[Jean-Paul]

Using X4079 version, but unable to say if the problem existed before for a while, I could notice, by trying starting with a 800 metric tons freight in a 1.05% step, that even with permanent sanding, and with cutoff set... at 0 %, wheelslip occurs when regulator is over 57 %. I don't understand, introduced OR parameters being without relation with steam admission at 0 % cutoff... Adhesion has been adapted "widely" to guarantee a possible start in these conditions (calculated). All train brakes are fully released, and tractive effort reached just before wheelslip is 125.6 kN. I attach .eng file, where you can see that adhesion parameters allow theoritically starting with previous sanding under rainy conditions (adhesion @ 0 is 0.3304*0.61 (rain) = 0.205, which gives 160.9 kN of theoritical max effort (no sanding !) - much more, in fact, that an American-built french 141 R could develop in these conditions... Without sanding.
Overall, how an engine having a closed cutoff (neutral position) could slip ???? :rolleyes:
I don't know... But I think it's really a bug !!!
Cheers !
Jean-Paul  OR_141R511.eng (36.84K)
Number of downloads: 477

[vince]

Jean-Paul,

Sometimes the unexplained wheel slip cause can be seen on the F5 HUD Debug Screen.

regards,
vince

[Jean-Paul]

vince, on 26 February 2018 - 03:34 PM, said:

Jean-Paul,

Sometimes the unexplained wheel slip cause can be seen on the F5 HUD Debug Screen.

regards,
vince

Hi, Vince
In fact, Slip monitor indicates tang© = more than 300 kN @ 58 % regulator. That's probably the reason why, right... But why tang© is not 0, considering that cutoff is closed ??? No effort on rods, then no effort on wheels... Logical, no ?
Must also say that permanent sanding, even before trying to start, seems not to have any effect on these parameters : slip factor remains, without or with, @ 0.20...
Best regards,
Jean-Paul

[vince]

Hi Jean-Paul,

I've noticed that almost all engines indicate slip when throttle is first advanced from idle to a run position.
I have also noticed slip when coasting downhill, no brakes or throttle.

Now that is quite impossible and is the reason that I mentioned the F5 HUD DeBug Screen. When the wheel slip occurs while coasting there was a lot of activity in the Loader Process, clearly tied to the wheel slip.
Conclusion? It's not actual 'wheel slip' but the game engine getting tied up in whatever it's processing.

best regards,
vince

[Jean-Paul]

vince, on 26 February 2018 - 07:04 PM, said:

Hi Jean-Paul,

I've noticed that almost all engines indicate slip when throttle is first advanced from idle to a run position.
I have also noticed slip when coasting downhill, no brakes or throttle.

Now that is quite impossible and is the reason that I mentioned the F5 HUD DeBug Screen. When the wheel slip occurs while coasting there was a lot of activity in the Loader Process, clearly tied to the wheel slip.
Conclusion? It's not actual 'wheel slip' but the game engine getting tied up in whatever it's processing.

best regards,
vince

Hi Vince,
That's certainly right... But how to do with a steam engine under rainy conditions ??? I did a run with only 350 hauled metric tons, and was also unable to start on the same 1.05 % step, whilst when same train runs on flat ground, steam engine could develop efforts widely larger than those resulting from adhesion calculations.!. It really seems to be a mess ! Of course, everything is OK when "advanced adhesion" button is desactived, but in this cas, adhesion remains the same, by dry, rainy or snowy weather... Why, also, cylinder cocks when open doesn't modify tractive effort ?
Is anybody able to explain how are estimated adhesion factors and attached parameters specifcally on steam engines ?
And are there not some bugs in the calculation process ? That's the question, I think !
Must add that I have no problem with my computer system : fps remain excellent, and load of processor widely under 100 % , even when wheelslip occurs (HUD F5 datas)...
Best regards,
Jean-Paul

[vince]

Jean-Paul, on 27 February 2018 - 09:52 AM, said:

Hi Vince,
That's certainly right... But how to do with a steam engine under rainy conditions ??? I did a run with only 350 hauled metric tons, and was also unable to start on the same 1.05 % step, whilst when same train runs on flat ground, steam engine could develop efforts widely larger than those resulting from adhesion calculations.!. It really seems to be a mess ! ...........snip..............................
Best regards,Jean-Paul

Hi Jean-Paul,
Yes . . . a mess I agree.
Much of the problems are in the engine files themselves plus the fact that OR is still under development.
Have you tried any other steamers under the same conditions?

I had problems with some engines which were all caused by bad engine file paremeters.
Try changing engines and see what happens. Be sure to use same the conditions for testing or it's not a test.
regards,
vince

[steamer_ctn]

SP 0-6-0, on 27 February 2018 - 12:30 PM, said:

ORTS physics are a mess and need overhauling. I will second that.

Thanks for your constructive, helpful and encouraging comment.

