From hard haul to high-tech: 50 years of truck development for the sake of the environment, safety, comfort and economy
Stuttgart
Apr 30, 2010
  • The truck technology of 2010 would have been the stuff of pipe dreams in 1960
  • End of the 1950s: a time of radical change in the truck industry
  • The 1960s: the LP series marks the dawn of the modern era
  • The 1970s: the "New Generation" (NG), the start of a long-running success story
  • The 1980s: turbos and a new style of driving
  • The 1990s: SK, Actros – focus on environmental and safety issues
  • The new millennium: trucks on the road to perfection
The European Union was still called the European Economic Community (EEC), Europe's best-known politicians were Konrad Adenauer, Charles de Gaulle and Nikita Khrushchev. On the cusp of the 1960s, the economy in western Europe at least had overcome the aftermath of the Second World War and many countries were beginning to flourish once again. Western Europe was growing closer, with previously bitter enemies becoming partners or even friends. A solid border divided western and eastern Europe into two blocs. Americans and Russians were engaged in a space race. International business relations called for transport links, but crossing the Alps was still an arduous task for long-distance truck drivers. Crossing borders was a laborious affair as complicated controls and customs barriers arose. Long-distance truckers roved around with deutschmarks, francs, lire, Swiss francs or Austrian shillings in their wallets. Trucks were on the threshold of the modern era, at the onset of a fast-paced and fascinating course of development.
The truck technology of 2010 would have been the stuff of pipe dreams
in 1960
This development entailed radical change at all levels, from safety through environmental protection, drive technology, economy and comfort to transport capacities. A little heard-of topic in 1960, heavy-duty trucks today meet the very highest standards in terms of active and passive safety and protection for other road users. Safety belts and mirror systems – not to mention electronic assistance systems – were the stuff of pipe dreams back in 1960.
The same applied to environmental protection: back in 1960, trucks were loud juggernauts enshrouding the world around them in clouds of exhaust fumes. 50 years on, they glide quietly along the motorways with low levels of emissions. In 1960 a truck boasting 150 kW or 200 hp and 700 Nm of torque was considered a powerhouse for shifting 32 tonnes. Several truck generations later, over twice the power and three times as much torque are adequate for moving around 40 tonnes. At the beginning of the 1960s around 50 l of diesel were required per 100 km in order to move a truck/trailer combination weighing 32 tonnes and measuring around 3.6 m in height. Today, 40 tonnes, 4.0 m high truck/trailer combinations move around Europe on a third less diesel.
Being a truck driver was hard physical work back in the sixties. Half a century later, air springs or parabolic springs have replaced giant trapezoidal spring assemblies, homely driver's cabs have succeeded their spartan predecessors, engine noise is muted rather than roaring, drivers enjoy air-conditioned cabs equipped with refrigerators rather than a bread-and-butter diet in cabs with makeshift shading, with fully automated transmissions at their fingertips as opposed to the heavy-going gearboxes of yesteryear. They sleep on well-sprung bunks designed according to the latest scientific findings, rather than on the simple old hard beds of old.
A truck such as the Mercedes-Benz LP 333 was very much state-of-the-art back then, though clearly worlds apart from the 2010 Actros – notwithstanding the fact that the two are distant relatives.
The end of the 1950s: a time of radical change in the truck industry
Around 1960, truck development was at a crossroads. The way ahead saw a transformation from truck/trailer combinations to semitrailer/tractor combinations, from the diesel engine with indirect injection to economical engines with direct injection, from the cab-behind-engine truck to the cab-over-engine variant. The then Daimler-Benz AG had been offering heavy-duty trucks in cab-over-engine variants as an alternative to the customary cab-behind truck models for some years. The first model was the LP 315, which appeared in 1955. The letter "L" stood for "lorry", while the "P" stood for the Pullman cab, named after an American railway designer who was renowned for his streamlined trains. The combination of digits in the model designation denoted a design number which applied to both the truck and its engine.
The cab-over-engine design created space for a separate sleeper berth for the two-man crew which was customary at the time, while the body platform was extended by one metre and the payload increased. A disadvantage was that the engine protruded into the cab. This also proved a drawback for servicing: engine oil was replenished in the cab after removing a cover – at an oil consumption rate of 0.4 l per 100 km, this was a regular exercise. The coolant was also topped up from inside the vehicle. A power output of 145 hp from an engine with a displacement of 8.3 litres, a six-speed constant-mesh transition and a top speed of 70 km/h were sufficient for long-haul operations. The more powerful LP 326 boasting a power output of 200 hp from a 10.8 l four-valve naturally aspirated engine went into operation from 1957, first in export countries and later in Germany. Truck engines were sensitive pieces of machinery: in the 1950s, drivers received a personal commendation for covering 100,000 km without a general overhaul.
A minimum power output of 6 hp per tonne of permissible gross weight applied for trucks in Germany as of 1958. An engine brake was compulsory on safety grounds. A litre of diesel cost the equivalent of 25 euro cents. The regulations in the EU as it was then were of an extremely patchwork nature. In Germany, for example, new regulations to protect the roadway entered into force in 1958. The maximum permissible length of truck/trailer combinations was reduced from 20 to 14 metres, while semitrailer/tractor combinations were allowed to measure 13 metres in length. The maximum weight for truck/trailer combinations was cut from 40 to 24 tonnes, with corresponding reductions in the permitted axle loads, while three-axle trailers were prohibited. These specifically German regulations led to different model series for the domestic and export markets respectively. The rules were similarly divergent among the various export markets, with a permissible gross weight for truck/trailer combinations of 36 tonnes in Italy as opposed to 35 tonnes in France. Meanwhile, the Netherlands imposed no limits at all on gross weight, but restricted the axle load to eight tonnes and the overall length to 18 metres.
