The Fifth Wheeler: Its Early History
As with all vehicles covered by rvhistory.com, this history of the fifth wheeler only goes up to 1939. There are many other online resources covering the post-WW2 history of this fascinating RV spin-off.
What is a Fifth Wheeler?
In the RV world, a 'fifth wheeler' is the name given to a trailer and tow vehicle combination which has the trailer's hitch located above or in front of (rather than behind) the tow vehicle's rear axle. The laws of physics make fifth wheelers the safest towable RV available today. Towing dynamics expert Collyn Rivers explains why here.
Although the physics of fifth wheelers is well understood, their history is less so. The fifth wheel has a long and fascinating development, evolving significantly over time in both purpose and design. We have broken down the early history of the fifth wheeler into four stages, each beginning with 'H':
Where Does the Name Come From?
In its simplest form the fifth wheel is a pivot allowing the horizontal rotation of either an axle or a trailer hitch. Its name comes from its circular form and that fact that it comprises the 'fifth wheel' of some four-wheeled vehicles.
Why Were they Developed?
In early days, four-wheel wagons were used less than two-wheeled carts. Two-wheelers were mechanically simple and easy to manoeuvre when pulled by beasts of burden. Whilst four-wheelers could carry more, they were hard to steer without a pivoting front axle. As anyone who has self-built or driven a go-kart (or 'billy cart') will know, a pivoting front axle is an essential steering mechanism for an unpowered four-wheeled vehicle. But oversteering a simple front axle changes the geometry of a vehicle's contact points with the ground (becoming more of a triangle than a rectangle), risking instability. The early fifth wheels on horse-drawn vehicles helped to overcome the instability issues associated with simple pivoting front axles by increasing the surface area on which a pivoting front axle rests and strengthening the connection between the axle and frame.
Stage One: Horses
Pivoting front axles are known to have been used in animal-drawn wagons of the Middle Ages, but recent research indicates they were also used by the Romans. A simple kingpin, or king-bolt, was used to secure the front axle to the wagon bed, reducing the wagon's turning circle and giving the animal(s) up front more freedom to move laterally. As wagon and coach technology improved, smaller front wheels further improved turning circles, allowing for wider wagon floors that could carry more goods.
In eighteenth-century Europe a circular 'wheel-plate' was added to the front axle kingpin to improve strength and stability of a turning carriage and improve weight carrying capacity. Instead of turning on a pin, wagon axles could turn on a round plate. Two plates were sometimes used on heavier carriages with lubrication in between - often horse fat.
An alternative solution to the unstable pivoting front axle was proposed by Erasmus Darwin (grandfather of Charles Darwin) in 1758. He proposed that the two front wheels should pivot independently at the end of a non-rotating front axle. This idea was later patented in 1818 (but not by Darwin) and became known as Ackermann steering.
Wheel-plated carriages combined with new forms of iron spring suspension meant that European carriages were mostly heavy. In America a lighter carriage was needed to travel longer distances over rougher terrain. Suspension and ironwork in particular needed to be light.
The fifth wheel of the horse-drawn carriage era was developed in the USA as a lightweight replacement for the European wheel-plate. It was still made of iron but was of smaller diameter, more ring-like and was usually less than a complete circle. Early versions were hand-forged from about 1830 and were made in a range of shapes from a full circle to a semi-circle and a horseshoe. It is not known who first developed the idea, since most US patents issued between 1790 and 1836 were destroyed by fire in 1836.
One of the earliest surviving fifth wheel patents (and indeed one of the earliest ever American patents) was that of Brown and Hicks of 1837, which showed a convex-plated fifth wheel that claimed to reduce road vibrations. This is available to download below:
Thereafter a regular series of improvements to fifth wheels and king-bolts were designed and patented in America until the end of the horse-drawn carriage era. Some of the most successful were the Everett Carriage Coupling (1850), the Herbrand Fifth Wheel (late 1880s) and the Wilcox Fifth Wheel (1905). The more advanced fifth wheels allowed a small turning circle, improved ride handling and goods carrying ability and included lubrication points.
Stage Two: Hybrids
The term 'hybrid' is used here to describe the transition period for the fifth wheel between horses and horsepower. With the advent of motorized vehicles at the turn of the twentieth century, the fifth wheel of a horse-drawn coach was not suitable for the new gasoline-powered vehicles. Steering of the first automobiles was adapted mainly from bicycles including some three-wheelers. The first automobile engines were small and light enough to be incorporated into a modified bicycle frame complete with driver and passengers. Early versions were steered using handlebars or geared handles, making fifth wheels unnecessary.
