Road roller
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, similar rollers are used also at landfills or in agriculture.
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).
Uses
Road rollers use the weight of the vehicle to compress the surface being rolled. Initial compaction of the substrate is done using a pneumatic-tyred roller, with two rows (front and back) of pneumatic 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 achieve a smooth surface. The knobs aid in compression due to the smaller area contacting the ground.
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
• Tandem roller
• Tractor-mounted and -powered
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 weight. When empty, the lighter machine is easier and cheaper to transport between work sites.
• Additional compaction may be achieved by vibrating the roller drums, making a small, light machine perform as well as a much heavier one. Vibration is typically caused by a free-spinning hydrostatic motor inside the drum to whose shaft eccentric weights have been attached.
• Water lubrication may be provided to the drum surface to prevent (for example) hot asphalt sticking to the drum
• Hydraulic transmissions permit greater design flexibility, while early examples used direct mechanical drives; hydraulics reduce the number of moving parts exposed to contamination.
• 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
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