Hello again folks!
Today we’re taking a look at the history of an often overlooked item indispensable to modern trucking, as well as having a considerable effect on recreational vehicles – namely, the fifth wheel.
The idea of pulling an unpowered object behind a power unit has obviously been around for thousands of years, such as a wagon or sled behind a horse, donkey, ox, etc.
But as with everything, the technology progresses and new innovations appear, and in regards to today’s subject, we look back to animal drawn wagons and an innovation of uncertain origins.
This innovation was the introduction of a pivoting mechanism between a wagon’s front axle and the main wagon frame; essentially the axle would have the hole, and the wagon the pin. As wagons typically had 4 wheels, this circular rotating mechanism became known as the “fifth wheel”.
This allowed for far better maneuverability of said wagon, and less strain on the pulling animal and the wagon itself.
This idea would last for many years, and be employed around the world.
The idea of using a non-animal power unit appears to have first been trialed in the UK in 1898, with two steam tractor builders, Thornycroft and T. Toward & Co Steam Motor Tractors, attaching a “wagon” (or trailer/lorry) to one of their steam tractors via a turntable mechanism. The Thornycroft setup is not well documented, but the T. Toward & Co was, and from period records sounds like a wagon with the aforementioned early fifth wheel setup was used, with the front axle removed, and the hole instead on the steam tractor, into which the wagon’s pin was dropped.
This setup proved very successful during various tests.
Moving on several years to 1915, we see the introduction a the clear predecessor to today’s modern fifth wheels – namely Charles H. Martin’s Rocking Fifth Wheel. This was, in fact, a wheel like assembly that moved with the trailer, and was not the easy hook/unhook setup we have today. “Rocking” was a reference the forward and back pivot allowed by the design. Also, they were originally offered as separate items – the fifth wheel and a rear axle assembly; the actual trailer design and construction was not provided by Martin’s company.
This Rocking Fifth Wheel would prove very successful, with Fruehauf Trailers producing trailers equipped with the setup. Though Fruehauf had originally designed their own fifth wheel setup in 1914, and offered them on ready to run trailers (thus inventing the idea of a “semi-trailer”), they would forgo their design for Martin’s in 1916. After adopting the Rocking Fifth Wheel, Fruehauf would produce trailers in tandem with Federal Trucks. During WW1, Fruehauf and Federal, both from Detroit, would contract with the US military to send a convoy of supplies and equipment from Detroit to the Norfolk, VA shipyards.
By 1920 Fruehauf would hit the million dollar mark in sales – a tremendous sum at the time.
In 1926 the next innovation would appear, designed and introduced by Fruehauf – the “automatic semi-trailer”. The automatic part came from the ability to hook and unhook with the mechanism contained in the fifth wheel, rather than the earlier system of lifting the trailer and lowering the kingpin into the fifth wheel plate’s hole. Obviously, this was a major breakthrough, as we’re using the same essential idea today, on everything from RVs to heavy haulers.
Trailers had of course existed before the introduction of the “semi-trailer”, but the names give an indication of the difference – a trailer fully trails the power unit, whereas the semi-trailer’s weight is significantly supported by the power unit, via the fifth wheel and kingpin connection, hence it only semi trails, and is in effect a single articulated vehicle.
Fifth wheels are sometimes put to uses other than attaching a trailer as well, such as a detachable towing unit/quick-swap, as seen below.
Well, that pretty well summarizes the history of the fifth wheel. It was more interesting than I expected, actually.
As always, thanks for reading, and I hope you enjoyed!