Some early automobiles were powered by steam, electricity and electric-gasoline engines. As these grew in complexity they became heavy and sometimes dangerous - in the early days a fair few burst into flames or exploded. Rather than forcing occupants to sit on top of a pressurized boiler or battery bank full of chemicals, some early manufacturers incorporated their engines into separate 'tractors' that towed a passenger or goods trailer. The tow hitch of these tractors was invariably above its rear axle. The tractor in effect became a mechanical horse, with a modified turntable to receive the trailer's hitch. These turntables improved turning circles and kept passengers away from the power source. Very little is known about the design of these turntables, so it is not possible to say if they inherited any design features from the carriage-based fifth wheel.
At the turn of the twentieth century the configuration of motorized tractor and trailer was used most extensively in France. One of its strongest proponents was De Dion Bouton, who used the De Dion Bouton Steam Bogie to tow a range of trailers for use as carriages, omnibuses and goods wagons. The 'bogie' could be quickly swapped between different trailer types, a useful attribute when promoting the technology to potential buyers. Electric vehicles also used tractors containing batteries and electric motor, such as the carriage used by Grand Duke Alexis in 1899 (shown at the top of this article) which used a Heilmann electric bogie as used in Heilmann's steam/electric railway locomotives.
Although the hitches of these hybrid vehicles are more correctly described as turntables rather than fifth wheels, the application of weight-sharing principles and improved stability offered by motorized tractor and trailer combinations were important milestones in the development of the fifth wheel principle in the haulage and recreational industries.
These transitional vehicles were less widely used in the USA and the UK, who focused their development efforts at the time on the single-chassis automobile and truck. Significantly, the tractor and trailer combination was used to pull the first motorized RVs of France and Belgium and inspired the first 'semi-trailers' of the trucking and omnibus industries.
Stage Three: Haulage
In the early twentieth century the potential of motorized vehicles to move goods quickly over short and long distances was soon realised by motorized vehicle manufacturers. The carrying capacity of single-chassis trucks increased along with the horsepower of engines, but the haulage industry wanted ever more capacity and faster loading and unloading times. The answer was the tractor and trailer combination - the first semi-trailers.
One of the first 'semi-trailers' was the Winton auto hauler of 1898. Made by the Winton Motor Carriage Company of Cleveland, Ohio, it was a rudimentary combination used to take Winton automobiles to their dealers. The trailer's hitch was placed above the rear axle of the tractor which was was another converted automobile.
In Europe one of the earliest systems of attaching a goods trailer to a motorized tow vehicle was developed by Théodore Pescatore of Liege in Belgium, owner of vehicle manufacturer Société Auto Mixte. In 1911 he applied for a patent for 'a new system of transporting heavy loads by motor vehicles'. It was in effect a hitch located above the rear axle of a 'tractor' which could be automatically engaged and disengaged by moving the tractor backwards or forwards in front of the trailer. His USA patent can be downloaded below:
Pescatore's patent includes a coherent summary of the problems faced by single-chassis trucks of the period including:
the lack of goods carrying space
the problem of (at the time unreliable) rubber tyres taking the full weight of goods at the same time as having to deliver propulsion (he proposed rubber tyres for the tow vehicle and iron rims for the trailer)
the vehicle having to remain inactive whilst goods were loaded or unloaded.
Pescatore believed that if the tow vehicle shared the weight of goods by placing the goods in a trailer hitched over the tow vehicle's rear axle, it gave the entire combination better traction and control. Rather than using a circular plate, Pescatore's trailer hitch slotted into an inclined 'V' above the tractor's rear axle, allowing a trailer to be connected and disconnected without manually raising the trailer.
Whilst Pescatore's hitch was not circular in the traditional fifth wheel sense, there is no doubt that Pescatore was one of the first to recognise that weight-sharing between tractor and trailer (achieved by placing the hitch above the rear axle of the tractor) increased stability and allowed greater loads to be carried - the key principle of today's semi-trailers and recreational fifth wheelers.
The Pescatore system was used in the recreational 'fifth wheeler' designed for Belgian Baron Crawhez in 1912, probably the first ever. This important early RV will have its own blog shortly.
In the USA there were literally hundreds of patents issued for fifth wheels between 1910 and 1920. These were nearly all modifications of traditional wagon fifth wheels for use in motorized vehicles, including goods vehicles. Features included ball bearings, anti-friction devices, hinged devices and automatic connecting devices. It is not possible to say, as some do, that one person 'invented' the fifth wheel coupling for use in motorized vehicles. The fifth wheel further evolved during this period to suit many different vehicle types, purposes and terrains, with US haulage companies either licensing an existing patented fifth wheel that suited their particular needs or developing their own.
The Martin Rocking Fifth Wheel of 1915 is sometimes credited as the 'first' fifth wheel, but according to patent records it was simply a hinged adaptation of earlier fifth wheels that allowed the fifth wheel to hinge laterally to better accommodate bumpy roads. It was however extensively marketed and used by Fruehauf from 1915 until 1919, after which the company developed its own system.
Between the two world wars there were significant advances in haulage fifth wheel technology, permitting the rapid development of the semi-trailer. This remains the most widely used form of truck today because it can handle large loads safely and be swapped out easily.
