Effects of Friction Modifiers within the Wheel/Rail Contact

Dr. Roger Lewis 

Portec Rail Group

As a train approaches a station, the level of friction between the wheels and the track must be high to reduce breaking distances and prevent wheel spin. Failure to ensure this may lead to derailment with potentially disastrous effects. Conversely, during cornering, the friction levels must remain low to prevent excessive wear on the rails.

In order to provide a varied level of friction throughout a train’s journey, traditionally sand was sprayed between the wheel and rail whenever a high friction level was needed. Although successfully varying friction levels, this was shown, perhaps unsurprisingly, to wear out the rails quickly.

The development of Friction Modifiers – substances which are sprayed onto the track in liquid form or applied directly to the wheel – has helped in controlling friction and minimising wear. We are developing laboratory based methods to determine how they work and to define a standard test protocol. This will aid the rail operators in knowing when, how much, and which product to apply.

We are also involved in work on the next generation of Friction Modifiers – where the knowledge we have gathered can be further applied to enhance their already beneficial properties. Our expertise is being used to help keep trains running safely and on time, while minimising the risk of accidents.