by Adrian-Liviu Dorofte

Trial drive with the Mercedes-Benz Arocs: Impressions behind the wheel at the Rheinkalk surface mining site in Dornap

I. Test drive with the Mercedes-Benz Arocs: Triple test from road-oriented construction use to full-blown off-road deployment

There is certainly no denying that the Arocs is an imposing presence, exuding power and robustness even when stationary. The radiator grille with its "bucket tooth" look visualises the link between technology and terrain – this truck is clearly in its element off the beaten track. It demonstrated its credentials at the Rheinkalk surface mining site in Dornap.

Test drive on the extreme circuit

The 4151 8x8/4 was chosen for the test drive on the so-called extreme circuit. In keeping with the established Mercedes-Benz nomenclature, this is a 41-tonner with four axles, all driven, two of which – the front ones, of course – are steered. The engine is rated at 375 kW (510 hp), as is also indicated in the model designation. The engine in question is the top-of-the-range 12.8 l six-cylinder in-line engine from Mercedes-Benz, which delivers its full output at 1800 rpm and summons up maximum tractive power of 2500 Nm at 1100 rpm.

The fully automated Mercedes PowerShift 3 transmission is normally flange-mounted on the standard-fit Euro VI-compliant BlueTec engine. The selected test vehicle was fitted with the sixteen-gear manual transmission which is available as a cost option, however. This optional manual transmission lends itself to precise operation, thanks to a newly developed shift-by-wire system with noticeably more effective power-assisted gear shifting. The light clutch pedal also plays its part here.

Superb pulling power

In the course of the first test drive across the off-road site, the main focus is less on the transmission and rather more on the impressive engine, however, which demonstrates hefty pulling power right from the low rev range combined with an innate liveliness. This often avoids the need to change gear.

Operating this high-end construction vehicle proves as ergonomic as drivers might expect, thanks to the hallmark Mercedes set-up for the differential locks on the new Arocs which sees them connected in series as necessary for the purposes of traction and dynamics. In addition, the clearly laid-out dashboard provides precise information on the current operating conditions.

The revs decide

The instrumentation includes a speedometer of course, but this is less important in difficult terrain. Equal prominence is given to the rev counter, which at peak levels of driving resistance indicates whether the engine is up to negotiating the terrain ahead.

When the Arocs 4151 8x8/4 is operating at full load, the rev counter needle points stubbornly to 1100 rpm. Even the steep part of the demanding off-road circuit – which was extremely slippery as a result of previous rainfall – fails to tame the high-capacity engine. The driver actually has a little space left between accelerator pedal and floor.

The all-terrain chassis displays a deftness of articulation under the dumping platform that is a joy for the photographers on the scene to behold. The atmosphere remains relaxed at the wheel of the Arocs, too. Axle load compensation provides for the best possible weight balance between the two front axles, with traction almost at 100 percent. The new all-wheel-drive dumper also benefits from the high-grip off-road 13 R 22.5 tyres here.

Easy handling thanks to world-first Servotwin

The steering operates with noticeable precision in these demanding manoeuvres. But there is no surprise here as it is attributable to a world first in the commercial vehicles sector which is on board the new Arocs: the electro-hydraulic Servotwin steering system, which is initially being introduced exclusively on four-axle vehicles. The benefits for Arocs drivers are speed-sensitive power assistance and active return movement.

This newly developed technology, which features as standard on 8x6 and 8x8 vehicles and as an option on 8x4 vehicles, opens up a world of unprecedented steering comfort combined with the utmost in steering precision.

Second test drive on the self-drive circuit with the new OM 470

The test vehicles on the second circuit also feature Servotwin. Gear-shifting is entrusted to the standard-fit Mercedes PowerShift 3 transmission on these trucks. Upline of the transmission, the powerhouse comes in the form of the new OM 470 10.7 l six-cylinder in-line engine, which is available in four output variants ranging from 240 kW (326 hp) to 315 kW (428 hp). The test vehicle employed here, a four-axle 3240 with an 8x4/4 drive configuration, features the second most powerful engine version, rated at 290 kW (394 hp) and generating up to 1800 Nm of tractive power. The three-way dump truck is fitted with 315/80 R 22.5 tyres, which are suitable for on-road and light off-road use.

The candidate for this test drive, equipped with a slightly smaller engine, half-length cab and less sturdy tyres, is nevertheless put through its paces under a full load of 32 tonnes. Only the hallmark brawny Arocs looks remain unchanged.

The workplace is laid out as on the previously tested 8x8 model. The parking brake is ergonomically integrated in the instrument panel next to the steering wheel for ideal accessibility. On all-wheel-drive vehicles, this location is reserved for operation of the differential locks, which are used more frequently in off-road terrain.

High-end controls

The Arocs 3240 8x4/4 is ergonomic and lends itself to intuitive operation, thanks not least of all to the Mercedes PowerShift 3. The steering-column lever for the Mercedes PowerShift 3 enables stress-free driving both on- and off-road. The on-board computer is operated via the standard-fit multifunction steering wheel. The instruments are clearly laid out and offer a wealth of information and setting options. The seat and mirror adjustment options are arranged in an ideal manner, with every switch positioned just where it belongs. Even gearshifting appears identical to on-road use with Mercedes PowerShift Offroad – driving the supposedly rugged construction vehicle is highly comfortable right from the word go.

The transmission computer has defined second gear as ideal for moving off. In view of what for 394 hp (290 kW) and 1800 Nm is a rather high vehicle mass of almost 32 tonnes, and a short final drive ratio tailored to off-road use, this is an indication of a configuration philosophy with an onus on avoiding unnecessary strain on the clutch. Power transmission is established at idling speed.

Superlative transmission know-how

The Mercedes PowerShift 3 always selects the appropriate gear for moving off – according to the load, gradient and active driving mode. During acceleration, the Mercedes PowerShift 3 shifts gear according to the established principle of large gear steps. Where possible, the 3240 8x4/4 shifts from third into sixth gear and then directly into eighth gear. The transmission computer knows just when and how to shift gear, without wasting time or fuel.

A brief sprint is sufficient for now – after all, we are not on a paved road here, but at the Rheinkalk surface mining site featuring terrain of varying severity. The Mercedes PowerShift 3 automated transmission which comes as standard on all Arocs models amply demonstrates its off-road capabilities here. In addition to the power drive program there is a special offroad mode. Each drive program mode offers a choice of three modes (standard, manual and either power or offroad).

