Correct issue with wheel slip on steam locomotives.

Author: peternewell

Source/Orts.Simulation/Simulation/RollingStocks/MSTSSteamLocomotive.cs

@@ -2299,6 +2299,7 @@ public override void Update(float elapsedClockSeconds)
             CylinderCocksPressureAtmPSI = 0;
             CabSteamChestPressurePSI = 0;
             CabSteamBoosterPressurePSI = 0;
+            SteamDrvWheelWeightLbs = 0;
 
             for (int i = 0; i < SteamEngines.Count; i++)
             {
@@ -2549,6 +2550,8 @@ public override void Update(float elapsedClockSeconds)
 
                 UpdateSteamTractiveForce(elapsedClockSeconds, tractiveforcethrottle, 0, 0, i);
 
+                SteamDrvWheelWeightLbs += Kg.ToLb(SteamEngines[i].AttachedAxle.WheelWeightKg / SteamEngines[i].AttachedAxle.NumAxles); // Calculate the weight per axle (used in MSTSLocomotive for friction calculatons)
+
             }
 
             UpdateTractiveForce(elapsedClockSeconds, ThrottlePercent / 100f, AbsSpeedMpS, AbsWheelSpeedMpS);
@@ -6358,10 +6361,8 @@ public override void AdvancedAdhesion(float elapsedClockSeconds)
                     float WheelMomentInertia = (linkedEngine.AttachedAxle.WheelWeightKg * linkedEngine.AttachedAxle.WheelRadiusM * linkedEngine.AttachedAxle.WheelRadiusM) / 2.0f;
                     float AxleMomentInertia = (linkedEngine.AttachedAxle.WheelWeightKg * AxleRadiusM * AxleRadiusM) / 2.0f;
                     float TotalWheelMomentofInertia = WheelMomentInertia + AxleMomentInertia; // Total MoI for generic wheelset
-
-                    SteamDrvWheelWeightLbs = Kg.ToLb(linkedEngine.AttachedAxle.WheelWeightKg / linkedEngine.AttachedAxle.NumAxles); // Calculate the weight per axle (used in MSTSLocomotive for friction calculatons)
-
-                    // The moment of inertia needs to be increased by the number of wheel sets
+                    
+                    // The moment of inertia needs to be increased by the number of wheels in each set
                     TotalWheelMomentofInertia *= linkedEngine.AttachedAxle.NumAxles;
 
                     // the inertia of the coupling rods can also be added
@@ -6379,7 +6380,6 @@ public override void AdvancedAdhesion(float elapsedClockSeconds)
                     axle.DampingNs = axle.AxleWeightN / 200;
                     // Calculate internal resistance - IR = 3.8 * diameter of cylinder^2 * stroke * dia of drivers (all in inches) - This should reduce wheel force
                     axle.FrictionN = N.FromLbf(3.8f * Me.ToIn(linkedEngine.CylindersDiameterM) * Me.ToIn(linkedEngine.CylindersDiameterM) * Me.ToIn(linkedEngine.CylindersStrokeM) / (Me.ToIn(linkedEngine.AttachedAxle.WheelRadiusM * 2.0f)));
-
                 }
 
                 axle.BrakeRetardForceN = BrakeRetardForceN / LocomotiveAxles.Count;

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

@@ -2293,7 +2293,6 @@ private void UpdateDriveWheelWeight(int index,  float masskg, int numberofengine
            var  LocoIdentification = Train.Cars[index] as MSTSSteamLocomotive;
             if (LocoIdentification != null)
             {
-
                 for (int i = 0; i < LocoIdentification.SteamEngines.Count; i++)
                 {
                     LocoIdentification.SteamEngines[i].AttachedAxle.WheelWeightKg = (MassKG / InitialMassKG) * LocoIdentification.SteamEngines[i].AttachedAxle.InitialDrvWheelWeightKg;

Source/Orts.Simulation/Simulation/RollingStocks/SubSystems/PowerTransmissions/Axle.cs

@@ -241,6 +241,19 @@ public void Initialize()
                     if (axle.DampingNs <= 0) axle.DampingNs = locomotive.MassKG / 1000.0f / AxleList.Count;
                     if (axle.FrictionN <= 0) axle.FrictionN = locomotive.MassKG / 1000.0f / AxleList.Count;
                     if (axle.NumberWheelAxles <= 0) axle.NumberWheelAxles = 1;
+
+                    // set the wheel slip threshold times for different types of locomotives
+                    // Because of the irregular force around the wheel for a steam engine during a revolution, "response" time for warnings needs to be lower
+                    if (locomotive.EngineType == TrainCar.EngineTypes.Steam)
+                    {
+                        axle.WheelSlipThresholdTimeS = 0.01f;
+                        axle.WheelSlipWarningThresholdTimeS = 0.005f;
+                    }
+                    else
+                    {
+                        axle.WheelSlipThresholdTimeS = 1;
+                        axle.WheelSlipWarningThresholdTimeS = 1;
+                    }
                 }
                 axle.Initialize();
             }
@@ -598,6 +611,7 @@ public float TransmissionEfficiency
         /// </summary>
         public bool IsWheelSlip { get; private set; }
         float WheelSlipTimeS;
+        public float WheelSlipThresholdTimeS = 1;
 
         /// <summary>
         /// Wheelslip threshold value used to indicate maximal effective slip
@@ -659,6 +673,7 @@ public void ComputeWheelSlipThresholdMpS()
         /// </summary>
         public bool IsWheelSlipWarning { get; private set; }
         float WheelSlipWarningTimeS;
+        public float WheelSlipWarningThresholdTimeS = 1;
 
         /// <summary>
         /// Read only slip speed value in metric meters per second
@@ -1102,7 +1117,7 @@ public virtual void Update(float elapsedSeconds)
             if (Math.Abs(SlipSpeedMpS) > WheelSlipThresholdMpS)
             {
                 // Wait some time before indicating wheelslip to avoid false triggers
-                if (WheelSlipTimeS > 1)
+                if (WheelSlipTimeS > WheelSlipThresholdTimeS)
                 {
                     IsWheelSlip = IsWheelSlipWarning = true;
                 }
@@ -1111,7 +1126,7 @@ public virtual void Update(float elapsedSeconds)
             else if (Math.Abs(SlipSpeedPercent) > SlipWarningTresholdPercent)
             {
                 // Wait some time before indicating wheelslip to avoid false triggers
-                if (WheelSlipWarningTimeS > 1) IsWheelSlipWarning = true;
+                if (WheelSlipWarningTimeS > WheelSlipWarningThresholdTimeS) IsWheelSlipWarning = true;
                 IsWheelSlip = false;
                 WheelSlipWarningTimeS += elapsedSeconds;
             }