Steam locomotive vacuum brake ejector

Registered by Dennis A T on 2015-06-12

There were generally 2 Ejectors on a vacuum braked steam locomotive. There was a "Large" Ejector which was used to rapidly exhaust the brake system when the brake controller was set to Release. Alternatively, the Large Ejector control could be operated directly if there was no Release sector on the brake controller. There was also a "Small" Ejector which could be left running to compensate for leakage while the train was in motion and thus avoid dragging brakes.

See bug 1391449 and the discussion, and also see Releasing the Vacuum Brake at


Blueprint information

James Ross
Dennis A T
Peter Newell
Series goal:
Good progress
Milestone target:
Started by
James Ross on 2016-12-14

Related branches



#3673 - Initial setup work for steam ejector - added control keys (J and Shft-J)
#3676 - add functionality for steam ejector steam consumption
#3686 - code changes to support further changes to vacuum brakes
#3699 - corrected problem introduced in #3686 (uncoupling cars causes crash)
#3999 - corrected problem in extended HUD whereby vacuum_piped cars were showing pressure in psi
#4000 - added missing application rate parameter to vacuum brakes
#4001 - made more vacuum brake parameters visible
#4003 - adjusted vacuum brakes to allow for pressure gradient
#4007 - added train pipe leakage, and initial small ejector operation to vacuum brakes
#4009 - corrected error introduced in #4007
#4010 - adjusted default values for vacuum braking
#4011 - adjust brake defaults
#4016 - removal of redundant code
#4017 - adjust application of Running Controller
#4032 - rework of vacuum based code to reflect more prototypical operation
#4035 - corrected problem with brakes not releasing when coupling to rear of train
#4036 - - corrected timing issue introduced in #4035
#4037 - adjustments to make coupling more robust
#4041 - - further adjustment to vacuum coupling
#4045 - - minor adjustments for HUD display
#4050 - adjust vacuum BP propagation logic
#4054 - further adjustments to BP propagation
#4055 - prepare for user input of ejector steam consumption rates
#4058 - added vacuum pump effects
#4059 - flag inserted to remove engine brake display if no controller defined.
#4062 - added independent engine braking to locomotives
#4063 - correct some issues introduced in #4062
#4064 - BC operation timings reversed
#4070 - adjustments to ejector performance curves
#4071 - enabled extra brake token, and adjusted operation of small and large ejector
#4072 - corrected uncoupling problem introduced
#4073 - adjust small ejector operation curve
#4077 - fix issue with diesel locomotive brakes not releasing
#4078 - Adjusted diesel brakes
#4080 - corrected problem with notch brake controller not going to EMERGENCY position
#4081 - adjustments to make coupling more robust
#4087 - equalising reservoir functionality allowed for in vacuum braking
#4089 - adjusted BP propagation code so that forward and rearwards propagation is time consistent.
#4091 - removed debug line, and changed controller type ( )
#4092 - corrected UoM issue, added rough check on input data
#4093 - remove debug message
#4099 - adjusted defaults values, and corrected issue with BP propagation for piped wagons
#4102 - added vacuum braking information to manual
#4117 - minor adjustments to locomotive vacuum brake.
#4118 - update to manual
#4119 - adjustments to Vac Res on vacuum brakes


Work Items

Dependency tree

* Blueprints in grey have been implemented.

This blueprint contains Public information 
Everyone can see this information.