Maximum tractive effort

The maximum tractive effort is the highest force that a vehicle can exert. The term tractive effort is usually used in connection with trains and rail locomotives. Like all forces, tractive effort is measured in newtons.

For a locomotive to accelerate from a stationary position, it must apply a force to overcome the static friction of the train, and to accelerate it against its inertia. To do this, a particularly high tractive effort is required, usually the maximum tractive effort of the engine is applied. This means that the engine works to produce the highest possible force that it can exert onto the wheels to cause movement or motion.

Few engines can maintain work at the maximum tractive effort for very long, but neither is it usually necessary for an engine to do this.

Once the train is running at a constant velocity the train no longer needs to overcome its inertia to remain at the same velocity, and hence must only provide power to compensate for frictional forces; the tractive effort can hence be reduced to at or below the continuous tractive effort.

A table to illustrate the speed the maximum tractive effort, continuous tractive effort and the speed at which the tractive effort should be reduced on a selection of trains operating in the United Kingdom:

The power at rail of a train follows the equation "power "(kW)" = force "(kN)" x speed "(m/s)

In general, it is more common for heavy freight trains (such as Class 59, Class 60 and Class 66 locomotives) to have a high maximum tractive effort due to the mass which they haul. Light freight trains (such as Class 56, Class 58 and Class 67 locomotives) and passenger trains (such as Class 33 and Class 43 / Intercity High Speed Train locomotives) usually have much lower maximum tractive efforts.

ee also

*Bollard pull
*continuous tractive effort
*power at rail
*power classification
*tractive effort

External links

* [http://www.twoof.freeserve.co.uk/motion1.htm A simple guide to train physics]
* [http://www.brightlemon.com/ma/what_use/TractiveEffortAccelerationAndBraking.doc Tractive effort, acceleration and braking]