LP/LPS 333: the "centipede" – one of the most unusual trucks of all time
The answer to the prevailing legal situation went by the name of Mercedes-Benz LP/LPS 333 (LP = tractor vehicle, LPS = semitrailer tractor). The striking design of this cab-over-engine vehicle is based on two steered front axles plus drive axle (LPS: steered leading axle). This configuration earned it the nickname of "centipede", which it has retained to this day. With a load of four tonnes on each of the front axles, eight tonnes on the drive axle plus 16 tonnes on the trailer, the LP 333 assured transport companies of a truck/trailer combination with a gross weight of 32 tonnes up to 1960.
Boarding the cabin took some effort, but the axle configuration resulted in excellent ride comfort and handling. The 10.8 litre engine with pre-chamber injection had a power output of 200 hp. Its maximum torque stood at 72 mkg, or 706 Nm. A synchromesh transmission with six gears transmitted the power from the engine. Despite a reference in the catalogue to a "foam covering", the operating noise from the engine entered the driver's cab virtually unabated. The catalogue also mentioned the heating which came as standard.
The driver sat at an ivory-coloured steering wheel which was positioned almost horizontally. Apart from a speedometer and a small rev counter, the most important source of information was an instrument cluster keeping the driver up to date on water, brake and oil pressure and the level of fuel in the tank. At the end of the turn signal lever a lamp flashed in sync with the turn signal indicator; a yellow lamp on the dashboard indicated low tyre pressure. Instead of today's spring brake, a ratchet brake kept the truck stationary, the driver pulling the lever several times in succession, accompanied by the characteristic noises.
The extreme restrictions were short-lived however. In 1960, an overall length of 16.5 metres for truck/trailer combinations and 15 metres for semitrailer/tractor combinations was permitted in Germany, together with a traction weight of 32 tonnes, which was raised to 38 tonnes in 1965. These developments effectively sidelined the LP 333, and the brief era of one of the most unusual trucks in the history of commercial vehicles came to an abrupt end in 1961.
Truck/trailer and semi-trailer/tractor combinations, cab-over-engine and cab-behind-engine trucks vie for supremacy
This did not signal the end of the general debate on truck/trailer and semitrailer/
tractor combinations and their respective variants, however. At the beginning of the 1960s, before the introduction of today's standardised pallet and container sizes, automotive journalists short-nosed or cab-behind-engine vehicles rather than cab-over-engine variants on account of their superior handling, despite the loss of loading length. For all their lack of technical elegance, cab-over-engine variants were regarded as a functional and economical solution. At the same time, the press championed synchromesh transmissions, along with adjustable driver's seats with hydraulic suspension and power steering. Shortly before the onset of the new decade, automatic load-dependent brake power distribution had become a legal requirement for semitrailer/tractor combinations, in order to limit the jackknifing for which such vehicles were notorious on slippery road surfaces.
The new short-nosed vehicles in 1959
The stringent regulations on vehicle lengths also influenced the design of the new cab-behind-truck vehicles from Mercedes-Benz, which first saw the light of day in 1959. These are known as short-nosed vehicles, with the engine protruding slightly into the cab to save space. The look of these vehicles was characterised by the lack of traditional wings, while the shape was reminiscent of the pontoon-type bodies of contemporary cars. The oval radiator grille was adopted from the cab-over-engine vehicles. In contrast to the earlier long-bonnet vehicles, the bonnet on these vehicles opened towards the front, earning it the nickname of "alligator bonnet". The launch model of the semi-forward control trucks was the L 337, which appeared in 1959, followed a year later by the slightly more powerful L 338 (later L 1418) and the L 334 (L 1620). Under the bonnet were six-cylinder in-line engines with an initial displacement of 10.8 litres which was subsequently increased substantially. Similarly to other trucks, the L 334 and its fellow semitrailer tractor, tipper and all-wheel-drive models were designed for the export market as two-axle variants with a permissible gross weight of 19 t.
The 1960s: the LP series marks the dawn of the modern era
New designs, new technology, new designations: in 1963 a new series of tractor vehicles from Mercedes-Benz shook up the commercial vehicles segment. The strictly cubic cab of the new LP 1620 cut a striking figure. The model designation itself indicated the dawning of a new era, the first two digits standing for the tractor vehicle's permissible gross weight of 16 tonnes while the two figures at the end referred to the power output of 200 hp. In terms of appearance alone, the new generation and its forerunner were worlds apart. The new vehicles featured a wide entrance, large windows and a spacious cab interior, with a very flat engine tunnel and a fold-away bed behind the seats.
Mercedes-Benz did without a tilting cab, but replaced the previous service points inside the cab with numerous maintenance flaps around the outside of the cab. The cab featured its own suspension – two rubber springs at the front and a leaf spring with two shock absorbers at the rear. The interior was spartan by modern-day standards: the seats were fitted to a tubular frame and items mentioned in the catalogue included the windscreen washing system which came as standard, an elastic shock-resistant rim on the dashboard and padded window cranks.
The LP 1620 represented a leap forward on a technical level, too. Innovations here included the ball and nut power steering in place of the previous worm and roller variant. The dual-line brake as opposed to the previous single-line variant also supplied compressed air during braking – a major advance on the safety front. And the new viscous fan operated only when required, thus saving fuel.
Direct injection engines lead to marked improvements in economy
A year later, the next important technical advance took place under the cabin, with direct-injection diesel engines of the OM 346 series replacing the previously used pre-chamber diesel engines in 1964. Generating a power output of 202 hp, soon to rise to 210 hp, with the same displacement of 10.8 litres, these new engines cut fuel consumption by up to a quarter in one fell swoop. This was a major benefit in the face of diesel prices averaging around 26 euro cents in Germany. Experts forecast optimum fuel consumption levels of 35 to 40 litres per 100 km for a four-axle combination with a gross weight of 32 t – an outstandingly low figure at the time. At a constant speed of 80 km/h the combination ran on 32 l per 100 km.
