Anything that might be suitable for transporting very heavy cargo in general, and then for off-road driving in particular, is banned in Germany after World War II. The victorious powers know all too well from their own experience how appropriately designed heavy trucks lend themselves to tank transportation. On 150 hp (110 kW) the Allies have set the upper limit for motorization. Semi-trucks, three-axle trucks and four-wheel drive, for example, are also off limits.
But these restrictions fall away relatively quickly over the course of time. And as early as 1950, Mercedes-Benz can bring a first all-wheel-drive truck, which, moreover, is not to be regarded as a quasi-military island solution like the previous all-wheel-drive trucks, but marches largely in step with its less off-road brethren, which are equipped with the common rear-axle drive (axle formula 4×2: i.E. A total of four wheels, two of them driven; all-wheel-drive: 4×4).
The LA 3500 makes a grandiose start
The prelude to this practice in all-wheel-drive trucks is the LA 3500 in 1950. Diesel six-cylinder OM 312 sells excellently right from the start. Will soon also find its way into export many thousands of times over. So there is nothing more obvious than to build a four-wheel drive version of this very bestseller.
However, to keep it within budget, the 4×4 is to adopt as many components as possible from the 4×2 version of the L 3500: Engine, radiator, clutch, change gearbox as well as rear axle, brakes and cab are common to both, for example. This not only saves additional effort and cost in production, but also makes life easier for the customer when it comes to spare parts and repairs.
In line with the 4×2 road version of the L 3500, the top speed of the LA 3500 (the "A" stands for "all-wheel") is 80 km/h. What is astonishing, however, is that there is hardly any difference between on-road and off-road trucks in terms of payload either: Only about 75 kilograms heavier than the 4×2's tipper chassis, that of the 4×4 comes along. The all-wheel-drive version of the semitrailer weighs as much as 65 kilograms less than that of the 4×2 vehicle.
Extremely low curb weight creates many advantages
For good reason, the developers have placed particular emphasis on keeping the curb weight of the new all-wheel-drive truck as low as possible. The factory describes the advantages at the time as follows: "The development of each individual part to favorable shaping according to the flow of forces and the use of high-quality materials results in the exceptionally low weight of the complete chassis of 2.585 to 2.680 kilograms yes according to wheelbase and specification." And further: "The result is a lower ground load, less sinking and better mobility in critical terrain than with other vehicles of the same size equipped with the same tires"."
The chassis of the LA 3500 is a very special design. The frame is particularly elastic, as the LA 3500 has to be particularly torsionally stiff in order to maintain contact with the ground at all times and thus provide traction on rough terrain. Particularly long front axle springs, mounted outside the frame, do their part to give the LA 3500 a remarkable torsional capacity.
The cab, however, must never be impaired in its function in the process. A rubber three-point mounting helps it achieve corresponding stoic properties: "Even with a completely twisted vehicle, it was possible", writes an impressed contemporary truck tester, "to open the two doors of the driver's cab without any difficulty, respectively. To close."
Two decades of all-wheel drive know-how convince
In a test carried out in 1953, a specialist journalist from the magazine "Das Nutzfahrzeug" was even more impressed by the new all-wheel-drive truck's off-road endurance: "What was amazing was that even on an incline of more than 50 percent, it was still (26,57°) succeeded in starting from a standstill with a gravel load of more than three tons." Behind this is know-how based on two decades of all-wheel-drive experience at the plant, which manifests itself in the LA 3500 as follows: A normal change-speed gearbox transmits the engine's torque (maximum 27 mkg at 1600 rpm, equivalent to around 265 Newton meters) to the unsynchronized five-speed change-speed gearbox that was common at the time.
A two-speed transfer case and a differential at the front and rear, however, make it possible to drive either all the wheels at the same time or only the rear wheels. Daimler-Benz dispensed with a third differential between the axles for a special reason; they saved the cost of it and of an additional lock: "In the absence of one, the advantage is to", According to the factory, " that if one of the two axles slips, the full engine torque is still transmitted to the ground via the second axle."
Differential locks were not yet part of the repertoire at that time. The off-road gear, which can be engaged via a transfer case, nevertheless increases the vehicle's climbing ability considerably. If this is 27 percent (15.11°) for the maximally loaded solo vehicle in the first road gear, it increases to a maximum of 43 percent (23.27°) when the off-road gear is engaged.
