Closer Look: Liebherr 50-tonne-class PR 766 dozer
The hydrostatic drive on Liebherr's new PR 766 means the diesel engine can be kept at a constant, optimally efficient speed, regardless of the load. The fact that speed fluctuations are avoided sets the Liebherr travel drive apart from all other large crawler dozer drive concepts currently available on the market, the company says. Essential drivetrain components are developed in-house and optimally coordinated, which increases the efficiency of the system as a whole.
In addition, the hydrostatic drive omits high-wear components, such as torque converters, multi-speed gearboxes, steering clutches and service brakes. Instead, high-quality and particularly reliable hydraulic pumps and hydraulic motors operate with virtually no wear. Intervals for changing the hydraulic oil can be extended to up to 8,000 operating hours if the hydraulic oil is monitored.
Technology and innovation
With operating weights of between 46,200 and 54,200 kg, the PR 766 is the successor model to the PR 764 and is powered by a 310-kW (422-hp) eight-cylinder diesel engine. The engine embodies the latest generation of Liebherr engine technology. First, an optimized combustion process minimizes particles while they are still inside the engine. Liebherr achieved this by developing its own common rail injection and engine control systems. Second, the exhaust gas aftertreatment uses selective catalytic reduction. As a result, the new Liebherr diesel engines surpass Tier 4/Stage IV/emission standards without the use of a diesel particulate filter.
As with all of Liebherr's Generation 6 crawler dozers, the PR 766 comes equipped with ECO function, which gives the operator a choice between high performance or maximum efficiency. In lightweight to moderately heavy applications, the ECO control system ensures increased efficiency and therefore additional fuel savings compared to conventional drive concepts.
Liebherr has another innovative feature on the Generation 6 machines: proactive power adjustment. Engine power is automatically increased for a short period based on the current demand determined by both internal engine and external machine parameters, such as the deflection of the drive joystick. As well as enhanced response, this results in a noticeable improvement in performance and torque.
When operating crawler dozers in low temperatures, Liebherr offers numerous special options, which have been developed in close collaboration with end users.
The PR 766 Litronic is equipped with an oscillating undercarriage which allows the track rollers to flexibly adapt to the surface. This significantly increases the machine's traction and smooth operation, particularly on stony ground. The elastic suspension reduces impact loads to a minimum. This not only increases comfort for the driver, but also improves the service life of the undercarriage and reduces the wear on the installed components and the steel structure.
The large cab in the PR 766 is identical to the operator's platform in the 70-tonne PR 776 crawler dozer launched in 2016. During the development of this new platform, the focus was placed on simple and safe machine operation, such as Liebherr's successful, single-lever operation that controls all driving and steering functions.
Special features in the cab include centralized controls and a touch-controlled colour display. The operator can use the central display to intuitively control important operating parameters, including the ECO function, the travel drive's response behaviour and the steering, and operational comfort and safety functions, such as the rear-view camera which is fitted as standard.
The operator can adjust the controls for travel, blade, and rear-mounted ripper to the most suitable ergonomic position. The ergonomically optimized shaping of the joystick makes working as comfortable as possible. The desired travel speed can be pre-selected on the joystick, allowing precise control, especially at low speed. The joystick for the rear-mounted ripper is a new feature and it can now be adjusted in two axes and serves as a handle for the operator during the ripping process.
An integrated seat contact switch automatically detects when the operator is in the seat, eliminating the need for a safety lever.
The four sides of the machine slope away from the cab for excellent viewing of the terrain, blade and ripper through the all-round panoramic window.
The LiDAT fleet management system, included as standard, provides comprehensive machine data via state-of-the-art communication to optimize operational planning and remote monitoring. The data is updated several times a day and can be conveniently called up at any time using a web browser. An automatic alarm can be set up for particularly important information, for example if the machine leaves a pre-defined zone or if a critical operating situation arises. HEG