Abstract: An assistance vehicle is connected to a dump truck on or at bases of ascending paths and power is supplied as auxiliary power from the assistant vehicle A to a driving motor in the dump truck. Because of this features a driving unit of the dump truck (a generator for supplying power to the driving motor in the dump truck or a generating engine for driving the generator) is required only to have the performance sufficient for running on horizontal paths, which enables size reduction of the driving unit and as a result cost reduction of the dump truck. Further the assistant vehicle is connected to the dump truck and moves together with the dump truck, so that a freedom degree of the dump truck for a traveling path can substantially be improved.

Abstract: An assistance vehicle (A) is connected to a dump truck (D) on or at bases of ascending paths (T1, T2), and power is supplied as auxiliary power from the assistant vehicle A to a driving motor in the dump truck (D). Because of this feature, a driving unit of the dump truck (D) (a generator for supplying power to the driving motor in the dump truck (D) or a generating engine for driving the generator) is required only to have the performance sufficient for running on horizontal paths (H1 to H3), which enables size reduction of the driving unit and as a result cost reduction of the dump truck (D). Further the assistant vehicle (A) is connected to the dump truck (D) and moves together with the dump truck (D), so that a freedom degree of the dump truck (D) for a traveling path can substantially be improved.

Abstract: A protective device for a front of a large-size dump truck, in which a driver's cab (13) is secured on a front side of a truck body (10) and a vessel (15) is, liftably from its front side, secured on a rear side of the truck body, is characterized in that a front protective guard (20) protruding forward from a position of the driver's cab is attached on a front end portion of the vessel.

Abstract: A pair of pumps deliver pressurized fluid to a steering control valve assembly controlling the operation of a steering cylinder. The steering control valve assembly diverts any excess of the incoming pressurized fluid to a hoist control valve assembly controlling the operation of a pair of implement hoist cylinders. The hoist control valve assembly also diverts any excess of the incoming fluid away from the hoist cylinder pair, this time to a retarder or brake system for cooling same. The retarder receives additional cooling fluid from a hydraulic torque converter, to which the fluid has been forced from another pump. On leaving the retarder the pressurized fluid is cooled and then delivered to a transmission lubricating circuit.