Just under 3.000 times the LA 3500 rolls off the production line
The market for such vehicles is definitely there. Whether it's the catastrophic condition of Germany's roads in the post-war period, the rustic conditions in export countries, or the wide range of construction jobs that came with the German economic miracle, almost 3.000 LA 3500 all-wheel-drive vehicles were produced at the plant from 1950 until the series was discontinued in 1961, just under 7.700 pieces are from the related LA 4500 series. By way of comparison, the basic L 3500 model (including its predecessor, the L 3250, which was only built briefly) rolled just under 52.000 times from the assembly line.
No wonder, then, that Daimler-Benz consistently extended the all-wheel-drive concept to other models. This was followed in 1953 by the 4.5-ton LA 4500, and in 1954 by the 145 hp (107 kW) with a payload of around 6 metric tons and a gross vehicle weight of 13.8 metric tons, which has also proven itself as the LG 315 in the tough day-to-day operations of the German armed forces. In 1957, the LA 321 short-wheeled truck designed for a gross vehicle weight of 9.25 metric tons and the LA 331 export model (15 metric tons gross vehicle weight) were added to the lineup. From 1958 onwards, the heavy two-axle LA 329 and LA 332 were mainly intended for Brazil.
For the European market, however, these classic long-wheelers were becoming increasingly unsuitable. Especially as very restrictive regulations on dimensions and weights come into force in Germany in the second half of the 1950s, for example, which give the front-wheel drive a strong boost. Daimler-Benz, however, considered the front-wheel drive to be a passing fad and offered such vehicles from 1955 onwards, for example in the form of the LP 315, but generally relied much more on newly designed short-wheel drive vehicles.
Short-hoods continue the all-wheel-drive tradition in a tried-and-tested manner
The compromise on wheels is represented by these short-hauled trucks, which were first presented in March 1959. Designers are forced to create as much space as possible for the loading area with limited external dimensions and, on top of that, to build as light as possible to ensure a maximum payload with an overall weight that is also rigidly limited.
In any case, the Kurzhauber had two advantages over the front-wheel-drive model. On the one hand, many drivers feel safer behind a hood – albeit a short one – than in the crumple-zone-less front steer. And on the other hand, the engine of the Kurzhauber protrudes only moderately into the driver's cab, thus still offering a kind of step-through. In this way, it also leaves enough room for a third seat between the driver and passenger (much in demand at the time), radiates less heat and less noise directly into the cab than the front-wheel-drive cab, which curves directly over the engine.
For the use of all-wheel-drive trucks as construction vehicles, the Hauber design offers yet another not inconsiderable advantage: the fact that the engine is positioned further forward results in more favorable traction conditions, especially on steep ramps, because the front axle has a lower tendency to lift off in extreme cases.
As early as 1959, the first all-wheel-drive version of the new short-hauber was introduced in the form of the middle-class LA 1113 (also supplied to Brazil in parts sets as the LAP 1113). Two years later, the LA 710 7.4-tonner follows, which can still be driven in Germany with a car driver's license. In the heavy-duty compacts, the all-wheel-drive trio LA 1518, LA 1620 and LA 1920 finally celebrated their premiere in 1964.
The LA 2220 and LA 2620 three-axle models derived from this model will be the epitome of the heavy, all-wheel drive construction vehicle for many years to come. In Germany, they are initially allowed a total weight of 22 tons, and can tow up to a maximum of 26 tons off-road.
Huge three-axle vehicles set new standards
All-wheel drive technology has made enormous progress. To prevent excessive tire wear, for example, a differential is installed in the transfer case between the two rear axles, which is then automatically locked when the off-road reduction is engaged. Pneumatic differential locks for the rear axles are available on request. At the same time, engaging the off-road gear activates the front-axle drive system. This type of engagement ensures particularly simple operation, with only a few mistakes being made.
In general, the drive axles work on spur gears on the wheels and translate the drive torque there. Daimler-Benz uses a drive axle with encapsulated homokinetic joints on the wheels as the driven front axle. The rear axles are the ten-ton axles common at the time with separate supporting bridge and drive shafts. This results in the unusual type of drive via separate drive shafts: They come from that newly developed three-shaft transfer case with compensation for the two drive shafts for the rear axle.
