A steamroller (or steam roller) is a form of road roller – a type of heavy construction machinery used for levelling surfaces, such as roads or airfields – that is powered by a steam engine. The levelling/flattening action is achieved through a combination of the size and weight of the vehicle and the rolls: the smooth wheels and the large cylinder or drum fitted in place of treaded road wheels.
The majority of steam rollers are outwardly similar to traction 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.
In many parts of the world, the term steam roller is still used to refer to a road roller, regardless of the method of propulsion. This typically only applies to the largest examples (used for road-making).
This article concentrates on steam-powered rollers; see road roller for a description of motor (eg diesel) rollers.
The majority of rollers were of the same basic configuration, with two large smooth wheels at the back and a single wide roll at the front. However, there was also a distinctive variant, the 'tandem', which had two wide rolls, one front, one rear (see photo
). This configuration is still used frequently for small motor road rollers
for use on minor pavement and road repairs.
Another variation was the 'convertible': a combined 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 (for example).
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. All traction engines were 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 was a single wide cylinder supported at either end. 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), the smokebox 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 drop down, rather than opening sideways, due to the limited access available.
The rear rollers were fitted with scraper 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 a scarifier 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 'extra' was a tar sprayer - a bar mounted on the back of the roller. This was not a common fixture.
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 the M1 motorway was made with the help of steam rollers.
A few steam rollers were still being used for road maintenance in the early 1970s, and this may go some way to explaining why road rollers are still colloquially known as steam rollers to this day.
Britain was a large exporter of steam rollers to the world over the years with the firm of Aveling and Porter
probably being the most famous and the most prolific.
Many other traction engine manufacturers built steam rollers, but after Aveling and Porter, the most popular were Marshall, Sons & Co., John Fowler & Co., and Wallis & Steevens.
In America, the Buffalo-Springfield Company was a large builder. J. I. Case made a roller variant of
their famed farm engines, but had a small market share. Other nations had makers including the Czechs, Swiss, Swedes, Germans and Dutch which produced steam rollers.
Many steam rollers are preserved in operating condition, and can be seen in operation during special live steam
festivals, where operating scale models
may also be displayed.
In popular culture
- UK steeplejack and engineering enthusiast Fred 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 an Aveling & Porter steam roller, registration no. DM3079. Built in 1912, it was a 10 ton slide-valve, single-cylinder, 4-shaft, road roller.
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 the Great Dorset Steam Fair in 2006, working in the road-mending demonstration.
- A steam roller was part of the 'supporting cast' in the British film, The Titfield Thunderbolt. The roller's encounter with a GWR tank loco in the film, and its real-life history and preservation are described here: The Titfield Thunderbolt.
- In the film Dad's Army, the Walmington-on-Sea platoon are sent on an exercise for Home Guard training. On the way, an incident that disables Jones's van results in Capt. Mainwaring commandeering a passing steam roller to tow the van to the exercise. Unfortunately, on arrival at the training camp, Mainwaring and Jones discover that neither knows how to stop the roller, and they end up flattening their tents and equipment.
- There is a 'steam'roller in the film Maximum Overdrive.
- There is also a steamroller in the film Sleeper.
- George the Steamroller is a fictional steamroller from the Rev W. Awdry's Railway Series books and also in the derived TV series, Thomas the Tank Engine and Friends. Buster the Steamroller, a member of "The Pack", has also appeared in the TV series.
- Roley is one of the main vehicle characters in the children's books and TV series, Bob the Builder. He is a green roller with a cab, enclosed power unit and no chimney, and so is obviously diesel-powered - nevertheless, his official title is Roley the Steamroller. This is another example of why the use of 'steam roller', to describe a modern road roller, still persists in the English language.
- The group Buffalo Springfield named themselves after a steam roller parked outside the house.
- The song Steamroller Blues was written and performed by James Taylor in 1970 and subsequently became a favourite of live concerts by Elvis Presley.
- In Marianne Moore's To A Steam Roller, she portrays the democratizing ability of the steamroller: "You lack half wit. You crush all the particles down / into close conformity, and then walk back and forth / on them" (3-5).
In Video Games
- Road Roller Association – 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.
(Article includes lots of detail about early Aveling roller design.)