Fix bug introduced to dynamic brake blending

Author: peternewell

Source/Orts.Simulation/Simulation/RollingStocks/MSTSLocomotive.cs

@@ -1834,7 +1834,7 @@ public void DynamicBrakeBlending(float elapsedClockSeconds)
                 {
                     if (DynamicBrakeBlendingForceMatch)
                     {
-                        float diff = target * MaxBrakeForceN - DynamicBrakeForceN;
+                        float diff = target * FrictionBrakeBlendingMaxForceN - DynamicBrakeForceN;
                         float threshold = 100;
                         if (diff > threshold && DynamicBrakeIntervention < 1)
                             DynamicBrakeIntervention = Math.Min(DynamicBrakeIntervention + elapsedClockSeconds, 1);

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

@@ -598,6 +598,8 @@ public virtual void LoadFromWagFile(string wagFilePath)
 
             MaxHandbrakeForceN = InitialMaxHandbrakeForceN;
 
+            FrictionBrakeBlendingMaxForceN = InitialMaxBrakeForceN; // set the value of braking when blended with dynamic brakes
+
             if (MaxBrakeShoeForceN != 0 && BrakeShoeType != BrakeShoeTypes.Unknown)
             {
                 MaxBrakeForceN = MaxBrakeShoeForceN;            

Source/Orts.Simulation/Simulation/RollingStocks/SubSystems/Brakes/MSTS/AirSinglePipe.cs

@@ -587,15 +587,15 @@ public override void Update(float elapsedClockSeconds)
                                 }
                             }
                         }
-                        if (loco.DynamicBrakePercent > 0 && Car.MaxBrakeForceN > 0)
+                        if (loco.DynamicBrakePercent > 0 && Car.FrictionBrakeBlendingMaxForceN > 0)
                         {
                             if (loco.DynamicBrakePartialBailOff)
                             {
-                                var requiredBrakeForceN = Math.Min(AutoCylPressurePSI / MaxCylPressurePSI, 1) * Car.MaxBrakeForceN;
-                                var localBrakeForceN = loco.DynamicBrakeForceN + Math.Min(CylPressurePSI / MaxCylPressurePSI, 1) * Car.MaxBrakeForceN;
-                                if (localBrakeForceN > requiredBrakeForceN - 0.15f * Car.MaxBrakeForceN)
+                                var requiredBrakeForceN = Math.Min(AutoCylPressurePSI / MaxCylPressurePSI, 1) * Car.FrictionBrakeBlendingMaxForceN;
+                                var localBrakeForceN = loco.DynamicBrakeForceN + Math.Min(CylPressurePSI / MaxCylPressurePSI, 1) * Car.FrictionBrakeBlendingMaxForceN;
+                                if (localBrakeForceN > requiredBrakeForceN - 0.15f * Car.FrictionBrakeBlendingMaxForceN)
                                 {
-                                    demandedPressurePSI = Math.Min(Math.Max((requiredBrakeForceN - loco.DynamicBrakeForceN)/Car.MaxBrakeForceN*MaxCylPressurePSI, 0), MaxCylPressurePSI);
+                                    demandedPressurePSI = Math.Min(Math.Max((requiredBrakeForceN - loco.DynamicBrakeForceN)/Car.FrictionBrakeBlendingMaxForceN * MaxCylPressurePSI, 0), MaxCylPressurePSI);
                                     if (demandedPressurePSI > CylPressurePSI && demandedPressurePSI < CylPressurePSI + 4) // Allow some margin for unnecessary air brake application
                                     {
                                         demandedPressurePSI = CylPressurePSI;

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

@@ -578,9 +578,10 @@ public Direction Direction
 
         public float TunnelForceN;  // Resistive force due to tunnel, in Newtons
         public float FrictionForceN; // in Newtons ( kg.m/s^2 ) unsigned, includes effects of curvature
-        public float BrakeForceN;    // brake force applied to slow train (Newtons) - will be impacted by wheel/rail friction
+        public float BrakeForceN;    // current braking force applied to slow train (Newtons) - will be impacted by wheel/rail friction
         public float BrakeRetardForceN;    // brake force applied to wheel by brakeshoe (Newtons) independent of friction wheel/rail friction
         public float BrakeShoeForceN;
+        public float FrictionBrakeBlendingMaxForceN; // This is the maximum force for the friction barke when it is blended with the dynamic brake
 
         // Sum of all the forces acting on a Traincar in the direction of driving.
         // MotiveForceN and GravityForceN act to accelerate the train. The others act to brake the train.