Climbing ability of 56 percent achieved
The bridge between the 220 SAE hp OM 346 direct injection engine (equivalent to 202 DIN hp/149 kW) and the transfer case beats a six-speed gearbox called AK 6/80, which helps the vehicle to a top road speed of just under 70 km/h with a rear axle ratio of 1 : 7.35. In road gear, the top speed in first gear is 8.5 km/h. With off-road gear engaged (ratio 1.82), this value is reduced to 4.7 km/h, but the climbing ability of the solo truck climbs from 28.9 (16.12°) to 56.2 percent (29.34°) as a result.
However, a whole series of other refinements make this new three-axle truck completely fit for extreme terrain. The backbone of the vehicle, for example, is an extremely sturdy fish-belly frame with riveted crossmembers, which is wider at the front than at the rear. Two lower and one upper maintenance-free control arm support the drive and braking forces of the rear axles, while the leaf springs only have to absorb the transverse and load-bearing forces.
Extremely off-road capable axle suspension
The engineers have taken particular care with the axle suspension: The rear double axle is center-mounted – both rear axles are supported by a strong leaf spring package, the free ends of which lie in slides on the axles. This design enables the unprecedented swing angle of 13 degrees up and down respectively. This results in full ground adhesion of the wheels. Thus optimum traction even under extreme conditions. Telescopic shock absorbers on the front axle ensure that the suspension of the steering axle can be kept relatively soft in the interest of good off-road capability without subjecting the springs and their suspensions to too much stress.
There is also more comfort than ever for the driver. The days of silent blocks as spartan cab suspension are passé. Truck tester short. Flush writes. His conclusion after several hours of driving: "You can't complain about noticeable signs of fatigue."
The comfort of the LA 2220 three-axle all-wheel-drive tipper, which was particularly high by the standards of the time, was further enhanced by other elements such as a fan-assisted supply of fresh or heated air, the setting of which could be regulated separately for the driver and co-driver. The driver's seat is not yet a swing seat of today's design, but it does offer triple adjustment and particularly good upholstery: the truck tester of the time: "This seat has obviously been designed quite carefully and always keeps the driver in an upright position, free of fatigue and ready for action."
A cabin of unprecedented comfort
In the cab itself, life is also made more pleasant by the padded sun visor, two storage compartments in the doors, glove compartment with lid and coat hooks on the wall. The cladding of the engine tunnel and the doors is designed to absorb sound. The headliner trim is made of perforated plastic. An offset steering column increases the clearance for the driver's foot, the flat steering wheel provides a clear view, and even tall drivers do not hit their heads on the ceiling thanks to the ample interior height.
The days of the old single-line brakes are also over. The new dual-line brake of the LAK 2220 not only takes into account the high total weight of the triple-axle, but also anticipates the regulations to be expected within the then European Economic Community (EEC). The solution from back then: One brake circuit brakes the front axle and the second rear axle. The second brake circuit is responsible for the first rear axle and the trailer. If, for example, one brake circuit fails due to damage, the other brake circuit remains fully effective. And for the trailer, it is now finally possible to fill the compressed air supply of the towed unit even when the trailer brake is applied. The cause of many accidents up to that point is that the trailer's compressed air supply is exhausted at some point during continuous braking downhill and the brakes of the motor vehicle no longer have much to offer in the long run against the thrust of the trailer.
Although Mercedes-Benz is steadily expanding its range of all-wheel-drive short-wheel-drive trucks (in addition to the heavy 16- and 22-ton trucks, there will soon also be new 9-, 13- and 15-ton trucks), the clock is gradually running out for short-wheel-drive trucks, at least in Europe.
Although the Kurzhauber remained an attractive export vehicle for decades, especially for the countries of the Middle East and the Third World – it was not until 1995 that the last Kurzhauber built in Wörth rolled off the assembly line – the European markets increasingly demanded front-wheel drive trucks from the 1960s onward.
Clever intermediate solution for all-wheel drive front steerers
For road transport and moderate construction applications, there are indeed some variants of the front-steer vehicles introduced in 1963 with the so-called cubic cab. However, since the presentation of the successor "New Generation" is already scheduled for 1973 and an own development of all-wheel drive variants for these trucks would no longer be worthwhile, the factory helps itself with the following procedure: From 1970 onwards, it simply fitted the existing cab-over-engines from Henschel, in which Daimler-Benz had held a 51 percent stake since 1968, with the new V-engines from the OM 400 modular series and the likewise new planetary axles – and in this way was able to offer all-wheel drive cab-over-engines after all.