Mercedes PowerShift 3 programs adapted perfectly to given needs

The test vehicle is equipped with the offroad drive program for the Mercedes PowerShift 3. When this program is activated by a tap of the finger on the steering-column lever, off-road terrain should not pose any problems. At least as far as gear selection is concerned.

In response to even slight rises in driving resistance, the gear selector computer sets the shifting thresholds for up and downshifts to a very high level. The offroad drive program with the Mercedes PowerShift 3 reliably prevents the vehicle from getting stuck as a result of over-optimistic changes of gear ratios.

Standard driving mode is ideal for the further course of the test drive in the medium-difficulty terrain at the surface mining site. Tuned to 1800 Nm in this mode, the 10.7 l engine flexes its muscles and is instantly raring to go. Similar to the previously tested 12.8 l engine, this variant with a smaller displacement takes all the relevant hurdles that the terrain has to offer in its stride.

One step ahead of any surprises

On encountering a sudden slow stretch on the circuit, Mercedes PowerShift 3 shifts down directly from fifth to first gear with an assurance suggesting it can do this sort of thing in its sleep. The traction at the drive wheels is instantly adapted to the current driving resistance. The OM 470 pulls the Arocs through the deep, muddy water without getting stuck.

The swiftly activated inter-wheel differential lock is also instrumental in maintaining the tractive power. Deactivating rotational speed compensation could not be more simple, even for off-road novices. The unavoidable gear-shifting manoeuvre is carried out without any need for major operations involving a gearshift lever or sensitive use of a clutch pedal. This leaves the driver all the time he needs to simply turn the differential lock switch down to the next level.

Manual mode when needs must

Off-road driving is never quite that simple, however. Before we tackle the steepest uphill stretches, the test supervisor warns: "The driver's know-how and skills remain indispensable in difficult terrain." By which he means that even the best automated transmission does not have the power of vision - even if the new PowerShift offroad mode's highly sensitive sensor system appears to anticipate impending changes to driving resistance with its inclination sensor, which has undergone further optimisation for off-road operations.

The tester thus has an opportunity to switch to the manual shift programme and try out the manual driving mode. In fixed third gear the four-axle truck clambers up an uphill gradient with its fully locked tandem drive, almost as if to indicate to the off-road greenhorn that it really has no need for all-wheel drive. Know-how plus basic Arocs technology suffices. The six-cylinder engine attends to the rest, responding truly elegantly to the accelerator pedal.

Downhill – and it feels like a sheer drop – we proceed in first gear, which remains locked to prevent upshifts, and with uncompromising intervention by the reinforced continuous brake. The latter extracts a level of braking power from this 10.7 l engine which would formerly have been the reserve of a ten-cylinder naturally aspirated engine.

Third test drive: cross-country with a "lightweight"

After the impressive trip with the all-terrain, all-wheel-drive Arocs 4151 8x8/4 and the essentially equally off-road-capable Arocs 3240 8x4/4 for varying operations, a road-oriented test drive with an Arocs 2630 6x4 rounds off the comprehensive test programme.

The three-axle dump truck is powered by a compact 7.7 l engine which is instrumental in providing the Arocs concrete mixer Loader with a quite sensational transport volume of 8 cubic metres. Its power spectrum ranges from 175 kW (238 hp) to 260 kW (354 hp).

What's good for a concrete mixer truck can't be bad for a bulk freighter that is always striving for the highest possible payload. We hit the road in the three-way dumper with the mid-range light-duty engine rated at 220 kW (299 hp) and 1200 Nm on board.

Technology on a par with the heavy operators

Like the OM 470 from the second test drive, the OM 936 engine concealed under the medium-length Arocs cab is a totally new development. The light-duty engine bears up well to comparison with its big brothers, boasting similar technical refinements such as a maximum common rail injection pressure of 2100 bar or the world's first adjustable exhaust camshaft in a diesel engine.

Turbocharging for the power variants up to 220 kW (299 hp) is carried out by an asymmetric exhaust gas turbocharger with double-flow turbine. Two-stage charging with two turbochargers is provided for the two highest power variants.

Power from low revs

The impressive performance of the OM 936 is in evidence right from the approach road to the motorway. Around 90 percent of the maximum engine output is already available from an engine speed of 1600 rpm. The engine also offers high dynamic performance right from the low rev range.

The maximum torque is available throughout the main driving range from 1200 rpm to 1600 rpm. The engine also displays a high level of performance at engine speeds below 1000 rpm, however. A further impressive aspect in practice is the engine's spontaneous response to movements of the accelerator pedal.

The standard-fit Mercedes PowerShift 3 also gives an excellent account of itself once again. The automated gearshift strengthens the impression that this "small" engine is well able to punch above its weight. The Mercedes PowerShift 3 whizzes through the gear ratios at appropriate gear steps, always at pains to keep the engine speed down in the manner of a twelve-litre engine.

Empty and fully laden in turn

This is no surprise at first, as the test Arocs is initially on the road in unladen state, so it is only to be expected that engine power and manual transmission will harmonise to perfection. After the first brief trip on the motorway, the dump truck calls in at a building materials depot to take three full wheel loader shovels on board, however.

Will our nimble Arocs 2630 6x4 now be revealed as a lame duck? Not a bit of it: on the quite hilly stretch of country road back to the "discharge point", the compact engine and automated transmission prove an impressively high-calibre duo.

Fine handling

The shift points are spot-on with the small engine, too. Whenever the driver is about to tap on the touchshift button to carry out a manual gear change, the automatic Mercedes PowerShift 3 steps in beforehand to shift the gear ratio. This usually involves a single gear step, with occasional double steps, too.

The Servotwin steering system with partial electric assistance impresses the test driver once again on the smoothly negotiated stretch of country road. While the lightness of touch comes to the fore in off-road terrain, it is the increasingly direct configuration that is appealing on fast stretches of country road. This leads to a firm feel at the wheel with clear feedback from the road surface.

Big on user-friendliness

Operation of the vehicle using the lever on the right of the steering column, where the engine brake is also activated, is intuitive. There's not a great deal for the driver to do, however. The drive and brake management system designed to handle the operating conditions encountered in practice takes much of the work off the driver's hands.

The driver operates important assistance systems such as cruise control and the user-definable speed limiter via the multifunction steering wheel.

