1933: Daimler-Benz presents the new semitrailer tractors
LZ 4000, LZ 6000 and LZ 8000
Jan 11, 2008
  • High level of flexibility in use with particularly high payloads
  • Systematic expansion of the Mercedes-Benz truck model range
  • Successful models designed on the basis of the Lo 2000
The new generation of semitrailer tractors from Daimler-Benz arrived on the scene at just the right time for industry. At the Berlin Motor Show from February 11 until 23, 1993, the company presented models LZ 4000, LZ 6000 and LZ 8000 for the three payload categories of four, six and eight tons. With these lightweight and easily maneuverable payload giants, Daimler-Benz expanded its commercial vehicle range more vigorously than ever before, offering customers an extremely diversified diesel-engined truck selection that was unmatched by any other commercial vehicle manufacturer.
Broader range than ever before
The timing was perfect: the range of diesel-engined Mercedes-Benz trucks had become broader than ever just in time for the economic boom which began in 1933 more or less over night. During the tough years of the preceding economic crisis, customers had quickly come to appreciate this economical type of engine. From the mid-thirties, most of the gasoline-engined trucks built by Daimler-Benz were destined for exports. From 1934, the payload category upwards of 5,000 kilograms was the exclusive domain of the diesel engine.
Cutting a fine figure
In terms of their heritage and engines, the new Mercedes-Benz semitrailer tractors differed substantially from conventional heavy-duty trucks at the time. The classic, iron-clad L 5000 truck of 1934, for instance, with 10.3 liter 120 hp six-cylinder engine had a payload capacity of five tons and a chassis weight of 5,800 kilograms; the LZ 6000 semitrailer tractor, by contrast, boosted a payload as high as 6,000 kilograms and a chassis that weighed in at just 2,700 kilograms.
High-speed diesel engine – the key to success
These improvements were made possible by diesel engines with relatively small swept volumes but high speeds (rated engine speeds exceeding the 2000/min mark for the first time) as well as by a lightweight tractor design. The engines were adopted from the lightweight Lo 2000 truck of 1932 and its heavy-duty offspring. The chassis design, too, was derived from this lightweight truck, the first ever to be fitted with a diesel engine as standard in the world. The engineers had further developed the Lo 2000, Lo 3000 and Lo 3500 into the semitrailer tractor models LZ 4000, LZ 6000 and LZ 8000.
The basic four-cylinder engine with a displacement of 3.8 liters, known from the Lo 2000 and then also used in the LZ 4000, developed 55 hp – it was this engine that achieved the breakthrough for automotive diesel engines in the first place. The somewhat more powerful, larger-bore version of this four-cylinder unit developed 65 hp from a displacement of 4.9 liters; this engine had proved itself in the Lo 3000 and was therefore also used to power the LZ 6000 semitrailer tractor. The six-cylinder version of the world’s first high-speed diesel engine had a displacement of 7.4 liters and an output of 95 hp; it was exclusively used for the top model in the semitrailer tractor range, the LZ 8000 with a payload capacity of eight tons and a gross combination weight of 14 tons.
Like its smaller brethren, it was fitted with an eight-speed gearbox ex factory, and for a good reason: a four-speed unit – customary in the Lo series – would definitely have been inadequate for gross combination weights of eight, eleven and fourteen tons, respectively. The restrictions still applicable to the eight-speed transmission were described in a contemporary brochure as follows: “In general, a semitrailer tractor should only be used on routes which run through predominantly level country. Uphill gradients must not be steeper than seven percent.
Always ready for service – right through to passenger transport
The major advantage of the articulated truck was – and still is – the fact that tractor and load-carrying unit can be disengaged. This made for a particularly favorable ratio of unladen combination weight to payload. In addition, distribution of the load to three axles permitted advances into payload ranges which had hitherto appeared to be out of reach. The time for three-axle units had not yet come, and the gross weight of two-axle trucks had been limited to just under eleven tons by a law which had come into force in 1933.
The articulated truck also had advantages in fiscal terms. In calculating taxes, the authorities only considered that share of the (unladen) semitrailer’s weight that rested on the tractor’s axles. The load carried by the third axle of the unladen combination was simply ignored. On top of this, operating an articulated truck meant that the operator could dispense with the staff that was indispensable for drawbar combinations – advertised at the time as follows: “A special advantage is the fact that the semitrailer tractor can be operated by the driver alone, meaning ONE-MAN OPERATION.
Compared to conventional drawbar combinations, the articulated truck was also much more flexible. Demountable platforms were as yet unheard of at the time, so operators of shuttle transport services or different superstructures had no choice but to use the semitrailer tractor – the only mode of transport permitting the use of different superstructure concepts and simply parking the load-carrying unit for loading or unloading while the tractor continued to be used profitably – even for passenger transport.
“Winged dragon” accommodating 170 passengers
Using tractors alternately for goods and passenger transport was the order of the day. During the boom in the thirties, the population had gained a level of mobility that could no longer be satisfied by the manufacturers of means of mass transport. The gap was filled by huge, articulated high-capacity buses nicknamed “winged dragons”. The largest of this kind was as long as 18.7 meters and carried as many as 170 passengers (seated and standing).
Additional version for a ten-ton payload
In the course of time, the 1933 trio was joined by another version, the result of systematic further development aimed at higher payload capacities. The new LZ 10 000 tractor was designed for a payload of ten tons; the vehicle was displayed by Daimler-Benz at the Berlin Motor Show in 1938; its ten-ton payload was made possible at a gross combination weight of just 17 tons and a chassis weight of the tractor of roughly 3,800 kilograms. This model was powered by the six-cylinder engine – still a slim unit – from the Lo 3500 but meanwhile boosted to 100 hp; its displacement was 7.3 liters, with a ten millimeter longer stroke but five millimeters less bore.
Abrupt end and belated renaissance
The promising concept did not, however, prevail for long. This was due to the fact that the Schell Program, the Nazi government’s plan to standardize vehicle production, ruled out the production of semitrailer tractors. And shortly after the war, semitrailer tractors were even explicitly banned by the allied forces.
This meant that the truck-and-trailer combination dominated the scene in Germany for decades. Since the nineties, however, when a length of 13.6 meters was permitted for semitrailers, the articulated truck has continuously been gaining ground – reducing the previously popular drawbar combinations to insignificance in Germany. The advantages introduced by the LZ series 70 years ago have long since become the standard in international long-distance transport by articulated trucks: great flexibility, ease of semitrailer replacement and particularly favorable payload ratios.
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