Jean-Paul, on 26 February 2018 - 03:16 PM, said:

Overall, how an engine having a closed cutoff (neutral position) could slip ???? :rolleyes:
I don't know... But I think it's really a bug !!!

The OR model probably did not contemplate that somebody would open the throttle wide up, with the reverser in the 0 position.

I will have a look, and "fix" this sometime next week.

Jean-Paul, on 26 February 2018 - 03:54 PM, said:

Must also say that permanent sanding, even before trying to start, seems not to have any effect on these parameters : slip factor remains, without or with, @ 0.20...

It is not realistic to apply sanding before commencing to move. If this did happen, it would create little piles of sand on the tracks, and add to the starting issues.

Jean-Paul, on 27 February 2018 - 09:52 AM, said:

I did a run with only 350 hauled metric tons, and was also unable to start on the same 1.05 % step, whilst when same train runs on flat ground, steam engine could develop efforts widely larger than those resulting from adhesion calculations.!.

There are a number of factors, including the starting resistance of the train, and the steepness of the slope, adhesive weight of the locomotive, driving technique, etc, that could make it difficult or impossible to start a train, especially on a wet slope.

The tractive effort, and the rotational forces are different values. For example, the tractive effort is an "average" value of the force available to move the train. The rotational force of a steam locomotive will vary as the wheel rotates, and it will reach a maximum value at certain points around the cycle. This maximum value can be in excess of the tractive effort, hence why it might seem that the locomotive is slipping before its tractive effort is reached. Diesels are different, and have constant rotational forces around the full cycle.

Do you have load tables for the locomotive in question?

After I have adjusted the code next week, I would be happy to participate in some additional testing if it is of interest. If so, it would be necessary to set an agreed scenario, and test set.

Thanks

EDIT: Just out of interest, it appears that this locomotive had a Factor of Adhesion = 3.88. Locomotives with FoAs less then 4 were more prone to wheel slip.

[ErickC]

It may not be "realistic," to sand before moving, but it happens all the time in the real world. And little piles of sand do indeed form.

At any rate, I noticed that "transient wheelslip" generally occurs during periods of high processing demands. Every locomotive I have will slip when moving from idle to 1, even light. I even tried setting the adhesion to extreme values and it still happens. I've learned to ignore it. Ain't no biggie.

[vince]

ErickC, on 27 February 2018 - 10:41 PM, said:

It may not be "realistic," to sand before moving, but it happens all the time in the real world. And little piles of sand do indeed form.

At any rate, I noticed that "transient wheelslip" generally occurs during periods of high processing demands. Every locomotive I have will slip when moving from idle to 1, even light. I even tried setting the adhesion to extreme values and it still happens. I've learned to ignore it. Ain't no biggie.

But the Buzzer!

regards,
vince

[ErickC]

Oh, I deleted the clip. I also deleted all of the default track sound clips because they're garbage.

[Jean-Paul]

ErickC, on 28 February 2018 - 12:11 PM, said:

Oh, I deleted the clip. I also deleted all of the default track sound clips because they're garbage.

More general answer :
In Europe, most of steam engines had a FoA < 4 for a simple reason : axle load was generally limited to 20 metric tons/axle (rarely 22 or 23 on a few lines ). The tested engine : 141 R was, in fact, an adaptated and improved version of light 141 USRA, delivered in France between 1945 and 1947 by Alco, Baldwin, Lima and MLW. So, in calculation of adhesion, isn't FoA influency widely overestimated, essentially because most of conceptors worked only on American locomotives, on which axle load may reach 30 t/axle ? In France, 141 R hauled coal trains from North to Paris suburbs with a load of around 1000 to 1200 met.tons on an itinerary with some steps approaching 1 %. Slowly, but surely, and I can ensure that North of France climate is not as dry as Nevada's one !! :p . As a child, I saw so many of these trains to affirm it's a fact !! On the French Riviera, where it also rains sometimes, they hauled the famous "Mistral" with an admitted max load of 800 metric tons, with a perfect regularity ! And what to say about our "Pacifics" whose FoA was around 3, authorized tu haul express up to 550 met.tons on Paris to Cherbourg line (Normandy... where it doesn't rain very much, but very often...::). So, I did an .eng giving, "on the sheet of paper", a reasonable adhesion. Curtius-Kniffler parameters are adapted to adherent mass (in fact, "ORTSDriveWheelWeight" is totally inoperative, didn't you notice it ?). MaxTractiveEffort is calculated on a basis of 75% cutoff and regulator wide open. In these conditions, answer is double :
- First hypthesis is that there is a mistake in calculation mode (wrong factor, unit conversion errors...)
- Second hypothesis is that a too rigourous approach of adhesion problems dwells to such complex calculations that wheelslip is the "default solution", by overcharge of processor...
The way by which steam modelzation has been approached is what we call in French "une usine à gaz" (no possible translation, but it means that anecdotic parameters have been taken in consideration with a priority against more important factors..).
When a railway director had to determinate a maximal load for an engine - let's take our 141 R - he started from its adhesion mass : 80 metric tons, and estimated that a wet rail has tipically an adhesion around 0.14. 80*0.14 = 11.2 metric tons, let's say around 110 kN. With 110 kN, taking in account inerty of friction wheelboxes and mechanism, on a step of 1 %, you can start with around 950 metric tons load without sanding, even if it's better to sand rail to avoid little wheelslips. Calculation is as simple as this ! And it's not me who explains this, but specialists like André Chapelon or Nigel Gresley...
Cylinder cocks were open, to allow not to apply the whole effort on wheels (they are completely unefficient, except for esthetic reasons, under OR...), ans I must precise that sanding is applied just BEFORE starting, because there is no interest to sand the rail behind the wheel you try to move...!!!
It remains that starting an heavy train by poor adhesion remains - and must remain - difficult.. But not impossible in the limits of reasonable physical parameters.
I also think, and that was a good idea, indeed, that acceleration of wheel is taken in account to minimize tractive effort. Well, but I agree with many to find its influence is excessive, this remark being valuable for all types of engines... With modern railcars, it may grow up to almost 20 % of initial effort, even with high coefficient of adhesion... Isn't it a bit too much ? Must say that having a little experience on driving railway engines, I know that you never must apply full power roughly.. but only at low speeds ! At 120 km/h (75 mph), a "loss by slip" of 10 % is clearly excessive on dry rail.
Best regards,
Jean-Paul

