For precisely 30 years, counting from the first-ever bus built by Benz & Cie., trucks and buses developed in parallel. Then, in June 1925, they began following different paths. Bus bodies had previously been mounted as a matter of course on conventional truck chassis which featured straight frames. This had meant quite a climb for the passengers. The new “low-floor” bus, produced in Gaggenau from 1925, ushered in a new era with a clearly more comfortable entrance height for passengers.
This, however, required a special chassis, one with a frame offset downward behind the front axle to continue straight on toward the rear end where an upward offset section provided space for the rear axle. This elaborate design resulted in a floor that was merely 670 millimeters above the ground.
Lowered center of gravity with a variety of advantages
A running board additionally subdivided the entrance into steps each a little over 300 millimeters high – this would even be quite acceptable for a present-day regular service bus. And the low frame had a number of other advantages. The resulting lower center of gravity improved the buses’ handling characteristics, for instance. This, in turn, clearly enhanced comfort as well as safety, especially the safety of country buses with heavily laden roof-mounted luggage racks. A contemporary brochure summed up these advantages as follows: “Due to the low position of the body, the vehicle handles more smoothly and rolls less than a bus with the conventional high design.”
What’s more, the buses with low frames and correspondingly lowered bodies were not as long-legged as their predecessors and therefore looked clearly more elegant. This visual departure from trucks served as a highly welcome distinguishing feature in local public transport, still a young branch of industry at the time.
Emancipation also included a dedicated long wheelbase. This, in turn, made it possible to accommodate virtually all passenger seats between the axles where ride is at its most comfortable. It also had the effect that the bodywork was subjected to reduced stresses overall. As a result, a lighter design could be adopted, “with favorable effects on tire wear and fuel consumption,” as the brochure informed customers in 1925.
No shortage of variants
Right from the start, Benz manufactured several different versions of the low-floor bus. The backbones for the bodies were frames with wheelbase lengths of 5,000 and 6,000 millimeters. The vehicles were available in urban and country bus versions as well as with different door configurations. Last but not least, Benz & Cie. manufactured buses for operation with conductors as well as so-called one-man buses.
The 7.3 and 8.4 meter long basic buses with model designations 2 CNa and 2 CNb were powered by existing four-cylinder gasoline engines which developed 40/45 hp and 50/55 hp from displacements of 6.3 and 8.1 liters, respectively – sufficient power for a top speed of around 40 km/h. According to the manufacturer, the smaller engine consumed 18 kilograms and the larger one 26 kilograms of gasoline on 100 kilometers – liters were not yet used as a unit of measurement at the time. The 7.3 meter long bus (with 5,000 millimeter wheelbase) carried up to 24 passengers while the longer version with 6,000 millimeter wheelbase and more powerful engine accommodated up to 32 seats.
It goes without saying, however, that buses had not become completely independent from truck development overnight. Even the new offset frame was based on a truck design. A little earlier, Benz had introduced the offset frame for garbage disposal vehicles to make the trash collectors’ tough job a little easier in that they no longer had to lift the heavy garbage bins as high up as before.