[NickonWheels]

I noticed this before, however I´m using traction tables for all new .eng files to modify (if it´s worthwhile).

[Csantucci]

Gehe, on 29 December 2019 - 05:37 AM, said:

Hi All,

beside the issue discussed above I found a changed behaviour related to diesel performance in the newest OR version
27th December, X1.3.1-108-g85be7602 which I would like to add to this topic.

For diesel locos not using tractive force tables the motive force and power are derived from the max power and max force statements in the eng files.
In this new version it looks like that there is a new kind of power reduction. If you have 100% throttle you get just 78.4% of the max power to the wheels.
You can see this factor of 78.4% also in the extended F5 HUD (locomotive view) as a load factor.

I would like to know what is reason behind this new behaviour? There was no change in my eng files.

I believe this has nothing to do with the reduction factor of 0.98 which is used in OR generally for diesels;
also the model used for warming up of the traction motors should not be of any significant effect here since the locos were "cold".


Best Regards
Gehe

i am a bit frightened of these changes in the way basic, original MSTS parameters are used. There are plenty of engines who have been modeled with their .eng parameters, who are used in activites that are tailored accordingly to the performance of such engines. I don't see it is advisable to change the performance of such engines after years of usage of them in OR.

[steamer_ctn]

Gehe, on 29 December 2019 - 05:37 AM, said:

beside the issue discussed above I found a changed behaviour related to diesel performance in the newest OR version
27th December, X1.3.1-108-g85be7602 which I would like to add to this topic.

I am unaware of any significant code changes in this area since v1.3.

Gehe, on 29 December 2019 - 05:37 AM, said:

If you have 100% throttle you get just 78.4% of the max power to the wheels.
You can see this factor of 78.4% also in the extended F5 HUD (locomotive view) as a load factor.

I can't comment on this specific value without seeing the specific locomotive, however I will make the following generic comments.

The code in effect defines Load% = Actual Output Power (Motive Force) / Diesel Prime Mover Output Power

The Motive Force value will vary depending upon the load on the locomotive, so light engines will not require as much motive force to move them, whereas heavily loaded locomotives will require more motive force to move them.

The Diesel Prime Mover Output power will be as defined in the ENG file.

So to illustrate, a couple of examples (which can be confirmed by testing).

In the case of legacy (MSTS defined) locomotives the Prime Mover output power is set equal to the Rail Power, as no other information exists in the ENG file to discriminate for OR.

Thus using the default Dash9 as an example, the Prime Mover power is set to 4400hp, and the maximum power to rail is also set to this same value (via the MaxPower parameter).

Hence, if the full amount of motive power is required to move the locomotive, then it is possible to see Load% up around 90%+. As far as I am aware, this has not changed between v1.3 and the most current unstable version, and can be verified by running an appropriate default Dash9 consist in both versions and comparing the results.

In the case of more recently configured locomotives, it will be dependent upon how the locomotive has been configured and what powers have been assigned to the above Powers in the ENG file. For example, if the prime mover output power has been set realistically, then it will always be higher then the maximum possible motive force that can be achieved, and thus lower % figures will be obtained.

For example, with my test locomotive the prime mover output power is 1888hp, whereas the maximum power to rail is 1560hp. Thus the maximum load% will only ever be about 82%, whereas it is more likely to be less then this value as the locomotive may not be producing maximum motive force (maximum power output). So a value of around 78% could in theory be obtained without too much trouble.

As suggested I don't believe any code changes will have affected this value since v1.3, and it is more a outcome of how the ENG file has been defined.

Remembering that there are differences between how a BASIC and ADVANCED locomotive is defined (ie different information Tables, etc).

Gehe, on 29 December 2019 - 05:37 AM, said:

I would like to know what is reason behind this new behaviour? There was no change in my eng files.

Can you provide me with an example ENG file that demonstrates the concern that you are raising?


Moving forward.
As suggested my I wanted to review some of the operation of the diesel code, and thus two questions come to mind:
i) What is this value used by the user for within the simulation?
ii) Given that some people have suggested that it is actually an efficiency value, what efficiency should it be expressing?

Thanks

[R H Steele]

steamer_ctn, on 29 December 2019 - 02:37 PM, said:

Moving forward.
As suggested my I wanted to review some of the operation of the diesel code, and thus two questions come to mind:
i) What is this value used by the user for within the simulation?
ii) Given that some people have suggested that it is actually an efficiency value, what efficiency should it be expressing?

