Evaluation of surface modification in a steel track for the rubber tyred Metro

The rubber tyred metro is a very popular transportation system in some countries, like in Mexico City where 12 lines transport around 5.5 million people every day. The rubber tyre rolls over a steel track subjected under different sources of contamination. Firstly, the rubber tyre accumulates contaminants all over the tread tyre, such as: oil, water, tyre debris, wear particles from the braking and electrical systems, garbage from platforms and steel debris among others. Due to these facts, contamination problems and the rainy season, the metro system suffers severe problems of adhesion. Dangerously, the trains present skidding and slipping problems. The operator must approach and leave the station at very low velocity to prevent accidents. This problem causes delays in the system transportation and discomfort. As a remedy, to reduce the low adhesion, technicians from the metro system have machined grooves on the steel track, however the problem has not been considerably reduced. This work aims to improve the coefficient of friction (CoF) machining the steel track surface with different macro textures. Tests were carried out by using a pendulum friction tester in laboratory. The values indicated an increase in the friction because the grooves help to evacuate water on both sides of the steel track. In addition, the wear rate of some pads from the pendulum increased, indicating a potential increase of wear of rubber tyres due to texturing.