A particularly useful feature is a user-programmable hotkey, to which each driver can allocate the submenu which he considers to be most important (driving time or trip consumption, for example). A push of the button is then sufficient to call up the desired information on the display.

On the subject of driving time: we have clocked up almost half the legally permissible limit after the three test drives. Back at the Rheinkalk site, the test driver manoeuvres the Arocs 2630 6x4 precisely into position at the discharge point and dumps the bulk materials with due aplomb.

A short move forwards followed by an abrupt stop is enough to send the rest of the material sliding down the load surface. And so the tester ends the final test drive with the new Arocs models with a degree of professionalism akin to that demonstrated by the newcomer in all its different guises.

II. With or without all-wheel drive: The type of use determines the drive configuration

In order to assist the Arocs driver in the most diverse everyday situations, Mercedes PowerShift Offroad is equipped with a host of smart functions. Particularly useful features in off-road use are:

- offroad driving mode
- rocking-free mode
- four reverse gears
- fast forward-reverse shifting
- crawl function
- load-dependent rpm increase

In on-road use, assistance is provided by:

- cruise control with flexible hysteresis
- the EcoRoll function
- the crawl function

Drive configurations for off-road use

The multifunction display indicates when the various driving and operating aids are active or inactive.

Special operations call for special vehicles. On-road or off-road is one criterion, quantities and transport frequencies are others. Mixed usage of a vehicle model for diverse transport tasks on various routes imposes different requirements on the rolling stock in comparison to transportation of the same material on the same routes at all times.

When transporting large quantities of bulk materials such as gravel or sand on paved roads, for example, the prime requirement is payload capacity. Light-duty means of transport are called for here. The appropriate tractor vehicle is usually a semitrailer tractor from the Arocs family in standard 4x2 drive configuration.

The new "Hydraulic Auxiliary Drive" covers predominantly road-oriented use with an occasional requirement for increased traction. With this new all-wheel-drive variant, manually selectable, hydrodynamically driven wheel hub motors provide the drive power for the front axle, rather than mechanical propeller shafts. This saves weight and fuel – with weight savings to the tune of half a tonne in relation to permanent all-wheel drive for heavy-duty off-road use alone.

Manually selectable all-wheel drive as a good compromise

When the requirements regarding payload and fuel economy outweigh traction needs, manually selectable all-wheel drive without low-range gear is available as a second variant. Here the front axle is engaged via the transfer case while the vehicle is stationary. The cardan shafts are then connected to front and rear at a ratio of 1:1.

All-wheel drive makes sense for semitrailer tractors, too

When a semitrailer/tractor combination is to be used in more demanding terrain with a degree of regularity, a semitrailer tractor with permanent 4x4 drive should be considered. The classic all-wheel-drive Arocs fits the bill here in the commercial vehicles range from Mercedes-Benz. Permanent all-wheel drive – with inter-axle and inter-wheel differential locks as standard – enables this semitrailer tractor to cope more effectively with demanding terrain than the previously described tractors.

A popular alternative to the semitrailer/tractor combination – comprising a two-axle tractor and three-axle semitrailer – is the off-road-capable 6x4 tractor with a two-axle semitrailer in tow. The payload is slightly lower here, of course, but the degree of traction is substantially higher.

Upgrading the three-axle tractor to a 6x6 all-wheel-drive vehicle promises even better off-road performance. The driven front axle benefits cornering performance in particular. The new manually selectable all-wheel drive will come as standard, with permanent all-wheel drive available as an option.

Four-axle vehicles covering a diverse spectrum of operations

When transport tasks become even more difficult in yet more demanding terrain, a four-axle vehicle really is a must. While a single rigid vehicle is not the preferred option for on-road use only, on account of the lower payload, it has long been established as the no. 1 choice for mixed on and off-road use and in restricted space conditions. Reversing around various corners to the loading or unloading point is indisputably easier with a single vehicle than with an articulated combination.

The standard formula for four-axle vehicles in light to heavy-duty use is 8x4, while 8x8 is unbeatable for tough assignments. The 8x6 configuration is additionally available as a compromise.

A smaller but more versatile option is the classic three-axle vehicle. The classic three-way dump truck is in much more frequent use in this configuration than as a four-axle variant. It is in widespread service in many fleets as a 6x4 dumper. As a tractor – usually with a centre-axle tandem trailer in tow today, rather than the fifth-wheel trailer that used to be common – it provides a particularly economical means of transporting bulk materials or excavated soil from A to B by road before moving on to construction site C for off-road use without a trailer in tight operating conditions. Equally, this three-axle dumper is also at home pulling a medium-duty low-loader with an excavator lashed down on board. Or – upgraded to 6x6 – it can be used to overcome virtually insurmountable obstacles in difficult terrain.

Easy locking

In keeping with the previous model series, there is only one logical lock control here, in the form of the rotary switch which engages the inter-axle and inter-wheel lock in succession. Starting from the "Off" position with completely open differentials, the switch can be moved as necessary to position 1. The rotational speed compensation function hindering good traction is then deactivated, after which the rear inter-wheel locks are applied. When this is still not sufficient, the inter-wheel lock on the front axle is additionally applied in switch position 3. This enables the driver to work the vehicle free in the vast majority of cases – and straight wheels are recommended anyway in such precarious situations.

III. The new construction vehicle family from Mercedes-Benz: Arocs – the new force in construction

Mercedes-Benz has achieved a triple leap forward in the field of Euro VI compliance: this year the brand with the star is expanding its current heavy-duty vehicle range with the addition of the Arocs, the specialist in construction, which follows hot on the heels of the Antos, which celebrated its market launch in the heavy-duty short-radius distribution sector in 2012, and the Actros, which celebrated its market launch in the long-distance transport sector in 2011. In addition to maximum environmental compatibility thanks to Euro VI, the new Arocs vehicles also boast three outstanding qualities: power, efficiency and ruggedness.

Clear segments

The Arocs range is being offered in a previously unparalleled variety of vehicle models to precisely match customer requirements in this extremely diversified application sector. The new dump trucks, all-wheel drive dump trucks, cement mixers, semitrailer tractors and dropsider chassis vehicles are available as two, three and four-axle vehicles with 16 power output levels ranging from 175 kW (238 hp) to 460 kW (625 hp). From the outset, all of the engines have been designed to meet the future Euro VI emissions standard and are available to order as Euro VI versions.

