A steam wagon (steam lorry or steam waggon) is a steam-powered road vehicle for carrying freight. It was the earliest form of lorry (truck) and came in two basic forms: overtype and undertype – the distinction being the position of the engine relative to the boiler. Manufacturers tended to concentrate on one form or the other.
Steam wagons were a widespread form of powered road traction for commercial haulage in the early part of the twentieth century, although they were a largely British phenomenon, with few manufacturers outside Great Britain. Competition from internal-combustion-powered vehicles and adverse legislation meant that few remained in commercial use beyond the Second World War.
Although the majority of steam wagons have been scrapped, a significant number have been preserved in working order and may be seen in operation at steam fairs, particularly in the UK.
Design features 
The steam wagon came in two basic forms. The overtype designs looked like a cross between a traction engine and a lorry. The front resembled a traction engine by having a cab built around a horizontal fire-tube boiler with a round smokebox and chimney (e.g. Foden). The back resembled a lorry in having a load-carrying body and being built around a chassis. (A traction engine is constructed around the boiler and has no separate chassis.)
The undertype designs have the engine under the chassis (although the boiler - usually a vertical type - remains in the cab), and generally resemble motor lorries rather than traction engines. Undertype designs often had the benefit of a more enclosed cab, and a much shorter length for the same carrying capacity.
The earliest examples of either type had steel or wooden wheels, later followed by solid rubber tyres. Various developments, such as fully enclosed cabs and pneumatic tyres, were later tried by companies in a bid to compete with internal combustion engine-powered lorries. Some wagons built to run on solid tyres were later converted to pneumatic tyres.
Early Years 
Following a relaxation in the legislation covering the use of steam-powered vehicles on common roads, manufacturers started to investigate the possibility of using steam power for a self-contained goods vehicle. Prior to this point, goods were carried in a trailer towed behind a traction engine, or more frequently a horse.
Despite legislation that severely restricted the unladen weight of wagons, steam wagon production began to flourish in the UK in the last decade of the 19th century. Manufacturers such as the Lancashire Steam Motor Company (later Leyland), Coulthard, Mann, Straker and Thornycroft were among the companies that began producing wagons at this time.
In 1901, several makers competed in the Aldershot trials for the War Department, with Thornycroft's gear driven undertype coming out as the winner ahead of Foden's early chain driven overtype. Both manufacturers built on this early success, with Foden patenting the essential features of the overtype wagon and deterring other manufacturers from attempting such a design.
Around this time the Yorkshire Patent Steam Wagon company began producing undertype wagons with their distinctive pattern of double ended boiler. In this period, many manufacturers made attempts to build steam wagons, often with only moderate success.
In 1906, Alley & McLellan launched the first Sentinel wagon, driven by a well designed, rugged engine with poppet valves, and an effective superheated vertical cross watertube boiler. It was a revolutionary design, and immediately took a large share of the market.
Also in 1906, Wallis & Steevens produced an overtype wagon that Foden viewed as an infringement of their patent. The matter led to a patent infringement case. In 1908 the matter was decided in Wallis & Steevens' favour, and upheld on appeal. This naturally led to a great expansion of overtype wagon production, with prominent traction engine companies drawing on their experience building steam tractors to produce wagons, with varying success.
The great transport demands of the World War I led to several of the premier wagon manufacturers - at the time, Sentinel, Clayton & Shuttleworth, Foden and Garrett, having almost their entire production ordered directly for the war effort. This opened up the home market for many other manufacturers to fill the vacuum. A company that entered the market in this period was Atkinson, with their undertype wagon design launched in 1916.
In the immediate post war era, several manufacturers who had previously been producing overtypes switched their focus to undertypes, attempting to compete with Sentinel. Among these companies were Clayton and Garrett. In 1922 Foden began producing the celebrated C-type overtype. It was not a revolutionary wagon, but had improvements such as a better driving position and the option of a windscreen. In 1923, Sentinel launched a much updated wagon, the "Super" Sentinel. In 1924, Fowler made their attempt to enter the undertype market. The various undertypes of the era were frequently fitted with windscreens to improve crew comfort. In the early 1920s, in an attempt to circumvent the weight regulations of the period and allow a higher capacity, several companies had experimented with the idea of an articulated trailer. With the brake and tyre technology of the era, such designs were often found to be difficult to control, with a propensity for jackknifing.In 1926, Garrett produced a rigid six wheeled wagon. Both Sentinel and Foden quickly brought out six wheelers, and these became a large percentage of the output of these manufacturers for the remainder of steam wagon production.
Around this period, Foden made several attempts to build undertypes, with the E-type being largely a failure. Yorkshire produced the updated "WG", "WH" (shaft drive) and "WJ" (six wheeler) wagons
The Last Stand 
By the beginning of the 1930s, the landscape was becoming difficult for steam wagon production. Many manufacturers had gone out of business, and many others had turned to internal combustion. The only major manufacturers who produced new designs in this period were Foden and Sentinel. In 1930, Foden launched their revolutionary "O-Type", better known as the "Speed-Six" and "Speed-Twelve" wagons. They were a valiant attempt at producing a modern steam wagon, but suffered from reliability problems, primarily due to issues with the boiler design. At the end of 1932, Foden turned to diesel wagons.