The new V-engines in the all-wheel-drive truck are available exclusively as V10s with 320 hp (235 kW). An eight-speed transmission with an additional creeper gear is responsible for the high power output. The frame is built on U-section longitudinal members spread at the front. And the new planetary axles, with their small differential, provide ground clearance never before seen in a tipper.
The front axle of these Henschel-Mercedes all-wheel-drive tippers, designated LAPK, is designed as a banjo axle with a bevel-ring gearbox and an external planetary gearbox. The rear axle of the two-axle LAPK 1632, for example, is based on the same design principle but also has a pneumatically actuated transverse lock. The transfer case retains the familiar three-shaft transfer case, which prevents distortion of the driveline. And the cab can be tilted, which ensures good and fast access to the innards under the cab.
But these all-wheel-drive tippers with Henschel cabs and Mercedes components are only a brief intermezzo that begins in 1970 and comes to an abrupt end in 1973. This is when Mercedes-Benz introduces the vehicles of the legendary "New Generation". And it's not the road variants but the construction vehicles that kick off the series.
With the New Generation, the construction vehicles drive ahead at
The factory presents the new construction vehicles as a "concept of reason", which originates from a sophisticated modular system and thus makes two things possible: " Extensive adaptation to the markets", as board member Rolf Staelin puts it, as well as the rear axle "prices in line with the market", as development manager Arthur Mischke adds. Mischke continues: "The modular system has been applied so systematically that a maximum of types for all transport needs has been made possible with a minimum of units and parts."
All engines in the 400 series have in common, for example, a bore of 125 and a stroke of 130 millimeters. This results in a displacement of 9.6 liters for the new OM 401 named
V6 unit, which is the smallest among the V-engines, producing 192 hp (141 kW) performs. For the 260 HP power class (191 kW), the 12.8-liter V8 is already well established in the heavy LP, as is the mighty V10 with 320 hp (235 kW) from 15.9 liters displacement. Compared with the past, this common parts concept has resulted in a considerable reduction in the variety of parts, which in turn makes life easier not only for production but also for the customer. Instead of 1.600 parts as the previous engine range, the 400 series, for example, now requires only 650 parts.
The same applies all the more to the new outer planetary axles of the New Generation, which are used not only in the construction variants but also in the road vehicles introduced in 1974 and which are still in service in the heavy-duty Mercedes-Benz construction vehicles of the modern era (the Actros, Atego and Axor series). Compared to the conventional two-axle series that have been replaced, the new planetary axles require only 220 parts instead of 480. This type of rationalization offers two advantages: more standardized parts mean larger production runs. Enable cost-cutting automation in production. At the same time, this makes it possible to increase the dimensions of units and parts and to build them with a longer service life. As a result, the planetary axles introduced in 1973 are an indispensable part of modern construction vehicles, not only because of their high ground clearance. They are also used because of their great robustness. Reliability highly valued.
Extensive all-wheel drive program right from the start
The New Generation can serve with all-wheel drive variants right from the start. Two-axle trucks are available with 170, 260 or 320 hp (125, 181 or 235 kW). Mercedes-Benz offers three-axle trucks with 260 and 320 hp for the 26-ton gross vehicle weight now permitted (181/235 kW). All-wheel-drive mid-size trucks with 10, 12 or 14 tons gross vehicle weight and 130 or 170 hp (96/125 kW) powerful in-line six-cylinder follow 1975. The 16.5-tonner 1719 retains the selectable front-axle drive, while all other all-wheel-drive vehicles now have permanent front-wheel drive. For the all-wheel-drive variants, the proven fish-belly frame is retained. With a rear axle swing angle of 13 degrees. However, two-stage leaf springs now work on the rear axles, and on the triple axles the spring carrier and the connection to the frame have become more stable. This improved pendulum suspension ensures a particularly organic power flow as well as a favorable power transmission. The all-wheel drive front axle not only offers particularly high ground clearance, but also a previously unheard-of steering angle of 42 degrees.
