Yes - I too am following this thread with great interest, and bafflement!
I am managing to bodge the steam hauled train brakes by changing them to air and adjusting the application rate, etc.
However, I have yet to find a way to match MSTS performance in terms of top speed, so on most passenger activities I cannot maintain the timetable using Open Rails.
Thanks for all your efforts to try to resolve the steam loco performance.
Mike
Re: Steam Physics
Moderator: Moderators
Re: Steam Physics
Martin Pope shared his TSM Compound model with me so that I could create some other Midland 4-4-0s (particularly the 700 class!)
So I thought I would have a try with the Compound physics in ORTS
So far I have found the performance of the 4P compound being a bit lacking and not really any better than the 3P simple that I have derived from it:
And that is in spite of applying the "old engines" adjustment mentioned above to the class 3 and leaving the compound on the default settings.
The performance of the "Belpaire" is probably about right (more testing needed for both) but the compound seems to be under-performing. I am going to compare my LMS Compound to the compound Atlantic given as an example on the Coals to Newcastle site to see if there is something more that I need to do to get the eng file correct.
So I thought I would have a try with the Compound physics in ORTS
So far I have found the performance of the 4P compound being a bit lacking and not really any better than the 3P simple that I have derived from it:
And that is in spite of applying the "old engines" adjustment mentioned above to the class 3 and leaving the compound on the default settings.
The performance of the "Belpaire" is probably about right (more testing needed for both) but the compound seems to be under-performing. I am going to compare my LMS Compound to the compound Atlantic given as an example on the Coals to Newcastle site to see if there is something more that I need to do to get the eng file correct.
Regards
Darwin
Darwin
Re: Steam Physics
Not too much idea of where to go now. The example OR compound file was very basic - four cylinder (mine is three) and slightly bigger ratio of volume of low pressure cylinders to high pressure cylinders... No magic in there.
Perhaps not surprising that the 4P does not perform any better than the 3P, when I look at the theoretical performance figures given on the HuD
3P simple: 1324 ihp TE: 20,100 lb
4P compound: 1346 ihp TE:20,400 lb
The tractive effort for the 3P is of course correct (simple calculation for a simple
) However the literature value for the tractive effort for the LMS compound is 22,600 lb, but I do not know how this is calculated. [My first thought on ways to deal with this would be to increase the size of the low pressure cylinders in the eng file, which I will try, however other ideas are welcomed, particularly if someone knows how ORTS is calculating the power output for a compound.] 
Perhaps not surprising that the 4P does not perform any better than the 3P, when I look at the theoretical performance figures given on the HuD
3P simple: 1324 ihp TE: 20,100 lb
4P compound: 1346 ihp TE:20,400 lb
The tractive effort for the 3P is of course correct (simple calculation for a simple
) However the literature value for the tractive effort for the LMS compound is 22,600 lb, but I do not know how this is calculated. [My first thought on ways to deal with this would be to increase the size of the low pressure cylinders in the eng file, which I will try, however other ideas are welcomed, particularly if someone knows how ORTS is calculating the power output for a compound.] Regards
Darwin
Darwin
Re: Steam Physics
I think you will find that the theoretical starting TE of the compound is with all cylinders in simple mode. The starting TE shown in the OR expanded HUD is at the moment of starting to move, which is usually before the max starting TE can be developed.
Re: Steam Physics
Thanks.
After further testing the Compound model proved quite satisfactory. (The fact that the Belpaire was almost the same in performance in early trials probably means that I will need to adjust that one!) I was quite happy with the Compound uphill and on the level. I still have not worked out how to stop it running away too wildly down the hills.
All models worked on so far had good boilers able to provide plenty of steam to the cylinders for the job they had to do. I might next try to look at the LMS 2-6-2 tanks - which were generally considered to have inadequate boilers.
Perhaps a bigger challenge to recreate would be the variations in the Jubillee class - with the original low superheat version somewhat lacking, but improved boilers making them into really good locomotives.
After further testing the Compound model proved quite satisfactory. (The fact that the Belpaire was almost the same in performance in early trials probably means that I will need to adjust that one!) I was quite happy with the Compound uphill and on the level. I still have not worked out how to stop it running away too wildly down the hills.
