In Technical History

Both Maybach and Reichsbahn experts were aware that the 175 hp of the G 4 b would not remain the measure of all things for long. And in fact, the customer soon brought a completely different goal to the table of the Friedrichshafen designers – an engine with 300 hp. Even though the Reichsbahn made the statement that they would not need more power at all, the new product was designed directly for 400 HP. Richard Lang, who was in charge of Maybach’s high-speed diesel engine projects from the outset, outlines it in a report as follows: “Contrary to this view, we had envisaged a power output of at least 400 hp from the outset, because we could imagine that the power requirement would continue to rise rapidly and because we also realised that we could achieve 400 hp with almost the same effort as 300 hp.”.

Although this engine, which was to bear the name G 5, could draw on the experience gained from the design and production of the G 4 a and b, there were once again no real role models for this next evolutionary stage. Again there was only little time available for a complex project. The Maybach engineers doubled the number of cylinders, turning the G 5 into a twelve-cylinder engine – a strategy that had already been applied to aircraft engines. The stroke volume of the G 4 a/b was increased from 140/180 mm bore/stroke to 150/200 mm. A centric linkage was also chosen in the hope of avoiding problems with the crankcase, but the engine was now subjected to greater stress. Despite all adversities, the G 5 was put to the test in 1930 – with an impressive 410 hp.

The Reichsbahn ordered three railcars, all equipped with another innovation, the electric power transmission, for which Maybach again cooperated with the E.V.A. The everyday suitability of the new vehicle was first tested from 1931 on the southern runway between Friedrichshafen and Ulm, before the radius was extended: “Our test runs, which for the smaller cars went at most to Biberach, now extended to Ulm, further to Geislingen and finally even to Göppingen. The stretch between Ulm and Geislingen and back was mainly used because of the large gradients (Geislinger Steige and Ulmer Rampe)”, says Richard Lang.

The resonance which the combination of a strong diesel with an electrical power transmission also experienced internationally was shown by the fact that experts of the French northern runway had travelled to these test drives and ended up ordering 29 drive units afterwards. The three railcars of the Reichsbahn were used in the following years as so-called express railcars between Frankfurt and Mainz. They bore the numbers VT 872 to 874.

Meanwhile, the plans for completely different performance levels literally picked up speed: Franz Kruckenberg caused a sensation in 1931 with the “Schienenzeppelin”, but the futuristic streamlined train powered by a propeller never made it beyond the experimental stage. Inspired by the “racing cigar”, the head office of the Reichsbahn near Maybach asked for a high-speed railcar with maximum travel speeds of 150 km/h. According to calculations by Maybach developers, 3,000 hp would be required for such an uptopian speed a few years ago – for a conventionally shaped train. However, research into the aerodynamics of railcars had also been carried out on Lake Constance, and the Zeppelin wind tunnel also provided first-class on-site testing facilities. What the result looked like and why the first test train of the new railway era should bear the name Fliegender Hamburger can be found in the next part of our series on the rail drive revolution.

Richard Lang: Einiges über die Triebwagen-Entwicklung. Maybach Motorenbau Werkszeitschrift: Friedrichshafen, Juli 1940.

Source and also an important reading tip for further reading: Wilhelm Treue, Stefan Zima: High-performance engines. VDI Verlag: Düsseldorf, 1992. The book is available antiquarian. We would like to point out that an extended new edition of the book is planned.

Photo: MTU Friedrichshafen GmbH
Maybach diesel engine type GO 5 (slightly modified successor of the G 5) on the test bench

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