Re: Steam Physics

Have you given it a go? Post your experiences, particularly things that worked well. Let the team know what works and doesn't work as they cannot test the software with every combination of routes, activities and content available for MSTS. OpenRails is actively being improved and is quickly approaching v1.0. This is a great place to discuss what you can do with OpenRails.

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Re: Steam Physics

Postby DarwinS on Fri Apr 07, 2017 4:36 am

@Rick

Please be patient. Guidance will be forthcoming... but for the moment there are no experts. There are a few folk here, trying to get things to work, but not yet being sure how to do so. Real life examples like the one you have given will help us to test things and try to make them work. Your offer of quickly constructing a "test" route might also be helpful.

We will be sharing things when we are fairly sure we have something to share. For the moment all the best available information is on the Coals to Newcastle website. http://www.coalstonewcastle.com.au/physics/
Regards

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Re: Steam Physics

Postby copperpen on Sun Apr 09, 2017 9:44 am

Rick

The Dorset Coast 6 route does not match the published gradient profile. The published profile is 1 in 50 ( 2% ), Upwey to Upwey Wishing Well, then 1 in 52 to the summit at the far end of Bincombe tunnel. The route is 2.4% Upwey to tunnel entrance then level to tunnel exit. That said, the currently available code does underpower steam locomotives a bit. We have been working to rectify that, but still have some loose ends to tidy up.

I have tried an MSTS eng file in both the current and the test code and in both cases an MSTS file fails to make the grade, which I did expect because MSTS itself gives a false impression of power. The good news is that with an OR eng file the as yet unfinished code does allow the light pacific with the load specified to gain the entrance of Bincombe tunnel without stalling.
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Re: Steam Physics

Postby rickloader on Sun Apr 09, 2017 5:49 pm

Hi Copperpen, thanks for testing the Light Pacific on Dorset Coast. I don`t have this route but my own WIP route is 1in 50 from Upwey to the North end of Bincombe tunnel (about 2 miles). I know how easy it is to stray on gradients, having ripped up my tracks 3 times.
It is encouraging to know that you can get the train to the summit in ORTS. Can you explain about the "unfinished code" ? I have sent Darwin some info about Bulleid Pacifics, and it would be a pity to concoct an ORTS .eng file, if you are updating the ORTS physics. maybe we should wait a bit?
Regarding power output, these were very capable locos in good conditions. A West Country produced the highest output in the 1948 trials at over 2000 DBhp, and the boiler was very effective. The limit was adhesion, and I believe they were not very successful on the similar 1 in 50 grades of the Somerset and Dorset. But ORTS already has a parameter for adhesion, and I think we should use this rather than downgrade the loco power output.
Regarding impatience. No, I`m not - enthusiastic rather. Having laboured mightily route building, I`m naturally disappointed if testing the route, I find my train stalled with a full head of steam.
So I`m very grateful that people are working on UK steam loco physics
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Re: Steam Physics

Postby copperpen on Sun Apr 09, 2017 7:33 pm

Rick
unfinished code.
If you look back through this thread you will see that it was felt the current steam code module was not providing full power to the other section of the code that deals with movement. As a result a small team has been testing successive iterations of the code to the point where it is felt to be much better, and any improvements would be minor. Peter who wrote the code and the subsequent amendments has other things in real life to deal with, and wishes to tidy up the code after making several changes. We then have to test a selection of other engines to make sure all is well, then probably release an update. Thus right now the new code is unfinished.

No need to "concoct" an OR eng file. There will be no changes to the format of that, with the choice of a basic no frills file, or adding some advanced parameters to it. No matter which method is used, it will work. So if you go to Peter's site, coalstonewcastle you can download the test MN or Hall which have an OR eng file and just by changing the boiler, fire and piston data along with the mass and shape information, you will have an OR eng file for whatever engine you wish. Might have to swap out the brake system as well.
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Re: Steam Physics

Postby GenmaSaotome on Tue Apr 11, 2017 7:08 am

WRT brake force, do understand the ideal force applied will have the objective of being just enough force so as to not lock up the wheel on an empty wagon. Loaded wagon could sustain much higher levels of force but for many years there wasn't equipment available to change the amount of force given actual conditions.

That problem was eventually solved with the empty/load lever (at least in North America) when some clever engineer realized the compression of the springs could be used to manipulate a lever that in turn would alter braking power.