The fastest final drive ratio for a top speed of 86 km/h – six km/h faster than was allowed for trucks in Germany – was a contributory factor to these fuel savings. The maximum torque stood at 72 mkg/687 Nm, which was sufficient for 32 tonnes, and even for the new statutory limit of 38 tonnes' gross weight and 18 m overall length. Brake tests revealed deceleration of 4.9 m/s2, equivalent to a braking distance of 28 metres from a speed of 60 km/h – around twice the required braking performance of at least 2.5 m/s2. The engines' capacity to cover 300,000 km before they were due for the first complete overhaul was exemplary.
Just under 50 l/100 km: the press begins measuring fuel consumption and speed
In the mid-1960s, trade journals began measuring fuel consumption and average speeds on standardised test circuits. In a test comparing four 38-tonners the Mercedes-Benz 1620 revealed a fuel consumption rate of 49.3 l/100 km and completed the course at an average speed of 49 km/h. It ran on the new belted tyres, which experienced testers considered capable of cutting fuel consumption by five percent. The engine oil required changing every 10,000 km back then, while the oil in the transmission and rear axle was due for changing every 20,000 km.
Weights and dimensions throughout Europe were still a real hotchpotch. A height of 4.6 m was allowed in Great Britain, while in Denmark the limit was set at 3.6 m. The permissible length of a truck/trailer combination varied between 14 m (Switzerland) and 22 m (Belgium). Semitrailer/tractor combinations with five axles were permitted to measure between 13 m (Great Britain) and 15 m (Germany and other countries) in length. In contrast to all other countries (2.5 m), Switzerland only tolerated a width of 2.3 m. The gross weight for a truck/trailer combination was set at 21 t in Switzerland, but 44 t in Italy. Semitrailer/tractor combinations were similarly restricted to 21 t in Switzerland, while Germany permitted 38 t.
The steady rise of engine power and torque
As permissible gross weights rose, Mercedes-Benz stepped up the available engine power. In conjunction with an increase in displacement to 11.6 l, power output rose in 1967 to 169 kW (230 hp), corresponding to 4.4 kW or 6 hp/tonne, with 81 mkp/795 Nm of torque. The new engine designation was OM 355. Two years later, 177 kW (240 hp) and 83 mkp/815 Nm were attained. Generating 169 kW (230 hp), the Mercedes-Benz LP 1623 as a 38 tonne truck/trailer combination attained an average speed of 48 km/h in test conditions, with fuel consumption at 44.2 l/100 km. This fuel consumption qualified as modest in the 1960s, following the switch to engines with direct injection. Drum brakes were to remain standard for some decades to come, while an air-assisted mechanical pistol-grip handbrake secured the combination when stationary.
With a long cab, 3600 mm wheelbase, 200 l of fuel and a non-synchronised six-speed transmission, the Mercedes-Benz LP 1624 semitrailer tractor weighed in at 6.2 tonnes without spare wheel. At a rated engine speed of 2200 rpm the truck attained a top speed of 85 km/h. The climbing ability with a towing weight of 38 tonnes was a rather modest 16 percent.
Exterior mirrors adjustable from inside the cab were now available from accessory retail outlets for companies keen to provide their drivers with all the latest mod cons. Disc brakes in heavy-duty commercial vehicles and exhaust emissions were slowly emerging as serious subjects for discussion. Stereo cassette units for cars came onto the market in North America. The spring-loaded parking brake became established for heavy-duty trucks, and retarder systems were introduced into truck technology.
The model range began to grow: an extended cab with two fixed beds was introduced in 1965, followed by three-axle semitrailer trucks with steered leading axle following on in the tradition of the legendary LPS 333. Two years later, Mercedes-Benz added three-axle variants with driven rear axles and with trailing axles to its long-haul truck range. 1969 saw the introduction of a tilting cabin, together with a raised roof.
1969 sees the launch of the 400 engine series
At the same time, the company also broke new ground on the engine front. The 400 engine series was introduced in 1969, beginning with a V10 with a princely displacement of 15.95 litres (model designation OM 403). This engine generated a power output of 235 kW (320 hp). The corresponding model designation Mercedes-Benz LP/LPS 1632 went on to acquire legendary status. The high power output was provided in anticipation of an announced impending legal requirement in Germany for trucks to have a power output of 5.9 kW (8 hp) per tonne. The corresponding legislation was shelved, but the engine remained and became a success story. A litre of diesel cost the equivalent of 28 euro cents at German filling stations. Mercedes-Benz continued to expand its new engine range, adding a V8 with a displacement of 12.8 and generating 188 kW (256 hp) of power for heavy-duty use in 1972. The tried and tested OM 355 in-line six-cylinder engine rated at 177 kW (240 hp) also remained in production.
The LP 1632 weighing in at 38 tonnes attained an average speed of 58 km/h under test conditions, with fuel consumption at precisely 48.1 l per 100 km. The maximum torque stood at 103 mkp/1010 Nm at 1500 rpm. Its noise level of 73 dB(A) at 80 km/h was considered good. The vehicle was fitted with a synchromesh eight-speed transmission featuring range change, that is, two levels of four gears arranged one over the other. An attempt to offer only synchromesh transmissions failed, as experienced drivers preferred the swift gear-changing that a non-synchromesh transmission offered in the right hands. Synchromesh transmissions did not become established until the next generation of Mercedes-Benz trucks. A long-haul truck/trailer combination weighing in at 32 tonnes and fitted with four rather than five axles represented an interesting alternative at the time. The 188 kW (256 hp) output of the Mercedes-Benz 1626 corresponded precisely to 5.9 kW (8 hp) per t here. In laden state the LP 1626 clocked up an average speed of 58 km/h at a fuel consumption level of 45.2 l per 100 km.
