[gpz]

disc, on 06 December 2015 - 06:18 AM, said:

But still using emergencyrescapacity as starting point, max brake force isn't considered, while the brake cylinder diameter (so as the volume) depends on the max force, because the pressure is fixed.

The brake force is calculated by

float f = MaxBrakeForceN * Math.Min(CylPressurePSI / MaxCylPressurePSI, 1);

no matter how you set up the initial values.

[disc]

gpz, on 06 December 2015 - 06:29 AM, said:

The brake force is calculated by

float f = MaxBrakeForceN * Math.Min(CylPressurePSI / MaxCylPressurePSI, 1);

no matter how you set up the initial values.

Yes, that's how the brake force is calculated from the percentage of pressure. But, that's not what i wrote about using the eng parameters i can make rolling stock that have 1 cm3 cylinder volume, and yet have 30000 kN maxbrakeforceN which is impossible in reality...
And then the players complain about why the game acts unrealistically, with unrealistic eng/wag parameters :)

[gpz]

disc, on 06 December 2015 - 07:22 AM, said:

And then the players complain about why the game acts unrealistically, with unrealistic eng/wag parameters

If I understand well that this is your primary concern, then I can say that just don't care about it. It might be also by intention. You must only ensure that game acts realistically with realistic parameters.

[Genma Saotome]

gpz, on 06 December 2015 - 04:48 AM, said:

Disc, don't try to guess the brake cylinder volume, it is available from the eng parameters, however it is tricky to get that, since it is indirect.

There is the "emergencyrescapacity" MSTS eng parameter. You have to divide it by the "emergencyresvolumemultiplier" to get the aux.cyl volume. If you further divide it by the "triplevalveratio", you get the brake cylinder volume. These MSTS parameters are all parsed for in AirSinglePipe.cs, the corresponding variables containing them are EmergResVolumeM3, EmergAuxVolumeRatio and AuxCylVolumeRatio, respectively.

So you don't need to implement any new default values for these, just use them. The only thing you might need to consider is adjusting the EmergResVolumeM3 default value, since that is set in eng files only rarely, so most of the eng-s are using the default we set.

Peter, what about older equipment that did not carry two reservoirs of air? Many cars built in North America before the 1930's had only one, often physically joined to the brake cylinder (K Brakes were either KC for combined or KD for divided).

A KC brake.



Such equipment was allowed on cars in interchange service (that would be almost all cars) up to 1952 or 53. IIRC cars built after 1937 were required to be built with AB brakes -- they had an emergency reservoir. For a handful of years before that some new cars were built with AB, others still with K.

Silhouette of the double reservoir used with AB Brakes.


Post WWII many such cars were scrapped, either worn out after many years of service or just too small to be worth changing the brake equipment, but were still common up to ~1950.


As a side note, I own copies of quite a few engineering drawings and many are the general arraignment of brake equipment for specific freight cars. It was very common for the draftsman to be required to document the maximum brake power and for many decades that was 70% of the empty car weight. Some were 65, a few others 60, but none over 70%. As I understand it, a higher value could cause the wheels to lock up and slide. Absent other information, this is calculation is a good data point for the value of MaxBrakePower() in .wags using either K or AB brakes.

[gpz]

The existence of emergency reservoir can be set at listing of available brake equipment types. E.g. for default dash9 it looks like this:

BrakeEquipmentType( "Triple_valve, Auxilary_reservoir, Emergency_brake_reservoir" )

If it is not listed here, it will not be used in simulator. Regardless of this, the reservoir volumes settings are calculated as I wrote above, since Kuju decided to set them up like this, not the other way, starting from brake cylinder. We may change this order once we will have our own eng file format.

(BTW in Europe the cars are not equipped with emergency reservoir at all, as I know.)

[disc]

gpz, on 06 December 2015 - 11:24 AM, said:

The existence of emergency reservoir can be set at listing of available brake equipment types.

So if i understand correctly, Emergency res is always there, and the capacity can be set in eng/wag, but it can be excluded from view and the simulation, if it's not listed in brakeequipment?

[gpz]

Yes, the variable is always parsed, but the reservoir is not effective if not listed as available equipment. But see the code, if you are modifying it, you have to be familiar with it anyways. :)

[disc]

from rev 3361 engine brake should take air from MSR. The next tasks are to make graduated release switched on/off from .eng, add an MU engine brake on/off .eng param, implement a simple blended brake control.

[steamer_ctn]

gpz, on 06 December 2015 - 04:48 AM, said:

There is the "emergencyrescapacity" MSTS eng parameter. You have to divide it by the "emergencyresvolumemultiplier" to get the aux.cyl volume. If you further divide it by the "triplevalveratio", you get the brake cylinder volume. These MSTS parameters are all parsed for in AirSinglePipe.cs, the corresponding variables containing them are EmergResVolumeM3, EmergAuxVolumeRatio and AuxCylVolumeRatio, respectively.

Is it possible to add a new OR parameter for the Auxiliary Reservoir, which would make it cleaner and easier for people configuring WAG files, rather then trying to calculate Emergency Reservoirs, and appropriate multiplication factors?

Having to specify the Emergency Reservoir, especially when it is not used on the vehicle seems to be very misleading to those trying to set up the physics.

This new "ORTSAuxilaryResevoirCapacity" parameter could be used by default whenever it is present in the WAG file, If it is not present in the WAG file, then the current arrangement could be used instead. In this way both OR or default MSTS WG file configurations could be used.

[gpz]

I don't think it is a good move starting duplicating already existing settings in the current data model, the eng file. Eventually the confusion will be unavoidable. Where should we write the clarifying specification? We don't have an official and obvious place for that, actually we don't even have an official eng file specification. It will be just tribal knowledge, thus will be forgotten. It would be better though to think on how our own new engine configuration file will look like.