[steamer_ctn]

Firstly to be crystal clear, in OR the diesel/electric adhesion model is completely different to the steam model, so it is not appropriate to make comparisons between them.

Jean-Paul, on 28 February 2018 - 10:07 PM, said:

More general answer :
The tested engine : 141 R was, in fact, an adaptated and improved version of light 141 USRA, delivered in France between 1945 and 1947 by Alco, Baldwin, Lima and MLW. So, in calculation of adhesion, isn't FoA influency widely overestimated, essentially because most of conceptors worked only on American locomotives, on which axle load may reach 30 t/axle ? ...........

You have provided quite a few comments, some of which, I currently don't understand, nor in some instances agree with.

I think that the best way to resolve this is to build a common testing environment so that we can both test with the same model so that results can be compared. This process will soon demonstrate whether calculations are flawed.

Is the SNCF R141 a freeware model? Can you build an appropriate consist up to the tonnage that you believe should be possible to start on a 1% slope? Ideally it would be easier to only have a single wagon in the consist to reduce the size of various transmissions.

Can you please provide the test consist, and the relevant download links for the locomotive and wagon.

Thanks

[Jean-Paul]

steamer_ctn, on 01 March 2018 - 02:29 AM, said:

Firstly to be crystal clear, in OR the diesel/electric adhesion model is completely different to the steam model, so it is not appropriate to make comparisons between them.


You have provided quite a few comments, some of which, I currently don't understand, nor in some instances agree with.

I think that the best way to resolve this is to build a common testing environment so that we can both test with the same model so that results can be compared. This process will soon demonstrate whether calculations are flawed.

Is the SNCF R141 a freeware model? Can you build an appropriate consist up to the tonnage that you believe should be possible to start on a 1% slope? Ideally it would be easier to only have a single wagon in the consist to reduce the size of various transmissions.

Can you please provide the test consist, and the relevant download links for the locomotive and wagon.

Thanks

Thanks for your answer. I did notice model wa quite different, but still have not understood how it is calculated. I attach a view from 141 R on flat ground, cutoff @ 0 %, wheelsliping while no effort is applied on the wheels, as described by HUD F5. Before testing anything, don't you think there is clearly a problem ? Which could occure with another engine, this one beeing not particular. How to slip without any effort applied, and all brakes liberated.. I don't know, and that's the problem !!
Best regards,
Jean-Paul

[Jean-Paul]

Jean-Paul, on 01 March 2018 - 11:14 AM, said:

Thanks for your answer. I did notice model wa quite different, but still have not understood how it is calculated. I attach a view from 141 R on flat ground, cutoff @ 0 %, wheelsliping while no effort is applied on the wheels, as described by HUD F5. Before testing anything, don't you think there is clearly a problem ? Which could occure with another engine, this one beeing not particular. How to slip without any effort applied, and all brakes liberated.. I don't know, and that's the problem !!
Best regards,
Jean-Paul 141_R_511.jpg

Oh... I add this view with regulator @ 55 % - before "wheelslipping" - just to explain that no force was applied before slipping, which would be = 0 because of wheelslipping... How to explain the two forces (tangential and static), whilst the only force existing at this instant is... gravity !??
Thanks,
Jean-Paul

Attached thumbnail(s)

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[Jean-Paul]

Lasr snapshot :
Just before wheelslipping, in a step of 1.0 %. Resulting forces are widely positive, tractive effort is around 60 % of amxi allowed by adhesion coefficient, but can't go further without slipping... An explanation, please !
Thanks,
Jean-Paul

Attached thumbnail(s)

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