The cab-over-engine vehicles remain in production
In parallel with the LP cab-over-engine variants, Mercedes-Benz also continued to produce the cab-behind-engine vehicles of the L series, including semitrailer tractor variants. One LS 1624 was on the roads in the mid-1960s with a towing weight of 38 tonnes, for example. A power output of 177 kW (240 hp), 83 mkp/ 815 Nm of torque, a non-synchromesh six-speed transmission (with optional splitter group) and axles with two transmission gears were characteris­tic features of the drive train. The cab interior was a spartan affair, with such mundane details as a second sun visor or a forked cam latch to prevent the doors from opening while the vehicle was in motion warranting a mention in the catalogue. The era of the cab-behind-truck vehicles did not come to an end in Germany until the next generation of trucks was introduced at the beginning of the 1970s. Export production continued for many years to come.
The 1970s: the "New Generation" (NG), the start of a long-running success story
Exactly ten years after the launch of the tractor vehicle with cubic cab, a generic change took place in two stages. The new buzzword was "NG" or "New Generation". The sea change was spearheaded by new tippers from Daimler-Benz in 1973, followed a year later by corresponding trucks for long-haul transportation. The onus under the new modular system was on obtaining a maximum spread of models from a minimum scope of assemblies and parts.
The engines of the 400 series were a case in point, now comprising V6, V8 and V10 with displacements of 9.6 l, 12.8 l and 15.95 l respectively, with identical bore and stroke dimensions and an almost square ratio of bore (125 mm) to stroke (130 mm). The power output ranged from 141 kW (192 hp) through 188 kW (256 hp) to 235 kW (320 hp), with a rated engine speed of 2500 rpm in each instance. The two more powerful variants were intended for long-haul transportation, with maximum torque of 83 mkp/815 Nm and 103 mkp/ 1010 Nm. Right from the market launch of these vehicles, Mercedes-Benz announced that future variants with a turbocharger were in store. The new planetary axles in place of the previous spur gear axles were extremely durable and offered the necessary reserve capacity to cope with high torques. Test reports praised the lack of smoke fumes from the exhausts of the new lorries, even during cold starting.
The new vehicles initially featured the familiar transmissions with six, eight and twelve gears. Mercedes-Benz soon began to deliver its heavy-duty trucks with new 16-speed transmissions too, however. The finely tuned yet broadly spread ratios in conjunction with high-geared drive axles resulted in low engine speeds at motorway vehicle speeds. Compared with the top speed of around 85 km/h for the LP 1632, by 1974 the calculated top speed for the Mercedes-Benz 1632 stood at 100 km/h. Six years later it rose by a further 20 percent in conjunction with thoroughly revised engines. The new planetary axles were indestructible, their dual transmission enabling numerous drive train variants. This was more than welcome in the face of fuel prices soaring to the equivalent of 44 euro cents per litre.
Well conceived aerodynamics save fuel
The new cab with rounded edges and a slightly inclined windscreen improved the vehicle's aerodynamics, again helping to reduce diesel consumption. Meanwhile, the hydraulically tilting cab soon became available in numerous variants, all produced with a single set of press dies. The short tipper cab from 1973 was complemented as of 1974 by a 600 millimetre longer version for long hauls. A mid-length variant was added in 1977, followed in 1979 by a wider and higher extra-large cab. A high-roofed variant was also added to this model series towards the end of its career in 1992.
Added comfort for drivers
Comfort had improved all round – with a marked reduction in interior noise thanks to better insulation, more headroom, better all-round visibility provided by front windows and triangular windows extending far down the front and sides of the cab and a steering wheel enabling adjustment to any of three positions for the top-of-the-range Mercedes-Benz 1632, the New Generation really lived up to its name. The rev counter featured a green range indicating economical driving for the first time. On the left of the steering wheel the new combination switch incorporated the indicator, windscreen wiper, high-beam, headlamp flasher and signalling horn functions. The co-driver's seat for the two-man crew featured a headrest and armrests.
The long-haul cabin was provided with a sophisticated suspension system, with two hairpin springs, vibration dampers and a stabiliser bar at the front. A parabolic spring with two vibration dampers absorbed jolts from bumpy road surfaces. The two-axle vehicles were fitted as standard with a two-stage leaf spring on the rear axle, in the form of a classic trapezoidal spring comprising nine main and seven auxiliary spring leaves. Three-axle variants featured an extremely long pendulum spring. The two- and three-axle variants were available as tractor vehicles and semitrailer tractors from 1975 with optional air sus­pension. A so-called fishbelly shape was characteristic of the frame for the NG vehicles. Tapered ends kept the overall height low. This design became broadly established in the coming years and decades. Belted tyres were optionally availab­le from the outset. These soon became widespread as well, as they rolled along more lightly, provided a better cushioning effect and offered longer service lives.
The topic of safety began to acquire growing importance. Dashboard and instrument panel were provided with foam-backed safety padding, handles and control levers were produced in a flexible material. Doors, door pillars, roof frame support and rear panel were provided with deformable plastic padding. Attachment points for the optionally available three-point automatic seat belts featured as standard. While great efforts were made to equip the vehicles with effective heating and ventilation, air conditioning remained a long way off, and was only very rarely encountered in European trucks.
The Mercedes-Benz 1632 sets a sensational new fuel consumption record
In 1976 a Mercedes-Benz 1626 and a 1632 competed on the market as drawbar combinations, each with a gross weight of 38 tonnes. Aerodynamically designed air deflectors were as yet unheard of, the platform bodies still featuring the typical, slightly angular roof-type top. The 1626 was fitted with a six-speed split transmission, while the more powerful variant featured an eight-speed variant. The 1626 completed the 800 kilometre test run at an average speed of 55 km/h and a fuel consumption rate of 43.1 l per 100 km. The 1632 clocked up 56 km/h at 47 l/100 km. In an individual test the Mercedes-Benz 1632 managed a fuel consumption level as low as 41.8 l/100 km – a sensational record performance at the time. The interior noise level at 80 km/h stood at 75 dB(A). Oil consumption of 2.5-3.0 l per 100 km was considered normal by testers and transport companies alike.