While the engines of the exclusively rear-wheel-drive trucks are installed lowered into the frame, the designers have generally suspended the engines and the transmission block of the all-wheel-drive variants separately in the frame. This trick enables the plant to achieve the smallest possible propeller shaft angle. The engine mounts themselves are the same in all New Generation vehicles: Mercedes-Benz uses two large-volume angular contact bearings with stroke limitation at the front and two wedge bearings with longitudinal fixing and stroke limitation at the rear.
Synchronized gearboxes make shifting easier
However, the all-wheel-drive vehicles now also come with synchromesh transmissions as standard. ZF 5S-1106 PA is the name of the eight-speed transmission with which, for example, the 2626 AK and the 2632 AK are equipped. To prevent incorrect operation, the transmission has an electronic-pneumatic lock to prevent incorrect shifting. A transfer case with lockable differential is fitted, which directs one third of the torque to the front and two thirds to the rear. However, a second transfer case is now blocked with the first rear axle (drive-through axle), which distributes the drive forces to the two rear axles. A longitudinal lock between the rear axles is standard, a transverse lock is available on request.
The customer can choose between three rear axle ratios for 75, 85 and 95 km/h final speed. In the new generation, the necessary deceleration is provided by rotary shoe brakes with a drum diameter of 410 millimeters, which are used uniformly on all axles. As standard, Mercedes-Benz also provides the all-wheel-drive variants with a further developed ALB (automatic load-dependent brake force control), which now also acts on the brakes of the front axle and no longer exclusively on the brakes of the rear axle(s).
While the pendulum spring of the three-axle all-wheel-drive models of the New Generation is familiar in principle, Mercedes-Benz is introducing a completely new cab suspension: at the front, the cab is supported in two pivot bearings with elastic rubber bushings. The cab sits softly at the rear. Low vibration on damped suspension struts. The workshop crews benefit from the particularly high cab tilt angle of 65 degrees – this allows extremely free access to the engine and assemblies.
The man at the wheel can carry out his daily checks conveniently via flaps in the front of the cab. A so-called cab-mounted gearshift ensures maximum quietness in the cab: when the cab is tilted, the steering and gearshift linkage are extended telescopically. This means that the gearshift lever can be permanently mounted in the cab, which is particularly effectively insulated against noise and heat or cold. The cabin of the new generation offers more operating comfort. Also more passive safety than ever.
The naturally aspirated engines show high persistence
But while particularly powerful engines with turbocharging and intercooling were already being introduced in the New Generation 80, construction vehicles were still denied such technology for the time being. The good old V10, however, now with a displacement of around 18 liters, helps at least the 1936 A built from 1980 to produce around 360 hp (265 kW), the maximum torque is 1304 newton meters. By way of comparison, the eight-cylinder OM 422 A turbo already produces 330 hp in road vehicles (243 kW) and a maximum torque of 1402 newton meters. From the supercharged V8 OM 422 LA, the engineers already get 375 hp (276 kW) and 1550 Newton meters. From 1980 onwards, however, the 1938 AS will also be an all-wheel-drive tractor unit with the most powerful of all Mercedes-Benz V8s.
From the major model update in 1980 (New Generation 80) onwards, however, the new standard engine for the always conservative construction industry was the 280 hp (206 kW) powerful OM 422 naturally aspirated engine. With this engine, Mercedes-Benz offers all-wheel-drive tippers as well as semitrailer tractors and chassis for special bodies.
The legendary 3850 AS heavy-duty tractor unit
Turbocharged and intercooled, the V10, which had now found its niche as a heavyweight naturally aspirated engine, received special honors from 1984 onwards. It now acts as a particularly potent 500 hp heart for the now legendary, all-wheel drive 3850 AS three-axle heavy-duty tractor, which can boast a whopping maximum torque of 2000 Newton meters.
This vehicle easily takes on a total towing weight of 220 tons and reaches the customer exclusively with a torque converter clutch and the new large-capacity cab, which laconically describes the work with the following words: "Even the external impression visually confirms the progress: 16.4 centimeters wider, eight centimeters higher, headroom 168 centimeters."
Spectacular four-axle with 8×8 axle formula
As a similarly spectacular highlight, heavy lumps with the axle formula 8×8 appeared in 1987 among the all-wheel-drive construction vehicles: all-wheel-drive four-axle trucks that could also follow a Leopard tank off-road if required. As 3528 AK or 3535 AK for 35 tons technical total weight, they are available with 14.6-liter V8 in naturally aspirated as well as turbo version and form the crowning glory of the in Germany only young species of four-axle trucks.
