Elvas Tower: Unstability of adhesion with Test version 1.5.1-237 - Elvas Tower

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Unstability of adhesion with Test version 1.5.1-237 With steam engines Rate Topic: -----

#1 User is offline   Jean-Paul 

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Posted 22 January 2023 - 10:38 AM

Hi !
I have noticed that, with Testing version T1.5.1-237, downloaded on January 20th, adhesion of steam engines is seriously deteriorated. In consequence, tractive effort is perpetually oscillating, even for weak values (and without prealable wheelslip). Observations were the same for my whole batch of steam engines : with 1.5.1-173, no problem, and with 1.5.1-237, unstable tractive effort, with up to 25 % oscillations. No repercussions on Diesel or Electric engines.
Thanks in advance to cure this very unpleasant problem !
Cheers,
Jean-Paul

#2 User is offline   Jean-Paul 

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Posted 22 January 2023 - 01:33 PM

Hi !
After examination, I can confirm a bug has appeared in calculation of wheelslip only with steam engines. Wheelslip calculation seems never to have a stable value, even for tractive efforts widely inferior to adhesion limits. It doesn't seem to affect electric or diesel engines. If we list changes between 1.5.1-237 and 174 (previous testing version), we can notice these two changes :
33903e0e Adjustments to wheel slip
87638fa1 Steam slip

which are probably the source of these new problems.
Driving a steam engine is simply impossible with this "evolution" ! Moreover if you need high efforts !
Cheers,
Jean-Paul

#3 User is offline   steamer_ctn 

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Posted 22 January 2023 - 04:44 PM

View PostJean-Paul, on 22 January 2023 - 01:33 PM, said:

After examination, I can confirm a bug has appeared in calculation of wheelslip only with steam engines. Wheelslip calculation seems never to have a stable value, even for tractive efforts widely inferior to adhesion limits. It doesn't seem to affect electric or diesel engines. If we list changes between 1.5.1-237 and 174 (previous testing version), we can notice these two changes :
Can you please run the latest Unstable version and see whether you get the same result.

You also might want to look at this thread as it talks about changes implemented, and todate no issues have been identified yet.

#4 User is offline   Jean-Paul 

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Posted 23 January 2023 - 01:39 AM

View Poststeamer_ctn, on 22 January 2023 - 04:44 PM, said:

Can you please run the latest Unstable version and see whether you get the same result.

You also might want to look at this thread as it talks about changes implemented, and todate no issues have been identified yet.

Hi,
I've just tried latest unstable version U2023.01.23.0737, and problem remains : constant and cyclic unstability of tractive effort, even for a reasonable one (Here, 90 kN for 80 t of weight on drivers (1.65m diameter - 2 cylinders, simple expansion), i.e. 11,25 % of adhesive weight - widely below a normal adhesion @ 67 km/h - here, calculated value is around 19 % ). I don't contest the fact that, in reality, tractive effort is not a constant, following the different phases of distribution. But, I should say that, perhaps, too much is too much...
I add a screenshot to illustrate the problem.
Cheers,
Jean-Paul

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#5 User is offline   steamer_ctn 

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Posted 23 January 2023 - 01:53 AM

View PostJean-Paul, on 23 January 2023 - 01:39 AM, said:

I've just tried latest unstable version U2023.01.23.0737, and problem remains : constant and cyclic unstability of tractive effort, even for a reasonable one (Here, 90 kN for 80 t of weight on drivers (1.65m diameter - 2 cylinders, simple expansion), i.e. 11,25 % of adhesive weight - widely below a normal adhesion @ 67 km/h - here, calculated value is around 19 % ). I don't contest the fact that, in reality, tractive effort is not a constant, following the different phases of distribution. But, I should say that, perhaps, too much is too much...
I add a screenshot to illustrate the problem.

Does the locomotive actually slip? It has a low FoA, so depending upon the tractive force, it may exhibit slip in dry conditions.

The code model was tested against a "known" test locomotive, see the thread that I referred to and it appeared to match the "real" world expectations, see the information with the test model. The test model also had a FoA of 3.9, and could be made to slip at full throttle, and starting, so your model may be a bit slippery under some conditions.