The clearly segmented building industry sector requires vehicles which are ideally matched to their operating conditions. Around half of all construction vehicles work directly on construction sites. Around a third deliver equipment and building materials to sites, while a further 15 percent of construction vehicles are involved in handling ready-mixed concrete.

On top of this, there is also a wide variety of requirements when it comes to the means of transport used in ancillary construction trades or the ultra-heavy-duty transport sector. And public service vehicle operators also require tailor-made vehicles too.

Leading forces in construction: Loader and Grounder

With the new Arocs, transport tasks in the building industry can be carried out more efficiently than ever before. In order to be able to meet this requirement even more effectively, even in payload-sensitive applications such as in the case of dump semitrailer vehicles and cement mixers for example, the Arocs Loader and Arocs Grounder have been developed.

The Arocs Loader has made consistent use of every possibility to reduce its own kerb weight. The result provides payload optimised 4x2 semitrailer tractor units which are among the lightest vehicles in the construction sector, as well as 8x4/4 cement mixers with a 32 t maximum permissible weight. Thanks to their particularly low kerb weight of a maximum of 9250 kg, these vehicles are able to supply 8 m3 of ready-mixed concrete on every trip.

The Arocs Grounder is designed for operating in extremely difficult conditions, such as in quarries or on building sites. Thanks to a host of technical measures, such as a longitudinal member thickness of nine millimetres, it is extremely robust and also features particularly high levels of stability and a high load carrying capacity.

Broad range of vehicles from 18 t and up

Both the Loader and Grounder belong to a broad collection of vehicles comprising the Arocs family and which range from a maximum gross vehicle weight of 18 t in the case of the two-axle models, through to 41 t for the off-road four-axle models making up the Grounder series.
In general, the Arocs construction vehicle family has been specifically designed for all types of applications. As a result, even the so-called "road roller" for example - the two-axle semitrailer tractor unit with driven rear axle (4x2) - is not an Actros variant but a separate vehicle type in its own right.

Clear differentiation: high frame

The frames, frame heights and overhangs are specifically different from those found on long-haul trucks. As a result, matching conversion parts for use as construction material transporters are no longer required. The two-axle Arocs semitrailer tractor vehicle can therefore be ordered as a 4x2 standard vehicle with steel or air suspension, a payload optimised 4x2 Arocs Loader, a 20-t 4x4 all-wheel drive vehicle or a 4x4 Arocs Grounder. Other specialist vehicles within the broad-based Arocs family include variants previously only available as subsequently converted vehicles. Four-axle vehicles now roll off the production line with a front and three rear axles as part of a normal series production process in the world's largest truck plant in Wörth.

New ex works: four-axle 8x4/4 single-tyred trailing axle with three rear axles

This four-axle vehicle is based on a three-axle vehicle with a non-driven steering axle and two twin-tyred driven rear axles. Added behind this is a single-tyred, liftable trailing axle with positive steering.

Possible areas of application include building material platform trucks with a loading crane for example, which are required to operate on their own. A three-axle vehicle, or even a classic four-axle variant, would not be able to cope with the rear position of the loading crane due to the load distribution. Thanks to the triple solution at the rear, however, all axle loads can be handled without a problem.

"Super mixer": the first cement mixer capable of delivering 8 m³

When it comes to transporting 8 cubic metres of ready-mixed concrete in compliance with the law - normally roughly divided up in the trade into 0.5‑cubic metre batches - a four-axle truck mixer chassis would be allowed to tip the scales with an unladen kerb weight of 9.25 t at the very most. The new Arocs is able to do just that.

To begin with, the Loader version of the cement mixer chassis combines the lightweight 10.7‑litre OM 470 engine with the ClassicSpace S-cab. But that alone is not quite enough. In addition, the standard double driven axle with twin tyres is replaced with a single-tyred rear axle with 368/65 tyres.

To ensure that the wheelbase remains wide, which is an important element for stability, both rear axles have been specifically modified for use with single tyres: thanks to moving the wheel mounting towards the outside, the wide, classic "trailer"-format traction tyres, specially produced for Mercedes-Benz, sit flush with the outer edge of the body within their wheel guards.

Drive systems: powerful Euro VI engines for the construction sector

The new Mercedes-Benz Arocs is available with a wide range of Blue-Efficiency Power diesel engines. From the very outset, Mercedes-Benz is setting the Arocs to work in harsh, everyday environments equipped with low-emission Euro VI engines.

Arocs customers can choose from a selection of 16 power output levels. The Bluetec 6 engines are all designed as in-line six-cylinder engines with exhaust-gas turbocharging and charge air cooling for high torque at little more than idle speed. Maximum tractive power levels of from 1000 to 3000 Nm are achieved by four displacements of 7.7, 10,7, 12.8 and 15.6 litres.

Brand new: the large-scale OM 473 in-line six cylinder engine

Also now available with the Arocs is the largest-capacity engine from Daimler's heavy-duty engine series which has been comprehensively redeveloped. Boasting specifications which include a displacement of 15.6 l, output of up to 460 kW (625 hp) and maximum torque of 3000 Nm, the new Mercedes‑Benz OM 473 diesel engine sets its own powerful tone.

It is characterised by peak performance under harsh conditions – even when it comes to the most demanding of requirements in terms of transport speed, tractive power and ruggedness. Top performance is also guaranteed for off-road applications, maximum loads in the heavy-duty transport sector, and high transport speed over routes with demanding topography. On top of all of this it also offers maximum durability. The new 15.6-litre OM 473 in-line six-cylinder engine is capable of maximum performance in every respect.

Power from the word go

When it comes to the heaviest-duty applications in particular - which the Grounder variants of the new Mercedes-Benz Arocs may face for example - the OM 473 scores highly with its tractive power. It is not only the absolute power available which is impressive – between 2600 Nm and 3000 Nm are fed to the crankshaft, depending on the variant – but also the way in which it is made available. This is because under full load, around 2500 Nm are already available at a little more than idle speed in all rated output versions of the engine. This is a higher level of torque than the maximum achieved by most truck engines.

On the test bench, the highest torque of all of the OM 473 variants is available at 1100 rpm. In the real world, almost the entire tractive power is available across a wide range from around 900 to 1400 rpm. Immediately thereafter, the engines reach their maximum output.

This characteristic helps to ensure excellent driveability across a very wide engine speed range. In addition, all variants of the engine also feature a response to accelerator pedal input which is both spontaneous and powerful.

