Situación de desarrollo de materiales sintéticos para guarniciones de freno de ferrocarriles

• Autores: H. R. Ehlers
• Localización: Revista A.I.T., ISSN 0378-3294, Nº. 10, 1976 (Ejemplar dedicado a: Simposio sobre Sistemas de Frenado en Ferrocarril), págs. 5-25
• Idioma: español
• Títulos paralelos:
  • Synthetic materials for railway brake liner present development
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• Resumen

  • During the last decades efforts have been concentrated upon improvement of materials for manufacturing of shoe and disc brake liners. Though the grey cast iron shoes have attained a very high resistance to wear, its life at present is overcome, in most cases of application, by those of synthetic material, which have autonomy between 2 and 13 times higher, depending on work conditions. Studies have shown that a series of passenger wagons fully equipped with plastic shoes attained double a working life in the rim than that of the grey cast iron ones. This greater duration is due to the smoothness of the rim external surface, because the roughness is reduced to a fraction of that found in the case of using grey cast iron shoes.

    Lecturer showed the problem of aggression to the rim and its relation with friction coefficient, and the proposed the deceleration manoeuvre to be independent of the type of vehicle to brake, as well as to standardize according with the friction coefficient selected. He also studied the problem of rim thermal conductivity, pointing out that, generally speaking, in using plastic shoes it its advisable to put rims which have a low carbon content material.

    In spite of the advantages of the plastic shoes, it should be borne in mind the power limitations implicit in the shoe brake procedure. For speeds about 140 km/h and permanent brakings, the danger exists with the grey cast iron shoes of creating so high a temperature into the wheels that the rim could break, or the whole wheel could suffer a permanent damage on its surface. For the shoe brakes, the maximum speed limit is fixed at 140 km/h in the case of the heaviest vehicles.

    The close relationship existing between disc brake liners and the high sped traffic development is pointed out. It is shown too, that disc brakes are by no means limited to be used exclusively in high sped vehicles, but they offer a very broad field of application in all those cases in which is interesting to handle limited thermal loads. Using disc brakes jointly with the shoe ones is very interesting. It exists brake liners appropriated to the more different cases of application and it is to be stand out the disponibility of syntherised shoes which withstand permanent temperatures up to 500 ºC and instant ones up to 800 ºC.

    Lecturer ends indicating that continuity of this material development calls for close cooperation between train manufacturers, railway administrations, brake manufacturers and liner manufacturers.