Rigid Dump Truck

Overview

A rigid dump truck is a two-axle off-highway hauler built to move very large loads of ore and overburden inside a mine. Unlike an articulated truck, the Main Frame is a single stiff structure with no centre joint, so the whole machine relies on its suspension and tyres for ground following rather than on a pivoting chassis. A truck in this class carries 180-220 t of payload, and when loaded the gross vehicle weight reaches 350-400 t. Almost everything about the design follows from those numbers: the tyres, the drive, the brakes, and the structure are all sized for a mass far beyond anything that travels on public roads.

The truck runs on six tyres, single on the front steering axle and dual on the rear drive axle. The Dump Body & Hoist sits over the rear of the frame and tips backward to discharge. Power comes from a large diesel engine, but the wheels are not driven mechanically. Instead the truck uses a diesel-electric drive, where the engine spins a generator and electric motors in the rear wheels do the work. This layout suits a heavy hauler because it removes the long mechanical driveline and gives smooth, controllable torque from a standstill up a grade.

Frame and Structure

The Main Frame is the backbone that every other system bolts to. Two box-section Frame Side Rail run the length of the truck and are tied together by welded Frame Crossmember into a stiff box that resists the twisting loads of one wheel dropping into a pothole while another stays high. At the rear of the frame the Body Hinge Pin carries the hinge pin the dump body rotates about, and the Hoist Cylinder Trunnion trunnions carry the base of each hoist cylinder. A Front Deck & Ladder and ladder over the engine bay give the crew safe access for daily service. Cast steel nodes and brackets are joined with a heavy Fastener Set at the high-stress corners.

Engine and Power Module

The prime mover is a V16 Diesel Engine, a quad-turbocharged V16 diesel of 60-95 L displacement producing 1500-2700 kW depending on the model. Four Turbocharger units feed compressed air through a Charge-Air Cooler to keep intake temperatures down and power up, which matters at the altitudes many mines sit at. Engine heat is rejected by a large Engine Radiator cooled by a hydraulically driven Cooling Fan that varies its speed to match demand and save parasitic power. Two Air Cleaner assemblies with preseparators strip mine dust before it reaches the turbochargers, and the Exhaust System routes gas up a vertical stack clear of the operator. Crank and accessory shafts run on an Oil Seal set rated for the dust and vibration of the duty.

Diesel-Electric Drive

The engine does not turn the wheels through a gearbox. It drives a Traction Alternator, a brushless AC traction alternator coupled to the flywheel. Its output passes through a Main Rectifier to form a DC link, smoothed by a DC-Link Capacitor Bank bank, and then two Traction Inverter units convert that DC back into variable-frequency AC to control the wheel motors independently. All of this sits in a Power Control Cabinet with the contactors and protection.

The same system handles braking. On a downgrade the wheel motors run as generators, and the power they produce is dumped into a Dynamic Retard Grid, a bank of resistors that turns the braking energy into heat. A Retard Grid Blower forces air through the grid so it can absorb the sustained load of a long loaded descent without the service brakes overheating. Dynamic retarding is the primary way the truck controls speed downhill, with the friction brakes held in reserve.

Axles, Suspension, and Steering

The Rear Drive Axle carries the drive. A fabricated Rear Axle Housing holds two Electric Wheel Motor units, each an enclosed AC induction motor cooled by a Wheel Motor Blower. Each motor drives a Planetary Final Drive, a double-reduction planetary set of roughly 30:1 built around a Helical Gear Pair and running on a Ball Bearing support. The rear wheels mount in dual pairs of Rear Tyre & Rim, radial off-the-road tyres up to 40.00R57.

The Front Steering Axle does not drive. It carries two Steering Spindle king-pin spindles steered by Steering Cylinder units linked through a Steering Tie Rod, with a single Front Tyre & Rim at each end. Ride is handled by the Hydropneumatic Suspension, four nitrogen-over-oil struts. The Front Suspension Strut doubles as the upper steering pivot, while the Rear Suspension Strut carries each loaded rear corner. Each strut has a Strut Charge Valve to set ride height, and a Pressure Sensor in each feeds the payload system.

Braking and Dump Body

Service braking uses a Oil-Cooled Disc Brake pack at every wheel, oil-cooled multi-disc units fed by a Brake Hydraulic Pump and accumulators, with their own Brake Oil Cooler and a Brake Control Valve. Dumping is done by twin Hoist Cylinder units, three-stage telescopic cylinders that raise the Dump Body Shell to about 45 degrees. The body is protected by a bolt-in Body Wear Liner, and oil for the hoist comes from a Hoist Pump, Hoist Control Valve, and Hoist Reservoir.

Cab, Fuel, and Controls

The operator works from a Operator Cab certified as roll-over and falling-object protection, with a Operator Seat on air suspension, a Steering Control orbital valve, an LCD Panel display, and a Cab HVAC Unit unit keeping the cab clean in dust. Fuel is held in a Diesel Fuel Tank of 3000-5000 L, drawn by a Fuel Transfer Pump through a Fuel Filter set and refilled at a Fast-Fill Coupling coupling. Tying it together, a Vehicle Control Unit coordinates the drive over CAN, a Payload Monitor weighs each load from the strut pressures, and a Wire Bundle runs the harness across the frame.