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Vacuum Brakes

General Description

All British First Generation DMUs used the Gresham & Craven quick release twin-pipe vacuum brake system, with the exception of the railbuses which had air brakes.

Release of the brakes is entirely independent of the exhauster speed and is obtained through the medium of a 'release reservoir' which is exhausted while the car is running.

General arrangement - showing a power car and driving trailer

Vacuum Brakes
  • A Driver's brake valve
  • B Passenger communication valve with operating lever
  • C Duplex gauge
  • D Feed valve
  • E Release reservoir
  • F Drivers safety device (DSD)
  • G Brake cylinders
  • H Hose and coupling for train pipe
  • J Hose and coupling for exhauster pipe
  • K Non-return valve
  • L Single gauge (guards van)
  • M Van valve
  • N Bend
  • P Hose and clips
  • Q Filter
  • R Automatic Isolating valve
  • S Exhauster
  • T Dummy and carrier (train pipe)
  • V Release valves
  • W Dummy and carrier (exhauster pipe)
  • X Hose and clips for cylinder
  • Y Hose (underframe to bogie)
  • Z Oil separator

Also of note is the direct admission valve beside the brake cylinders, and the Passenger Communication and Guards Emergency Valve. When operated, these valves admit air into the train-pipe, giving a full brake application with no time delay.

Cab plaque

Some types of DMU had this plaque fitted to drivers desk when new.

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