The only remaining player in the market was Sentinel. In 1933, they launched their "S" type wagons. A fast, well thought out and reliable design, it was a valiant attempt to maintain the steam wagon market. Despite this, in 1938, production ceased, except for 100 wagons produced in the early 1950s for the Argentine government, and a solitary wagon produced for the home market.
Commercial Use 
While steam wagon use greatly diminished in the 1930s due to the effects of the Salter report, many wagons were converted to pneumatic tyres and saw later use. Another use, where wagons often retained solid tyres, was as tar sprayers. Steam wagons also saw use by local authorities into the 1950s. Standard Sentinel waggons were still in commercial use internally at Brown Bayley Steels during the 1960s.
Why road steam disappeared in the UK 
Road steam disappeared through becoming uneconomical to operate, and unpopular with British governments. By 1921, steam tractors had demonstrated clear economic advantages over horse power for heavy hauling and short journeys. However, petrol lorries were starting to show better efficiency and could be purchased cheaply as war surplus; on a busy route a 3-ton petrol lorry could save about £100 per month compared to its steam equivalent, in spite of restrictive speed limits, and relatively high fuel prices and maintenance costs.
Throughout the 1920s and 1930s successive governments placed tighter restrictions on road steam haulage, including speed, smoke and vapour limits, and a 'wetted tax', where the tax due was proportional to the size of the wetted area of the boiler; this made steam engines less competitive against domestically produced internal combustion engined units (although imports were subject to taxes of up to 33%).
As a result of the Salter Report on road funding, an 'axle weight tax' was introduced in 1933 in order to charge commercial motor vehicles more for the costs of maintaining the road system, and to do away with the perception that the free use of roads was subsidising the competitors of rail freight. The tax was payable by all road hauliers in proportion to the axle load; it was particularly damaging to steam propulsion, which was heavier than its petrol equivalent.
Initially, imported oil was taxed much more than British-produced coal, but in 1934 Oliver Stanley, the Minister for Transport, reduced taxes on fuel oils while raising the Road Fund charge on road locomotives to £100 pounds a year, provoking protests by engine manufacturers, hauliers, showmen and the coal industry. This was at a time of high unemployment in the mining industry, when the steam haulage business represented a market of 950,000 tons of coal annually. The tax was devastating to the businesses of heavy hauliers and showmen, and precipitated the scrapping of many engines.
Steam lorry manufacturers 
There were almost 160 manufacturers of steam wagons.
Many traction engine builders also built forms of steam lorry, but some firms specialised in them.
John I. Thornycroft & Company was an established marine engineering company that successfully spawned the Steam Carriage and Wagon Company for the production of steam-powered road vehicles. They supplied steam lorries to the British Army, commercial steam wagons and vans, steam cars (for a few years), and buses – London's first powered bus was a Thornycroft double-decker steam bus.
Manufacturers who specialised in the construction of steam lorries include:
- Bristol Wagon & Carriage Works Ltd Built steam wagons from 1904 to 1908
- Leyland Steam Motor Co. - Founded in 1896-1907, then became Leyland Motors Ltd (Steamers built till 1926).
- Mann's Patent Steam Cart and Wagon Company
- Sentinel Waggon Works
- Sheppee – UK company, also built steam cars (briefly)
- Steam Carriage and Wagon Company (later, Thornycroft), Basingstoke
- Yorkshire Patent Steam Wagon Co.
In popular culture 
The 1928 film The Wrecker features a spectacular crash between a passenger train and a Foden steam lorry stuck on a level crossing. The scene was filmed at Herriard on the Basingstoke and Alton Light Railway, in one take, and destroyed both the steam wagon and the SECR F1 class locomotive.
The 1975 Disney film One of Our Dinosaurs is Missing featured a steam lorry in a (literally) supporting role. It was used as the 'getaway vehicle' for the theft of a large dinosaur skeleton from the Natural History Museum. It was involved in a lengthy chase sequence through the streets of London – as a result, the steam lorry – and the dinosaur – featured prominently on the film's posters and video/DVD case artwork. The lorry was based on an unknown prototype: a long-wheelbase undertype, with a small vertical boiler mounted unconventionally off-centre in the cab, and no windscreen.
See also 
|Wikimedia Commons has media related to:
Overtype steam wagons
|Wikimedia Commons has media related to:
Undertype steam wagons
- "Motor Transport. County Council Haulage II Petrol V. Horse". The Times. 12 February 1921.
- "Motor Transport. The New Legislation". The Times. 6 April 1922.
- "Motor Taxation. Vehicles Using Fuel Oil (Letters)". The Times. 24 March 1933.
- "Tax On Heavy Oils". The Times. 9 March 1934.
- "The World's Commercial Vehicles 1930-1964 - a Record of 134 Years of Commercial Vehicle Production",
G.N. Georgano, Temple Press Books, 1965 – information accessed via the Shires Publication "Steam Wagon".
- The World Encyclopedia of trucks, by Peter J Davis, ISBN 1-84309-201-8
- The World Encyclopedia of Trucks
- Hanomag & Henschel web site featuring both German companies (part in English)
- Mitchell, Vic; Smith, Keith (1984). Branch Lines to Alton. Midhurst, West Sussex: Middleton Press. ISBN 0-906520-11-8.