Thanks

That's one of the concepts I've had the most trouble grasping. Thanks to help from some patient ET members I think I've learned. I'll go a little out on a limb: when Bob Boudoin refers to the efficiency of a diesel locomotive he is referring to the accumulated losses through the "transmission system". RailHP/TractionHP equals locomotive efficiency ( 85% for example ). Traction HP being the input hp to the generator/alternator. Losses from the generator/alternator, traction motors and gearing ( transmission system ) are accounted for in this scheme.
However, to confuse the issue, I've also found legacy engine files referring to the efficiency as the total sum of losses from BHP ( MaximalPower in OR ) to RailHP. Moreover, some legacy engine files refer to the MaxPower value as "Traction HP". (is that a confusion with RailHP?)
I also thought there was some discrepancy in how the HUD expressed diesel locomotive efficiency. I'm not so sure about that opinion anymore -- at present I think the Load% percentage expressed in the HUD is accurate ( it may need some fine tuning ). I do know, from emails with Bob Boudoin that he has reservations about how OR handles diesel locomotives with AC traction. My understanding is that OR was built to model DC traction and does a good job...but it falls short with AC traction and that may have some bearing on the Load% expressed in the HUD. It may be beneficial for someone with more understanding of the issues than myself contact Bob and get his views on the subject.

[steamer_ctn]

I have uploaded another test locomotive.

This one is somewhat interesting as it has two diesel prime movers providing input to the generators. Looking quickly at it I have tried turning the engine off and back on again, but it doesn't seem to work. I am wondering if this has broken the OR model?

I would be interested to see if anybody has a working two engine model for comparison.

[steamer_ctn]

R H Steele, on 29 December 2019 - 03:48 PM, said:

That's one of the concepts I've had the most trouble grasping. Thanks to help from some patient ET members I think I've learned. .............

Thanks for the feedback.

Every time there is a power conversion, there will be some loss off efficiency (power) due to the conversion process. So depending upon what is being looked at the efficiency will vary. For example if one is only interested in the generator efficiency then we should be just looking at that, if we are interested in the transmission (gearing) efficiency then we need to look at that. Some publications are interested in looking at the overall locomotive efficiency, and hence consider the output power compared to the input power, potential power in the furl source.

So this comes back to my first question, what are we using the info in the sim for, and why do we need it? What relevance does it have?

[NickonWheels]

Quote

This one is somewhat interesting as it has two diesel prime movers providing input to the generators. Looking quickly at it I have tried turning the engine off and back on again, but it doesn't seem to work. I am wondering if this has broken the OR model?

I would be interested to see if anybody has a working two engine model for comparison.

I just tried a test locomotive with two prime movers. Shutting one off when at full throttle causes the efficiency of the meant engine goes immidiately to zero (which is correct as the generator cuts out as works with single engine locomotives) but the effiiciency of the other engine still running goes above 100% while the rpm of the stoppend engine are still on their way down. For now it seems that traction tabes work for dual-engined locos, at least when they use two of the same type (unlike some mixed engines like in the PR43C 3600 + 700 horsepower) but when stopping an engine the efficiency must go down like with single engined locos, which basically means an abrupt loss in traction.

[edwardk]

I have to wonder if this work should have been released under a different release category. We have to remember that when OR was just released, maxPower would have reflected the hp minus the efficiency rating. People would have started updating maxPower with the full hp once they discovered OR took care of this in the code. Now, people are expected to go through another round of hp changes. There are probably issues that still exist with the physics that need to be found and fixed.

One question is this. If realistic parameters are used, how close is the train operation to real life operation?

[steamer_ctn]

edwardk, on 30 December 2019 - 03:28 PM, said:

I have to wonder if this work should have been released under a different release category. We have to remember that when OR was just released, maxPower would have reflected the hp minus the efficiency rating.

Thanks for raising this concern.

Can you point to the references suggesting that MaxPower should be equal to HP - Efficiency.

edwardk, on 30 December 2019 - 03:28 PM, said:

One question is this. If realistic parameters are used, how close is the train operation to real life operation?

That is the main reason that I try to use test models that have a supporting railway test report.

Both of these models, as indicated, have had a BR test report done on them, so it is possible to find accurate information for the parameters, and test results that can be used to compare the models performance.

So give them a go and see what you think. (The ENG files may require further tweaking, or similarly the code may need some changes).

[NickonWheels]

Quote

Both of these models, as indicated, have had a BR test report done on them, so it is possible to find accurate information for the parameters, and test results that can be used to compare the models performance.

This might be nice for vehicles based on real models (althouth there is no way of getting all the nesessary information for many stuff), but for custom-made models it would need a chance of inserting custom values. Luckily this is possible in regards of diesel engine performance.