Open Rails Diesel Parameters for Advanced Modellers
Aim - this section describes the "advanced" settings for diesel related parameters in Open Rails (OR)
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
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.
| Parameter | Description | Recommended Input Units | Suggested settings | Typical Examples |
|---|---|---|---|---|
| IdleRpM ( x ) | Idling rpm of prime mover. | No UoM accepted - value in rpm | As per locomotive specifications. | IdleRpM ( 455 ) |
| MaxRpM ( x ) | Maximum normal operating rpm of prime mover. | No UoM accepted - value in rpm | As per locomotive specifications. | IdleRpM ( 850 ) |
| StartingRpM ( x ) | Starting rpm of prime mover. | No UoM accepted - value in rpm | As per locomotive specifications. | IdleRpM ( 360 ) |
| StartingConfirmRpM ( x ) | Starting confirmation rpm of prime mover. | No UoM accepted - value in rpm | As 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 rpm | As 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 rpm | As 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 rpm | As 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 rpm | As per locomotive specifications. | RateOfChangeDownRPMpSS ( 10 ) |
| MaximalPower ( x ) | Maximum output power of prime mover. | Power - W, kW, HP Default - W | As per locomotive specifications. | MaximalPower ( 1880hp ) |
| IdleExhaust ( x ) | Number of exhaust particles at IdleRPM. | No UoM accepted - value only | As per locomotive specifications. | IdleExhaust ( 5 ) |
| MaxExhaust ( x ) | Number of exhaust particles at MaxRPM. | No UoM accepted - value only | As per locomotive specifications. | MaxExhaust ( 50 ) |
| ExhaustDynamics ( x ) | Exhaust particle multipler at transient. | No UoM accepted - value only | As per locomotive specifications. | ExhaustDynamics ( 10 ) |
| ExhaustDynamicsDown ( x ) | Multiplier for down transient (Optional) | No UoM accepted - value only | As per locomotive specifications. | ExhaustDynamicsDown ( 0.5 ) |
| ExhaustColor ( x ) | Exhaust color at steady state. | No UoM accepted - value only | As per locomotive specifications. | ExhaustColor ( 00 fe ) |
| ExhaustTransientColor ( x ) | Exhaust color at RPM changing. | No UoM accepted - value only | As per locomotive specifications. | ExhaustColor ( 00 fe ) |
| MinOilPressure ( x ) | Minimum oil pressure. | Pressure - psi, kPa, bar, inHg Default - psi | As per locomotive specifications. | MinOilPressure ( 40 ) |
| MaxOilPressure ( x ) | Maximum oil pressure. | Pressure - psi, kPa, bar, inHg Default - psi | As per locomotive specifications. | MinOilPressure ( 90 ) |
| MaxTemperature ( x ) | Maximum engine temperature. | Temperature Difference - degC, degF Default - degC | As per locomotive specifications. | MaxTemperature ( 120 ) |
| Cooling ( x ) | Engine cooling method. | Value - Cooling 0=No cooling, 1=Mechanical, 2= Hysteresis, 3=Proportional | As per locomotive specifications. | Cooling ( 3 ) |
| TempTimeConstant ( x ) | Rate of temperature change | Time - h, m, s Default - s | As per locomotive specifications. | TempTimeConstant ( 720 ) |
| OptTemperature ( x ) | Normal temperature | Temperature Difference - degC, degF Default - degC | As per locomotive specifications. | OptTemperature ( 90 ) |
| IdleTemperature ( x ) | Idle temperature | Temperature Difference - degC, degF Default - degC | As 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.
DieselPowerTabThe diesel power table specifies the output power of the diesel prime mover at various revolutions of the prime mover.
Where:
x = prime mover revolutions (No UoM accepted - RpM)
y = Output power (No UoM accepted - W)
The diesel consumption table specifies the amount of diesel being used by prime mover at various revolutions of the prime mover.
Where:
x = prime mover revolutions (No UoM accepted - RpM)
y = diesel fuel consumption (No UoM accepted - l/hr/rpm)
The throttle rpm table specifies the revolutions of the prime mover at various throttle settings.
Where:
x = throttle setting (%)
y = prime mover revolutions (No UoM accepted - RpM)
The diesel torque table specifies the torque of the prime mover at various revolutions.
Where:
x = prime mover revolutions (No UoM accepted - RpM)
y = torque (No UoM accepted - N)
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
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
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
)
)
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
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
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.
- The diesel locomotive has been designed to start with a certain starting tractive force and "apparent" adhesive coefficient. The apparent adhesion coefficient can be calculated by dividing the Maximum (Starting) Tractive Effort by the Weight on the Drive Wheels.
- Determine the speed point where the starting tractive force starts to decline. For example, on this tractice effort graph it will be the point where the blue and brown lines intersect, ie approximately 10mph.
- Using the point above, (ie Adhesion Coefficient @ speed) adjust the "C" value in the Curtius_Kniffler curve until the curve passes through this point. This spreadsheet can be used to perform this operation. The
ORTSCurtius_Kniffler parameter value will be shown in the spreadsheet as the graph is adjusted.
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.
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
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