Designed for heavy duty operations, the 560 hp Astra HD 9 86.56 8×6 with a GVW of 60-tonnes can replace a dumper in opencast mines.
Story by: Gianenrico Griffini
The Astra HD9 86.56 8×6 is by no means a conventional off-road truck. Premiering at the Bauma fair in Munich, Germany, which is dedicated to construction vehicles and machines, and mining equipment, the Astra HD9 86.56 is among the top models in the portfolio of the Italian truck manufacturer. The Astra brand belongs to the CNH industrial Group, and 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. The opportunity to test it presented itself recently in a quarry in Northern Italy near Piacenza. Equipped
with a Cursor 13 Euro 6 12.8-litre six-cylinder in-line engine that produces 560 hp at 1,900 rpm, and a peak torque of 2,500 Nm at 1,000 rpm, the Astra HD9 86.56 looks remarkable.
Retarder and engine brake to slow down safely
Like all Iveco heavy-duty (and medium-duty too) engines, the Cursor 13 Euro 6 engine uses a Hi-SCR system for pollutants after-treatment, that does not require an exhaust gas recirculation circuit (EGR). With the Hi-SCR solution there is no need of active regeneration for the diesel particulate filter (DPF), a feature that increases the energy efficiency of the engine and lowers its fuel consumption. The Cursor 13 is equipped with Iveco Super Engine Brake, which is capable of a maximum braking power of 463 kW at 1,900 rpm. The engine, which uses an electronically-controlled variable geometry turbocharger (EVGT), is coupled to a ZF Astronic 16AS 2631 TO 16-speed (plus two reverse gears) automated transmission. The transmission, controlled by an off-road software, has two operational modes, namely fully automatic or manual (sequential).
The powertrain of the Astra HD9 86.56 8×6 rigid tipper is coupled to a Steyr VG2700 disengageble transfer case, which allows a distribution ratio of the drive torque (front and rear) of 1: 2.6. Apart from the Super Engine Brake, the HD9 86.56 8×6 is equipped with an hydraulic retarder (Intarder), integrated to Astronic automated transmission. Both the Intarder and the engine brake are actuated by a 5-stage multi-function lever (which is also used for setting up the cruising speed), located on the right side of the steering column. The first two stages activate the Super Engine Brake, whilst the remaining three also involve the hydraulic retarder. Maximum braking torque is thus provided.
Weighing 24,100 kg, the HD9 86.56 is equipped with a 24 cu. m. Cantoni tipper (specially developed for Astra). The superstructure is made of high strength steel, which has a thickness of 12 mm at the bottom. The side walls are 8 mm thick. A hydraulic gull-wing tail opening design, the superstructure (tipper body) is fitted with an oversized cab guard. The oversized cab guard is designed for mining site operations. Reaching a maximum tilting angle of 58-degrees, the tipper body is equipped with an electronic weighing system, which shows the relevant data on a control display placed in front of the driver’s seat.
Heavy duty components
The structure of the HD9 86.56 and all the mechanical components have been engineered for heavy-duty tasks. The first drive axle is a double reduction Kessler unit with a loading capacity of 20-tonnes. The third and the fourth axle are also a Kessler (double reduction) unit. They each have a loading capacity of 20-tonnes. The 10 mm C-section chassis side members, spaced by 820 mm, are made of high yield steel with 6 mm reinforcing internal C-profiles. The HD9 front suspension – first and second axle – feature parabolic springs. They are supplemented by hydraulic shock absorbers and two stabilisers (one for each axle). Those of the tandem (cantilever type) have five parabolic leaves (40 mm x 100 mm) swiveling on a central pin.
The braking system of the Astra HD9 86.56 8×6 heavy-duty tipper is drum brake based. There are drum brakes on all axles with the possibility of excluding the anti-lock device (ABS) at speeds below 15 km per hour. The use of 325/95 R24 tyres has the tipper having a high ground clearance. This is crucial to the smooth functioning of the truck as it will spend much of its life travelling over 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. The two not only ensure driver ergonomy they also help to retain high level of functionality required by extreme off-road missions.
At the steering wheel
The HD9 86.56 ZF Astronic automated gearbox does a good job in off-road operations. This is due to the fast (and higher revs) gearchanging, managed by the off-road transmission software. The automated gearbox, however, requires some special precautions, especially on the most demanding terrain. When tackling the most demanding terrain, it is better to use the gearbox in manual mode, pressing two times the D (Drive) button on the dashboard. The right speed can be selected using – with an upward and downward movement – the multi-function lever on the right side of the steering column. Once this operation is done, the engine is in a position to provide high torque at low revs (from 1,000 rpm). 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, due to the good suspension setting. Remarkable is the steering angle. It does not seem to have been heavily affected by the 8×6 chassis architecture.
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