Prior to this, such vehicles could only be registered with exceptional approval, because the relevant paragraphs had subsumed the four-axle vehicle under the heading "Excessive road use". Nevertheless, construction trucks with four axles will soon no longer be a rarity: resourceful contemporaries discovered that it is legally possible to add a fourth axle to the three-axle truck, which is then legally registered as a trailer – without a drawbar, but with its own license plate.
In the late summer of 1981, the trailer factory Theodor Meierling presented one of the first of these so-called coupled trailers, which quickly won the approval of customers as a stealthy four-axle trailer with a total weight of 32 tons. In 1984, however, the legislator granted a modest 30-ton gross vehicle weight to the genuine four-axle truck (with two steered front axles), which had now been made acceptable by decree, and to which the 32-ton coupled trucks had to make way in return.
However, the four-axle vehicle only became interesting for most customers in 1986, when the legislator also granted the real four-axle vehicle a total weight of 32 tons, thus making a payload of 17 to 18 tons possible for the tipper. Just one year later, Mercedes-Benz can now even offer an all-wheel drive version of the four-axle truck, which, like all four-axle trucks, was initially built by the commercial vehicle company Arbon & Co Wetzikon (NAW) in Switzerland. It was not until the 1990s that production of the four-axle trucks moved to Wörth.
440 hp (324 kW) as the top engine of the SK all-wheel-drive models
The heavy all-wheel-drive vehicles already came from the Heavy Class (SK), which replaced the New Generation 80 from 1988 onwards. However, little changes in all-wheel drive technology, even though the engines become increasingly powerful. 440 HP (324 kW) and a maximum of 1900 Newton meters of torque from the still 14.6-liter OM 422 LA are available as the maximum engine for the 8×8 as well as the 6×6; for the 4×4 as a construction vehicle, 380 hp (279 kW) and a maximum of 1775 Newton meters from a new 12.8-liter V8.
In 1997, Mercedes-Benz finally introduced the Actros series of construction vehicles as the SK successor, with the all-wheel drive variants continuing to range seamlessly from 4×4 to 8×8. The VG 1700 and VG 2400 units also continue to function as transfer cases. As standard, however, the Actros construction vehicle is equipped with a hydraulic-pneumatic gearshift instead of a mechanical one, which reduces the number of variants. Four standardized connecting lines from the driver's cab to the shift cylinders on the transmission replace the multitude of traditional shift linkages that had been common up to then.
Off-road EPS in the Actros construction vehicle
As an alternative, however, Mercedes-Benz now also supplies the new Actros construction vehicles with an EPS semi-automatic system (Electronic Power Shift) specially designed for construction, the special feature of which is greatly reduced shift times: Whenever the driver engages the longitudinal lock, the EPS shifts particularly quickly, at least in the lower range group. In conjunction with the locking gear, the possible EPS preselection time also increases from 10 to 30 seconds.
As a treat for the construction industry, the new Actros cab comes with an optional extra called the "construction package," which includes an oil jacket coat rack, helmet and hammer holders, and a solid step on the outside of the vehicle that makes it much easier for the driver to inspect the tipper body. The plant also modernized its underbody: instead of the weight-intensive. Relatively hard trapezoidal springs Mercedes-Benz now supplies the new construction vehicles with maintenance-free parabolic springs on all axles. Hydraulic shock absorbers all around do their part to ensure high ride comfort.
Sophisticated front axle load compensation for the Actros four-axle truck
The developers are particularly proud of the unique new front axle compensation for four-axle vehicles, which provides the two steered front axles with fully effective axle load compensation up to an obstacle height of 100 millimeters. When driving over obstacles, the axle positions are shifted vertically by means of pivoting levers and tie rods, which prevents undesirable axle load changes. This improves ride comfort beyond the tarmac, also improves traction and prevents overbraking of a single axle. The load on the components of the unit is thus reduced, as is tire wear.
As far as the brakes themselves are concerned, however, the all-wheel-drive variants do not enjoy the benefits of disc brakes: they retain drum brakes all round, as the risk of damage would be too great in tough off-road operation. However, the drum-braked all-wheel-drive Actros also offers electronic brake control.
