Variable Mass()
#1
Posted 01 March 2016 - 04:37 PM
The question came to mind when I was reviewing some locomotive specifications and saw an 8t difference between unfueled and fully fueled... and the .eng file specification was in the middle.
Varying weight will have an effect upon both braking and friction; The locomotive I was reviewing was almost always used in sets of 4 units, often 5 or 6 and so the combined extent of potential variation could be as much as 48t. I would expect that number would be greater on modern locomotives as they are so much heavier. The difference between empty and fully loaded open tops cars is often 4-5X the weight of an empty car.
#2
Posted 02 March 2016 - 12:35 AM
Genma Saotome, on 01 March 2016 - 04:37 PM, said:
The question came to mind when I was reviewing some locomotive specifications and saw an 8t difference between unfueled and fully fueled... and the .eng file specification was in the middle.
Varying weight will have an effect upon both braking and friction; The locomotive I was reviewing was almost always used in sets of 4 units, often 5 or 6 and so the combined extent of potential variation could be as much as 48t. I would expect that number would be greater on modern locomotives as they are so much heavier. The difference between empty and fully loaded open tops cars is often 4-5X the weight of an empty car.
At least for the cars provided with the OR-specific freight animations (continuous type) the mass is variable and depends on the amount of freight load.
#3
Posted 02 March 2016 - 12:50 AM
#4
Posted 02 March 2016 - 05:14 AM
Real world experience w/US railroading: And an engine with a large (3000 US gal.) tank that's full will hold the rail better than one tha's near empty.
#5
Posted 02 March 2016 - 06:22 AM
#6
Posted 02 March 2016 - 07:39 AM
Freight cars are rather interesting in this regard too. European railways had freight cars as early as the 1920's with manually-set brake proportion levers (Empty/Load Lever) under the car, usually with 2 or 3 positions that were to be set depending on the car's load, to ensure that loaded cars could be run with reasonable braking performance without risking skidding on the empty cars. In modern cars, these manual valves are often replaced with automatic proportioning valves, which offer continuous adjustment of braking power. Similar valves are also found in modern North American cars, especially cars with fairly large differences between empty and loaded weight, such as coal gondolas.
#7
Posted 02 March 2016 - 09:17 AM
- Friction()
- MaxBrakeForce()
- DerailRailForce()
- DerailBufferForce()
- actual adhesion
Do they also change as the weight changes?
#8
Posted 02 March 2016 - 12:32 PM
#9
Posted 02 March 2016 - 01:34 PM
Csantucci, on 02 March 2016 - 12:32 PM, said:
Does the freight animations use the main FrictionForceN calculations in the MSTSWagon file?
If so, friction relies on the Davies co-efficients multiplied by the speed of the train. The Davis co-efficients are calculated externally to OR, and they do take into account the mass of the wagon (but only a full or empty wagon scenario). Therefore, for the main friction calculations (and possibly freight animations), variable weight is not considered at this time, but is fixed at the value of the Davies co-efficients in the WAG file.
To adjust the friction values for a wagon with a changing mass, the full suite of Davies formulas would need to be incorporated (and this wouldn't allow for some freelancing by modellers with different Davies co-efficients) into OR, with a means to differentiate between the different wagon types.
Alternatively, perhaps the full and empty Davis co-efficients could be included in the WAG file, and a sliding calculation done between these two limits to adjust the friction with a changing mass.
#10
Posted 02 March 2016 - 01:44 PM