Mercedes Benz

OFFICIAL PRESS RELEASE

Stuttgart, Germany, Jul 10, 2008

* Extremely spacious cab with a high level of comfort

* New direct-injection engines replaced pre-combustion chamber engine

* Maximum engine power gradually increased to 320 hp


Daimler-Benz AG was able to demonstrate its class at the IAA International Motor Show in September 1963 both in terms of its passenger cars and its trucks. While among the sedans there was the first Mercedes-Benz 600 to admire, the commercial vehicle line also made an excellent impression in the heavy class with its new cab-over-engine truck, LP 1620. Even the name of the model revealed that this represented a revolution in attitude. Model designations that were difficult to interpret and revealed little (such as the “LP 333” for example) were on their way out, to be replaced by abbreviations with transparent meanings, the first two digits of which referred to maximum gross vehicle weight and the last two digits to rated power.

Spatial miracle with optimal visibility

And even a fleeting glance at the cubically designed cab revealed that the previous cab-over-engine trucks and this new series were worlds apart. Whereas the former were characterized by a split windshield, a high engine tunnel and a tight squeeze on entering, the new LP 1620 represented a genuine spatial miracle with an engine tunnel that is only 170 millimeters high and with a considerably widened panorama from the driver’s seat. In addition, a substantially increased front overhang created space for the two invitingly wide steps which enabled easy access to the cab.
The context within which the plant is responding to vastly changed general conditions with the new LP 1620 has many facets. From a modern perspective, economic conditions at the time are absolutely ideal: The average unemployment rate throughout Europe is barely 1.5 percent and the average price of a barrel of oil is less than two dollars (from 1950 to 1973).

All-rounder approach emerges

Nevertheless, two situations were beginning to crystallize: Firstly, the capacities of Daimler-Benz in Mannheim (medium-duty trucks) and Gaggenau (heavy class) could no longer meet the forecast higher demand for production. Hence the decision was taken in 1964 to set up centralized production in Wörth, to commit Mannheim to engine supply and Gaggenau, on the other hand, to supply axles and transmissions.
In any case, Daimler-Benz had already decided at that time to target the upper middle class segment and above for passenger cars but to operate as an all-rounder for commercial vehicles. This strategy bore fruit: Growth in commercial vehicles between 1960 and 1970 speaks for itself – production climbed from 64,478 to no less than 196,149 units during that period.

Regulations soon relaxed again

On the other hand, where trucks are concerned politics has always had a role to play – at times tougher than at others, but always rather unpredictable nevertheless. Transport Minister Seebohm gave truck users a memorable shock in the second half of the 1950s whe he introduced radical measures relating to permissible dimensions and weights. He was soon forced to relax his radical plans however, and instead of the planned 12.0 meters, a total length of 16.5 meters has now been permitted in Germany since 1960. Nor could the total weight reduction to 24 metric tons be implemented in the long term, and since July 1, 1960 32 metric tons have remained the maximum.

Future belongs to the cab-over-engine truck

But one thing was clear: In the future there was to be no stopping the cab-over-engine truck as a means of transport, which was superior to conventional models owing to the length limitations. Consequently it was only logical that the sophisticated cubic cab concept, which was capable of adaptation for use with everything from light trucks to heavy trucks, proved a very successfully successor to the ‘island’ solutions of the cab-over-engine truck from the 1950s.

However, a tilting cab could not yet be bestowed upon the new LP 1620. With the cubic cab such a design only arrived in 1969, along with the new V-engines. Nevertheless, the design engineers had at least ensured that for maintenance and repair work the cumbersome removal of the engine hood was no longer necessary, unavoidable on its predecessors. This was made possible by a substantial number of widely varying flaps at cab hip level, which also gave the new vehicle the nickname of “advent calendar”. There were two such openings at the front.

To begin with, it was also possible to fold the entrance forward and then, from 1965 onwards, elegantly upwards. This ensured that many procedures, such as adjustments to the injection pumps or checking V-belt tension, could be conducted from inside without having to open the engine cover in the cab.

Dual-line brakes for increased safety

At the beginning of its career the design engineers provided the LP 1620 with a number of technical refinements such as a hydraulic recirculating ball steering – instead of the previously used hydraulic cam-and-lever steering – and dual-line brakes. These were to be followed by many others within the scope of continuous model improvement. The new braking system pumped fresh compressed air into the system even during the braking procedure and thus at last eliminated the risk of brakes failure on long downhill stretches owing to insufficient pressure. This had always been a possibility with the traditional single-line braking system.