All models worked on so far had good boilers able to provide plenty of steam to the cylinders for the job they had to do. I might next try to look at the LMS 2-6-2 tanks - which were generally considered to have inadequate boilers.
Perhaps a bigger challenge to recreate would be the variations in the Jubillee class - with the original low superheat version somewhat lacking, but improved boilers making them into really good locomotives.
Regards
Darwin
Darwin
Re: Steam Physics
WRT running away downhill, that could be due to the lack of a proper vacuum braking system. The current version does not allow for setting and lap to hold. There is also train resistance to fiddle with, the Davis constants and bearing types, curve resistance where applicable by setting correct wheelbase in the eng/wag files. Sometimes, just closing the throttle is sufficient to either maintain speed, slow down or reduce the amount of speed increase when running downhill.
-
steamer1960
- Getting the hang of things now
- Posts: 51
- Joined: Thu Feb 02, 2006 11:18 am
Re: Steam Physics
Thanks for an interesting thread.
As the current principal developer for the steam locomotive code I would like to offer a few comments.
In starting to develop the code my guiding principles have always been:
i) To provide as realistic as possible look and feel for locomotive performance (ie it should look and perform "right", but may not be 100% accurate to real life, as most performance information for steam locomotives is empirical (derived by running tests and fitting formula to the results)). Therefore some compromises have needed to be made.
ii) Ideally it should be "easy" for anybody to setup a reasonably accurate ENG / WAG file. I was hoping that this would overcome some of the challenges that I believe exist at the moment with the accuracy of some MSTS ENG files.
With item ii) in mind, I established the Coals to Newcastle site ( http://www.coalstonewcastle.com.au/physics/)to share the test locomotives and stock that I use for code development, to share some of the information that I found during my research, and also to provide examples of ENG and WAG file configurations.
Some functions and features of the code are relatively mature, and further changes would not be expected, however OR is continually being refined and improved with new features, so unless we freeze all future development, new parameters can be expected. For example, I am currently finishing off variation of the train physics with load and this may require potential changes to a lot of locomotives and wagons. Perhaps the best way to manage this is to check and revise parameters each time a major OR release is done, ie v1.0, v1.1, etc.
It should be noted that when testing a locomotive in OR, the full train consist should be adjusted to OR "standards" as the performance of the wagons (friction, etc) can impact the performance of the locomotive.
As has been pointed out, my time is spread thin between, researching, code development and maintaining the Coals to Newcastle site, however I have a strong desire to ensure people get the best out of OR. Thus, it would be great if some people would be willing to work with me to assist me in maintaining, adding and clarifying information on the Coals to Newcastle site. Hopefully this would be a large benefit to the Train Simming community.
This work would include some revision of ENG and WAG files from time to time, testing features, proof reading of site to provide suggested edits to improve the information contained on the site.
Anybody interested?
As the current principal developer for the steam locomotive code I would like to offer a few comments.
In starting to develop the code my guiding principles have always been:
i) To provide as realistic as possible look and feel for locomotive performance (ie it should look and perform "right", but may not be 100% accurate to real life, as most performance information for steam locomotives is empirical (derived by running tests and fitting formula to the results)). Therefore some compromises have needed to be made.
ii) Ideally it should be "easy" for anybody to setup a reasonably accurate ENG / WAG file. I was hoping that this would overcome some of the challenges that I believe exist at the moment with the accuracy of some MSTS ENG files.
With item ii) in mind, I established the Coals to Newcastle site ( http://www.coalstonewcastle.com.au/physics/)to share the test locomotives and stock that I use for code development, to share some of the information that I found during my research, and also to provide examples of ENG and WAG file configurations.
Some functions and features of the code are relatively mature, and further changes would not be expected, however OR is continually being refined and improved with new features, so unless we freeze all future development, new parameters can be expected. For example, I am currently finishing off variation of the train physics with load and this may require potential changes to a lot of locomotives and wagons. Perhaps the best way to manage this is to check and revise parameters each time a major OR release is done, ie v1.0, v1.1, etc.
It should be noted that when testing a locomotive in OR, the full train consist should be adjusted to OR "standards" as the performance of the wagons (friction, etc) can impact the performance of the locomotive.