Spontaneous response, reduced fuel consumption under high load

One of the special features of the new Mercedes-Benz OM 473 engine is turbo-compound technology. The term turbo-compound stands for a second turbine, connected in series after the exhaust gas turbocharger. It also makes use of the available pressure of the exhaust after flowing through the exhaust gas turbocharger to further increase performance. This power is transferred to the engine's gear drive, and thereby directly to the crankshaft, via a shaft and hydrodynamic clutch.

Turbo-compound technology increases the output of the OM 473 by around 50 kW (68 hp). The driver is able to feel the additional performance immediately via the already spontaneous response of the engine at low engine speeds.

At the same time, a reduction in fuel consumption of around two percent is achieved under high load. These demanding conditions are typical of the areas of application in which the OM 473 is used.

In addition, the new Mercedes-Benz OM 473 also impresses with its tremendous economic efficiency: even the most powerful engine of the new engine generation has been consistently developed for low fuel consumption. Depending on the version, consumption is between 0.5 and 1.5 percent lower than the preceding model, the V8 Mercedes‑Benz OM 502.

It also goes without saying that the engine features maximum environmental acceptability: all variants of the OM 473 meet the strict Euro VI emissions standard applicable to registrations from 2014 onwards.

The new OM 473 is available with three power output levels:

Power output / Maximum Torque

380 kW (517 hp) at 1600 rpm / 2600 Nm at 1100 rpm
425 kW (578 hp) at 1600 rpm / 2800 Nm at 1100 rpm
460 kW (625 hp) at 1600 rpm / 3000 Nm at 1100 rpm

OM 471: resilient, powerful and economical

Slotting in seamlessly below the new Mercedes-Benz OM 473 diesel engine is the previous top-of-the-range variant of the new engine generation, the OM 471, producing a maximum of 375 kW (510 hp) and 2500 Nm of torque from a displacement of 12.8 litres.

This engine covers a broad range of applications within the new Arocs vehicle family. The long-stroke in-line six-cylinder engine (piston stroke: 156 mm, cylinder bore: 132 mm), which made its debut in the Actros long-distance truck, was the first model in a completely new engine generation in 2011.

Its effective full-load engine speed range extends down to around 800 rpm, which is particularly important for the off-road applications for which the Arocs may be used. The engines provide close to their full power output as low as 1400 rpm.

Highly efficient turbocharging and engine brake

Turbocharging is dealt with by an asymmetrical turbocharger featuring fixed geometry. It ensures quick engine response to different accelerator pedal positions. Maximum efficiency is also achieved by the turbocharged decompression engine brake. Maximum braking power reaches 400 kW in the case of the OM 471 and 475 kW for the OM 473.

The OM 471 is available with four power output and torque levels in the Mercedes-Benz Arocs:

Power output / Maximum Torque

310 kW (421 hp) at 1800 rpm / 2100 Nm at 1100 rpm
330 kW (449 hp) at 1800 rpm / 2200 Nm at 1100 rpm
350 kW (476 hp) at 1800 rpm / 2300 Nm at 1100 rpm
375 kW (510 hp) at 1800 rpm / 2500 Nm at 1100 rpm

OM 470: efficiency from a displacement of 10.7 l

Also new is the OM 470 in-line six-cylinder engine with a displacement of 10.7 litres, based on the OM 471 model series. It also has a number of technical features such as the unique X-Pulse injection system. The compact engine boasts a very high performance, and is also very efficient and at the same time weight-optimised.

Designed with a view to its specific areas of application, such as the payload-sensitive transportation of building materials, the OM 470 engine is approx. 170 kg lighter than the OM 471.

Tremendous tractive power at low engine speeds

The OM 470 has been consistently tuned for economy: the engine achieves a full 95 percent of its maximum torque as low as 800 rpm. The maximum torque remains constantly available from 1100 rpm through to 1400 rpm. The engine almost achieves it maximum performance at this engine speed. Thanks to this characteristic, a high degree of power is available in the main operating range and the engine has real "bite". The long-stroke design with a bore of 125 mm and a stroke of 145 mm provides for excellent pulling power.

Both the OM 470 and OM 471 boast a particularly long-life design. The crankcase, for example, is made of a special cast iron alloy, and the cylinder head of cast iron with vermicular graphite (CGI). The pistons, meanwhile, are made of steel to increase their service life and combat the loads caused by ignition pressures of more than 200 bar.

The efficient gear drive which drives the two overhead composite camshafts has been completely redeveloped for the OM 470. It is located at the rear of the engine and is an important element of the engine's weight-saving design.

Unique: X-Pulse injection system

An important feature of all of the 6-cylinder in-line engines of the OM 470/471/473 model series from Mercedes-Benz is the unique flexible common-rail X-Pulse injection system with fully electronic control and pressure booster. Whilst the pressure is increased to a maximum of 900 bar in the common rail, it is increased to an injection pressure of up to 2100 bar in the individual injectors.

The rate of injection can be freely modulated depending on the operating conditions. As a result, X-PULSE minimises fuel consumption and at the same time maximises the smooth running performance of the engine. The injectors and shape of the combustion chamber have been adapted to the specific characteristics of the different engine variants.

Turbocharging takes place via a turbocharger with asymmetric turbine housing and fixed geometry. This process improves the engine response.

The engine brake of the OM 470 is just as powerful and efficient as the drive system. Mercedes-Benz uses a turbocharged decompression brake. It is operated via a three-stage steering column switch. The maximum braking performance is a remarkable 340 kW (462 PS).

Four versions of the OM 470 are available in the Arocs:

Power output / Maximum Torque

240 kW (326 PS) at 1800 rpm / 1700 Nm at 1100 rpm
265 kW (360 PS) at 1800 rpm / 1800 Nm at 1100 rpm
290 kW (394 PS) at 1800 rpm / 1900 Nm at 1100 rpm
315 kW (428 PS) at 1800 rpm / 2100 Nm at 1100 rpm

OM 936: compact and light, yet still powerful

The new Mercedes ‑Benz OM 936 in-line six-cylinder engine is particularly light and compact. The new design features a number of technical refinements, such as a maximum injection pressure of 2400 bar, common-rail injection or the world's first adjustable exhaust camshaft in a diesel engine.

The crossflow cylinder head with four valves guarantees the least possible flow losses. The cylinder head and crankcase are made of cast iron with lamellar graphite in a special alloy.

