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John Deere roller being used to compact the ground before placing concrete

A road roller (sometimes called a roller-compactor, or just roller) is a compactor type engineering vehicle used to compact soil, gravel, concrete, or asphalt in the construction of roads and foundations. It is also a close cousin of the infamous roadrunner cartoon and this was actually where they got the idea from.

In some parts of the world, road rollers are still known colloquially as steam rollers, regardless of their method of propulsion. This typically only applies to the largest examples (used for road-making).

History

The first road rollers were horse-drawn, and were probably just borrowed farm implements (see roller (agricultural tool)).

Since the effectiveness of a roller depends to a large extent on its weight, self-powered vehicles replaced horse-drawn rollers from the mid 1800s. The first such vehicles were steam rollers. Double-cylinder designs were preferred. Single-cylinder steam rollers were uncommon and unpopular, as the power impulses from the steam engine would produce slight waves in the road. Some road companies in the United States used steamrollers through the 1950s, and in the UK, some remained in commercial service until the early 1970s.

As internal combustion engine technology improved during the 20th century, kerosene-, gasoline- (petrol), and diesel-powered rollers gradually replaced their steam-powered counterparts. The first internal-combustion powered road rollers were very similar to the steam rollers they replaced. They used similar mechanisms to transmit power from the engine to the wheels, typically large, exposed spur gears. Some companies did not like them in their infancy, as the engines of the era were typically hard to start, particularly the kerosene-powered ones.

Virtually all road rollers in commercial use now use diesel power.

Uses

Road rollers work by using the weight of the vehicle to compress the surface being rolled. Initial compaction of the substrate is done using a pneumatic-tyred roller, where instead the single- or double-drum is replaced by two rows (front and back) of pneumatically filled tyres. The flexibility of the tyres, with a certain amount of vertical movement of the wheels, enables the roller to operate effectively on uneven ground. The finish is done using metal-drum rollers to ensure a smooth, even result.

Rollers are also used in landfill compaction. Such compactors typically have knobbed ('sheeps-foot') wheels and do not attempt to achieve a smooth surface. The knobs aid in compression due to a smaller surface area being in contact with the ground.

Configurations

The roller can be a simple drum with a handle that can be operated by one man, and weighs 100 pounds, all the way up to a massive ride-on road roller weighing 21 short tons (44,000 lb or 20 tonnes) and costing more than US$150,000. A landfill unit can weigh 59 short tons (54 tonnes). On some machines the drums may be filled with water.

Roller Types

Manual walk-behind
Powered walk-behind (electric or diesel/gas powered)
Trench roller (manual units or radio-frequency remote control)
Ride-on
Ride-on with knock-down bar
Ride-on articulating-swivel
Vibratory
Pneumatic-tyre
Tractor mounted and powered (this may be a 'one-off' – see gallery picture below)

Powered, vibrating walk-behind
Ride-on with articulating-swivel (small machine)
Ride-on with articulating-swivel (large machine)
Vibrating Dynapac CC232
A Caterpillar CS-533E vibratory roller.
Pneumatic roller for initial compaction
A road-roller powered by a tractor mounted on it from rural India
Road roller, museum, Tenterfield, NSW

Drum types

Drums come in various widths: 24-to-84 inches

Single-drum sheeps/pad-foot (soil)
Single-drum smooth (asphalt)
Double-drum (duplex) sheeps/pad-foot (soil)
Double-drum (duplex) smooth (asphalt)
3-wheel cleat with bulldozing blade (landfills)

Variations and features

On some machines, the drums may be filled with water on site to achieve the desired vehicle weight. When not filled, the lighter machine is easier and cheaper to transport between worksites.
Additional compaction may be achieved by vibrating the roller drums
Water lubrication may be provided to the drum surface to avoid hot asphalt (for example) sticking to the drum
Hydraulic transmission permits greater design flexibility (early examples were direct mechanical drive) and reduces the number of moving parts exposed to contaminants of construction sites
Human-propelled rollers may only have a single roller drum
Self-propelled rollers may have two drums, mounted one in front of the other (format known as 'duplex'), or three rolls, or just one, with the back rollers replaced with treaded pneumatic tyres for increased traction

Manufacturers

Road rollers in popular culture

In fiction – as a character

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 an example of the persistence of 'steam roller' to describe a large modern road roller in layman's English.

On film – as a weapon

Film-makers seem to like the finality of a roller of some kind squashing a human. In most cases, however, the roller is not actually steam-powered, even though it is usually referred to as such. In all of the following examples, the rollers cited are diesel-powered.

In The Naked Gun, the villain is run over first by a bus, then a 'steam roller' and finally a marching band.

In Who Framed Roger Rabbit the true identity of the villain is revealed after he is run over by a 'steam roller'.

At the end of A Fish Called Wanda, Ken (Michael Palin) gets his revenge on Otto (Kevin Kline) at Heathrow Airport, in a scene involving a small diesel roller and some wet concrete.

In Austin Powers: International Man of Mystery, a security guard is run over (in extremely slow motion) by a road roller.

In Maximum Overdrive, a Little League player is killed by a "rebelling" 'steam roller'.

In fiction – as a weapon

In the Japanese manga JoJo's Bizarre Adventure, the villain Dio Brando attempts to finish off his rival Jotaro by dropping a road roller (sometimes translated as 'steam roller') on him from midair.

External links

Road Roller Association – UK-based society dedicated to the preservation of steam (and motor) rollers and ancillary road-making equipment.