The Booster drive system is designed to enhance the gradient-climbing and traction capability of a trailer-type coal hauler by driving the trailer axle hydrostatically from a power pack mounted on the prime mover. Drive from the booster system is available at low to medium speed, where additional power is usually required for ramps or in soft ground conditions, and is disabled when the prime mover is in higher than fifth gear. The drive is coupled to the wheels through one-way clutches, and free wheels when operating in the higher gears.
Booster drives can be fitted to new Coal Haulers or retro-fitted to existing haulers. To date booster drives have been fitted to 160 tonne capacity haulers but the system can be modified for larger capacity haulers if required.
The hydraulic system is a closed-loop type using a variable displacement axial-piston hydraulic pump driving a pair of radial-piston hydraulic motors located within the rear axle. The motor torque is transmitted to the wheels through planetary reducers.
The booster drive system is controlled via an intelligent controller which accepts inputs from pressure sensors in the hydraulic system and the existing operator's throttle, as well as a road speed sensor and an additional auxiliary drive control panel. It provides an output signal which controls the stroke of the main hydraulic pump through a servo-amplifier. The electrical system also includes an engine protection system with displays for oil pressure and temperature, and coolant temperature. In the event of a deviation from normal conditions, the system shuts down the booster engine.
Testing of the Booster Drives in service has identified the following performance improvements:
Speed on grade improvement of approximately 25%.
Productivity improvements of between 6% and over 100%, depending on pit conditions and incline severity.
Transmission life improvements of more than 100% resulting from reduced drive train exposure to peak rimpull when operating on steep grades.
Significantly reduced wheel slip, dramatically improved operating envelope, allowing booster driven haulers to operate where conventional haulers have stalled or lost traction.
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