Stage Four: Hedonism
This section is about the history of fifth wheel use in recreational vehicles.
The first RVs to use the fifth wheel principle were also the first ever RVs and were developed in France. The steam-drawn RVs of Prince Oldenburg (1896, shown above and used as the logo of rvhistory.com) and Monsieur Rénodier (1897) both used the fifth wheel principle. By this we mean that the weight of a single-axle trailer was shared with a tractor using a hitch located above (or just behind) the tractor's rear axle.
In both cases the tractor was the De Dion Bouton Steam Bogie. These two combinations weighed 5 tonnes and 7.5 tonnes respectively, so the fifth wheel arrangement was the only way of moving such weight in some safety. It kept their wealthy owners well clear of the unpredictable steam boilers of the time and allowed for tight turning circles, essential for the owners to show off their new contraptions in city streets.
The RV built for Baron Crawhez by Auto-Mixte Pescatore of Belgium in 1912-3 was an altogether more sophisticated tractor-trailer combination and will be covered separately.
Glenn H. Curtiss
In the USA it is generally accepted that the first recreational fifth wheelers in that country were developed by aviator, aircraft manufacturer, automobilist and RV designer Glenn Curtiss. So far as we currently know this is correct. Curtiss will have his own blog shortly.
For now we will simply clarify his contribution to the development of the fifth wheel, since Curtiss designed and built many RVs and not all were fifth wheelers. Curtiss developed RVs in three stages:
A small number of 'Pullman-type' camp cars use using fifth wheels between 1918 and 1919. These were for the personal use of Curtiss and his half-brother Carl Adams and were developed jointly. They did not go into production since they were too large and heavy, but they did serve as prototypes for the smaller Adams Motorbungalo
The Adams Motorbungalo built between 1920 and 1924, the production versions of which were not fifth wheelers
The Curtiss Aerocar built from 1928 to 1940 - these were definitely fifth wheelers
Curtiss patented his prototype camp car in 1921, with the patent being granted in 1922:
This patent focused less on the hitch mechanism and more on the camp car's layout. It details the measures Curtiss undertook to retain the structural integrity of a long, heavy trailer with double-height floor levels and fold-out beds. The production vehicle called the Adams Motorbungalo was a smaller and more conventional RV trailer than the early prototypes. It used a conventional ball and socket hitch attached to the rear of a tow vehicle.
Although the fifth wheel concept was abandoned for the Adams Motorbungalo (probably due to the trailer's weight and the need for it to be towed by standard automobiles), Curtiss did use the fifth wheel principle on commercial vehicles such as this 1921 'trailer bus':
When the Curtiss Aerocar came along in 1928, Curtiss re-applied his early fifth wheel experiences in RVs on a grand scale. He used aircraft design principles to reduce the weight of the trailer and supplied both tractor and trailer hitch in the fifth wheel format. To link the two he used a newly patented fifth wheel called the Aero Coupler. It used an inflated aircraft tyre placed horizontally within a frame on the rear bed of the tractor. When the trailer pin was dropped into the tyre's hub, the tyre absorbed movements in all directions, giving a much smoother ride whilst retaining stability at higher speeds.
The Aero Coupler patent can be viewed here:
The Curtiss Aerocar was one of the safest RVs ever developed thanks to the Aero Coupler hitch, clever suspension and the lightness of its chassis. It could reach hitherto unknown speeds of 60 to 70 mph without causing discomfort to the occupants (who were allowed to travel in the trailer). Despite Curtiss' untimely death in 1930, Curtiss Aerocars continued to be produced until the start of the Second World War. Many variants were produced including luxurious models for wealthy businessmen.
Other Fifth Wheel RVs of the 1930s
There were a number of other fifth wheelers manufactured in the USA in the 1930s.
In 1935 a road builder called Clyne Ternon used an International pick-up truck to tow his 'house trailer' using an unusual fifth wheel hitch that allowed the trailer to be coupled and uncoupled just by raising or dropping the tailgate.
In 1938 an altogether more exotic fifth wheeler was built for millionaire publisher Myron Zobel by Schult Trailer Coach. Known as the Continental Clipper, its interior "was panelled with Australian satinwood and figured aspen and the walls were of tufted pigskin". The story of this RV is told in Zobel's 1955 book The 14-Karat Trailer.
Industrial designer Brooks Stevens designed a Land Cruiser based on a Curtiss Aerocar for millionaire Bill Plankington. It can be viewed here .
The early history of the fifth wheeler shows that this simple piece of technology has survived for hundreds of years through the horse-drawn to the motoring era. It has done so by adaptation. At no stage did anyone 'invent' the fifth wheel, but rather it had numerous milestones and incremental improvements that allowed new forms of haulage and leisure to develop.
With thanks to Collyn Rivers for supplying an article written in about 2000 on this topic as background for this blog. Visit rvbooks.com for further information on fifth wheelers and RV towing dynamics.