Editing Steamroller (section)

==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.

===Smokebox===
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 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.

===Special equipment===
The front and rear rolls were usually 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 accessory was a '''tar sprayer''' – a bar mounted on the back of the roller. This was not a common fixture.