Asteamroller (orsteam roller) is a form ofroad roller – a type of heavy construction machinery used for leveling surfaces, such as roads or airfields – that is powered by asteam engine. The leveling/flattening action is achieved through a combination of the size and weight of the vehicle and therolls: the smooth wheels and the large cylinder or drum fitted in place of treaded road wheels.

Ruston Proctor steamroller (road roller)

Steamroller byAveling and Porter from early 20th century. On display at theGangaramaya Temple inColombo.

The majority of steam rollers are outwardly similar totraction engines as many traction engine manufacturers later produced rollers based on their existing designs, and the patents owned by certain roller manufacturers tended to influence the general arrangements used by others. The key difference between the two vehicles is that on a roller the main roll replaces the front wheels and axle that would be fitted to a traction engine, and the driving wheels are smooth-tired.

The wordsteamroller frequently refers to road rollers in general, regardless of the method of propulsion.^[1]

Before about 1850, the word steamroller meant a fixed machine for rolling and curving steel plates for boilers and ships.From then on, it also meant a mobile device for flattening ground.^[2]An early steamroller was patented by Louis Lemoine in France in 1859 and demonstrated sometime before February 1861.^[3] In Britain, a 30-ton steamroller was designed in 1863 byWilliam Clark and partner W.F. Batho.^[4][5] Having failed to impress the British municipal road authorities it was transferred toKolkata where it continued to work.^[5]

The companyAveling and Porter was the first to successfully sell the product commercially and subsequently became the largest manufacturer in Britain.^[4] In 1866 they produced a prototype roller with 3-foot wide (90 cm) rollers fitted to the rear of a standard 12nominal-horsepower-traction engine. This experimental machine was described by local papers as 'the world's first steamroller' and it caused a public spectacle.

In 1867, the steam road roller was patented and the company began production of the first practical steam roller – the new machine's rollers were mounted at the front instead of the back and it weighed in excess of 30 tons. It was tested on the Military Road inChatham, Star Hill inRochester and inHyde Park,London and the machine proved a huge success. Within a year, they were being exported around the world, including to France,India and the United States. ANew York City chief engineer said of one of these, that "in one day's rolling at a cost of 10 dollars, as much work was accomplished as in two days' rolling with a 7 ton roller drawn by eight horses at a cost of 20 dollars a day."^[6] The heavier rollers were found to be hard to handle and the weight of the machines was reduced to around 10 tons.^[4]

Aveling and Porter refined their product continuously over the following decades, introducing fully steerable front rollers andcompound steam engines at the 1881Royal Agricultural Show. The move to asphalt for road construction resulted in the demand for steamrollers that could rapidly reverse so they could roll the tar while still hot.^[7] Machines that could do this were introduced in the first decade of the 20th century.^[7]

Production ended around 1950.^[8]

The majority of rollers were of the same basic 3-roll configuration, gear-driven, with two large smooth wheels (rolls) at the back and a single wide roll at the front (in actuality, the wide roll usually consisted of two narrower rolls on the same axle, to make steering easier). However, there was also a distinctive variant, the "tandem", which had two wide rolls, one front, one rear. Those made byRobey & Co used their standardsteam wagon engine andpistol boiler fitted in a girder frame with rolls and a chain drive to produce a quick-reversing roller suitable for modern road surfaces such astarmacadam and bituminousasphalt.^[9] A number of Robey & Co. tandem rollers were modified to make a further variant, the tri-tandem, which was a tandem with a third roll, mounted directly behind the rear one. Robey supplied the parts, but the modification was undertaken by Goodes of Royston.^[9] Ten tandem and two tri-tandem Robey rollers survive in preservation,^[10] and one of the tri-tandems is known to have been used to construct parts of theM1 motorway.

A variation of the basic configuration was the "convertible": an engine which could be either a steam roller or a traction engine and could be changed from one form to the other in a relatively short time –i.e., less than half a day. Convertible engines were liked by local authorities, since the same machine could be used for haulage in the winter and road-mending in the summer.

Although most steam roller designs are derived from traction engines, and were manufactured by the same companies, there are a number of features that set them apart.

The most obvious difference is in the wheels. Traction engines were generally built with large fabricated spoked steel wheels with wide rims. Those intended for road use would have continuous solid rubber tyres bolted around the rims, to improve traction on tarmac. Engines intended for agricultural use would have a series of strakes bolted diagonally across the rims, like the tread on a modern pneumatic tractor tyre, and the wheels were typically wider to spread the load more evenly.

Steam rollers, on the other hand, had smooth rear wheels and a roller at the front. The roller consisted of a pair of adjacent wide cylinders supported at both ends. This replaced the separate wheels and axle of a traction engine.

In the conventional arrangement, the front roller is mounted centrally, forward of the chimney. In order to allow enough clearance from the boiler (and hence a larger front roll), thesmokebox is extended forward substantially at the top to incorporate a support plate on which to mount the bearing for the roller assembly. This gives the distinctive, hooded look to the front of a steam roller. It also necessitates a different design of smokebox door – it has to hinge up or down, rather than opening sideways, due to the limited access available. Access to the boiler tubes for cleaning is limited and the brush usually has to be inserted through the small gap between the top of the roll and the fork.