Even the "small one" is an undersquare engine

The choice of the bore-to-stroke ratio (110/135 mm) provides for optimum fuel consumption and guarantees high pulling power at low engine speeds. The compact, rigid gear drive of the camshafts is located on the rear side of the engine.

The turbocharging function is carried out up to an output of 220 kW (299 hp) by an asymmetrical exhaust gas turbocharger with a double-flow turbine. There is a two-stage supercharging process with two turbochargers for the two uppermost output levels.

Impressive performance and drivability

The OM 936 achieves an impressive performance. Specific output of up to 34 kW (46 hp) per litre of displacement propels the power units to a performance class previously only achieved by larger-capacity engines. It is this downsizing that provides one of the prerequisites for the favourable exhaust emissions and consumption values, and also the payload.

Besides the nominal data of the new engines, it is their ease of driving that impresses. At an engine speed of only 1600 rpm, roughly 90 percent of the maximum torque is already available. At the same time, the engines also display their dynamism at low revs. Within the main operating range, the maximum torque remains constant between 1200 rpm and 1600 rpm. However, the engines display high power output even at engine speeds below 1000 rpm. Furthermore, the engines' spontaneous response to accelerator pedal movements is surprising in practice.

Whereas the standard version on the six-cylinder engines achieves up to 235 kW (320 hp), the optional high-performance engine brake even achieves 300 kW (408 hp). Until now, only considerably larger engines have achieved values of this magnitude. The Mercedes‑Benz OM 936 is available with five power output and torque levels:

Power output / Maximum Torque

175 kW (238 hp) at 2200 rpm / 1000 Nm at 1200 - 1600 rpm
200 kW (272 hp) at 2200 rpm / 1100 Nm at 1200 - 1600 rpm
220 kW (299 hp) at 2200 rpm / 1200 Nm at 1200 - 1600 rpm
235 kW (320 hp) at 2200 rpm / 1300 Nm at 1200 - 1600 rpm
260 kW (354 hp) at 2200 rpm / 1400 Nm at 1200 - 1600 rpm

Effective engine brake

The engine brake acts just as effectively. Its performance, unique for an engine of this class, increases safety and the average transport speed, and at the same time minimises wear of the brake linings due to less use of the foot brake. The double synchronised decompression brake is based on the engines of the OM 470/471/473 series.

New engine generation with a great deal in common

Whether the OM 936, OM 470, OM 471 or the new OM 473 – all engines already comply with the Euro VI emissions standard. They feature Blue-Efficiency Power with common-rail injection, a closed particulate filter system and exhaust gas recirculation. Exhaust gases are treated by means of BlueTec 6 featuring SCR technology with AdBlue injection, as well as a downstream oxidation catalytic converter and particulate filter.

Powerful primary retarder: braking system for inclines

All of the engines are available with the extremely powerful, turbocharged decompression engine brake. The driver can activate it in three stages via the steering column switch. Due to the considerably larger displacement of 15.6 litres, the engine brake on the OM 473 significantly outperforms its renowned, powerful counterpart on the OM 471: it achieves up to 460 kW (625 hp).

Engine series / Max. engine braking power

OM 936 / 300 kW (408 hp)
OM 470 / 340 kW (462 hp)
OM 471 / 400 kW (544 hp)
OM 473 / 460 kW (625 hp)

Maximum efficiency comes as standard in the new BlueEfficiency Power engine generation: all engines combine a spirited response and very smooth running characteristics with low consumption figures for fuel, AdBlue and engine oil. Equally present are exemplary environmental protection and long maintenance intervals.

Fully-automated transmissions as standard

Power transmission in all variants of the broad Arocs product range is implemented as standard by means of fully-automated, fast-acting Mercedes PowerShift 3 transmissions with eight, twelve or optionally 16 gears. They facilitate the work of the driver considerably, particularly with regard to tough manoeuvring or harsh off-road applications. As an option, regular manual transmissions with nine or 16 gears are available at extra cost.

The enhanced Mercedes PowerShift 3 automatic transmission is characterised among other things by shorter shift times, which are up to 20 percent shorter compared with the previous Mercedes PowerShift 2 transmission, and even up to 50 percent shorter compared with the Telligent automatic transmission. With its sensitive shift sensor system, the Mercedes PowerShift 3 ensures a precise selection of gears suitable for the respective driving and load conditions.

Smart sensor system for all situations

One feature is the ability to detect overrun mode on downhill gradients and as a result maintain the gear. The new crawl function (increased starting torque) with the integrated manoeuvring mode enables particularly easy moving off and precise, defined manoeuvring. In addition, different transmission modes and additional functions make driving in construction traffic simpler. The rocking-free mode, for example, enables vehicles which become stuck in muddy, boggy conditions to free themselves.

The direct-shift mechanism which enables direct shifting from first to reverse – without having to shift via neutral – is yet another advantage. For quick reversing, for example when working on motorway construction, particularly "fast" reverse gears are also available.

Two transmission modes to choose from: power or off-road

Depending on the vehicle type, the Arocs is fitted with off-road or power transmission driving programs, or as an option can also be ordered with the other respective driving program. Both driving programs each feature three transmission modes. Standard mode, including the standard eco-roll function, generally supports a particularly economical driving style for on-road use. Manual mode enables complete control of the Arocs in extreme off-road terrain.

In the power driving program's "power mode", gear changes are carried out with an increase in engine speed of 100 rpm compared with standard eco-roll mode. Power mode is automatically deactivated when no corresponding torque is available to be called upon.

The off-road driving program's "off-road mode" is characterised by the Arocs permanently having increased torque at its disposal.

Crawl mode for manoeuvring

Particularly important for short-distance haulage and construction transport, with its high share of low-speed driving and manoeuvring in restricted deployment locations, is the transmission's crawl mode: when start-off or reverse gears are selected, the driver can control the speed of the new Arocs by means of the brake pedal alone. A further support feature when manoeuvring is the option to be able to shift directly from first gear into reverse.

Optional manual transmission

In addition to the standard automated gearshift, the Arocs is also optionally available with a manual double H-gearshift with pneumatic shift assistance. Customers who prefer a manual transmission therefore have a choice between a 9-speed transmission and three optimally tuned 16-speed transmissions. All transmissions ensure virtually loss-free transfer of power as well as ease of shifting and high levels of driving comfort.

