forest railway]]s. 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.

The link-and-pin coupler proved unsatisfactory because:
* It made a loose connection between the cars, with too much [[slack action]].
* 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. 
* When a car happened to be turned 180 degrees one would have to look for a link. 
* Railroads progressively began to operate trains that were heavier than the link-and-pin system could cope with.

In Britain link-and-pin couplers were common on narrow gauge industrial and military railways, and eventually evolved into a form that could be reliably coupled when the train was stationary. 

The [[Panama Canal locks#Mules|Panama Canal mule]]s, the locomotives used to guide the ships through the locks of the [[Panama Canal]], have link and pin couplers and side buffers. This design was chosen so that these normally solo operating locomotives could be coupled to another locomotive in the event of a breakdown. On straight track, the link and pin coupler is used. Since the vertical curve between the straight track sections and the ramp between the lock chambers has a very small radius, the difference in height would be too great for a link and pin coupler, so the locomotives must be pushed through these sections uncoupled by using the side buffers. They have an extra high buffer plate to prevent the buffers from buffer-locking in tight vertical curves.

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