The 1980s: turbos and a new style of driving
The new decade got off to a rousing start for Mercedes-Benz with the introduction in 1980 of a thoroughly revamped range of heavy-duty trucks designated "New Generation 80" (NG 80). After much deliberation, the brand now focused on turbo engines. For long-haul purposes, the spotlight fell on the V8. Now going by the name of OM 422, its displacement increased to 14.6 l, with a power rating of 184 kW (250 hp, model designation as two-axle variant: Mercedes-Benz 1625) as a throttled engine, rising to 206 kW (280 hp, model 1628) as a naturally aspirated engine. Top of the range were a turbo engine rated at 243 kW (330 hp, initially for buses only) and a turbo engine with charge air cooling which generated 276 kW of power (375 hp, designation 1638).
The bore to stroke ratio tended towards the high-torque undersquare variant, at 128 to 142 mm. The 1040 Nm of torque offered by the Mercedes-Benz 1628 was standard for a gross weight of 38 tonnes, while the 1400 Nm of the 1633 was more than ample. The 1550 Nm of torque generated by the Mercedes-Benz 1638 as the most powerful variant came in for much praise. Robust engines also meant economic efficiency – 500,000 km before an overhaul represented the state of the art at the beginning of the 1980s.
In addition to increased power and torque, in the wake of the two so-called oil crises the focus was also on low fuel consumption, with diesel fuel now at around 60 euro cents per litre. Plenty of power and torque at moderate revs and 16-speed transmissions with close ratios helped this cause. High gearing now meant around 1600 rpm at 80 km/h, and the motto in drivers' training at Mercedes-Benz was "through villages in eighth gear". This meant 1000 rpm and a whole new, eco-friendly style of driving. Aerodynamic features also helped to reduce fuel consumption. From air deflectors on the edges of the cab to the multi­dimensional roof spoiler tested in the wind tunnel, the NG 80 had a very different look to the previous NG series, although the basic shape of the cab remained the same.
Cabs with more home comforts
The interior of the cab sported a similarly new look. New features here were a generally more homely interior, a steering wheel lock and starting by ignition key in place of the traditional starter button. The precise markings on the centrally positioned rev counter and the three-dimensional roof spoiler both came in for special mention in test reports.
Together with the extra-large cab which was introduced at the same time (initially only for the top-of-the-range 1638 model), drivers benefited from new comfort features such as an electrically adjustable exterior mirror on the right and an electrically operated right-hand side window. The parabolic springs which now featured as standard also resulted in a lasting improvement to comfort.
The power offered by a Mercedes-Benz 1638 was sufficient even to cope with the exacting demands of transportation in Sweden, with a permissible gross weight of 50 tonnes on seven axles. With the 38 tonnes permitted in Germany, the most powerful Mercedes-Benz revealed a fuel consumption level of exactly 33.2 litres per 100 km under test conditions, clocking up an average speed of 65.6 km/h – astounding economy in view of the engine's power output. The Mercedes-Benz 1628 also put in a good showing at only just over 38 litres per 100 km, clocking up a circuit speed of around 60 km/h. In the middle of the field was the Mercedes-Benz 1633, with fuel consumption of 37 litres per 100 km and an average speed of 65 km/h.
The heavy-duty tippers and the long-haul trucks for export produced by Mercedes-Benz at this time featured a high-powered V10 naturally aspirated engine based on the V8 variants, with a massive displacement of 18.3 litres. Its power output of 352 hp was the result of some precise calculation work: 8 hp per tonne was a mandatory requirement in Italy. When multiplied by the 44 tonnes of permissible gross weight, this resulted in an engine power of precisely 352 hp.
Digital technology as the basis for new safety systems
At the onset of the 1980s the new age of digital technology opened up new possibilities in the area of control electronics. In keeping with the company's traditions, Mercedes-Benz exploited the new opportunities to pioneer a revolution in safety technology. In 1981 the brand launched the ABS anti-lock brake system for heavy-duty commercial vehicles. Safe braking on road surfaces which differ on the left- and right-hand sides, steerability during emergency braking, no jackknifing during braking – ABS marked the beginning of a new era. Acceleration skid control (ASR) duly followed as the next innovation. Essentially functioning as the reverse of ABS, ASR served as a traction aid and safety system.
The automation of clutch and transmission was already a talking point for the development engineers at Mercedes-Benz at the time of the launch of the NG 80 generation. In the face of increased fuel prices, the main focus here was on the economic benefits offered by such technology. Another key consideration was relieving the strain on the driver.
A technical revolution: curtains up for automated manual transmissions
In 1985 Mercedes-Benz sparked a revolution by fitting its heavy-duty trucks with electropneumatic power shift (EPS) as standard. This was the result of logical thinking by the company – considering that automated manual transmissions assisted the driver and reduced fuel consumption, it was only right to install them as standard. A handy joystick replaced the traditional shift lever, requiring only a gentle tap as the clutch was pressed to change gear – a development which eased the driver's workload considerably. The shift lever was no longer mechanically connected to the transmission, serving solely as a signal transmitter. Gear changes were initiated by actuating the clutch in accordance with the recommendations output by the electronic brain. Alternatively, the driver was able to preselect a gear and engage it by stepping on the clutch.
Meanwhile, the new power variants of the V8 engine, rated at 260 kW (354 hp, 1600 Nm of torque) and 320 kW (435 hp, 1765 of torque) were reaping the plaudits. The leap in performance was vast, with a 1635 now boasting more torque than the 1638. And in the face of the foreseeable limits on pollutants in exhaust emissions, an electronic diesel regulation system (EDR) was introduced for the engines. The maximum injection pressure soared from 175 bar to almost 1000 bar. Mercedes-Benz spoke of an integrated drive concept – a perfectly coordinated combination of engine, transmission and drive axle. One upshot of these developments was a low engine speed of just 1300 rpm at a motorway speed of 80 km/h. The cost factor was more critical than ever, with a litre of diesel having risen to 68 euro cents in Germany. Weight-optimised frames reduced the weight of a two-axle semitrailer tractor to just under seven tonnes – despite the wealth of comfort features which were now incorporated, from effective noise insulation through suspension seats and all manner of electric and electronic aids to temperature control in the cab. The results make fascinating reading: the new Mercedes-Benz 1644 revealed record-breaking credentials at fuel consumption of 33.0 litres per 100 km and an average speed of 67.7 km/h. Interior noise was also low, at just 68 dB(A) at a speed of 80 km/h. The heavy­weight Mercedes-Benz 1635 fell only just short of such figures, at 33.9 l/100 km and an average speed of exactly 66 km/h.
