Rigid Dump Trucks

A rigid dump truck, also called a rigid hauler, off-highway truck or mining truck, is a heavy dump truck built on a single stiff chassis with the body, cab and axles all mounted on one frame. It is designed to carry very large loads of rock, ore or earth over haul roads inside quarries, open-pit mines and large earthworks sites. Unlike an on-road tipper, it is too wide and too heavy to travel on public roads, and it is usually delivered to site in pieces and assembled there.

The rigid dump truck is the workhorse of surface mining and large-scale quarrying. It works in a loop with an excavator, a shovel or a wheel loader: the loading machine fills the body, the truck hauls the material to a crusher, a stockpile or a waste dump, tips it and returns. On good haul roads, and over long distances, few machines move material at a lower cost per tonne.

Brief History of Rigid Dump Trucks

In the early twentieth century, heavy hauling on quarries and construction sites relied on rail wagons, horse-drawn carts and modified road trucks. The first purpose-built off-highway dump truck is generally credited to Euclid, a company from Ohio in the United States, which introduced its Model 1Z rear-dump hauler in 1934. The Euclid name became almost a synonym for off-highway trucks in the following decades, and the business later passed through several owners, including General Motors, before ending up with Hitachi.

After the Second World War, demand from open-pit mines, dam building and motorway construction pushed payloads steadily upwards. Diesel-electric drive, borrowed from locomotive practice, appeared on large trucks from the 1960s and made it possible to build haulers with far greater capacity than mechanical drivelines could handle at the time. Caterpillar, Komatsu, Terex, Wabco, Unit Rig and others competed in the growing mining market. By the end of the twentieth century the largest trucks carried well over 300 tonnes, and in 2013 the Belarusian manufacturer BelAZ presented the 75710, a diesel-electric truck with a claimed payload of about 450 tonnes. Today the market ranges from quarry trucks of around 35 to 100 tonnes to ultra-class mining trucks, and it is at the centre of the move towards autonomous and electric haulage.

How a Rigid Dump Truck Works

The rigid dump truck has a simple layout: a two-axle chassis, a cab placed high on one side, a large engine at the front and a steel body tipped by hydraulic cylinders.

Chassis and axles. A heavy box-section frame carries the engine, cab and body. The front axle steers, and the rear axle, usually fitted with twin tyres, carries most of the load and is driven.
Mechanical drive. Smaller and mid-size trucks use a diesel engine, a torque converter and an automatic powershift transmission driving the rear axle through a differential and final drives.
Electric drive. Many large mining trucks use a diesel engine to turn an alternator. The electricity powers traction motors in the rear wheels, which also work as generators during retarding.
Suspension. Hydro-pneumatic or oil-gas suspension cylinders on each wheel absorb shocks from uneven haul roads and protect the frame and the operator.
Body and tipping. The dump body, often with a V-shaped or flat floor and a canopy over the cab, is raised by two or more hydraulic hoist cylinders to discharge material to the rear.
Braking and retarding. On long downhill hauls, the truck holds its speed with a hydraulic or electric retarder, while oil-cooled wet brakes provide service and emergency braking.

Types of Rigid Dump Trucks

Quarry and Construction Trucks

Trucks of about 30 to 100 tonnes payload, usually with mechanical drive. They serve quarries, cement plants, large civil works and smaller mines, and can be moved between sites on low loaders after partial dismantling.

Mining Trucks

Trucks from about 100 to 250 tonnes payload, working in open-pit coal, copper, iron ore and gold mines. Both mechanical and diesel-electric drive are common in this range.

Ultra-Class Trucks

The largest haulers, with payloads of roughly 300 tonnes and more. They are almost always diesel-electric, run on very large radial tyres and are matched to rope shovels or large hydraulic excavators.

Special Bodies and Variants

Rigid chassis are also fitted with coal bodies of large volume, water tanks for dust control, service and fuel modules, and bottom-dump or side-dump arrangements for specific mine layouts.

Size Classes

Class	Typical payload	Typical use
Quarry	about 30 to 60 t	Quarries, cement plants, civil works
Mid-size	about 60 to 150 t	Large quarries, smaller open-pit mines
Large mining	about 150 to 250 t	Open-pit mines
Ultra-class	about 300 t and more	Large open-pit mines

Figures are indicative.