In other respects, too, the new all-wheel-drive vehicles are all about state-of-the-art technology and maximized customer benefits: high-strength steel for the longitudinal and cross members of the frame optimizes weight. Despite high torsional elasticity, the design allows extreme bending stiffness. Additional strength is provided, among other things, by pressure distribution plates that specifically stabilize the frame at highly stressed points. The new Bau-Actros is also packed with low-maintenance and maintenance-free parts. One of many examples of this is the use of rubber molecular bearings for the suspension of the springs. This is also one of the reasons why the central lubrication system can be dispensed with.
An all-wheel drive range without equal
Following the 2002 model update of the Actros, the special feature of which is an extremely luxurious cab unconditionally designed for driver-friendliness, the heavy trucks with all-wheel drive are in better shape than ever before. Up to 41 tons total technical weight and 510 hp (375 kW) from a 16-liter V8 (which meets the Euro 4 and Euro 5 emission standards) are offered, for example, in the current 8×8 flagship of the Actros all-wheel-drive fleet. The 6×6 Actros are also equipped with maximum 510 hp (375 kW) available. For 4×4 vehicles, performance of up to 480 hp (353 kW) are available.
However, the all-wheel-drive range of Mercedes-Benz trucks is by no means limited to the Actros series. For those who prefer a little less, the weight-optimized Axor heavy-duty truck series in the form of the all-wheel-drive 1823, 1828 and 1833 two-axle models is the answer. The driving force is provided by 230, 280 and 330 hp (169, 206 or 243 kW) inline six-cylinder units from the 900 engine series. And the mid-range Atego is available as an all-wheel-drive two-axle truck in tonnages from 10 to 15 tons. At the heart of these two-axle vehicles are both four- and six-cylinder engines from the 900 series, with output ranging from 180 to 280 hp (132 to 206 kW).
In the name of maximum customer benefit: construction variants of the Actros 3
Finally, the third-generation variants of the Actros presented at the IAA 2008 are better equipped than ever for the tough life on the construction site. For the all-wheel-drive models, the familiar configurations of 4×4 to 8×8 remain unchanged. There is now for example a new protection plate for oil pan, engine and radiator. Four millimeters thick, this high-strength stainless steel part is a particularly striking chin that curves up from the substructure a good hand's width into the front of the new construction Actros, almost like a front spoiler.
Like a mini cowcatcher, the additional fold-down step-up bar then frames this ensemble in a visually successful manner at the front. Three beads in the protective plate itself soften the appearance. Corresponding perfectly with the three cooling slots one floor higher in the radiator grille. The result is a particularly beefy appearance that is ideally suited to a construction vehicle.
The headlamp guards are also particularly robust and are now made of black steel instead of plastic. Whereas a quick release of these grids ensures that a sponge can gain access immediately. If there is a threat of attack from behind, the Actros 3 in construction versions with likewise steel-gridded taillights will be able to counter it. A steel canopy over the taillights keeps out mischief from above, such as dripping concrete.
Extra protective plate for the tank
And finally, attacks on the soft part of the tank can be countered by a further protective plate, which is easy to remove and refit and simple to clean. The Actros 3 variants have also gained from the new roof rails, which now complement the optional driver-side step on the side of the vehicle in greater detail than before: the hand knows exactly where it belongs in the traverse to the rear. The first step of the entrance has been completely redesigned and now reacts flexibly not only to longitudinal but also to transverse loads.
This new part, which can also be retrofitted to older Actros trucks, is called a "pendulum entry". A practical feature: if the horizontal tread plate of the step is damaged, it is not necessary to replace the entire unit, but only the plate itself.
Reinforced mirror housings, further upgraded interior
Last but not least, the new mirrors of the Actros 3 in build version are particularly well equipped to withstand damage. Roughly corrugated and insensitive plastic characterizes their backs. Whipping branches and the like will therefore hardly leave any traces in the form of ugly scratches.
In the interior, the Bau-Actros always marches in nice step with the road vehicles, even if the wallpaper is generally a bit more robustly designed. This begins with the new instrument panel, which now also features four noble chrome-framed clocks. This continues with sunblinds at the front and, for the first time, on the two side windows as well.
Also available is the new, special and absolutely standard Actros rubber floor mat that came with the Actros 3 for road vehicles. The construction vehicles can also be used with the optional folding table on the passenger side, which is an excellent place to have a snack.
