[copperpen]

I have just compared simple adhesion with advanced adhesion using a basic MSTS file such as a normal end user would be using. There is a 16% difference between the two, with simple adhesion having the higher figure for the axle out force.

[Gehe]

That is exactly what I mean: The simple model provides more axle output force.
Simple acceleration tests Show that the figures shown in the HUD do also apply.
The train using the advanced adhesion model accelerates slower.

The difference depends on the force: The larger the tractive force the larger the difference.
I guess it is somehow related to the wheelslip.

The 10 % stated by me appears at a modest force for a 80 ton loco : 50kN
The 16% observed by you will be related to larger forces.

Also in reality the micro slip necessary to have a tractive force costs some power / force but I guess this may be in the range of 0.5-2%.


Gehe

[disc]

So what is this curtius kniffler parameter? What does it mean, where can i get it for a certain locomotive? The manual writes nothing about where these numbers come from.

[copperpen]

This is the most comprehensive description I have found

The maximum transmittable tractive effort is calculated by the
formula
        F = µ·m·g

where m is the total weight on driving axles, and g = 9.81 m/s².

According to Curtius/Kniffler, when rails are dry, µ is 
dependent from the speed in the following way:

        µ = 0.161 + 7.5/(v+44)

where v is the speed in km/h. For starting tractive effort and 
dry rails, you calculate with µ = 0.33 (for v = 0), which can 
sink down to µ = 0.1 in unfortunate conditions (wet rails, 
great humidity). [The formula for steam locomotives is slightly
different.]

But of course F is also limited by the power of the motor, by
the formula

        F = P/v

where P is the power at the wheel. Above a certain speed, this 
is lower than µ·m·g. At low speed, you can't transmit all the 
power that your motor/transmission delivers, otherwise the 
wheels would slip. At high speed, you don't reach this point
because of the limited power.

[disc]

Which tells the same as i found: nothing. Still don't know what are those numbers, and where are they come from. What is 0.161, or 44, 7.5?

[copperpen]

The only thing I am sure about is the 0.161. That is the C/K dry rail co-efficient with the rail vehicle in motion. I still have not found a worked example though.

[eugenR]

disc, on 21 January 2016 - 10:21 AM, said:

Which tells the same as i found: nothing. Still don't know what are those numbers, and where are they come from. What is 0.161, or 44, 7.5?

This is an empiric formula:

F = µ·m·g
µ = 7,5/(44+v) + 0,161 (Enter v in Km/h)

Curtius/Kniffler have made intensive tests with real trains and found, that this Formula with this values cover the best the reality of traction force over the different speeds.

Here they have published here work:
Curtius E, Kniffler A (1950) Neue Erkenntnisse über die Haftung zwischen Triebrad und Schiene.
Elektrische Bahnen Vol. 21, Heft 9: Seiten 201-210

[disc]

If all the numbers should be the same always, then whats the point of these parameters in eng/wag? And what considers the ratio of driven, and non driven wheels?

[disc]

So looking at the code, this adhesion/axle thing is a partially implemented, abandoned project by Matej Pacha, just like the diesel simulation, which is also have the skeletons of missing features.

BTW the power loss is influende mostly by axle inertia. Lower inertia -> lower losses, but too low (unrealistic, below 500 kgm2) inertia makes the simulation unstable, with wildly changing wheelslip.

[Hamza97]

Even if the code is abandoned, I have seen that it works actually, Here on IR, we have a locomotive which had high tendency to slip, which I couldn't get with standard MSTS parameters, but by using the ORTSAdhesion parameter, I was able to get wheel slip match with real world.

Above is only true for rainy weather. The adhesion and related physics is still far from reality in normal conditions, where you can pedal to metal any locomotive from 0 speed and it will not slip.....:p