Main Manufacturers

Caterpillar, with a range from quarry trucks to the ultra-class 797 series.
Komatsu, with mechanical and electric drive trucks and the 930E and 980E families.
Liebherr, which builds diesel-electric mining trucks such as the T 284.
Hitachi Construction Machinery, with the EH series of electric drive trucks.
BelAZ, the Belarusian maker with a very wide range of mining trucks.
Volvo Construction Equipment, with its range of rigid haulers.
XCMG and other Chinese manufacturers, increasingly active in the mining market.

Main Uses of Rigid Dump Trucks

Hauling ore and waste rock in open-pit mines.
Moving blasted rock from the face to the primary crusher in quarries.
Bulk earthmoving on dams, motorways, airports and other large civil projects.
Removing overburden in coal and mineral mines.
Service roles, such as water trucks for dust suppression on haul roads.

Rigid or Articulated?

The choice between a rigid and an articulated dump truck depends mainly on ground conditions, haul road quality and the scale of the job.

Ground. Articulated trucks, with all-wheel drive and a pivoting joint, cope better with soft, wet and uneven ground. Rigid trucks need firm, well-maintained haul roads.
Payload. Rigid trucks reach payloads far beyond the largest articulated trucks, which usually stay below about 60 tonnes.
Speed and cost per tonne. On good roads and long hauls, a rigid truck is typically faster and cheaper to run per tonne moved.
Tyre wear. Rigid trucks can suffer higher tyre wear on poor roads, since only the rear axle is driven and the load is concentrated.
Mobility between sites. Smaller articulated trucks are easier to move from job to job. Large rigid trucks usually stay on one site for years.

Planning and Operating Tips

Match truck and loader. The loading machine should fill the body in a small number of passes, typically three to six, without overloading.
Invest in haul roads. Good grades, drainage, width and surface maintenance reduce fuel use, tyre wear and frame damage more than almost any other measure.
Manage payload. Onboard weighing systems help avoid both underloading, which wastes trips, and overloading, which shortens component life.
Watch the tyres. Mining tyres are costly and sometimes in short supply. Pressure and temperature monitoring and careful road design extend their life.
Plan the fleet. Fleet management software and cycle time analysis help decide how many trucks each loader needs and reduce queuing.

Safety

The size of a rigid dump truck creates large blind spots around the machine, particularly at the front and on the side opposite the cab. Collisions with light vehicles, pedestrians and other trucks are among the most serious risks on mine sites. Most operations separate light and heavy traffic, use berms or windrows along the edges of haul roads and dumps, and require radio contact before approaching a truck. Proximity detection, cameras and collision avoidance systems are widely used. Other hazards include loss of braking on downgrades, tyre fires and explosions, rollover at the dump edge and fatigue on long shifts. Access to the cab uses ladders or powered stairways with three points of contact, and maintenance on raised bodies must use body props or locks.

Trends and Technology

Autonomous haulage is now established in large open-pit mines. Systems such as Komatsu FrontRunner and Cat Command allow trucks to run without an operator on board, supervised from a control room. Trolley assist, where trucks draw power from overhead lines on uphill ramps, is used at some mines to reduce diesel consumption. Manufacturers and mining companies are testing battery-electric, hydrogen and dual-power trucks as part of decarbonisation plans. Onboard sensors, payload monitoring, tyre management systems and remote diagnostics feed fleet management software that plans maintenance and optimises cycles.

Key Terms

Payload: the weight of material a truck is designed to carry per load.
Haul road: the dedicated road network on which the trucks travel inside a mine or quarry.
Retarder: a system that slows the truck on downgrades without using the service brakes.
Diesel-electric drive: a drive in which the engine powers an alternator and electric motors drive the wheels.
Pass matching: sizing the loading machine so it fills the truck in a set number of bucket passes.
Trolley assist: overhead power lines that supply electricity to trucks on uphill sections.

Frequently Asked Questions

What is the difference between a rigid dump truck and a tipper truck? A tipper is a road vehicle, legal on public roads, with a payload usually below about 30 tonnes. A rigid dump truck is an off-highway machine, much wider and heavier, used only on sites and haul roads.

Why do large mining trucks use electric drive? Electric drive avoids very large mechanical transmissions, provides strong retarding on downgrades and suits high power outputs. It also prepares the truck for trolley assist and alternative power sources.

Can a rigid dump truck travel on public roads? Generally no. Its width, weight and tyres exceed road limits. Smaller units are transported on low loaders, often with the body removed, and large trucks are assembled on site.

How many trucks does one excavator need? It depends on the haul distance, road conditions and loading time. Planners calculate the cycle time of each truck and add trucks until the loader works without long waits.