Add information for manual, and adjust information message.

Author: peternewell

Source/Documentation/Manual/physics.rst

@@ -1041,14 +1041,15 @@ a factor to reduce the value of M.E.P.
 
 Thus our formula from above becomes::
 
-    TE = Cyl/2 x (0.85 x BP x d2 x s) / D
+    TE = Cyl/2 x (C x BP x d2 x s) / D
 
 Where:
 
 - BP = Boiler Pressure (gauge pressure - psi)
-- 0.85 -- factor to account for losses in the engine, typically values
+- C = factor to account for losses in the engine, typically values
   between 0.7 and 0.85 were used by different manufacturers and railway
-  companies.
+  companies. Default is set @ 0.85. User can change by adding the 
+  ``ORTSTractiveEffortFactor`` parameter to the ENG file.
 
 Factor of Adhesion
 ..................

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

@@ -1256,11 +1256,11 @@ public override void Initialize()
 
             // ******************  Test Locomotive and Gearing type *********************** 
 
-            // if the maximum cutoff for the locomotive is less then the default value, then decrease it so that tractive effort is not excessive. 
-            // At some future stage it may be worthwhile to add an extra parameter to the ENG file to allow user setting.
-            if (CutoffController.MaximumValue < TractiveEffortFactor && Simulator.Settings.VerboseConfigurationMessages)
+            // If the maximum cutoff for the locomotive is less then the default tractive effort constant value, then flag to the user to check. See this reference - 
+            // https://babel.hathitrust.org/cgi/pt?id=wu.89089676290&view=1up&seq=510&skin=2021&q1=booster
+            if (CutoffController.MaximumValue < TractiveEffortFactor && Simulator.Settings.VerboseConfigurationMessages && ( CutoffController.MaximumValue < 0.7 || TractiveEffortFactor >= 0.85))
             {
-                Trace.TraceInformation("Maximum Cutoff {0} is less then the TractiveEffortFactor {1}, is this correct?", CutoffController.MaximumValue, TractiveEffortFactor);
+                Trace.TraceInformation("Maximum Cutoff setting {0} is less then the TractiveEffortFactor {1}, is this correct?", CutoffController.MaximumValue, TractiveEffortFactor);
             }
 
             if (SteamEngineType == SteamEngineTypes.Compound)