Novelty in the all-wheel-drive truck: a rain sensor and automatic transmission
There is no lack of refinements, such as the new compressed air gun for quick cleaning of the cab or the light and rain sensor, which is only available in conjunction with tinted windows. Dipped headlights or windshield wipers are automatically activated as soon as circumstances require it.
And the new construction Actros comes with the automated twelve-speed transmission of the Powershift family: not as standard as on the road scooters, but at least with a special construction soft- and hardware. For example, particularly robust and durable steel-forged transmission arms are specially designed for the rough conditions offroad.
In the software, a so-called power off-road mode celebrates its premiere, which is intended to ensure crisply short shift times and the right bite for hard ground. Two fast reverse gears do their part to speed up operations without the option of turning (in tunnels, for example). Finally, the free-swing mode will prove particularly useful on construction sites, where the truck can get stuck more often than not.
Vertical exhaust pipes adjustable in height and direction
But that's not all: on the rear wall of semitrailer tractors and platform trucks, there is now a new optional worklight that – when installed centrally – illuminates an area of ten by five meters. Also to be found directly in the rear of the cab is the new concept for the raised exhaust: two- and three-axle models now come with a stainless steel exhaust pipe that can be variably adjusted in height and blow-off direction.
As a complete vehicle, Mercedes also supplies the new tippers in an additional version that takes full account of use on the road paver. The so-called road finisher package includes, for example, a high-mounted taillight, side reflectors and shortened mudguards with folding splash flaps.
Highly off-road capable heavies: The Mercedes Zetros
As a completely new representative of the off-road fraction, another highlight will be on display at the IAA 2008 alongside the construction variants of the Actros 3: the new, all-wheel-drive Mercedes-Benz Zetros. Not only does it add a particularly off-road capable variant to the all-wheel-drive truck portfolio, but it can also be seen as a continuation of the Unimog with a focus on transporting particularly heavy loads. Basically the Zetros comes with all-wheel drive. Is available as a two- as well as a three-axle model. The payload of the two-axle model (1833 A 4×4) ranges from 4 to 6 tons, and the payload of the three-axle model (2733 A 6×6) from 7 to 10 tons. The all-wheel-drive base comes from the civilian colleagues Actros and Axor.
Customized cabin: layout suitable for air freight
But where the Zetros is headed is immediately apparent from the low height of the specially redesigned cab, which is only partly based on what is already available in the company's modular system: the interior is based on the Global Cockpit of the Axor, while the doors are from the Unimog. Otherwise, however, the layout is completely new and specially designed for rail and air transport of all kinds. In transport aircraft such as the Hercules C 130 or the Transall C 160, it fits almost straight away. Also, the dimensions are exactly the same as what is prescribed internationally for the track.
And that is no coincidence. After all, the vehicle is not only intended for disaster relief, rapid intervention in forest fires or for the energy sector, but also for use in international peace missions, for example.
Form follows function: Renaissance of the hood design
Hence the renaissance of the hood design, which is unique for European trucks today: For example, it not only creates a particularly large amount of space in the cabin for passengers. It is also, and without great risk of overloading the front axle, particularly suitable for those armors that are supposed to make the vehicle immune to abruptly exploding mines and ballistic attacks. The conditions in Iraq or Afghanistan, for example, have meant that demand for vehicles like the Zetros has risen steadily over the past few years. Last but not least, for possible repair. Maintenance such a hood folded up faster than a classic forward control tilted. Very important in extremely low temperatures in regions where minus 50 degrees Celsius is nothing unknown: The crew can stay in the cabin while the service team works on the technology.
Typical design, practical technology
The art of the Zetros, which incidentally with its distinctive radiator grille shows clear echoes of the current off-road vehicles with the star, is to build the appropriate hood from the series production kits. Not only the interior of the cab, but also the steering system are taken from the Global Cockpit of the Axor. From which the Zetros also has the engine: the 330 hp (243 kW) powerful six-cylinder 900 series.
The axles of the Zetros are the tried-and-tested 7-series external planetary axles, which date back to the New Generation, but are still indispensable in heavy construction trucks today. The brakes and suspension are as rustic as the expected applications: leaf springs on all axles and drum brakes stand for technology that is as uncomplicated as it is robust.