The front and rear rolls were usually fitted withscraper bars. As the vehicle moved along, these removed any surface material that had become stuck to the roll, to prevent a build-up of material and ensure a flat finish was maintained.

Some steam rollers were fitted with ascarifier mounted on the tender box at the rear. They could be swung down to road level and used to rip up the old surface before a road was remade.

Another accessory was atar sprayer – a bar mounted on the back of the roller. This was not a common fixture.

Britain was a major exporter of steam rollers over the years, with the firm ofAveling and Porter probably being the most famous and the most prolific.

Many othertraction engine manufacturers built steam rollers, but after Aveling and Porter, the most popular wereMarshall, Sons & Co.,John Fowler & Co., andWallis & Steevens.

In America, theBuffalo-Springfield Roller Company ^[d] was a large builder.J. I. Case made a roller variant of their farm engines, but had a small market share. Other nations had makers including the Czechs, Swiss, Swedes, Germans (notablyKemna) and Dutch which produced steam rollers.

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  United States-built 1924 Buffalo Springfield steam roller: avertical boiler design with tandem rolls. Note position of firebox door, facing out of frames.
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  Other side of same roller showing offset driving position: driver faces boiler controls (i.e. 'backwards') and steers with right hand
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  An early "Kemna" Steamroller

In the UK, a number of companies owned fleets of steam rollers and contracted them out to local authorities. Many were still in use into the 1960s, and part of theM1 motorway was made using steam rollers.^[11] A few steam rollers were being used for road maintenance in the early 1970s, and this may go some way to explaining why diesel-powered rollers are still colloquially known assteam rollers today.

Many steam rollers are preserved in working order, and can be seen in operation during speciallive steam festivals, where operatingscale models may also be displayed. At some of the UKsteam fairs and rallies, demonstrations of road building using the old techniques, tools and machines are re-enacted by 'Road Gangs' in authentic dress. Steam rollers feature prominently in these demonstrations. The annualGreat Dorset Steam Fair has a section dedicated to road-making machinery, including a line-up of working steam rollers.

A number of steamrollers ended their working lives in children's playgrounds to provide something for children to play on.^[12][13]

Two popular American bands were named after steamrollers,Buffalo Springfield andMannheim Steamroller.Parni Valjak (trans.Steamroller) is the name of the popular Croatian and Yugoslav rock band, and the group has used the name Steam Roller on their English language releases.^[14]

Two different steamrollers appear as prominent characters in theThomas & Friends television series; George and Buster, both of whom are based on the Aveling-Barford R class design.

Britishsteeplejack and engineering enthusiastFred Dibnah was known as a national institution in Great Britain for the conservation of steam rollers and traction engines. The first engine he restored to working order was anAveling & Porter steam roller, registration no. DM3079. Built in 1912, it was a 10-ton slide-valve, single-cylinder, 4-shaft, road roller.^[15] Originally named "Allison", after his first wife, Fred renamed the engine "Betsy" (his mother's name) following his divorce – Fred's view being "wives may change but your mother remains your mother!" This roller was featured in many of Fred's early television programmes. It may still be seen at steam rallies in Britain and was in steam at theGreat Dorset Steam Fair in 2011.

AuthorTerry Pratchett instructed his collaboratorNeil Gaiman that anything Pratchett had been working on at the time of his death should be destroyed by a steamroller. Pratchett's daughter and literary executor Rhianna Pratchett also stated that she had no desire to try to finish her father's work or continue theDiscworld franchise without him. Accordingly, Pratchett's assistant Rob Wilkins brought Pratchett's computer hard drive to theGreat Dorset Steam Fair, where a steamroller was driven over it.^[16]

The steamroller has a strong symbolism of an irresistible, onward-pushing force. TheImperial Russian Army was nicknamed "steamroller" duringWorld War One, as it was huge in size, and Russia initiated the war with an offensive. The "Russian Steamroller" is one of thepersonifications ofRussia, along with theRussian bear,double-headed eagle andMat Zemlya.

• History of steam road vehicles
• Traction engine
• Roller (agricultural tool) – for farm rollers
• Roller (disambiguation) – for other types of roller
• List of steam energy topics
• Paddy's motorbike – nickname for another type of compaction vehicle.
• Thomas Green & Son builders of steam rollers, but better known for motor rollers.

• Burton, Anthony (2000).Traction Engines: Two Centuries of Steam Power. Leicester: Silverdale Books.ISBN 1-85605-533-7.
• Ranieri, Malcolm (2005).Traction Engine Album. Ramsbury: Crowood Press.ISBN 1-86126-794-0.

• Road Roller AssociationArchived 7 May 2016 at theWayback Machine – UK-based society dedicated to the preservation of steam (and motor) rollers and ancillary road-making equipment.
• "Steam Dinosaur" – world's oldest surviving traction engine: immediate ancestor of Aveling's earliest rollers.
• Fred Dibnah's roller 'Betsy' – The story of Betsy's restoration
• The New England Wireless and Steam Museum Buffalo-Springfield Steam Macadam Roller