On the fan there was also a modification. Previous fans, which were driven by the V-belt and always guzzled power, were replaced on the LP 1620 by a modern viscous fan from Behr, which was thermostatically controlled and only cut in when required.
Although that helped to save the odd drop of gasoline, it could not conceal the fact that the days were numbered for the use of pre-combustion chamber engines in heavy trucks. Compared to the modern direct injection engines they were gradually becoming a little conspicuous as a result of their drinking habits. That is why on the LP 1620 Daimler-Benz replaced the long-serving 200 hp pre-combustion chamber engine, the OM 326, with the new direct injection engine, the OM 346, only one year after introduction of the vehicle.

Fuel consumption drastically reduced

Practically the only features which this engine had in common with its predecessor were the engine block and the displacement of 10.8 liters. Substantial investments were made in the new 210 hp design, which operated at a higher brake mean effective pressure and therefore required modified intakes, combustion chambers and pistons. However, it was worth the trouble: Fuel consumption dropped by up to one quarter, the way had been paved for a further increase in power and, what is more, the new engine remained almost totally unaffected by teething troubles. In terms of reliability the newcomer almost immediately overshadowed its predecessor, which was forever keeping the warranty system on its toes.

However, the political world alone, with its demand for 6 hp per metric ton, ensured that 210 hp could never be the upper limit. With the gradual switch from the 32-mt truck to the 38-mt truck, the output of the new direct injection engine was forced to increase accordingly. 1967 finally saw the introduction of the 230 hp version, two years later displacement was increased to 11.6 liters and another 10 hp were added.

Model range expanded considerably

In the meantime the LP 1620 from 1963 had been joined by a respectable family of modern heavy cab-over-engine trucks. They ranged from the LP 1418, specially designed for light operations such as furniture removal, to three-axle rigid trucks and semitrailer tractors for virtually any operation imaginable. Those special three-axle semitrailer tractors, equipped with two steered front axles, have remained legendary to this day, and in the form of LP 2020 to LP 2024 from 1967 onward they succeeded the LP 333, which became known as the “millipede”. These vehicles admirably combine optimal driving qualities and minimal tire wear.

Continuously cab refinements

From 1956 onwards the customer also had a choice between the original cab and one 200 millimeters longer, with two fixed bunks, the width of which was 600 millimeters at the top and a comfortable 730 millimeters at the bottom. In addition, on the shorter cab version the original single-part folding bunk had been superseded by a two-part folding bunk, of which only one part needed to be raised when driving. That created additional storage space for all the essential items necessary on board on long hauls. A variety of cab versions – particularly luxurious ones – were supplied by external body contractors such as Doll and Wackenhut.

Unconventional solution for all-wheel drive cab-over-engine trucks

However, one specialty could not be handled by the trucks with the cubic cab: all-wheel drive two-axle and three-axle trucks. Since the arrival of the “new generation” was beginning to make its mark commercially and therefore a second internally-developed cab-over-engine truck in parallel to the well-established semi-forward control models did not seem economically viable, the plant resorted to an unconventional solution. It provided the existing cab-over-engine truck made by Henschel, in which Daimler-Benz had held a 51% majority interest since 1968, with the new V8 and V10 engines as well as the equally new planetary axles, and in this way it still retained a presence in all-wheel drive cab-over-engine trucks.

New V10 for 8 hp per metric ton

The new V-engines were already available on trucks with the cubic cab from 1969 onwards. At the International Motor Show in Frankfurt Daimler-Benz presented new two-axle and three-axle rigids as well as semitrailer tractors that were fitted with this new engine from the newly designed 400 model series. At 320 hp the new V10 satisfied transport minister Leber's demand for 8 hp per metric ton, although at the last minute the regulation was not implemented. With these new V-engines there now came a tilting version of cab. The tilting cab was recognizable by its doors reaching low down to the level of the bumper and its slightly higher roof.

It was small wonder then that the 320 hp V10, with its huge 16-liter displacement, was soon followed by a gentler and lighter-built version in the form of the V8 introduced in 1972 which had a displacement of 12.8 liters and achieved a rated output of 256 hp. In parallel to all this, the 240 hp in-line six-cylinder OM 355 soldiered on boldly and cheerfully accompanied the model series to the end of its days in 1974. Only certain export models as well as the versions with rear-axle air suspension remained a part of the range until 1975. The light LP 1424, successor to the 1418, successfully held its own against the “new generation” introduced in 1973 for a little longer and even managed to reach the year 1976 before the lights finally went for that model as well.









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