If it can be shown that the test model is not aligning with the test expectations then I am happy to have a closer look at it.

#6 User is offline   Jean-Paul 

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Posted 23 January 2023 - 02:19 AM

Hi,
I should add that the problem becomes cartoonish at higher speeds. I've tested the same engine @ around 55mph, with an enforced adhesion by changing CK coefficients : I could observe that effort on axle could vary from 1 to 4, overating at maximum the OR MaxPower, by reaching 2700 kW (!) and lowering down to 700 kW (normal stabilized power, at this speed, is around 1500 kW). Calculation processes are permanent, even in this case, when I stabilized my speed... Really think it's a big problem !! I noticed that now, "number of substeps" appears in the dedicated window with steam engines (it was previously only the case with diesel or electric ones).. and here, number of substeps remains very high (more than 50), even with a constant speed.
Certainly, this innovation may seem to be amazing, at first glance, on very heavy trains, because it enhances slipping perception... I think it's absolutely awful in normal conditions of use (seen from an european point of view : lighter engines, lighter trains). My test engine, here, is a mixed-traffic one.. Problem is much more important with a speed locomotive, whose adheasion is limited... Undriveable is, I'm afraid, the more appropriated word. Of course, a steam engine is not easy to drive... but not impossible !
For now, that's clear, i give it up with testing versions, and stay to 1.5.1-174 !
Cheers,
Jean-Paul

#7 User is offline   Jean-Paul 

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Posted 23 January 2023 - 02:57 AM

View Poststeamer_ctn, on 23 January 2023 - 01:53 AM, said:

Does the locomotive actually slip? It has a low FoA, so depending upon the tractive force, it may exhibit slip in dry conditions.

The code model was tested against a "known" test locomotive, see the thread that I referred to and it appeared to match the "real" world expectations, see the information with the test model. The test model also had a FoA of 3.9, and could be made to slip at full throttle, and starting, so your model may be a bit slippery under some conditions.

If it can be shown that the test model is not aligning with the test expectations then I am happy to have a closer look at it.

Hi !
Well, well... FoA is only a coefficient, whose interest is only indicative, and concerns only uses of full regulator and cutoff openings. Whatever is the value of FoA, it has no importance if you only practice cutoff (or regulator) openings compatible with the adhesion. More, I don't say it's abnormal to slip... Never said that ! I have parametered hundreds of engines, and slipping is not, for me, an unknown concept.
The problem is that those cyclic variations of mentioned importance are unrealistic (or, at least, widely exagerated). Look at this screenshot, with a steam engine whose FoA is 4.7, i.e. between 4 and 5, no ?
I won't do any comments.
Cheers,
Jean-Paul

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#8 User is offline   Jean-Paul 

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Posted 23 January 2023 - 09:20 AM

Hi !
This problem means a lot to me... So, I have tested the same engine that the first one, only modifying its weight, and its DriveWheelWeight. By this way, I obtained a FoA of 8.7. (Total weight = 215.5 mtons, Adh weight = 180 mtons)
Test reveals exactly the same problem as previous, i.e. a strong oscillation of tractive effort (more than 300 % dispersion), totally unrealistic, except with a totally staggered distribution. I precise that,otherwise, test engine has conserved same boiler, and cylinders that in its real version. Parameters are those of a real french SNCF 141-R.
I let you see, with this screenshot, which completly excludes the hypothesis of a wheelslip tendency. So, that's clearly the model of steam engine which is seriously affected by this modification, alas...
Cheers,
Jean-Paul

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#9 User is offline   steamer_ctn 

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Posted 23 January 2023 - 11:59 AM

Can you post the ENG files for both locomotives.

#10 User is offline   Jean-Paul 

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Posted 23 January 2023 - 12:11 PM

View Poststeamer_ctn, on 23 January 2023 - 11:59 AM, said:

Can you post the ENG files for both locomotives.

Hi !
Here are the files :
- 231-D-710 (FoA = 4.7)
- 141-R-1207 (FoA = 3.9 To get a FoA of 8.7, it needs to increase weight up to 115.5 t and ORTSDriveWheel up to 180 t.
Plus associated tenders : 22-C fits with 231-D, and 30-R-1207 with 141-R-1207.
Cheers,
Jean-Paul

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