Fifth Wheels Aren't Round?

Ever wonder why we call them fifth wheels?

The term fifth wheel comes from a similar coupling used on four-wheel horse-drawn carriages and wagons. The device allowed the front axle assembly to pivot in the horizontal plane, to facilitate turning. Basically a wheel was placed on the rear frame section of the truck, which back then only had four wheels; this wheel that was placed on the frame was the "fifth wheel", hence the name. The trailer needed to be raised so that the trailer's pin would be able to drop into the central hole of the fifth wheel.

Fifth wheels were originally not a complete circle and were hand forged. When mass production of buggy parts began in the early 19th century, fifth wheels were among the first products to be made. There were a number of patents awarded for fifth-wheel design. Edward and Charles Everett of Quincy, Illinois patented a type of fifth wheel in 1850, followed by Gutches' metallic head block and fifth wheel in 1870 and Wilcox fifth wheel in 1905.

The invention of the fifth wheel for motorized trucks is often credited to US inventor Charles H. Martin of the Martin Rocking Fifth Wheel Co. who invented the device in 1915

The Fruehauf Trailer Corporation helped to make the Martin Rocking 5th Wheel a success by installing them on their popular new semi-trailer design. August Fruehauf invented the semi-trailer in 1914 with their own 5th wheel hitch. They adopted the Martin Rocking 5th wheel in 1916. By 1916 Fruehauf was producing semi-trailers in tandem with Federal Truck. These two Detroit companies also contracted with the military in WWI sending a convoy of supplies, men and equipment from Detroit to Norfolk, Virgina shipyards for travel to the front in Europe.^[2]