Aim - this section provides an overview of the typical operation of special steam effects on the steam locomotive, and describes how to define these effects in Open Rails (OR) WAG and ENG files.
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Overview of Key Steam Effects on NSWGR Steam locomotives
The ancilliary devices on a steam locomotive, such as the air compressor and water injectors are typically powered by steam from the boiler. Steam for these devices are piped around the locomtive. Thus a steam locomotive can have steam exhausting from it at various locations. Using a NSWGR P Class (C32) locomotive as an example the principal steam powered devices are shown in the diagram below, and their basic operation described.
- Stack - smoke from the combustion of the fuel (coal, wood, etc) was exhauted out of the smoke stack. Steam exhaust from the steam cylinders was exhausted out of the stack as well, which created additional draught for the fire, and sometimes gave the smoke emission a "puffing" appearance.
- Steam cylinder cocks - steam could condense in the steam cylinders to become water. Water in the steam cylinders could severley damage the cylinders when they were in operation, so cocks were placed in the steam cylinders which the locomotive driver could open and blow water condensation out of the steam cylinders. Typically the steam cocks were located at either end of the steam cylinders and were operated jsut prioring to moving the train, or as they train started to move.
- Air compressor - to provide the necessary air supply for the Westinghouse air brake system an air compressor was fitted to the locomotive. Typically the exhaust steam from running the air compressor was exhausted into the smoke box of the locomotive.
- Turbo-generator - On some locomotives electric marker and headlights were installed, and this required a small electric generator to be fitted. This generator was driven by a turbine with the steam exhausting directly to the atmosphere.
- Whistle - steam whistle were mostly fitted to steam locomotives with steam used to operate them being exhausted to the atmosphere.
- Safety valves - were fitted as a safety feature to reduce the boiler pressure if it became excessive. The safety valves were designed to open at slightly higher pressures then the maximum boiler pressure, and by exhausting the steam to the atmosphere excess heat was removed from the boiler, which in turn reduced the boiler pressure.
- Water injector - On most locomotives steam powered water injectors were used to push water from the tender into the boiler of the locomotive. Most of the steam was mixed with the water and ended in the boiler, however a small amount was exhausted out of a drain pipe near the injector. Typically two injectors either side of the locomotive were fitted.
The actual locations of the actual steam effects may vary slightly from locomotive to locomotive.
Steam Effects Code - Structure and layout in Open Rails
Steam exhausts on a steam locomotive can be modelled in OR by defining appropriate steam effects in the SteamSpecialEffects section of the ENG file. Each effect has a name which must be included in the ENG file, and these names are shown in the following section.
OR supports the following special steam effects:
- Stack (named StackFX) - represents the smoke stack emissions. This effect will appear all the time in different forms depending upon the firing and steaming conditions of the locomotive.
- Steam cylinders (named CylindersFX and Cylinders2FX) - two effects are provided which will represent the steam exhausted when the steam cylinder cocks are opened. The effects are provided to represent the steam exhausted at the front and rear of each piston stroke. These effects will appear whenever the cylinder cocks are opened, and there is sufficient steam pressure at the cylinder to cause the steam to exhaust, ie, when the regulator is open (> 0%).
- Air compressor (named CompressorFX) - represents a steam leak from the air compressor. Will only appear when the compressor is operating.
- Turbo-generator (named GeneratorFX) - represents the emission from the turbo-generator of the locomotive. This effect operates continually. If a turbo-generator is not fitted to the locomotive it is recommended that this effect is left out of the effects section which will ensure that it is not displayed in OR.
- Whistle (named WhistleFX) - represents the steam discharge from the whistle.
- Safety valves (named SafetyValvesFX) - represents the discharge of the steam valves if the maximum boiler pressure is exceeded. It will appear whenever the safety valve operates.
- Water injectors (named Injectors1FX and Injectors2FX) - represents the steam discharge from the steam overflow pipe of the injectors. They will appear whenever the respective injectors operate.
NB: If a steam effect is not defined in the SteamSpecialEffects of the ENG file, then it will not be displayed in the simulation.
Note: It is good practice to put notes into the ENG and WAG files to act as reminder for any assumptions made, or define which steam efect is being referenced. These notes can be made with comment statements as shown below:
Comment ( Injector - Left )
Within each individual steam effect the following information is defined:
- Effect name - name defining which effect is defined (see above text for a list of the names).
- Effect location - location on the locomotive (given as an x, y, z offset in metres from the origin of the wagon shape).
- Effect direction - direction of emission (given as a normal x, y and z).
- Effect nozzle width - size of the exhaust nozzle in metres.
Location and Direction - Typically the origin point is in the centre of the locomotive, with the x, y and z axis describing a location referenced to this point. When looking to the front of the locomotive from the cab:
- X axis - to the right (+ve), or left (-ve)
- Y axis - in up (+ve) or down (-ve) direction.
- Z axis - to the front (+ve) or back (-ve) of the origin.
The typical structure of the steam effects section for a ENG files is as follows:
Effect Name (
Effect nozzle width
Note: It is important to ensure that the opening and closing brackets for the steam effects section match up, otherwise errors maybe generated.
Code Segments for Various Steam Effects Examples
The steam effect examples on this page represents use of the steam configuration parameters described above to define different types of steam effects.
This type of code goes into the ENG file.
Typically the lines shown in red text are the only ones that would need to be changed to suit individual locomotives.
To locate an effect, use the "PosTool" positioning tool in Shape Viewer to correctly define the location of the steam effect. Put the values determined by PosTool into the location and direction fields, and start OR to test the effect. PosTool is available from TrainSim.
Steam cylinder cock
This is a example of how the steam cylinder cocks can be set up. Note that there are two different effects representing the two ends of the piston stroke. It is suggested that these are "reversed" on the opposite sides of the locomotive.
Comment ( Cylinder - Left/Rear )
-1.0485 1.0 2.8
-1 0 0
Comment ( Cylinder - Left/Front )
-1.0485 1.0 3.7
-1 0 0
Comment ( Cylinder - Right/Rear )
1.0485 1.0 2.8
1 0 0
Comment ( Cylinder - Right/Front )
1.0485 1.0 3.7
1 0 0
This is a example of how the air compressor(s) can be set up. Note that in this instance there are two compressors on the locomotive, so the same effect can be used twice at different locations to model this effect.
Comment ( Compressor - Back )
-1.15 2.65 -1.75
-1 -1 0
Comment ( Compressor - Front )
-1.15 2.65 -1.15
-1 -1 0
A working excample demonstrating the above concepts has been built using the Atlantic on the stock page. Give the locomotive a run to test the functionality and look at the SpecialSteamEffects section in the ENG file for a view of how to set up these effects.