The adhesion of electric locomotives

After the results of previous investigations have been considered, the paper describes measurements of adhesion made on electric locomotives on the recently electrified lines between Manchester, Sheffield and Wath. Measurements were made under controlled conditions with the aid of the mobile testing plant on one driving axle of a locomotive, the tractive effort of this axle being separately regulated, and on all driving axles of a locomotive in normal condition, while the adhesion of locomotives working trains in service was observed by the use of dynamometer cars. It is shown that there exists a relationship between adhesion and speed, and between adhesion and water on the head of the rail, while variations in adhesion were found to occur between different parts of the track. A subsidiary investigation revealed that considerable variation occurred in the values of the locomotive axle loads during running. Various methods of temporarily improving adhesion were investigated, such as the use of sand or of certain esters. The conclusions are particularly considered in relation to the working of trains up the Wentworth incline; recommendations are made as to the methods of driving to be employed under difficult conditions; and a modification to the locomotive control to increase adhesive performance is described.