Disable derailment coefficient for "dummy" cars

Author: peternewell

Source/Orts.Simulation/Simulation/RollingStocks/MSTSWagon.cs

@@ -491,9 +491,15 @@ public virtual void LoadFromWagFile(string wagFilePath)
             {
                 CarAirHoseHorizontalLengthM = 0.3862f; // 15.2 inches
             }
-            
+
+            // Disable derailment coefficent on "dummy" cars. NB: Ideally this should never be used as "dummy" cars interfer with the overall train physics.
+            if (MSTSWagonNumWheels == 0 && InitWagonNumAxles == 0 )
+            {
+                DerailmentCoefficientEnabled = false;
+            }
+
             // Ensure Drive Axles is set to a default if no OR value added to WAG file
-            if (WagonNumAxles == 0 && WagonType != WagonTypes.Engine)
+            if (InitWagonNumAxles == 0 && WagonType != WagonTypes.Engine)
             {
                 if (MSTSWagonNumWheels != 0 && MSTSWagonNumWheels < 6)
                 {
@@ -509,6 +515,10 @@ public virtual void LoadFromWagFile(string wagFilePath)
                     Trace.TraceInformation("Number of Wagon Axles set to default value of {0}", WagonNumAxles);
                 }
             }
+            else
+            {
+                WagonNumAxles = InitWagonNumAxles;
+            }
 
             // Should always be at least one bogie on rolling stock. If is zero then NaN error occurs.
             if (WagonNumBogies == 0)
@@ -1369,8 +1379,8 @@ public virtual void Parse(string lowercasetoken, STFReader stf)
                     break;
                 case "wagon(inside": HasInsideView = true; ParseWagonInside(stf); break;
                 case "wagon(orts3dcab": Parse3DCab(stf); break;
-                case "wagon(numwheels": MSTSWagonNumWheels= stf.ReadFloatBlock(STFReader.UNITS.None, 4.0f); break;
-                case "wagon(ortsnumberaxles": WagonNumAxles = stf.ReadIntBlock(null); break;
+                case "wagon(numwheels": MSTSWagonNumWheels= stf.ReadFloatBlock(STFReader.UNITS.None, null); break;
+                case "wagon(ortsnumberaxles": InitWagonNumAxles = stf.ReadIntBlock(null); break;
                 case "wagon(ortsnumberbogies": WagonNumBogies = stf.ReadIntBlock(null); break;
                 case "wagon(ortspantographs":
                     Pantographs.Parse(lowercasetoken, stf);
@@ -1455,7 +1465,8 @@ public virtual void Copy(MSTSWagon copy)
             AuxTenderWaterMassKG = copy.AuxTenderWaterMassKG;
             TenderWagonMaxCoalMassKG = copy.TenderWagonMaxCoalMassKG;
             TenderWagonMaxWaterMassKG = copy.TenderWagonMaxWaterMassKG;
-            WagonNumAxles = copy.WagonNumAxles;
+            InitWagonNumAxles = copy.InitWagonNumAxles;
+            DerailmentCoefficientEnabled = copy.DerailmentCoefficientEnabled;
             WagonNumBogies = copy.WagonNumBogies;
             MSTSWagonNumWheels = copy.MSTSWagonNumWheels;
             MassKG = copy.MassKG;

Source/Orts.Simulation/Simulation/RollingStocks/TrainCar.cs

@@ -198,6 +198,7 @@ public static Interpolator SteamHeatBoilerFuelUsageGalukpH()
         public float CarCouplerFaceLengthM;
         public float DerailmentCoefficient;
         public float NadalDerailmentCoefficient;
+        public bool DerailmentCoefficientEnabled = true;
         public float MaximumWheelFlangeAngleRad;
         public float WheelFlangeLengthM;
         public float AngleOfAttackRad;
@@ -630,6 +631,7 @@ public Direction Direction
         protected float RouteSpeedMpS; // Max Route Speed Limit
         protected const float GravitationalAccelerationMpS2 = 9.80665f; // Acceleration due to gravity 9.80665 m/s2
         protected int WagonNumAxles; // Number of axles on a wagon
+        protected int InitWagonNumAxles; // Initial read of number of axles on a wagon
         protected float MSTSWagonNumWheels; // Number of axles on a wagon - used to read MSTS value as default
         protected int LocoNumDrvAxles; // Number of drive axles on locomotive
         protected float MSTSLocoNumDrvWheels; // Number of drive axles on locomotive - used to read MSTS value as default
@@ -1484,7 +1486,7 @@ public void UpdateTrainDerailmentRisk(float elapsedClockSeconds)
             // To calculate vertical force on outer wheel = (WagMass / NumWheels) * gravity + WagMass / NumAxles * ( (Speed^2 / CurveRadius) - (gravity * superelevation angle)) * (height * track width)
             // Equation 5
 
-            if (IsPlayerTrain)
+            if (IsPlayerTrain && DerailmentCoefficientEnabled)
             {
                 if (CouplerForceU > 0 && CouplerSlackM < 0) // If car coupler is in compression, use the buff angle
                 {