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Oct 11, 2006
- Ideal to meet the new demand for six hp per ton
- Catching up with competitors in terms of engine output
- Four-valve technology as early as the 1950s
In the mid-1950s, truck production branched out into as many as three different directions. Conventional trucks were as much in demand as ever and produced in large numbers. Increasingly, however, customers insisted on being supplied with cab-over-engine trucks which the company initially produced in cooperation with external bodybuilders but soon began to manufacture in-house. In the German market, however, there was, for the time being, no way around completely new concepts for reduced dimensions and weights.
Like no other truck in its day and age, the cab-over-engine model LP 333, launched in 1958 and known as the “ millipede” on account of its two steered front axles, complied with the new legal regulations (which went down in German history as the Seebohm Laws, named after the Minister of Transport who had initiated them). At the same time, however, the company increasingly had to serve export customers as well in the mid-1950s – customers who needed particularly robust and high-powered trucks, and for whom the top-of-the-range vehicle at the time, the L 315, was simply not powerful enough.
Differing regulations in Europe
While Germany headed towards a maximum permissible gross combination weight that was to be limited to 24 tons (from previously 40 tons), the upper limits applicable in Italy and France were 36 and 35 tons, respectively. In the liberal Netherlands, no limit was specified for the gross combination weight at the time but axle load was restricted to eight tons and the maximum permissible length of a truck to 18 meters.
The L 315 was extremely popular in Germany and headed the sales charts of Daimler-Benz in the heavy-duty segment by a wide margin. Slowly but gradually, however, the OM 315, in production from 1950 with an output of 145 hp developed from a displacement of 8.3 liters, was getting a bit long in the teeth, especially in the light of the expected request for six hp per ton. And the permissible gross weight of 12.25 tons for the conventional truck tended to leave a lot to be desired. After all, German competitors meanwhile had an impressive number of trucks with gross weights up to 16 tons on offer.
Output boosted by just under 40 percent
The answer from Mercedes-Benz was the L 326 –> a conventional truck which at least externally was difficult to distinguish from the familiar L 315. Like the latter, the L 326 boasted a portly radiator grill which tapered like the bow of a ship. It equally featured a driver’s cab which was relatively frugal in terms of its size and appointments – and could not deny its ancestor, the L 6600 truck launched back in 1950.
In terms of its inner values, however, the L 326 represented a quantum leap ahead, catching up with the competitors’ most powerful vehicles and preparing the ground for developments in the post-Seebohm era. For export, the conventional truck’s permissible gross weight was a proud 17,500 kilograms, which was limited to 15,000 kilograms for trucks to be operated in Germany. Compared to the OM 315 in the L 315, engine output in the L 326 was boosted by some 38 percent to 200 hp. The special features of the new OM 326 with a displacement of 10.8 liters included a bore increased from 112 millimeters (as in the OM 315) to 128 millimeters as well as a cylinder head with four instead of two valves.
Mercedes-Benz offered platform truck, dump truck and semitrailer tractor versions of the L 326 and added the LP 326 cab-over-engine version to the range as early as 1957. Externally, the latter differed from its predecessor, the LP 315, in that it had a cab with lateral quarterlights and a shorter front overhang, making a shorter entry step necessary. Under the laws applicable at the time, this transitional cab-over-engine model had the advantage that it could still be operated with a 16-ton or 24-ton trailer until 1960, provided it had been regis-tered before January 1, 1957.
L 326 discontinued as early as 1958 – but not the OM 326In January 1958, however, the LP 326 had to make way for the LP 333 – the “Seebohm truck”. Production of the conventional L 326 was discontinued in the same year. Its successors in the export markets were the L 332 and the extremely robust conventional L 334 designed for permissible gross weights of 18.5 – 19 tons. Both trucks were powered by the OM 326 engine which had a maximum output of 172 hp.
The German market was dominated, for a short while, by trucks which complied with the Seebohm Laws: cab-over-engine and conventional models with a gross weight of twelve tons. In the LP 333, however, the 200-hp OM 326 from the L 326 continued to work with all its vigor – and also went on to power the heavy-duty versions of the new short-nose trucks which were produced at the Gaggenau plant from 1959.
The German stand-alone approach to dimensions and weights only prevailed until 1960. After that, a gross combination weight of 32 tons and a maximum truck-and-trailer length of 16.5 meters (instead of 14 meters as before) were permitted again. Nevertheless, there was nothing to prevent the successful advance of the cab-over-engine design, at least on European roads. But even as late as 1963, when Mercedes-Benz launched the new cab-over-engine trucks from the so-called cubic generation, the tried-and-tested 200-hp OM 326 pre-chamber diesel continued to work under the new sheet-metal skin – an engine which had made its debut back in 1956, in the L 326 conventional truck.