Steamroller

A steamroller (or steam roller) is a form of road roller – a type of heavy construction machinery used for leveling surfaces, such as roads or airfields – that is powered by a steam engine. The leveling/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, and the driving wheels are smooth-tired. The word steamroller frequently refers to road rollers in general, regardless of the method of propulsion.

History

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. An early steamroller was patented by Louis Lemoine in France in 1859 and demonstrated sometime before February 1861. In Britain, a 30-ton steamroller was designed in 1863 by William Clark and partner W.F. Batho. Having failed to impress the British municipal road authorities, it was transferred to Kolkata, where it continued to work. The company Aveling and Porter was the first to successfully sell the product commercially and subsequently became the largest manufacturer in Britain. In 1866 they produced a prototype roller with 3-foot-wide (90 cm) rollers fitted to the rear of a standard 12-nominal-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 in Chatham, Star Hill in Rochester and in Hyde 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. A New 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." The heavier rollers were found to be hard to handle, and the weight of the machines was reduced to around 10 tons. Aveling and Porter refined their product continuously over the following decades, introducing fully steerable front rollers and compound steam engines at the 1881 Royal 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. Machines that could do this were introduced in the first decade of the 20th century. Production ended around 1950.

Configurations

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. They were better for rolling asphalt which drove demand from the 1920s. Those made by Robey & Co used their standard steam wagon engine and pistol boiler fitted in a girder frame with rolls and a chain drive to produce a quick-reversing roller suitable for modern road surfaces such as tarmacadam and bituminous asphalt. 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. Ten tandem and two tri-tandem Robey rollers survive in preservation, and one of the tri-tandems is known to have been used to construct parts of the M1 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. A rare type with only four built were embankment rollers with twin wheels at both the front and back rather than a single roller at the front. They were used in the construction of reservoirs.

Design features 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.

Wheels 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.

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