Meanwhile, the permissible weights were also on the rise: truck/trailer and semitrailer/tractor combinations were permitted to weigh up to 40 t in Germany in 1986, accompanied by an increase in the permissible drive axle load from ten to 11.0 t, subsequently rising again to 11.5 t in 1989. Europe retained its patchwork character with regard to weights and measures. The length of truck/trailer combinations was now limited to 18 m in most of Europe, but semitrailer/ tractor combinations varied in length between 15 m (Germany, Greece, Ireland) and 16.5 m (Spain). The permitted weights for truck/trailer and semitrailer/tractor combinations revealed even greater discrepancies, ranging from 28 t in Switzerland and 32.5 t in Great Britain to 44 t in Belgium, Denmark and Italy and 50 t in the Netherlands.
The 1980s: turbos and a new style of driving
As the decade drew to a close, the Mercedes-Benz NG 80 trucks were still going strong. "The Mercedes-Benz semitrailer tractor ... still holds its ground well against the latest new models," a comparative test at the beginning of 1988 concluded. Meanwhile, there was no let-up in development efforts, with the heavy-duty range from Mercedes-Benz which was introduced at the beginning of the 1980s coming in for another thorough revamp. NG (New Generation) now made way for the SK series. The new series was immediately identifiable by the side windows with inclined sill and a brawny, wide radiator grille. The contours of the cab were retained, but under the hood things altered dramatically.
The new series featured thoroughly revamped engines, for example. The V8 (now designated the OM 442 series) now had a displacement of 15.1 litres as a naturally aspirated engine, while the turbo engines retained the previous 14.6 litres. The V8 was now available in the power ratings 260, 290, 354 and 435hp (191, 213, 260 kW). Top of the range was a variant rated at 353 kW (480 hp) offering 2000 Nm of torque – the most powerful truck on Europe's roads. Ignition pressures of 140 bar and higher gearing up to a theoretical top speed of around 140 km/h, equivalent to 1200 rpm at 80 km/h, helped to cut fuel consumption. The rated engine speed dropped from 2300 rpm to 2100 rpm – as compared to 2500 rpm when the 400 series was launched – an indication of totally different engine performance characteristics.
The maintenance intervals increased to 45,000 km in long-haul transport operations – the longest in this segment. The new model designations beginning with '17' ('19' for defined export countries) referred to the increased permissible gross weight. The Mercedes-Benz 1748 takes 40 tonnes in its stride, notching up outstanding test results at an average speed of 72 km/h and fuel consumption of only around 34 l per 100 km. Meanwhile, fuel prices relaxed briefly, dropping to an annual average of 45 euro cents per litre.
The V6 evolves into an engine for long-haul transport
A supercharged V6 with a displacement of just under eleven litres and a power rating of 243 kW (330 hp) romped around between the V8 variants, much in the same manner as the V8s themselves used to do. This was a special variant intended above all for the high-volume combinations with extremely short cabs which were popular at the time. Mercedes-Benz was proud of its super-short cab with elegant top sleeper which continued to offer full fore/aft adjustment of the driver's seat, in contrast to other makes. The short vehicle combinations were short-lived, however, the EU quickly nipping their further development in the bud by prescribing a maximum length for loads, resulting in turn in a minimum length for cabs. The introduction of the new SK series signalled the end of the good old V10, its era finally over after around 20 years.
Increased brake power, lighter transmissions
Mercedes-Benz refined numerous aspects of its heavy-duty trucks. Apart from moving along more briskly, their braking performance was also enhanced by the introduction of the constantly open throttle, an additional valve in the cylinder head. A new generation of transmissions was also launched, produced in-house for the first time and provided with a lightweight aluminium housing. The semi-automatic transmission by the name of EPS came as standard for engines rated at 213 kW (290 hp) or over.
In the cab the dashboard arched towards the driver, back lighting brightened up the instruments, the heating and ventilation controls were inclined towards the driver, conjuring up a genuine cockpit feel in the SK series. A smaller steering wheel, velour covers for cabs of medium size and above, more stowage facilities, a clothes compartment in the large cab – the fixtures and fittings were becoming increasingly comfortable. And seat belts were supplied in height-adjustable design.
The 1990s: SK, Actros – focus on environmental and safety issues
Meanwhile, attention focused on environmental issues. Euro 0 had been in force since 1988. The exhaust emission limits for the next standard, Euro 1, were now defined, becoming mandatory in 1993. Euro 1 stipulated a maximum level for particle emissions for the first time. Trucks were also expected to be quiet now, with a green sticker indicating that they met this requirement. Mercedes-Benz responded to these new standards back in 1991, with the LEV engines (LEV = low emission vehicles). Thanks to innovative internal measures, the heavy-duty engines met the exhaust emission standards stipulated in Euro 1 two years before they entered into force.
