[steamer_ctn]

#3507 has now been committed which is the first attempt to implement an "advanced adhesion" model for steam locomotives. As indicated earlier in the thread, steam locomotives do not have consistent force applied to their wheels during a full revolution, and therefore do not follow the diesel and electric locomotive adhesion models.

This patch attempts to take these differences into account.

However geared steam locomotives, which do not have "cranked" wheels, and therefore tend to behave like diesels are not impacted by this patch.

To see the impact of the patch, try running a steam locomotive in clear, raining and snowing conditions. It will behave differently under these three scenarios as the coefficient of friction between the rail, and locomotive wheels will be different in each of these three cases. In snowing conditions it may be necessary to reduce the load hauled by the locomotive.

To use this functionality, the "Advanced adhesion model" needs to be selected.

[copperpen]

Although steam driving wheels do now slip, the Force information page now shows NaN% for wheelslip when using steam locomotives. This means that there is no HUD info indicating wheelslip is happening.

[steamer_ctn]

 copperpen, on 09 April 2016 - 03:47 AM, said:

Although steam driving wheels do now slip, the Force information page now shows NaN% for wheelslip when using steam locomotives.

Thanks for the feedback.

I have added a small modification (#3508) to correct this error in the Forces Information HUD.

 copperpen, on 09 April 2016 - 03:47 AM, said:

This means that there is no HUD info indicating wheelslip is happening.

There should have already been red text ("Wheel slip") appearing in the main HUD whenever the locomotive was experiencing a wheel slip scenario.

[copperpen]

Still NaN% in the Forces HUD, red wheelslip message shows. In one locomotive I tried there was not even any wheelslip info in the forces HUD, just a line that stated advanced adhesion was in use. That was using an unmodified MSTS eng file.

[steamer_ctn]

 copperpen, on 10 April 2016 - 02:49 AM, said:

Still NaN% in the Forces HUD, red wheelslip message shows. In one locomotive I tried there was not even any wheelslip info in the forces HUD, just a line that stated advanced adhesion was in use. That was using an unmodified MSTS eng file.

Can you give a couple of sample freeware locomotives, with download links, to see the effects that you are experiencng?

[copperpen]

Not entirely sure what is going on here now. I just tried your AU_Hall test locomotives and this time the MSTS file showed NaN% and the OR adv file only showed that the advanced adhesion model was on.

[steamer_ctn]

Thanks for the ongoing feedback.

Hopefully the Force Information HUD display is now working correctly in #3510.

Most of the information shown in the top section of the Forces HUD is relevant only to the Diesel adhesion model (such as Solver, Substeps, Forces, etc), and not the steam adhesion model, so it is not relevant to show it. For the steam adhesion model, only the Friction Conditions, ie the friction coefficient, is shown in the Forces HUD.

Relevant Forces information for wheel slip is shown in the Steam Locomotive HUD.

[copperpen]

OK, so we steam users do not have the full amount of force information available to diesel and electric users on that page. In that case, the force page is reading correctly, but perhaps we should be looking at taking that force information from the steam locomotive information page and putting it into the main Forces page. Now, exactly what parameters is the wheelslip system using because it is a part of the steam locomotive data that should be tunable to some degree because some engines were more prone to slipping than others even in dry conditions.

On a side issue, but one that is having an impact on steam users is a new problem that has surfaced since the introduction of slipping. I was not aware of it until today, but engines that use Variable1 in the sms files no longer have the steam chuff sound, whereas those that use the variable Speed do. Post by hroch in http://www.elvastowe...rs-since-x3504/ refers, and I can confirm this is indeed true.

[steamer_ctn]

 copperpen, on 11 April 2016 - 01:51 AM, said:

OK, so we steam users do not have the full amount of force information available to diesel and electric users on that page. In that case, the force page is reading correctly, but perhaps we should be looking at taking that force information from the steam locomotive information page and putting it into the main Forces page.

I will have a look at that, especially if it eliminates the need for all the info on the steam HUD.

 copperpen, on 11 April 2016 - 01:51 AM, said:

Now, exactly what parameters is the wheelslip system using because it is a part of the steam locomotive data that should be tunable to some degree because some engines were more prone to slipping than others even in dry conditions.

Slip will occur once tangential tread force on the wheel exceeds the static friction force between the rail and the wheel.

The two key parameters which influence slip will therefore be:
i) Friction Coefficient which is dependent upon the track conditions
ii) weight on the drive wheels.

This later one will directly influence the FoA (factor of adhesion). The ideal design FoA was > 4.0.

If a locomotive was more prone to slipping, then it is likely that the weight on the drive wheels was too low.

Some other factors that can influence slip are:
i) worn cylinders - this can cause increased tractive effort
ii) worn wheels - can slip at lower static friction forces.

 copperpen, on 11 April 2016 - 01:51 AM, said:

On a side issue, but one that is having an impact on steam users is a new problem that has surfaced since the introduction of slipping. I was not aware of it until today, but engines that use Variable1 in the sms files no longer have the steam chuff sound, whereas those that use the variable Speed do. Post by hroch in http://www.elvastowe...rs-since-x3504/ refers, and I can confirm this is indeed true.

Hopefully fixed in #3511

[hroch]

Coefficient of friction between wheels and rail is dependent on speed too. Is not static as in OR.
http://5at.co.uk/ind...adhesion-2.html
Player, modeler must have the ability to set coefficient of friction as for diesel and electric locomotives. All the steam locomotives do not have the same coefficient of friction.