Locomotive wheelslip

Spin referred to in the context of wheel-rail systems fachsprachlich the spin of a driven wheel on a rail as a result of driving forces that exceed the maximum static friction force. Whiplash protection devices conforming to prevent this.

The decisive factor for transmission of train and braking forces from the wheel on the rail is the friction between wheel and rail. This is described by the static friction coefficient representing the ratio of maximum train or braking force to the acting normal force. On dry rails of the static friction coefficient is about 0.3 (at sandblasted rails even higher ) in wet rails, in particular in combination with other contaminants, in some cases significantly lower.

A tensile force acts on the wheel circumference, the result is a fundamental referred to as slip relative movement between wheel and rail surface, the amount of which depends on the acting force and speed. Approaching the tension of the maximum frictional force, the slip initially larger ( macro-slip ) until it comes to a decoupling between wheel and rail when the value exceeds the maximum frictional force and the wheel rotates uncontrollably faster than that corresponding to the vehicle speed. This condition is referred to as the skid. Spin leads to increased wear on the rail head and wheel running, in addition may result from Übertourung or sudden catching of the wheelset drive damage.

For the transmission of braking forces is similar; Accordingly, the following motion states between wheel and rail can be distinguished:

• Roles ( Wheel speed ≈ driving speed)
• Spin ( wheel circumferential » driving speed)
• Sliding ( circumferential wheel " driving speed)

Anti-skid

If there is a spin of the wheel sets, it is the first bar countered by a reduction in tension and especially in block-braked vehicles by applying the brake with low pressures of up to 1.0 ( anti-skid brake). This can be captured quickly hurling axes, also the wheel contact surfaces are cleaned and roughened by the lubricating film. Then (or preventive ), in order to increase the friction coefficient to be blown on certain axes sand from a Sandungsvorrichtung under the wheels.

For older vehicles, such as the 110 series, is responsible for the adaptation of the driving power to the Reibwertmaximum and operation of the anti-skid brake the driver. Newer vehicles, for example, the DB series 218 and 111 can detect a spin cycle automatically, then the drive power limit temporarily and sanden if necessary. Any additional functionality provides an adhesion value capture ready, which detects the maximum coefficient of friction and the tensile force regulates expects. The first vehicles with a relatively weak version of such a device was about the series 143 Nowadays it is possible ( such as in the 101 series ), with the pressure recording and radsatzweise variable drives fully exploit the entire static friction potential, sometimes even by utilizing higher coefficients of friction in Super slip region.