The Comet had 4 GM 6/110 series engines as the main propulsion units driving through Alison lock up torque converters bolted onto the engines, the engines were coupled up to a gearbox in groups of 2, each final drive was driven by 2 engines and forward and reverse was selected in the final drive as there was no clutches the engines had to be shutdown to change direction of travel. There were also 2GM 4/71 series engines that drove 120v DC generators these ran at 1500 rpm and they supplied power for the lighting, AC, Buffet, air compressors gearbox oil pumps and fuel lift pumps.
There were 4 braking systems on the train, a straight air brake (as used on trucks), a electric pneumatic straight air brake which caused the brakes to apply and release at the same time throughout the entire train, operated on 24volts. A Westinghouse automatic brake which was used in emergency, the deadman worked on this system and the mechanical handbrakes 2 on the power vans and one on each carriage.
up until the 60's there was no Westinghouse brake, if you were to run out of air only brake was the handbrakes. Was told it happened a few times.