Another aspect of this issue is over time the actual brake shoe material changed thereby allowing greater force to be applied with causing the wheel to skid.

Bottom line, the correct values to set in .wags and .engs will almost always be some percentage of the empty weight and that percentage will increase the closer one is to the present.

Unfortunately Open Rails does not provide for the empty/load lever, which is a bit of a shame when you've got 10,0o0 short tons on a 1.75% downhill grade....

For myself, interested in North American equipment in the late steam / early diesel era, the correct value for MaxBrakeForce() will be in the range of 60-70% of the empty freight car weight. Because both passenger cars and locomotives have far less difference in weight empty to loaded, the amount of force they can apply will be much greater because the empty weight is so close to the loaded weight.

Hope this helps.
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Re: Steam Physics

Postby DarwinS on Tue Apr 11, 2017 7:34 am

Thanks Genma... I think it is a different issue, we in UK, are waiting for vacuum brakes to work properly in OR. When that is solved then we should be able to work with the correct brake forces. :)
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Re: Steam Physics

Postby rickloader on Tue Apr 11, 2017 9:42 am

Using ORTS parameters,I have got my Bulleid light pacific to maintain 75 mph on an undulating level track. 100% regulator 30% cut off 1600 dbhp. 374 tons 11 coaches. CTN data modified and Copperpen`s coach data.
So it will at least time a train. 1600hp seems a lot at 75 mph. Wouldn`t this be expected to take the train to much higher speeds?
Hill climbing results in a down ward power spiral still leading to a stall on 2%. Once I managed to clear the summit at 2mph
speed TE DBHP regulator cut off
14mph 23k 607 100% 62%
5mph 25k 105 100% 62%
stalled 25k - 100% 62% B pressure 245psi
At stall the HUD shows each car exerting -1499 lb. Seems very high? If our 33 ton British coaches are exerting excess drag, might this explain the poor hill climbing?
Here is my ORTS .eng data
Comment ( *** General *** )
Type ( Engine )
WagonShape ( DR_BR_WC_34102.s )
Size ( 2.47672m 4.04923m 13.567954m )
Mass ( 172000lb )
WheelRadius ( 37in )
NumWheels ( 6 )

Comment ( *** Friction *** )
ORTSBearingType ( Roller )

Comment (Type: Steam - Standard, Speed: 170km/h, Axles: 6, Bearings; Roller, Area: 7.194m2, Weight: 78t tons (metric), DrvWeight: 65.938 tons (metric), Drag: 1 )
ORTSDavis_A ( 1448.04 )
ORTSDavis_B ( 11.6711 )
ORTSDavis_C ( 1.5 )
Comment ( Copperpens figures )
Comment ( *** Curve Resistance and SuperElevation *** )
CentreOfGravity ( 0m 2m 0m )
ORTSTrackGauge ( 4ft 8.5in )
ORTSUnbalancedSuperelevation ( 6in )
ORTSRigidWheelbase ( 15.0ft 0.0in )
Comment ( *** ORTSGeneral *** )
ORTSSteamLocomotiveType ( Simple )
ORTSDriveWheelWeight ( 112500lb ) Comment ( Weight on Drive Wheels - 50.2 tons uk )

Wagon ( DR_BR_WC_34102 )
Type ( Steam )
IsTenderRequired( 1 )
MaxPower ( 1500kW )
MaxForce ( 31000lbf )
MaxVelocity ( 107mph )
WheelRadius ( 37in )
NumCylinders ( 3 )
Sanding ( 1e9mph )
NumWheels ( 6 )
Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( "490*(ft^3)" )
ORTSEvaporationArea ( "2375*(ft^2)" )
ORTSSuperheatArea ( "545*(ft^2)" )
ORTSBoilerEfficiency ( 0.0 0.83 20.0 0.825 40.0 0.78 60.0 0.75 80.0 0.7 100.0 0.65 120.0 0.625 ) Comment ( - Customisation of Boiler Efficiency -)