The new model designations, 1831, 1834, 1838, 1844 and 1850, indicated not only the new power ratings but also the new permissible gross weights which now applied: 18 tonnes for two-axle vehicles, while the limit for truck/trailer and semitrailer/tractor combinations remained unchanged in Germany at 40 tonnes. This was much more than a simple name change – with the exception of the two most powerful engine variants, Mercedes-Benz returned to the former smaller displacement volumes of 9.1 l (V6, OM 401 series) and 12.8 l (V8, OM 402 series). Apart from the displacement and the combination of 125 mm bore and 130 mm stroke, the engines had nothing in common with their predecessors, however. All the new engines were equipped with a turbocharger and charge air cooling – the grand era of naturally aspirated diesel engines from Mercedes-Benz was now over. The maximum injection pressure topped the 1000 bar mark for the first time, the rated engine speed fell once again by 200 rpm to 1900 rpm. The flagship broke new ground with a power output of 370 kW (503 hp), accompanied by a strapping 2020 Nm of torque.
As for other makes of vehicle too, Euro 1 signalled the end of fantastically low fuel consumption levels for the time being. The top-of-the-range model cruised along at 80 km/h at just 1200 revs, with fuel consumption of 36.4 l/100 km at a speedy 72.3 km/h. By comparison, the new Mercedes-Benz 1831 with a V6 turbo-diesel engine rated at 230 kW (313 hp) ran on 33.5 l per 100 km at an average speed of just under 70 km/h when used as part of a 32 tonne combination.
Electronic fuel injection control: reconciling economy with environmental needs
Stricter exhaust emission standards needed to be reconciled with increased requirements for economic efficiency. In 1994, Mercedes-Benz introduced EDC ("Electronic Diesel Control"), a new electronic fuel injection control system, in anticipation of Euro 2. Diesel fuel was now injected at a maximum pressure of 1250 bar. At the same time, the ongoing increase in power throughout the evolution from NG to NG 80 to SK continued unabated. In 1994 the 400 series attained a new peak with 390 kW (530 hp) of power and 2300 Nm of torque from the V8. The most powerful engine from Mercedes-Benz ran on 36.6 l of fuel per 100 km, sweeping along at 72.8 km/h. A litre of diesel fuel was now back down to an average price of 58 euro cents in Germany. The SK series underwent further refinements. The steering wheel was scaled down to just 450 mm in diameter, while the interior was appointed more attractively. The safety belt was now mandatory for truck drivers, too. Meanwhile, changes were afoot, with rumours of a totally new type of heavy-duty truck in the offing from Mercedes-Benz.
The Actros – a new chapter in the history of commercial vehicles
Ever stricter regulations on exhaust emissions – Euro 3 was impending in 1997 –, growing comfort expectations and the desire for greater safety led to a revolution in truck design in 1996 which went by the name of Mercedes-Benz Actros. The all-new heavy-duty Actros truck from Mercedes-Benz represented a new watershed in truck history, with many of its features setting new bench­marks. The cab, for example, was available as a short, mid-length or long variant, flat or high, with the flat-floored Actros Megaspace version as top of the range. The cab was gently suspended on air bellows. Although the windscreen was less inclined than on previous vehicles in order to free up space inside the cab, the development engineers nevertheless managed to achieve an overall improvement in aerodynamics. The berth was up to 75 centimetres in width, with plenty of stowage space underneath. Controls and buttons extended towards the driver from the right. The cab was impressively spacious, with even the L cab for long-haul use offering 25 percent more volume than the previous extra-large cab. The Megaspace version with flat floor added even more space. The Actros was nevertheless lighter than its predecessor, one contributory factor here being the use of six-cylinder engines in the standard power categories.
500 series: a completely new generation of engines
Six- and eight-cylinder engines in a V-arrangement were once again to be found under the cab. The newly developed 500 engine series was a quite different proposition from its predecessor, however, featuring fuel injection by individual unit pumps, four valves per cylinder and individual fully electronic cylinder control. The six-cylinder engines with a displacement of twelve litres covered four power variants in the range from 230 kW (313 hp) to 315 kW (428 hp). The eight-cylinder engines with a displacement of 15.9 litres generated power outputs in variants ranging from 350 kW (476 hp) to a maximum of 420 kW (571 hp). The engines were characterised by low revs, powerful torque of up to 2700 Nm and variable, wear-dependent service intervals of up to 100,000 km in long-haul use. The maximum injection pressure now stood at 1800 bar. The outstanding economic efficiency of the Actros was highlighted by the fact that the first engine overhaul was only due after covering at least one million kilometres.
The drive train comprised a 16-speed transmission, the familiar planetary axles and the standard Telligent gearshift system – a further development of EPS. The clutch was intended for emergencies only. The Telligent automatic gearshift system was a fully automatic option which operated similarly to a converter transmission without any intervention on the part of the driver.
The revolutionary brakes on the new Actros
The brakes on the new Actros were no less revolutionary. Disc brakes on all axles, EBS Electronic Brake System, increased system pressure – for the first time, the brakes on a truck displayed all the refinements of a car's brake system, with ample braking power into the bargain. The braking distance was reduced dramatically. A wear harmonisation system calculated the loads on the individual wheels with sufficient accuracy to ensure uniform wear on all linings, thus minimising visits to the workshop. Together with electronically controlled disc brakes on the semitrailer, the entire vehicle combination braked harmoniously. As a logical step, Mercedes-Benz immediately began to offer trailer axles with the new brake too, triggering the next revolution in the trailer segment.
While buyers tended to concentrate on the Actros with V6 engine for cost and weight reasons, the V8 was an exciting proposition in its own right. The Actros 1848 with a power output of 350 kW (476 hp) displayed an outstanding fuel consumption level of 33.3 l/100 km under test conditions while cruising along at a sprightly 73 km/h. Apart from its spaciousness, another major advance in the Megaspace cab was its extremely low noise level - 66 dB(A) at 80 km/h was tantamount to a gentle purr. The top-of-the-range model offered quite superlative engine performance, the V8 in the Actros 1857 clocking up just 1125 rpm in top gear at 85 km/h. Mercedes-Benz soon refined the Actros with additional stowage facilities, new surface finishes and fabrics.