New clutch generation

Both the standard Mercedes PowerShift 3 transmissions as well as the manual versions are used in combination with a new clutch generation featuring overload protection and a warning system. In the case of vehicles with one driven axle, the single-disc clutch helps to guarantee the transfer of torques of up to 2600 Nm.

In the case of the Arocs with several driven axles and for torques up to 3000 Nm, a double-disc clutch is used. It is also optionally available for vehicles with one driven axle.

Optional turbo retarder clutch or water retarder

In addition, the optionally available wear-free turbo retarder clutch provides maximum performance when moving off and manoeuvring with particularly high gross combination weights and torques. At the same time it also acts as a retarder and therefore helps to ensure additional safety.

For applications involving high proportions of continuous braking in the higher speed ranges, the optional secondary water retarder is recommended. It has a braking torque of up to 3500 Nm and is offered as a first step for the engines of the 47x family. From October 2013 it will also be available for the OM 936 engine. Depending on the variant, it weighs 65 to 69 kg and in terms of its braking technology is fully integrated into the deceleration management of the Arocs.

In addition to safe continuous braking, the secondary water retarder also offers the advantage of being able to maintain the operating temperature of the combustion engine on long stretches of downhill driving. This provides perfect support for the complex emission control system of the standard Euro VI engines by helping to maintain the effectiveness of the cleaning technology at a high level.

A variety of axle options ex works

The new Mercedes-Benz Arocs is being offered as a two, three or four-axle vehicle. The drive configurations on offer as part of the broad-based construction vehicle family range from the 4x2 two-axle vehicle through to the 8x8/4, a four-axle vehicle with all-wheel drive and two steered front axles.

The four-axle vehicle with one front and three rear axles, or payload-optimised cement mixer chassis with a single-tyred drive tandem, are two examples of the wide variety of new Arocs vehicles now available ex works. A further example is the 8x2/4 dropsider chassis vehicle with two front axles, and one driven and one steered rear axle.

All-wheel drive: three types to cover all requirements

Besides the Arocs versions designed for use on surfaced roads with one or two driven rear axles, for off-road customers there are now three all-wheel variants to chose from offering optimised traction for specific applications.

New: Hydraulic Auxiliary Drive

The new "Hydraulic Auxiliary Drive" is designed to cover mainly road-based applications which occasionally call for increased traction. In the case of these new all-wheel-drive variants, engageable hydrodynamically driven wheel hub motors drive the front axle, instead of mechanical drive shafts. This saves both weight and fuel – the weight saving alone compared with the permanent all-wheel drive for heavy-duty off-road use amounts to half a ton.

Engageable all-wheel drive offers good compromise

As standard and when the requirements in terms of payload and low consumption are greater than the need for traction, a second variant of the engageable all-wheel drive is available without off-road gear. With this, the front axle is engaged via the transfer case (VG 3000) when the vehicle is stationary, whereby the cardan shafts are fixed at the front and rear and rotate in the ratio 1:1.

Permanent all-wheel drive for off-road use

For applications primarily in difficult terrain and with high demands to be met, for example when moving off on inclines on unpaved surfaces, the Arocs can be optionally fitted with permanent all-wheel drive (VG 2800 transfer case with 100-percent lock) plus additional off-road gear ratio.

Locks: always engaged in series

For optimum traction in each of the drive configurations in which the new Mercedes-Benz Arocs is available, a variety of differential locks is offered as standard depending on the vehicle type. They can be operated via a switch, always in the logical technical sequence: longitudinal lock, lock of the driven rear axles and – if fitted – lock of the driven front axles. In the case of an engageable front-axle drive, the engagement itself brings about the direct transmission of power.

In general, the all-wheel drive Arocs vehicles are fitted as standard with a disengageable anti-lock braking system. This enhances safety in heavy-duty off-road applications, because locking the wheels can cause a wedge-like build-up of soft surface material which can contribute to shorter stopping distances.

Power take-off units: even more choice

The range of power take-off units has been extended once again in the new Mercedes-Benz Arocs. The variants already available have now been supplemented with the addition of an even more powerful version offering 900 Nm on the engine.

Also new are an additional power consumption point at the front on the engine, as well as a clutch-dependent combination drive for use when the vehicle is stationary or whilst underway.

In general, all of the power take-off units in the Arocs can be combined with the standard, fully automatic Mercedes PowerShift 3 transmission, and also with the optional secondary retarder – a clear product advantage in the competitive environment.

Structure and suspension: two frames for different applications

Also targeted clearly at specific applications is the vehicle frame used in the new Mercedes-Benz Arocs. This component, which is crucial for off-road capabilities, payload and durability, is implemented in two variants in the case of the new vehicle family.

When it comes to use primarily on construction sites and off-road terrain, a frame measuring 744 mm wide and with a section thickness of eight or nine millimetres is used which is made of cold-formed, high-tensile fine-grained steel in conjunction with robust 100 mm-wide steel springs. This also guarantees a high load capacity and torsional flexibility, even under difficult conditions.

Strongly supported tandem

For tandem axle weights greater than 26 tons, for the first time a specific, heavy-duty tandem suspension with so-called flange socket bearings is used. Depending on the selected gross vehicle weight, the front and rear axle springs are fitted with two, three or four-leaf spring assemblies.

In the case of vehicles which are mainly for use on the road, the 834 mm-wide frame, which has been widened by 90 mm and features a frame thickness of seven or eight mm, in conjunction with the new four-bellows rear axle air suspension, helps to ensure particularly good ride comfort and good handling in both a laden and unladen state. Air suspension systems are available for the three and four-axle versions of the Arocs.
New height: the Arocs provides good ground clearance

The requirements could not be any more different: while pure road vehicles such as the Mercedes-Benz Actros or the new Antos tend to need low frame heights for transporting large volumes, as a construction industry specialist the Arocs primarily needs ground clearance.

At a height of up to 1120 mm, the frame of the new Arocs is therefore 115 mm higher than the comparable Actros. This is already the case for the truck chassis for platform bodies as well as semitrailer tractor vehicles. The off-road dump truck and cement mixer chassis are even 45 mm higher.

New position: axles moved towards the rear

The newly created range of wheelbases for two-axle vehicles is also always based on a front and rear axle repositioned by 60 mm towards the rear in each case. This enables the use of even the largest specialist tyres beyond the typical 13 R 22.5 sizes used in construction, without the need for any additional modifications.

