Open Rails Diesel Parameters for Advanced Modellers

Aim - this section describes the "advanced" settings for diesel related parameters in Open Rails (OR) ENG files.

NB: These parameters are intended for advanced modellers who have an understanding of the information required, and have access to appropriate information.

If you wish to provide any feedback on this page, please use the contact page. It would br great to have some feedback as this helps to ensure the accuracy of the information and models.

Index

Advanced Prime Mover Setup

Tractive Force Curves

Curtius - Kniffler Formula

Moment of Inertia


Advanced Prime Mover Setup

An ADVANCED configuration allows the user to configure different incremental changes into the prime movers operation, such as special power settings at certain throttle settings. It also supports the configuration of multiple prime movers for locomotives with more then one prime mover. Where two diesel prime movers are present it is possible to turn one prime mover

The British Rails Class 55 "Deltic" locomotive was an example of a locomotive with two prime movers, and provides a good example of how to set up an ADVANCED prime mover configuration.

The typical code for a diesel prime configuration with X prime movers would look something like the following:


ORTSDieselEngines( X
Diesel (
             Configuration parameter
             Configuration parameter
             ...
             ...
             ...
             Performance table
             Performance table
             ...
             ...
)

Diesel (
             Configuration parameter
             Configuration parameter
             ...
             ...
             ...
             Performance table
             Performance table
             ...
             ...
       )
)

Configuration Parameters

The configuration parameters shown in the following table are required to be used in each diesel prime mover.

ParameterDescriptionRecommended Input UnitsSuggested settingsTypical Examples
IdleRpM ( x )Idling rpm of prime mover.No UoM accepted - value in rpmAs per locomotive specifications.IdleRpM ( 455 )
MaxRpM ( x )Maximum normal operating rpm of prime mover.No UoM accepted - value in rpmAs per locomotive specifications.IdleRpM ( 850 )
StartingRpM ( x )Starting rpm of prime mover.No UoM accepted - value in rpmAs per locomotive specifications.IdleRpM ( 360 )
StartingConfirmRpM ( x )Starting confirmation rpm of prime mover.No UoM accepted - value in rpmAs per locomotive specifications.IdleRpM ( 460 )
ChangeUpRpMpS ( x )Sets the slope of the actual RpM as it moves towards the desired RpM in an upward direction.No UoM accepted - value in rpmAs per locomotive specifications.ChangeUpRpMpS ( 50 )
ChangeDownRpMpS ( x )Sets the slope of the actual RpM as it moves towards the desired RpM in a downward direction.No UoM accepted - value in rpmAs per locomotive specifications.ChangeDownRpMpS ( 40 )
RateOfChangeUpRPMpSS ( x )Determines how fast the actual RpM approaches the desired RpM in the upwards direction.No UoM accepted - value in rpmAs per locomotive specifications.RateOfChangeUpRPMpSS ( 10 )
RateOfChangeDownRPMpSS ( x )Determines how fast the actual RpM approaches the desired RpM in the downpwards direction.No UoM accepted - value in rpmAs per locomotive specifications.RateOfChangeDownRPMpSS ( 10 )
MaximalPower ( x )Maximum output power of prime mover.Power - W, kW, HP Default - WAs per locomotive specifications.MaximalPower ( 1880hp )
IdleExhaust ( x )Number of exhaust particles at IdleRPM.No UoM accepted - value onlyAs per locomotive specifications.IdleExhaust ( 5 )
MaxExhaust ( x )Number of exhaust particles at MaxRPM.No UoM accepted - value onlyAs per locomotive specifications.MaxExhaust ( 50 )
ExhaustDynamics ( x )Exhaust particle multipler at transient.No UoM accepted - value onlyAs per locomotive specifications.ExhaustDynamics ( 10 )
ExhaustDynamicsDown ( x )Multiplier for down transient (Optional)No UoM accepted - value onlyAs per locomotive specifications.ExhaustDynamicsDown ( 0.5 )
ExhaustColor ( x )Exhaust color at steady state.No UoM accepted - value onlyAs per locomotive specifications.ExhaustColor ( 00 fe )
ExhaustTransientColor ( x )Exhaust color at RPM changing.No UoM accepted - value onlyAs per locomotive specifications.ExhaustColor ( 00 fe )
MinOilPressure ( x )Minimum oil pressure.Pressure - psi, kPa, bar, inHg Default - psiAs per locomotive specifications.MinOilPressure ( 40 )
MaxOilPressure ( x )Maximum oil pressure.Pressure - psi, kPa, bar, inHg Default - psiAs per locomotive specifications.MinOilPressure ( 90 )
MaxTemperature ( x )Maximum engine temperature.Temperature Difference - degC, degF Default - degCAs per locomotive specifications.MaxTemperature ( 120 )
Cooling ( x )Engine cooling method.Value - Cooling 0=No cooling, 1=Mechanical, 2= Hysteresis, 3=ProportionalAs per locomotive specifications.Cooling ( 3 )
TempTimeConstant ( x )Rate of temperature changeTime - h, m, s Default - sAs per locomotive specifications.TempTimeConstant ( 720 )
OptTemperature ( x )Normal temperatureTemperature Difference - degC, degF Default - degCAs per locomotive specifications.OptTemperature ( 90 )
IdleTemperature ( x )Idle temperatureTemperature Difference - degC, degF Default - degCAs per locomotive specifications.IdleTemperature ( 70 )
Performance Tables

There are a number of performance tables that also included in the diesel prime mover configuration, and these are described below.

