Universal locomotive
A universal locomotive (from the Latin universus = total, whole) or all-purpose locomotive is a locomotive that can be used in both freight and passenger train services .
For railway companies that are active in both operating segments, universal locomotives are attractive, as in this way the operational requirements can be covered with a few different series, which has a favorable effect on development and maintenance costs. Since universal locomotives can be used for a wide variety of tasks, scheduling is simplified and downtimes are reduced.
Even in the era of steam locomotives , attempts were made to develop universal locomotives . However, this failed mostly because of the fundamental problem that high speeds can only be achieved with steam locomotives with large wheel diameters, but such locomotives do not achieve high tractive effort. The closest thing to this goal in Germany was the class 41 standard steam locomotive designed as a freight locomotive . The last attempt by the Deutsche Reichsbahn in the GDR to create a universal locomotive with the 25.10 series was unsuccessful.
The first locomotives that could be used for freight train operations as well as for fast passenger trains were therefore diesel-hydraulic traction vehicles with shiftable transmissions , such as the vehicles of the V-160 locomotive family : Depending on the gear engaged, either high starting tractive forces or a high top speed (up to 140 km / h).
Electric traction vehicles with AC technology , however, remained a priority for only one mode can be used, such as the DB - Series 110 and 140 . Only in Austria was the concept of the universal locomotive taken up with the commissioning of the 1042 series as early as the 1960s, while in Germany genuine universal locomotives only found their way with the development of three-phase drive technology. The pioneer here was the 120 series . Today, various manufacturers offer corresponding locomotives.
One obstacle to the universal locomotive is the problem of resonance : Every mechanical system has a natural frequency at which it tends to oscillate . Express locomotives were mostly designed supercritically ; in a speed range somewhere below 50 km / h they began to “hop” or “pound”. Even if this was only noticed by the train driver, it meant - if such locomotives were "misused" for slow trains - considerable wear and tear. With slow - and later also with universal locomotives - the challenge for the design is to set the resonance frequency range above or below the usual travel speeds.