BoilerLength ( 5.0m )
BoilerVolume ( "431*(ft^3)" )
BoilerEffectivity ( 1 )
BoilerResponsiveness ( 1.22 )
CoalBurnage ( 5.0lb/hp/h )
MaxBoilerOutput ( 24000lb/h )
ExhaustLimit ( 24000lb/h )
MaxBoilerPressure ( 250psi )
SuperHeater ( 1.20 )
SafetyValvesSteamUsage ( 8000lb/h )
SafetyValvePressureDifference( 4.5 )
PrimingFactor ( 1 )
SteamMinPrimingLevel ( 1 )
SteamPrimingReductionWithCylinderCocksOpen ( 0.5 )
SteamPrimingPowerLossProportion ( 0.9 )
SteamPrimingWaterUsageIncreaseProportion ( 5 )
Comment ( *** Cylinders *** )
CylinderStroke ( 24in )
CylinderDiameter ( 16.3in )
CylinderVolume ( "8.7*(ft^3)" )
Comment ( cyl vol is total of 3 cyl? )
CylinderEffectivity ( 1 )
ORTSCylinderEfficiencyRate ( 1.0 ) Comment ( Set to other value if cylinder performance to be "degraded" )
Comment ( ORTSCylinderPortOpening ( 0.12 ) )

CylinderCocksPowerEfficiency ( 0.8 )
SteamCylinderCocksOperation( Manual )
Comment ( *** Fire *** )
ORTSFuelCalorific ( 13700btu/lb )
ORTSGrateArea ( "38.3*(ft^2)" )

ShovelCoalMass ( 14lb ) Comment (For manual fireman?? )
Comment( ORTSBurnRate( 0.0 100.0 9000.0 1000.0 17500.0 2000.0 24000.0 3000.0 29000.0 4000.0 33000.0 5000.0 ))


MaxFireMass ( 1000lb )
IdealFireMass ( 850lb )
MaxWaterMass ( 2108lb )
BasicSteamUsage ( 15lb/h )
BasicCoalUsage ( 112lb/h )
ShovelCoalMass ( 14lb )
SteamFiremanMaxPossibleFiringRate(4414)
MaxTenderCoalMass ( 11200 lb )
MaxTenderWaterMass ( 50000lb )
SteamMaxSmokeUnitsReleaseRate( 3 )
SteamSmokeUnitsPerPoundOfFuel( 2 )
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Re: Steam Physics

Postby systema on Tue Apr 11, 2017 9:23 pm

I don't know how long your 2% gradient is but 2% is quite steep for a steam loco. I would expect the loco to be able to climb this though. Not sure about how your mixture of MSTS and OR parameters might work out the power generated.

The drag caused by gravity alone for a 33ton coach on a 2% gradient is 1478 lbf (0.02 x 33 x 2240), so your coaches are probably OK.

Looks like you might have a couple of things in the wrong place for OR.

This type of info should be in the second wagon section

Comment ( *************General Information****************** )

ORTSSteamLocomotiveType ( Simple )
Type ( Steam )
WheelRadius ( 37in )
NumWheels ( 3 )
ORTSDriveWheelWeight ( 67.06t ) comment(66UKT)
Sanding ( 25mph )

Num wheels refers to the 3 driving axles.

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Re: Steam Physics

Postby copperpen on Wed Apr 12, 2017 11:07 am

Rick

I would not expect your locomotive and consist to do any better on a 2% grade that it has at present. That is because the existing code does underpower the steam locomotive. I see you are using 250psi as the max boiler pressure. Looking at the cylinder size, is this an original light pacific, or a rebuild. If original, then 280psi is the figure to use.

Unlike MEP, TE and DBHP, indicated HP increases with speed because it is a measure of the actual work done by the cylinders. The maximum speed a train will reach is a balance between power and resistance. Where the two meet is the maximum achievable. This varies on level, up or down grades. As the train slows on the up grade, the indicated HP gradually drops but the MEP rises as longer cutoff is applied.
An alternative set of Davis figures to try is ORTSDavis_A ( 399 ) ORTSDavis_B ( 18 ) ORTSDavis_C ( 0.733 ).

Mick

If I am correct, this 2% grade is on the line Weymouth to Bournemouth through Upwey. The 2% grade is about 2 miles long, preceded by a mile at about 1.3%. The train has no room to build speed so is relying on power alone to make it up the hill.