As has been pointed out, my time is spread thin between, researching, code development and maintaining the Coals to Newcastle site, however I have a strong desire to ensure people get the best out of OR. Thus, it would be great if some people would be willing to work with me to assist me in maintaining, adding and clarifying information on the Coals to Newcastle site. Hopefully this would be a large benefit to the Train Simming community.
This work would include some revision of ENG and WAG files from time to time, testing features, proof reading of site to provide suggested edits to improve the information contained on the site.
Anybody interested?
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systema
- Very Active Forum Member
- Posts: 3829
- Joined: Mon Sep 08, 2003 8:00 pm
- Location: The Heart of Cheshire
Re: Steam Physics
Regarding The Midland Compound and Belpaire performance I have been looking into it.
For the 220 psi Compound, Wikipedia quotes 21,840 lbf as the Theoretical TE. OR shows 21,600 lbf in the HUD which is quite close. I don't know how the compound TE is calculated in OR. The number of HP and LP cylinders in the eng file makes no difference to the result, even if NumCylinders is set at 0 for either or both. Therefore, I don't know if OR can distinguish between 4 and 3 cylinder compounds.
I calculated TE for the Belpaire at 18,674 lbf with 180psi BP and 19.5in cylinders.
A rebuilt Belpaire with 200psi BP and 20.5 in cylinders gives TE of 22,932 lbf, which is quite an improvement.
Don't forget performance will be modified by the weight and adhesive weight, the Compound being 62t/39t and the Belpaire 53t/35t respectively. Therefore on the face of it the performance between the Belpaire and Compound looks fairly similar. However, a Compound should be able to run on a longer cut off at the same efficiency and therefore go faster, if I understand the theory correctly. I don't know if OR emulates this.
Mick Clarke
MEP
For the 220 psi Compound, Wikipedia quotes 21,840 lbf as the Theoretical TE. OR shows 21,600 lbf in the HUD which is quite close. I don't know how the compound TE is calculated in OR. The number of HP and LP cylinders in the eng file makes no difference to the result, even if NumCylinders is set at 0 for either or both. Therefore, I don't know if OR can distinguish between 4 and 3 cylinder compounds.
I calculated TE for the Belpaire at 18,674 lbf with 180psi BP and 19.5in cylinders.
A rebuilt Belpaire with 200psi BP and 20.5 in cylinders gives TE of 22,932 lbf, which is quite an improvement.
Don't forget performance will be modified by the weight and adhesive weight, the Compound being 62t/39t and the Belpaire 53t/35t respectively. Therefore on the face of it the performance between the Belpaire and Compound looks fairly similar. However, a Compound should be able to run on a longer cut off at the same efficiency and therefore go faster, if I understand the theory correctly. I don't know if OR emulates this.
Mick Clarke
MEP
Heading North and East
[album 86570 OR_Supporter_Logo_Red.jpg]
[album 86570 OR_Supporter_Logo_Red.jpg]
Re: Steam Physics
Hello all,
More testing suggests both Compound and Belpaire were over performing. Anyway I think I am getting to grips with a way tinkering with the Physics, having spent some time playing with these 4-4-0s and the Fowler and Stanier 2-6-2 tanks.
I think I have the Compound about right - though it still seems that to get performance right on level track, it is not as good as climbing hills and it should be and in compensation can run faster down them. So overall keeps time.
I think I will be happy to get some locos in the right ball park and will be happy to see others make further improvement as time goes on.
Incidentally my testing is not very scientific - it is based on trying to reproduce on the road performances recorded in the past, (much study of British Locomotive Practice and Performance in old copies of the Railway Magazine). Anyway it will be limited by errors in distance and gradient in MSTS routes. (Some routes will not be used for testing as they seem to lack some gradients!)
Already the eng files are much easier to write than for MSTS, and performance out of the box is much better.
Hopefully I can be of help to steamer1960 here by sharing my own experience.
More testing suggests both Compound and Belpaire were over performing. Anyway I think I am getting to grips with a way tinkering with the Physics, having spent some time playing with these 4-4-0s and the Fowler and Stanier 2-6-2 tanks.
I think I have the Compound about right - though it still seems that to get performance right on level track, it is not as good as climbing hills and it should be and in compensation can run faster down them. So overall keeps time.
