No easy mission
Designed and built for heavy-duty operations, the Astra HD 9 86.56 8×6, with a gross vehicle weight of 60 t, can replace a dumper in opencast mines. Its driveline is based on a Cursor 13 engine rated at 560 hp, coupled to a 16-speed automated gearbox. GIANENRICO GRIFFIN reports
The Astra HD9 86.56 8×6, tested in a quarry in northern Italy near Piacenza, is by no means a conventional off-road truck. Shown as a world premiere at the last edition of Bauma in Münich – the German exhibition dedicated to construction vehicles, machines and equipment for the mining sector – the 60-t gross vehicle weight (GVW) HD9 86.56 is among the top models in the portfolio of the Italian truck manufacturer, a brand that belongs to the CNH Industrial Group.
It has been designed for heavy-duty missions in extreme working environments typical of the mining-extractive sector – in which it can replace a rigid dumper – and the oil industry.
The HD9 86.56 is equipped with a Euro-6 Cursor 13 engine, rated at 417 kW (560 hp) at 1 900 r/min, with a peak torque of 2 500 Nm from 1 000 r/min.
Retarder and engine brake to slow down safely
Like all Iveco heavy- and medium-duty engines, the Cursor 13, Euro 6 uses the Hi-SCR system for after-treatment of pollutants, which does not require the exhaust gas recirculation (EGR) circuit
Moreover, with the Hi-SCR solution there is no need for active regeneration of the diesel particulate filter (DPF), a feature that decreases the energy efficiency of the engine and lowers its fuel consumption.
The engine, which uses an electronic-controlled variable-geometry turbocharger (EVGT), is coupled to a ZF AS Tronic 16AS 2631 TO 16-speed (plus two reverse gears) automated transmission.
The transmission is controlled by off-road software and has two operational modes: fully automatic or manual (sequential). The powertrain of the 8×6 rigid is completed by a Steyr VG2700 disengageble transfer case, which allows a distribution ratio of the drive torque (front/rear) of 1:2,6.
The Cursor 13 is equipped with Iveco Super Engine Brake, capable of a maximum braking power of
463 kW at 1 900 r/min. In addition to the Super Engine Brake, the HD9 86.56 8×6 is equipped with a hydraulic intarder, integrated to AS Tronic automated transmission.
Both the intarder and the engine brake are actuated by a five-stage multifunction lever, which is also used for setting the cruising speed, and is located on the right side of the steering column.
The first two stages activate the Super Engine Brake, while the remaining three also involve the hydraulic retarder, providing the maximum braking torque. The braking system is based on drum brakes on all axles, with the possibility of excluding the anti-lock braking system (ABS) at speeds below 15 km/h.
The HD9 86.56, which has a tare weight of 24 100 kg, is equipped with a 24 m3 Cantoni tipper (specially developed for Astra), made of high-strength steel, 12-mm thick on the bottom and eight-millimetres thick on the side walls.
The tipper, with a hydraulic gull-wing tail opening, is complemented by an oversized cab guard, designed for mining site operations. The tipper reaches a maximum tilting angle of 58°, and is equipped with an electronic weighing system that shows the relevant data on a control display placed in front of the driver’s seat.
The structure of the vehicle and the mechanical components have been designed for the heavy-duty applications. The first axle is a double-reduction Kessler unit (always double reduction) as are also the third and fourth axles, with a loading capacity of 20 t each. The ten-millimetre C-section chassis side members, spaced 820 mm apart, are made of high-yield steel with six-millimetre reinforcing internal C-profiles.
The HD9 front suspensions – first and second axles – feature parabolic springs supplemented by hydraulic shock absorbers and two stabilisers (one for each axle), while those of the cantilever-type tandem rear axle have five parabolic leaves (40 mm x 100 mm) swivelling on a central pin.
The 8×6 is equipped with 325/95 R24 tyres. This solution allows an increase in the ground clearance of the main driveline components, a crucial feature for a vehicle designed for uneven terrain with deep potholes and large stones.
Despite the heavy-duty design of the truck, driver comfort has been increased thanks to the correct calibration of the cab suspension and the redesigned interior, which ensures driver ergonomics while retaining the high level of functionality required by extreme off-road tasks.
At the steering wheel
WIth its automated gearbox, the HD9 86.56 does a good job in off-road operations. This is due to the fast (and higher revs) gear changing, managed by off-road transmission software.
The automated gearbox, however, requires some special precautions, especially on the most demanding terrain. In these conditions, it’s better to use the gearbox in manual mode, by pressing the D (Drive) button on the dashboard twice.
The right speed can be selected using the multi-function lever on the right-hand side of the steering column – with a movement upwards or downwards. Once this operation is complete, the Cursor 13 will provide high torque at low revs (from 1 000 r/min).
The same predictive driving style is needed to engage, in advance, the differential locks, using the knobs on the console close to the driver’s seat. The intarder-enhanced engine brake provides a powerful braking action, even when the truck is fully loaded.
A pleasant surprise is the comfort level of the cab as a result of the good suspension settings. Remarkably, finally the steering angle seems not to be heavily affected by the 8×6 chassis architecture.
As regular readers of FOCUS know, this magazine has been appointed an associate member of the International Truck of the Year (IToY)! FOCUS is the sole South African magazine to have joined this prestigious body. One of the advantages of this association is access to exclusive articles, specially written for FOCUS by ITOY jury members. This is one such article.