A new method for the assessment of traction enhancers and the generation of organic layers in a twin-disc machine

Low adhesion presents a major concern for many rail operators. Railway vehicles under these circumstances can experience a serious loss of braking capability giving rise to dangerous situations such as platform overruns and signals passed at danger. One cause of adhesion loss is autumn leaf fall, Fulford C.R. (2004) [1] . Leaves are run over by the wheels of a train and a chemical reaction occurs between the leaf and the rail steel, Cann P.M. (2006) [2] . This forms a black layer on the rail which when wet causes very low friction. These leaf layers have also been shown to be isolating and can interfere with railway signalling systems. Traction enhancers (also referred to in this paper as traction gels) have been developed as a new technique in combating the problems caused by leaf contamination. They consist of sand particles suspended in a water based gel and are designed to be delivered to the rail by the trackside or via mobile application systems. The aim of this work was to develop a technique for generating a representative leaf layer on the surface of a twin-disc rail specimen and using this to develop a test methodology for assessing the performance of a traction gel in terms of adhesion recovery, wear and its effect on wheel/rail isolation. A new repeatable method for generating a low traction leaf layer on the rail disc was developed. The traction gel tested was proven to quickly restore adhesion back to close to dry levels. The wear rate of the rail disc with the traction gel was lower than for a dry/uncontaminated contact. Isolation of the leaf layers and traction enhancer were measured using a representation of aTI21 track circuit. This method can be used in the selection and benchmarking of other traction enhancing products before they are trialed in the field.