I think I will be happy to get some locos in the right ball park and will be happy to see others make further improvement as time goes on. Incidentally my testing is not very scientific - it is based on trying to reproduce on the road performances recorded in the past, (much study of British Locomotive Practice and Performance in old copies of the Railway Magazine). Anyway it will be limited by errors in distance and gradient in MSTS routes. (Some routes will not be used for testing as they seem to lack some gradients!)
Already the eng files are much easier to write than for MSTS, and performance out of the box is much better.
Hopefully I can be of help to steamer1960 here by sharing my own experience.
Regards
Darwin
Darwin
-
systema
- Very Active Forum Member
- Posts: 3829
- Joined: Mon Sep 08, 2003 8:00 pm
- Location: The Heart of Cheshire
Re: Steam Physics
Darwin,
Having looked at the CoalstoNewcastle website OR only models a non receiver 4cylinder compound at the moment. It would be great for us in the UK if a Midland/LMS style 3 cylinder compound could eventually be modelled.
I would be quite happy to try and help Peter on this in some way.
The Belpaire being a standard simple loco should give roughly the correct performance providing all the main inputs are correct. See the ctn for this as well as getting correct info from orion
http://orion.math.iastate.edu/jdhsmith/term/slindex.htm
Davis formula need to be used for all rolling stock resistance. These can be found using Fcalc.
For the time being I would try and set up the Compound as Simple with all parameters the same except 2cylinders of 19.5x26in.
Mick Clarke
MEP
Having looked at the CoalstoNewcastle website OR only models a non receiver 4cylinder compound at the moment. It would be great for us in the UK if a Midland/LMS style 3 cylinder compound could eventually be modelled.
I would be quite happy to try and help Peter on this in some way.
The Belpaire being a standard simple loco should give roughly the correct performance providing all the main inputs are correct. See the ctn for this as well as getting correct info from orion
http://orion.math.iastate.edu/jdhsmith/term/slindex.htm
Davis formula need to be used for all rolling stock resistance. These can be found using Fcalc.
For the time being I would try and set up the Compound as Simple with all parameters the same except 2cylinders of 19.5x26in.
Mick Clarke
MEP
Heading North and East
[album 86570 OR_Supporter_Logo_Red.jpg]
[album 86570 OR_Supporter_Logo_Red.jpg]
Re: Steam Physics
I am finding that using the Davis figures generated by Fcalc causes too much resistance when moving. So I use them as the starting point, having set up all the other engine parameters with correct data. I also use the CTN OR test track which has a large level oval, a section which is all curves, and several gradients in the inner sector.
So, using the Fcalc figures I set off with a reasonable load on the hook and see what the maximum speed is in that configuration. Usually it falls way short of expectations. The Compound for example, double headed with 9 BR MK1s would just about creep past 40mph. By reducing that in stages The consist will now accelerate up to 55MPH in a reasonable distance and continue to increase speed up to 63.3mph and maintain that speed on 90% throttle and 24% forward gear. With a lighter, shorter train speed would be higher.
The Davis figures I use on my coaching stock are
ORTSDavis_A ( 482.68 )
ORTSDavis_B ( 11.1877 )
ORTSDavis_C ( 0.4952 )
ORTSBearingType ( Roller )
Turning to compounding in particular, the web site clearly states that the current code is set up to use the Woolfe system which was not used in this country far as I am aware. The Wolfe system has no LP receiver, passing steam directly from HP to LP cylinders. I don't think it includes the direct admission starting valve for the LP cylinder either.
So, using the Fcalc figures I set off with a reasonable load on the hook and see what the maximum speed is in that configuration. Usually it falls way short of expectations. The Compound for example, double headed with 9 BR MK1s would just about creep past 40mph. By reducing that in stages The consist will now accelerate up to 55MPH in a reasonable distance and continue to increase speed up to 63.3mph and maintain that speed on 90% throttle and 24% forward gear. With a lighter, shorter train speed would be higher.
The Davis figures I use on my coaching stock are
ORTSDavis_A ( 482.68 )
ORTSDavis_B ( 11.1877 )
ORTSDavis_C ( 0.4952 )
ORTSBearingType ( Roller )
Turning to compounding in particular, the web site clearly states that the current code is set up to use the Woolfe system which was not used in this country far as I am aware. The Wolfe system has no LP receiver, passing steam directly from HP to LP cylinders. I don't think it includes the direct admission starting valve for the LP cylinder either.