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Re: Steam Physics

Postby rickloader on Wed Apr 12, 2017 3:36 pm

Thanks for your comments.
Darwin has kindly sent me an improved, tidier ORTS .eng. Have now climbed the Bank, 12mph at summit, 220 psi. (Tangmere was 19mph). Can now maintain 70 + mph on the level (374 tons), so will be able to time service trains! Thanks Darwin!
I have not yet manged to get OR to recognise a custom .eng in the OpenRails folder, hence my mix of MSTS and OR parameters.
The Bulleid pacifics were originally 280 psi, but were all soon reduced to 250 to save maintenance costs. In practice it seems the full 280psi was seldom seen in the steam chests.
Yes, the Upwey/Bincombe bank is as Copperpen describes it. Do please watch the video I gave earlier in the post : it is a real treat!
In service conditions,with varying engine states, rail conditions, the risk of a Bulleid slipping to a standstill was too great, and such heavy trains would have been banked. But the Video of Tangmere shows the loco would not have stalled with a full head of steam and dry rails.
As a result of the kind help with .eng files, I can now time a service train in OR, so I am happy to wait for changes to the code.
As an ordinary user with little mathematical ability the present requirements for OR are a bit daunting. I think many users will give up and return to MSTS. I think maybe to input the OR data as an "include" file maybe helpful. Or better still, a utility to write a .eng from dialed in parameters.
Thanks again for the help, rick
Last edited by rickloader on Wed Apr 12, 2017 4:18 pm, edited 1 time in total.
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Re: Steam Physics

Postby systema on Wed Apr 12, 2017 4:14 pm

I would say an OR file is no more daunting than an MSTS file. Its just a matter of substituting the right basic parameters. The advanced ones are a little more difficult but once you get the hang its not bad. I am sure there will be plenty of help when we are ready to go with the new code. For me the OR file is much more logical and likely to give a better result.

You can have MSTS and OR files side by side if you wish. Just make sure there is an Open Rails Folder in the Loco or Wagon main folder with the appropriate files within.

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Re: Steam Physics

Postby DarwinS on Wed Apr 12, 2017 4:48 pm

I think in the future there will be a lot more 'Open Rails' locomotives and rolling stock. Certainly I have some "MSTS" stock in production that will now be released only with OR eng and wag files, plus I intend to upload replacement OR eng and wag files for all of my older uploads. This will happen after vacuum brakes have been implemented in OR - so it may be some time away.

Once that is done I will want to look at stock created by others that I make use of. In some cases I am sure content creators will begin to make their own OR files available. In other cases perhaps they would be happy for myself and other willing people to edit files for them. There is a question about where the creators can not be contacted - perhaps in that case new OR files could be uploaded as "unofficial patches".

As Mick says it is straightforward if you have all the information. As with other things on here there are usually people around willing to help. I certainly would never have achieved much with MSTS or OR without the help of others. In due course there will probably also be tutorials and aids available.
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Re: Steam Physics

Postby systema on Fri Apr 14, 2017 10:57 pm

Rickloader,

I have set up a test Unrebuilt Light Pacific with 280 psi Boiler and all the correct inputs. On the CTN test track I reached 75mph fairly easily if not that quickly with 362t load on dead flat track, using 12-15% cut off. On a 2% incline I was able to start from a stand and reach 14mph steady speed for well over 2 miles with the same load. Cut off of 50% required after full 75% to get going. It was not possible to start on the 2% in rain but the train could make the climb with a running start. This is a slightly enhanced version from basic with a mediocre (but not default) Boiler Efficiency and Low Cylinder Initial Pressure drop. Hopefully it will do better by the time we sort everything out. It won't ever be able to do a wet start on the incline though. The Davis figures used are higher than those given to you by Copperpen, ie they are the calculated resistance figures from real world tests that we are using (not Fcalc Davis).

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Re: Steam Physics

Postby rickloader on Sat Apr 15, 2017 9:26 pm

Thanks Mick for testing a light pacific. Your result sounds more like it should be. When everything is sorted out perhaps you would share the file please.
About 1954 the boiler pressure was reduced from 280 to 250lb. It was said this made little difference to the performance. I wonder if this is true in ORTS? ( I run with 250)
I think it is correct to be unable to start from a stand in the wet on the 2%. Bulleid pacifics were so prone to slipping that they were usually banked on climbs with heavy trains, even though their power output suggested they should cope. In wet or icy conditions, or a poor loco, it was too big a risk to let them go solo. But we have seen that Tangmere could do it in good conditions!
Thanks, rick
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