A headstock of a rail vehicle is a transverse structural member located at the extreme end of the vehicle's underframe. The headstock supports the coupling at that end of the vehicle, and may also support buffers, in which case it may also be known as a buffer beam. The headstocks form part of the underframe of a locomotive or a railroad car. The headstocks of locomotives, railcars and cabcars also support headlamps and the hoses for air brakes, vacuum brakes as well as the cables for train control and head end power.
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Length over headstocks
A commonly used measurement relating to a rail vehicle is its length over headstocks, which is the length of the vehicle excluding its couplings or buffers (if any).
An alternative expression for length over headstocks is length over coupler pulling faces, usually applied to Janney couplers.
Typical values
Goods wagons built according to the Calthrop narrow gauge system were 25 feet (7.62 m) over headstocks.
A typical standard gauge wagon headstock length might be 60 feet (18.29 m), or more.