Update tractive force direction

Author: peternewell

Source/Orts.Simulation/Simulation/RollingStocks/MSTSDieselLocomotive.cs

@@ -760,7 +760,7 @@ protected override void UpdateTractiveForce(float elapsedClockSeconds, float t,
                 DieselEngines.HandleEvent(PowerSupplyEvent.StopEngine);
             }
 
-            ApplyDirectionToTractiveForce(ref TractiveForceN);
+            ApplyDirectionToTractiveForce(ref TractiveForceN, 0);
 
             // Calculate the total tractive force for the locomotive - ie Traction + Dynamic Braking force.
             // Note typically only one of the above will only ever be non-zero at the one time.

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

@@ -2401,7 +2401,7 @@ protected virtual void UpdateTractiveForce(float elapsedClockSeconds, float t, f
                 AverageForceN = w * AverageForceN + (1 - w) * TractiveForceN;
             }
 
-            ApplyDirectionToTractiveForce(ref TractiveForceN);
+            ApplyDirectionToTractiveForce(ref TractiveForceN, 0);
 
             // Calculate the total tractive force for the locomotive - ie Traction + Dynamic Braking force.
             // Note typically only one of the above will only ever be non-zero at the one time.
@@ -2456,7 +2456,7 @@ protected virtual void UpdateAxleDriveForce()
         /// <summary>
         /// This function applies a sign to the motive force as a function of the direction of the train.
         /// </summary>
-        protected virtual void ApplyDirectionToTractiveForce(ref float tractiveForceN)
+        protected virtual void ApplyDirectionToTractiveForce(ref float tractiveForceN, int numberofengine )
         {
             if (Train.IsPlayerDriven)
             {

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

@@ -6059,7 +6059,7 @@ protected override void UpdateTractiveForce(float elapsedClockSeconds, float loc
             // Update tractive effort across all steam engines
             for (int i = 0; i < SteamEngines.Count; i++)
             {
-                ApplyDirectionToTractiveForce(ref SteamEngines[i].TractiveForceN);
+                ApplyDirectionToTractiveForce(ref SteamEngines[i].TractiveForceN, i);
 
                 TractiveForceN += SteamEngines[i].TractiveForceN;
 
@@ -6122,6 +6122,45 @@ protected override void UpdateTractiveForce(float elapsedClockSeconds, float loc
         }
 
 
+        /// <summary>
+        /// This function applies a sign to the motive force as a function of the direction of the train.
+        /// </summary>
+        protected override void ApplyDirectionToTractiveForce(ref float tractiveForceN, int numberofengine)
+        {
+            if (Train.IsPlayerDriven)
+            {
+                // If booster engine tractive force will only ever be in the forward (+ve) direction
+                if (SteamEngines[numberofengine].AuxiliarySteamEngineType == SteamEngine.AuxiliarySteamEngineTypes.Booster)
+                    return;
+
+                switch (Direction)
+                {
+                    case Direction.Forward:
+                        //tractiveForceN *= 1;     //Not necessary
+                        break;
+                    case Direction.Reverse:
+                        tractiveForceN *= -1;
+                        break;
+                    case Direction.N:
+                    default:
+                        tractiveForceN *= 0;
+                        break;
+                }
+            }
+            else // for AI locomotives
+            {
+                switch (Direction)
+                {
+                    case Direction.Reverse:
+                        tractiveForceN *= -1;
+                        break;
+                    default:
+                        break;
+                }
+            }// end AI locomotive            
+        }
+
+
         /// <summary>
         /// Normalise booster engine crank angle so that it is a value between 0 and 360 starting at the real crank angle difference
         /// </summary>