While the commercial vehicles segment remained absorbed by the Actros, the development engineers at Mercedes-Benz were already working away in the background on totally new methods of aftertreatment for exhaust gases in anticipation of future emissions limits. Years were to elapse before the results of this work came to fruition in concrete products. New dimensions were now permitted, with truck/trailer combinations extending up to a length of 18.75 m and semitrailer/tractor combinations up to 16.5 m.
The new millennium: trucks on the road to perfection
On the cusp of the new millennium, Mercedes-Benz was the first truck manufacturer to present the ESP electronic stability programme at the Frankfurt International Motor Show in the year 2000. At the same time, the brand also announced the Telligent distance control system (also known as adaptive cruise control) and the SPA lane assistant. ESP prevents the truck from swerving or tipping over within the bounds of physical possibilities by specifically intervening in the engine management and brake systems. With adaptive cruise control the driver is able to set a minimum distance from the vehicle in front within certain limits. The truck then maintains this distance automatically. The lane assistant emits an acoustic warning when the truck passes over carriageway boundaries, before the vehicles leaves the road. All three systems were introduced for the first time in trucks from Mercedes-Benz and raised safety standards substantially.
Safety was not the be-all and end-all, however. In the face of diesel prices at 80 euro cents at German filling stations, economy was also a central concern. The impending switch from Euro 2 to Euro 3 was a further factor here, with numerous specialists warning of marked increases in fuel consumption. Tests showed that the engine development engineers at Mercedes-Benz had managed to reconcile cleaner engines with consumption levels barely higher than those of the previous generation, however. Actros was soon to be complemented by the new Axor. With a six-cylinder in-line engine under its cab, this truck focused on combining a high payload with the lowest possible costs. The Actros remained the truck of choice for long-haul transport, however.
A driver's dream: the second-generation Actros
The Actros's best-in-class position was underscored by a comprehensive facelift in the summer of 2002, presenting drivers with a completely new cockpit featuring harmonious sweeping lines. New instruments, a steering wheel with control panel, high-quality materials offering saloon comfort, an optional "single cab" with reclining seat, a sophisticated air-conditioning system, a bed with point-elastic springs – the Actros was a driver's dream. The engines under the cabins offered a slight increase in power and above all plenty of torque. The 500 series now spanned the range from 235 kW (320 hp) to 335 kW (456 hp) for the V6 and 370 kW (503 hp) to 425 kW (578 hp) for the V8. The technical changes were accompanied by maintenance intervals of up to 120,000 km for a further improvement in economy. The integral rear end of the frame accommodated the air vessel and starter batteries, plus a light two-bellows air suspension system on semitrailer trucks. At the front, a bold radiator grille proudly defined the new generation. The six-cylinder versions were fitted with a new, lightweight and economical hypoid rear axle.
The results were impressive, with the Mercedes-Benz Actros 1841 (300 kW/408 hp) displaying a fuel consumption of just 32.8 l/100 km under test conditions, at an astoundingly high average speed of 73.2 km/h. As such, the second-generation Actros was also a truck to win the hearts of transport companies. The Actros 1854 with V8 engine and 395 kW (537 hp) of power outstripped its "junior" with an average speed of precisely 75 km/h on long hauls, with fuel consumption at a very moderate 35.8 l/100 km.
BlueTec technology: clean and economical in one
Fuel consumption and exhaust emissions were in the spotlight once again in the autumn of 2004. In the face of the impending exhaust emission standards Euro 4 (from autumn 2005) and Euro 5 (autumn 2008), Mercedes-Benz introduced the new BlueTec engine technology featuring an SCR system. An aqueous solution containing synthetic urea (trade name AdBlue) is injected under controlled conditions into the exhaust gas, rendering harmful exhaust gas constituents harmless. The combustion process is also optimised. This system results in increased power and torque combined with reduced particle emissions and a noticeable drop in fuel consumption.
Such sophistication would have been inconceivable for the development engineers of previous decades. Then again, they would have found engine power in the order of 440 kW (598 hp), 2800 Nm of torque, ignition pressures of 180 bar and injection pressures of 1800 bar equally hard to imagine. The same goes for the non-synchromesh Powershift transmission which caused such a sensation when it was introduced by Mercedes-Benz in the summer of 2006. Twelve gears suffice for the high-torque engines, and the automation which features as standard now renders synchromesh superfluous to requirements after decades of service. The driver can leave the Actros to shift gears of its own accord, or intervene as he sees fit by recourse to a host of options at his fingertips. As a result of this technology, the Actros 1844 gets by on just 32.8 l per 100 km and cruises along at a sprightly 74 km/h. The flagship Actros 1860 combines maximum power with a surprising level of economy, consuming 35.4 l of fuel per 100 km at an average speed of 75.6 km/h on demanding routes – a real turn-up for the books. And such performance is a real boon in the face of a diesel price of 112 euro cents per litre.
Active Brake Assist: a unique safety system
The Mercedes-Benz Actros also offers a standard of safety unparalleled by any other truck. As a logical development of adaptive cruise control, the Actros has featured an automatic emergency brake since 2006. Active Brake Assist (ABA), also known as the advanced emergency braking system, initiates emergency braking in the event of an unavoidable collision with a vehicle ahead, after emitting graduated warnings. A digital tachograph became mandatory in 2006 - 53 years after compulsory introduction of the tachograph.
Additional refinements for the Actros as of 2008
Meanwhile, the ongoing development of the Mercedes-Benz Actros continues apace. Since the summer of 2008 it has been raising the standards once again, with more direct steering and further optimisation of the Powershift trans­mission. The stationary air conditioning undergoes a similar revamp, with the air compressor and water pump now operating on demand. This saves fuel – a timely improvement in the face of a diesel price averaging 133 euro cents at the pumps in Germany. The driver is assisted by a rain and light sensor. Newly designed instruments are arrayed before him. A shaving mirror and towel holder add a touch of home comfort. The bed now features a level control facility and a compressed air supply assists in cleaning this functional yet elegant workplace on wheels. The Mercedes star is all its has in common with its predecessors of 50 years ago.
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