Multiple traction - type of train traction using two ( double traction ), three ( triple traction ) or more locomotives located in the head (front of the train), with each locomotive being served by a separate locomotive crew . The most common double (double) traction when using two locomotives. The multi-unit system (CME), in which several locomotives with integrated control circuits, is served by only one locomotive brigade, is a kind of multiple traction.
Most often, multiple traction is found when using steam locomotives , less often on diesel locomotives (especially early ones) and electric locomotives (for example VL61 ), since the latter mainly involve CME control. Sometimes there is multiple traction, in which locomotives, according to the strength of automatic couplings, are distributed along the length of the train, however, it is worth distinguishing a train with this type of traction from a combined one made up of several ordinary trains. It is also worth distinguishing multiple traction from the use of a locomotive pusher and from sending locomotives in a “hot” / “cold” state in the head of the train.
This type of traction is mainly used if it is necessary to increase the mass or technical speed of the train. Often such increased traction has to be used in steep mountain passes. For example, on the main highway Lviv - Stryi - Beskydy pass - Batevo - Chop through the Carpathians , a 23-km pass section Lavochnoe - Beskydy tunnel - Volovets with a slope of 29 thousandths is allocated - this is the section with the steepest slope on the trunk lines of the former USSR. Here, freight trains ascend to the Beskydy tunnel, and then go downhill under multiple traction of 2-3 locomotives and, in addition, are pushed by a pusher locomotive . The section uses 2-section locomotives VL11M .
This type of traction is sometimes used in post-Soviet subways by motor vehicles. The specific power of motor vehicles is small, but it is enough for most work. Nevertheless, sometimes it becomes necessary to transport heavy goods (usually tanks for washing tunnels or with pumped water), for which they use two motor vehicles each with their own drivers, since upgrading them to a system of many units is not economically feasible. Unlike railways, where, as a rule, radio communications are used to synchronize the work of locomotive crews, in the subway they use just a signal system with beeps.
Content
Multiple Traction Examples
- To increase the weight of trains by increasing the total traction force of locomotives.
- The opposite situation also happens - the number of locomotives is increased to increase the braking effect when driving trains on long descents.
- To increase driving speeds by increasingpower density .
- With low reliability of locomotives, so that in case of breakdown of one of the locomotives, the second could bring the train to the nearest main station. This practice is used, for example, in holiday retro trains with old steam locomotives, when due to their low reliability a diesel locomotive is included in the tail of the train (more often, a shunting one).
- In the case of transportation of hazardous (e.g. nuclear waste) goods, when the probability of a train stopping due to a locomotive breakdown should be excluded.
Drawbacks of Multiple Traction
The use of multiple traction requires an increase in the number of locomotive brigades, as well as locomotives. Also, if several locomotives are used, a frequently occurring difference in their traction forces is inevitable, which, in combination with an increase in the speed of movement, can lead to an accident . The most striking example of such a case is the collapse of the imperial train in the Russian Empire .
4 sections of a diesel locomotive at the head of a train
See also
- Tender (wagon)
- Pusher locomotive
Links
- A freight train overcomes the pass with double traction and a pusher in the tail ( Soktuy - Kharanor stage , Chita II - Karymskaya - Tarskaya - Borzya - Zabaikalsk section (→ KVZhD ), Chita region of ZabZhD ; Nerchinsky ridge )