[hroch]

Hello,

When changes precipitation intensity using key Alt - = and adhesion proportional to rain/snow/fog is selected OR calculates BaseFrictionCoefficientFactor vice versa.

my option:

In start OR precipitation intensity is 0.01 and AdhesionFactor=Conditions is 53%:

precipitation intensity is 0.02=max rain and AdhesionFactor=Conditions is 61%:

precipitation intensity is 0=no rain and AdhesionFactor=Conditions is 45%:


Please repair, when the OR start the AdhesionFactor=Conditions was 61%. When the precipitation intensity is zero, the AdhesionFactor=Conditions should be 100%.

Thanks.

[Coolhand101]

I can also confirm this problem.

To restore adhesion back to 100% with no rain, can only be done by the Alt+P weather mode keys for rain off!

Thanks

[Hamza97]

I too agree with above two folks... Increasing precipitation leads to INCREASE of adhesion rather than other way around. Same for decreasing precipitation... :wtf01:

[Csantucci]

I've checked the code. Apparently this is wanted, because there is a comment in the code which says: "note lowest friction will be with lightest precipitation value". So it would be nice if the author of this part of code explained this.

[Coolhand101]

Csantucci, on 10 April 2018 - 10:40 AM, said:

I've checked the code. Apparently this is wanted, because there is a comment in the code which says: "note lowest friction will be with lightest precipitation value". So it would be nice if the author of this part of code explained this.

Thinking about it, that is correct. In the real world, light drizzle/rain is worse than heavy rain.

Thanks

[Csantucci]

Coolhand101, on 10 April 2018 - 12:25 PM, said:

Thinking about it, that is correct. In the real world, light drizzle/rain is worse than heavy rain.

Thanks

That was my suspect too

[hroch]

Sorry for my bad explanation. It is very difficult for me to translate from the Czech language into the English language.

This I meant:

1. ( red in the picture )

• This phase does not work correctly in the OR.

2. ( green in the picture )

• This phase work correctly in the OR.

[Csantucci]

OK, that's clear now. The modification is easy to do, however what should be the precipitation intensity that provides the minimum of adhesion? Should it very near to zero (when very few rain drops fall adhesion almost immediately drops to the minimum value), or should it be 0.01?

[steamer_ctn]

The original adhesion model was implemented by a developer who is no longer actively involved. My suspicion is that is was not completely finished, as it appeared to suffer from some instability under some conditions.

I did some work to try and make it more stable, however found it to be quite complex and I was never able to fully understanding some of the logic and formula around how it was developed. Whilst I improved the stability somewhat, I was never able to completely eliminate it (though it appears to be reasonably stable under most circumstances).

In doing this work, and developing the steam adhesion model, I did extensive research on trying to understand the relevant values of adhesion coefficient for different scenarios.

As has been suggested this research indicated that greater slip would occur during light rain as opposed to heavy rain. Some other factors to be considered are fog, as, at its heaviest, it could also be considered equivalent to a light rain scenario. I was never completely comfortable with the intent of the rain and fog variation algorithims, so they were predominantly left "as is".

Typically the Curtiss-Kniffler formula for clear conditions is used as a base for the adhesion coefficient. Typically this value is around 0.33. By comparison Dew or fog = can be somewhere between 0.09 and 0.15.

I am struggling to remember what the Conditions figure in the HUD actually tells us. The true adhesion coefficient value is shown below this figure as the "Loco Adhesion" value. So for example if the Adhesion factor correction is set at 100%, dry conditions should be 33% (0.33). Similarly for rain it is 18%, and snow 13%.

These values are higher then some of the values that I came across in my research, but there never seemed to be a definitive value, and to a certain extent that makes sense as it would vary depending upon a number of factors.

From time to time some people have expressed concern about the amount of slip that they experience in snow conditions with a heavy load.

Thus I am not sure whether the conditions value if the best one to be using as the reference point for any changes to the code.

[hroch]

Csantucci, on 11 April 2018 - 01:03 AM, said:

My opinion is that the lowest value for the adhesion coefficient should be at 0.01 precipitation intensity, because the OR is triggered at this value of intensity precipitation. It should be the same as when it is not checked adhesion proportional to rain/snow/fog.

steamer_ctn, on 11 April 2018 - 08:51 PM, said:

Typically the Curtiss-Kniffler formula for clear conditions is used as a base for the adhesion coefficient. Typically this value is around 0.33. By comparison Dew or fog = can be somewhere between 0.09 and 0.15.

Curtiss-Kniffler formula is just a theory. The same story as realistic train resistance and train resistance calculated by the Fcalc.
For example the Czech diesel locomotive:

Max adhesion force 188kN. The weight of the locomotive 77.8t. Adhesion factor=F/(m.9.81) 188/(77.8*9.81)=0.246 in zero speed. If I set this value in OR using the ORTSAdhesion parameter ( Adhesion factor correction is set at 100% ), when it's snowing the adhesion value is is already small.

steamer_ctn, on 11 April 2018 - 08:51 PM, said:

From time to time some people have expressed concern about the amount of slip that they experience in snow conditions with a heavy load.

The best solution would be to introduce new parameters to the eng file ORTSWeatherCoefficientForRain and ORTSWeatherCoefficientForSnow. The range of values akccepted from the eng file would be 0.4 to 0.8. Default value for rain 0.607 and for snow 0.4. Is it complicated to program when the item is selected adhesion proportional to rain/snow/fog? When the OR is started to set coefficient of rain from the eng file. On heavy rain ( precipitation intensity=0.02 ) add 8% when is no rain 100%. Sorry for my bad English.