Re: Steam Physics
That is strange, you and I seem to get vastly different values out of F Calc.
I have set my LMS carriages up using parameters from F Calc and I am happy with the result. The performance I am getting seems reasonable and if anything I go too fast. For an 8 wheel bogie carriage of mass 32t-uk (= 32 * 1.106 tonnes ) I get the following values:
ORTSBearingType ( Friction )
ORTSDavis_A ( 162.6 )
ORTSDavis_B ( 1.075 )
ORTSDavis_C ( 0.02928 )
I have approximated the cross-sectional area to 8m^2 to try to allow for the shape of the body and roof and some open space underneath... For older vehicles built to slightly less width and height I would normally put in 7m^2 (or even 6) for cross sectional area.
I have set my LMS carriages up using parameters from F Calc and I am happy with the result. The performance I am getting seems reasonable and if anything I go too fast. For an 8 wheel bogie carriage of mass 32t-uk (= 32 * 1.106 tonnes ) I get the following values:
ORTSBearingType ( Friction )
ORTSDavis_A ( 162.6 )
ORTSDavis_B ( 1.075 )
ORTSDavis_C ( 0.02928 )
I have approximated the cross-sectional area to 8m^2 to try to allow for the shape of the body and roof and some open space underneath... For older vehicles built to slightly less width and height I would normally put in 7m^2 (or even 6) for cross sectional area.
Regards
Darwin
Darwin
Re: Steam Physics
The nearest I can readily find to a worked example for British rolling stock is this:
Carriage rolling resistance: R = (1.1 + 0.021v + 0.000175v2) kg/tonne - from Koffman applying to BR coaches.
from http://www.5at.co.uk/index.php/definiti ... tance.html
Those figures would presumably give A=35.76 kg B=0.6828 kg/v and C=0.005689 kg/v^2 for my 32t-uk carriage (32.51t), presumably assuming roller bearings. (Units of mass here being kg, not sure about velocity so will assume km/h... but FCalc figures are in lb and mph...
35.76 kg = 78.85 lb (which is about half what I get from FCalc), The B term at 1.506lb/v seems very close to what I got from F Calc, and C at 0.01254 lb/v^2 is somewhat different, but probably I should factor in the units of velocity for B and C. (Am I correct then to say that 0.6828 kg/km/h = 2.423 lb/mph and 0.005689 kg/(km/h)^2 = 0.03250 lb/(mph)^2) That looks very close in the C term!
Help needed with this please. [Would it not be easier to have OR calculate the values for the Davies equation rather than the content creator? - type of bearing, number of axles, and mass or all specified, for area it might not be too far off (other than for high speed trains) to calculate it as a rectangle from x and y in the Size () parameter.]
In the meantime I will have a try with the compound as a 2 cylinder simple. One day it would be nice to have the Smith system working, including starting as a simple and moving the regulator across to compound position. (However I shall not complain if that is in the far distant future as it sounds somewhat complicated to model.) On the subject of regulators I am still using the following lines from MSTS for modelling the twin port regulator:
Comment ( xxx Regulator MSTS parameters not sure if used in ORTS xxx )
RegulatorValveType ( Twin_port )
RegulatorSecondValveStartPosition ( 0.5 )
RegulatorPilotValveExponent ( 1.7 )
RegulatorSecondValveExponent ( 1.7 )
RegulatorPilotValveFullOpenning ( 0.3 )
RegulatorMainValveInitialOpenning ( 0.4 )
Carriage rolling resistance: R = (1.1 + 0.021v + 0.000175v2) kg/tonne - from Koffman applying to BR coaches.
from http://www.5at.co.uk/index.php/definiti ... tance.html
Those figures would presumably give A=35.76 kg B=0.6828 kg/v and C=0.005689 kg/v^2 for my 32t-uk carriage (32.51t), presumably assuming roller bearings. (Units of mass here being kg, not sure about velocity so will assume km/h... but FCalc figures are in lb and mph...