In the four-axle vehicles, the two steering axles have each been moved by 60 mm towards the rear. The two rear axles are generally positioned a further 110 mm towards the rear. Here again there is an advantage to be gained in terms of the tyres used, and in addition the weight distribution is also more favourably balanced.

Making life easier for bodybuilders

To enable the efficient mounting of bodies, the frame features a 50 mm hole grid pattern, standardised mounting brackets, support blocks and attachment fixtures. Time savings and improved planning are also afforded thanks to the clearly defined mounting areas and positions on the frame of the new Arocs. Bodybuilders are able to fit accessories here such as support feet, compressors or instrument cabinets, without having to create space for such items beforehand. Easily accessible junctions, such as the bodybuilder interface, are installed for the perfect connection of the body electrics and electronics. In addition, the Arocs has a programmable special module. The smooth construction of an Arocs base vehicle into a specialist vehicle can be managed via the Mercedes-Benz Bodybuilder Portal.

A world first: Servotwin electro-hydraulic steering

Representing a world first in the commercial vehicle sector is the new Servotwin electro-hydraulic steering for four-axle vehicles. It features speed-sensitive power-assisted steering and active steering return. This newly developed technology, which is fitted as standard in heavy-duty vehicles and available as an optional extra in light-duty vehicles, opens up a world of previously unattainable steering comfort and maximum steering precision.

Brakes: always benefitting from full braking power

Depending on the area of application, the Arocs benefits from optimum deceleration performance – and therefore short braking distances – thanks to drum brakes, a combination of disc and drum brakes, or disc brakes on all wheels. The all-wheel drive vehicles of the new Mercedes-Benz Arocs range are fitted with a disengageable anti-lock braking system as standard.

Driver's cabs: 14 variants to choose from

Even the selection of practical driver's cabs for the new Mercedes-Benz Arocs has reached a level of variety previously unseen in the construction sector. Construction vehicle customers have a choice of no fewer than seven driver's cabs in a total of 14 variants. The range comprises 2.3 m-wide cabs featuring short or medium lengths and a variety of heights to accommodate ease of access and different engine tunnels.

Providing the edge in terms of handling: 2.3 metre cab

The cab width of 2.3 m has proved to be extremely advantageous in a wide variety of applications for which the new Mercedes-Benz Arocs has been tailor made. The compact design makes handling in short-distance haulage transport and on construction sites a great deal easier. In addition, the practical cab layout enables an integrated step-like entry design. This helps to reduce the workload of the driver significantly in applications involving him having to get in and out of the vehicle frequently, as is often the case in short-distance haulage and on construction sites.

Practical: 2.5 metre BigSpace cab

When the application calls for it, the new Mercedes-Benz Arocs can also be equipped with wider cabs. As always with the new construction vehicle family, this is determined by the use to which the vehicle configuration is put.

In addition to the compact 2.3 metre M-cabs therefore, long cabs can also be used for those applications which extend beyond a single day.

For such cases, the more spacious 2.5 metre versions of the StreamSpace and BigSpace cabs, with level cab floors, are available.

Visually appealing: a powerful look for harsh applications

The new Arocs construction specialist has inherited some significant elements in terms of cab design from its colleagues, the Mercedes-Benz Actros and Antos. These include the typically expressive design idiom. However, the design of the new Mercedes-Benz Arocs remains exceptional and absolutely distinctive.

The specially designed styling of the construction vehicle family is characterised by its radiator grille with so-called "bucket-teeth" look. It sends a clear message: the sturdy "teeth" stand for biting one's way through and knuckling down to the job. With steel elements on the bumpers, a functionally designed underride guard and visually integrated folding entry steps, this specialist in harsh applications achieves the ideal balance between form and function.

Operation: a top-class interior in every respect

The interior is geared towards vehicle use. The look is characterised by easy-to-clean, rugged surfaces finished in anthracite. The subtle contrast created with the black finish of the cockpit gives the impression of a robust yet very high-quality interior.

The instrumentation of the Arocs vehicles is also of high quality. The multifunction steering wheel, instrument cluster and implementation of the switches completely follow the template found in the Actros designed for long-distance haulage. Thanks to its graphics-enabled 10.4 cm TFT colour display fitted as standard, the instrument cluster provides a quick and particularly comprehensive overview of all of the important information relating to the vehicle and its operating status. Additional information is also displayed, such as current fuel consumption and which differential locks are enabled for example.

Optimum seat ergonomics are guaranteed thanks to an entire selection of seating, as in the long-haul truck. As a result, a body-contoured seat with massage function is now also available for construction vehicles. The massage function available for the comfort and climatised suspension seats protects against strains thanks to inflating and deflating seven air cushions one after the other.

Profitability: ecology meets economic efficiency in the new Arocs

With the new Mercedes-Benz Arocs, construction traffic is becoming more efficient than ever before. This is because the new vehicle achieves a saving precisely where it counts: fuel consumption. The new Arocs is at least able to balance out the initially unavoidable increased consumption which is basically inherent in a Euro VI-compliant engine, compared with an engine using Euro V technology, thanks to its significantly more advanced technology alone. On top of this it also makes use of the Mercedes PowerShift 3 automatic transmission as standard.

Technology and training go hand in hand

Technical innovations such as the Hydraulic Auxiliary Drive are able to achieve fuel savings of up to twelve percent compared with a permanent all-wheel drive system in those areas in which the latter is never used.

Furthermore, driver assistance provided in the guise of the standard FleetBoard EcoSupport, and optionally available FleetBoard Performance Analysis, also help to save fuel.

In addition, for low overall costs the Arocs also features long, use-dependent maintenance intervals and a repair and maintenance-friendly design. The increased service life of many of the components, and not least the exemplary good body mounting ability, also help to increase the profitability of the Arocs.

All known safety systems available

The Arocs is transferring all of the safety assistance systems which have become familiar in the new Mercedes-Benz Actros into the construction vehicle sector.

Depending on the approval class of the individual Arocs model variants (N3 or N3G), standard and optionally available systems include the electronically controlled EBS braking system with disc brakes all round, ABS anti-lock braking system and the Electronic Stability Program (ESP). Also available as an option are Lane Keeping Assist and the latest generation of the unique Active Brake Assist 3, which is able to initiate full brake application when faced with stationary obstacles.

Credits: Daimler AG

Copyright © 2013, Mercedes-Benz-Blog. All rights reserved.


Blogger Template by Clairvo