Sentence:  The leading locomotive of the double-headed 3.5 p.m. Manchester Piccadilly-Plymouth shed the <WSD>contact shoe</WSD> of its pantograph, which bounced back along the roof and hit the pantograph of the second locomotive, which thereupon lost its <WSD>contact shoe</WSD> also. 
Meaning of the word marked with <WSD> tags:  A part of a pantograph on a train or tram which, when raised, maintains contact with an overhead electric wire.