DieselPowerTab

The diesel power table specifies the output power of the diesel prime mover at various revolutions of the prime mover.

DieselPowerTab( x1 y1 x2 y2 .................. xn yn)

Where:
x = prime mover revolutions (No UoM accepted - RpM)
y = Output power (No UoM accepted - W)

DieselConsumptionTab

The diesel consumption table specifies the amount of diesel being used by prime mover at various revolutions of the prime mover.

DieselConsumptionTab( x1 y1 x2 y2 .................. xn yn)

Where:
x = prime mover revolutions (No UoM accepted - RpM)
y = diesel fuel consumption (No UoM accepted - l/hr/rpm)

ThrottleRpMTab

The throttle rpm table specifies the revolutions of the prime mover at various throttle settings.

ThrottleRpMTab( x1 y1 x2 y2 .................. xn yn)

Where:
x = throttle setting (%)
y = prime mover revolutions (No UoM accepted - RpM)

DieselTorqueTab

The diesel torque table specifies the torque of the prime mover at various revolutions.

DieselTorqueTab( x1 y1 x2 y2 .................. xn yn)

Where:
x = prime mover revolutions (No UoM accepted - RpM)
y = torque (No UoM accepted - N)

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Tractive Force Curves

Allows the content modeller to input actual tractive force curves for the locomotive.

Open Rails Use

Open Rails uses a standard default set of values for all diesel and electric locomotives, and the defaults should suit most content modellers.

However, if a modeller wants to customise these values to specific values the following parameter statement should be added to the ENG file.

ORTSMaxTractiveForceCurves( a (x1 y1 x2 y2 .................. xn yn))

Where:
a = throttle setting (as a fraction between 0 and 1)
x = speed (Speed - m/s, mph, kph, km/h, kmph, kmh. Default (with NO UoM included) - m/s)
y = Tractive Force (Force - N, kN, lbf, lb. Default (with NO UoM included) - N)

Any number of value pairs can be used, as long as there are more than two pairs, and the info is always in pairs.

As an example, the current Open Rails default values would look like the following statement, if entered through the ENG file:

ORTSMaxTractiveForceCurves(
0 (     0 0     4.67 0     6.66 0    8.88 0     13.32 0     17.76 0     22.22 0     26.64 0     31.08 0     35.52 0     39.96 0     )

1 (     0 222400    4.67 222400     6.66 168134     8.88 129436     13.32 88515     17.76 65385     22.22 50707     26.64 43145     31.08 37363     35.52 28467     39.96 22240 )
)

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Curtius - Kniffler Formula

Allows the content modeller to input actual curves for the locomotive adhesion.

For a more detailed description of the formulas postulated by Curtius - Kniffler, and the variance of Coefficient of Friction with speed refer to the description of Adhesion. It is also suggested that the user reads this section as well, Tractive Effort

Open Rails Use

Open Rails uses a standard default set of values for all diesel and electric locomotives, and the defaults should suit most content modellers who are working with early generation locomotives, however for modern generation models where the apparent adhesion coefficient is greater then 33% it will be necessary for the Curtius - Kniffler parameter to be set.

To set the Curtius - Kniffler parameter the following parameter statement should be added to the wagon section of the ENG file. Each of the individual parameter values represents a value from the Curtius - Kniffler formula. When adjusting the curve position, and hence the value of adhesion, it is suggested that only the "C" value in the parameter below be increased or decreased to achieve the desired outcome.

ORTSCurtius_Kniffler ( A B C D )

Where:
A = First parameter of Curtius - Kniffler formula.
B = Second parameter of Curtius - Kniffler formula.
C = Third parameter of Curtius - Kniffler formula.
D = Correction parameter for the output of formula (Typically defaults to 1.0).

As an example, the current Open Rails default values would look like the following statement, if entered through the ENG file:

ORTSCurtius_Kniffler ( 6.18 44 0.161 0.7 )

Suggest Method to Set Coefficient of Friction

The following process can be used to calculate and set the adhesive coefficient for modern locomotives. It will require access to published force and weight information for the locomotive.

This paper describes early attempts to improve the adhesion of locomotives. More modern locomotives have computer controlled wheel slip physics which have significantly improved adhesion values. Particular attention is drawn to Fig 4 in this paper which indicates that a locomotive can be either horsepower or adhesion limited. So if a locomotive is calculated as having an adhesion value less then the default, it will not always be a given that the adhesion should be reduced. It merely means that the locomotive may not be able to take advantage of the available adhesion due to a low power output.

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Moment of Inertia

Allows the content modeller to input actual values for the locomotive moment of inertia.

Open Rails Use

Open Rails uses a standard default set of values for all diesel and electric locomotives, and the defaults should suit most content modellers.

However, if a modeller wants to customise these values to specific values the following parameter statement should be added to the ENG file.

ORTSInertia( x )

Where:
x = moment of inertia (kgm^2)

As an example, the current Open Rails default values would look like the following statement, if entered through the ENG file:

ORTSInertia( 7287 )

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