Bogie, E1T/5, from the APT-E trailer cars, British Railways, 1972.

The APT-E is a semi-permanently coupled articulated train. Unlike the power cars, which have dedicated leading bogies carrying traction motors, the APT-E’s unpowered trailer cars are suspended at either end by a common bogie. This has the advantage of reducing the number of bogies and wheels as well as reducing the overall weight of the train, while making for a more comfortable ride and potentially increasing seating capacity.

On initial testing in 1972, the Swinging Arm Bogie (SAB) design suffered from ‘hunting’ oscillation and was unstable at high speed. They were replaced with the E1T bogie, a modified, unpowered version of the APT-E’s power bogies that reused the steering beam from the SAB. This beam links the cars together and is part of the bogie steering. This bogie, E1T/5, linked the two trailer cars together when running in a four-car configuration.