35.76 kg = 78.85 lb (which is about half what I get from FCalc), The B term at 1.506lb/v seems very close to what I got from F Calc, and C at 0.01254 lb/v^2 is somewhat different, but probably I should factor in the units of velocity for B and C. (Am I correct then to say that 0.6828 kg/km/h = 2.423 lb/mph and 0.005689 kg/(km/h)^2 = 0.03250 lb/(mph)^2) That looks very close in the C term!
Help needed with this please. [Would it not be easier to have OR calculate the values for the Davies equation rather than the content creator? - type of bearing, number of axles, and mass or all specified, for area it might not be too far off (other than for high speed trains) to calculate it as a rectangle from x and y in the Size () parameter.]
In the meantime I will have a try with the compound as a 2 cylinder simple. One day it would be nice to have the Smith system working, including starting as a simple and moving the regulator across to compound position. (However I shall not complain if that is in the far distant future as it sounds somewhat complicated to model.) On the subject of regulators I am still using the following lines from MSTS for modelling the twin port regulator:
Comment ( xxx Regulator MSTS parameters not sure if used in ORTS xxx )
RegulatorValveType ( Twin_port )
RegulatorSecondValveStartPosition ( 0.5 )
RegulatorPilotValveExponent ( 1.7 )
RegulatorSecondValveExponent ( 1.7 )
RegulatorPilotValveFullOpenning ( 0.3 )
RegulatorMainValveInitialOpenning ( 0.4 )
Regards
Darwin
Darwin
Re: Steam Physics
Thinking that the C factor in the Davis equation is the one that has increasing effect at the highest speeds, perhaps it would be better to overestimate this rather than underestimate. For my LMS carriages if I took the width over body multiplied by the height to top of roof then I would get an area of 10.35 m^2 and the final value would be:
ORTSDavis_C ( 0.03788 )
[... if the values of x and y from the .wag file were used that would give an area of 10.88 m^2 and ORTSDavis_C ( 0.03981 ) ]
ORTSDavis_C ( 0.03788 )
[... if the values of x and y from the .wag file were used that would give an area of 10.88 m^2 and ORTSDavis_C ( 0.03981 ) ]
Regards
Darwin
Darwin
Re: Steam Physics
I have started looking at the Compound again, using an eng file for a two cylinder simple.
Giving it 19.5 in cylinders seems to make it somewhat overpowered and the boiler is unable to provide enough steam.
The following has given me realistic performance in hill climbing:
Comment ( *** Cylinders *** )
NumCylinders ( 2 )
CylinderStroke ( 26in )
CylinderDiameter ( 19in )
ORTSCylinderEfficiencyRate ( 0.9 )
ORTSCylinderInitialPressureDrop( 0 0.96 50 0.76 100 0.65 150 0.61 200 0.58 250 0.55 300 0.47 350 0.31 )
ORTSCylinderBackPressure( 0 0 200 1 400 2 600 4 800 6 1000 8 1400 14 )
SteamCylinderCocksOperation ( Manual )
I am now going to see how this works for higher speed running.
Sorry, I meant to include somewhere a note in units for the benefit of others. If you are going to measure length in feet ORTS likes it to be in feet and inches, it does not understand fractional feet, so you need to enter 3ft 6in rather than 3.5ft.
Giving it 19.5 in cylinders seems to make it somewhat overpowered and the boiler is unable to provide enough steam.
The following has given me realistic performance in hill climbing:
Comment ( *** Cylinders *** )
NumCylinders ( 2 )
CylinderStroke ( 26in )
CylinderDiameter ( 19in )
ORTSCylinderEfficiencyRate ( 0.9 )
ORTSCylinderInitialPressureDrop( 0 0.96 50 0.76 100 0.65 150 0.61 200 0.58 250 0.55 300 0.47 350 0.31 )
ORTSCylinderBackPressure( 0 0 200 1 400 2 600 4 800 6 1000 8 1400 14 )
SteamCylinderCocksOperation ( Manual )
I am now going to see how this works for higher speed running.
Sorry, I meant to include somewhere a note in units for the benefit of others. If you are going to measure length in feet ORTS likes it to be in feet and inches, it does not understand fractional feet, so you need to enter 3ft 6in rather than 3.5ft.
Regards
Darwin
Darwin