Re: Steam Physics

[DarwinS]

Sorry too much copying and pasting here. There was never any intention to change the cylinder sizes on the Princess. No wonder I was consuming too much steam.

[systema]

Unfortunately it is correct that only a non-receiver compound is currently modeled. Maybe in the future this might change, however as they say, I would not hold my breath while waiting.

Is there one compound model that is representative of all British models?

The Midland and LMS 3 cylinder compounds are pretty essential for UK Simmers. This loco was in widespread use up to about the mid 50's and lingered into the early 60's. Every steam enthusiast in Britain knows about the Midland Compounds. So if only one new set of code was to be considered this would be it.

Mick Clarke
MEP

[systema]

Peter,

Regarding the new Physics fcalc page, I have studied this. I have also looked at the 5AT website many times on this topic and always end up confused. I do not find the various formulas on 5AT very helpful as they are all in different units and tend to generalise inputs such as a carriage or freight car with no reference to area or bearing types etc.

The worked Wardale example you have given for a 32UK ton carriage results in A = 350.695, B = 24.10235 and C = 0.772307.

Assuming 90 square feet for a UK carriage Fcalc Davis gives A=723, B=10.69, C=0.679. This is quite a bit different so I have no idea what's going on.

Please note Fcalc does not distinguish between roller and friction bearings for the Davis Calculation. Also the speed input in Fcalc.exe is irrelevant when calculating Davis. Any speed gives the same output. This is totally logical as the Davis uses speed to calculate the resistance at any given speed.

I am now going to try and get my head round Wardale's Locomotive formula and see how it compares.

Mick Clarke
MEP

[systema]

So I have had a look at Wardale's Locomotive resistance formula. This is even more confusing as it does not state what type of loco or what unit of speed the formula is based on. It is however already in Newtons.

Wardale states for a locomotive
R~ (45+0.24v+0.0036v^2)N/tonne

I think we have to assume its a steam loco otherwise A is far too high. For 100 tonne loco with 50% on the drivers, area 9.5m^2 and 6 axles
Fcalc gives, A=6314, B=32.9, C=5.46.

Wardale adjusting to weight of wagon
A=4500, B=24, C= 0.36
Assuming formula is for km/hr then to get m/s multiply B by 3.6 and C by 3.6x3.6.
A=4500, B= 86.4, C=4.66

Again this is quite a bit different!

Remaining very confused
Mick Clarke
MEP

[DarwinS]

Princess corrected. This is what I now have that seems to work (and hopefully will do for a King too!) It was certainly good for a heavy load - 500 tons - so will need also to try it for faster running with a lighter load now.

Comment ( *** Cylinders *** )
NumCylinders ( 4 )
CylinderStroke ( 28in )
CylinderDiameter ( 16.25in )
ORTSCylinderPortOpening ( 0.120 )
ORTSCylinderInitialPressureDrop( 0 0.98 50 0.91 100 0.85 150 0.80 200 0.74 250 0.73 300 0.72 350 0.72 )
SteamCylinderCocksOperation ( Manual )

It would certainly be nice to see the Smith-Wordsell compound system working, but I think we can be patient for that. (The Irish Compounds also used this system I believe.)

Yesterday I started playing with Jubilees. Strange that where the Princess is a little fast uphill and a little slow down that the model I have for Jubilees is the other way round (passing 90mph on 1 in 200 downhill with 300 tons but not climbing hills quite as well as I would like).

In this case the Engine (Cylinders) worked straight out of the box:

Comment ( *** Cylinders *** )
NumCylinders ( 3 )
CylinderStroke ( 26in )
CylinderDiameter ( 17in )
ORTSCylinderEfficiencyRate ( 1.0 )
SteamCylinderCocksOperation ( Manual )

As there were at least eight different 3A boiler designs fitted to the class then there is a need to check which boiler was with which loco at the time of any recorded performance. First some testing with this boiler gave a reasonably good performance:

Comment ( boiler and firebox represent sloping throatplate with 132 small and 21 large tubes )
Comment ( this boiler fitted to 39 locos @ July 1939 )

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( 383ft^3 )
ORTSEvaporationArea ( 1572ft^2 )
MaxBoilerPressure ( 225psi )
ORTSSuperheatArea ( 235ft^2 )
MaxSteamHeatingPressure ( 80psi )
ORTSBoilerEfficiency( 0.0 1.0 160 0.48 )
ORTSBoilerEvaporationRate ( 13.60 ) Comment ( Evaporation limited by draughting/exhaust )
SafetyValvePressureDifference( 5 )

Comment ( *** Fire *** )
ORTSGrateArea ( 31ft^2 )
ORTSFuelCalorific ( 13200btu/lb )
ORTSSteamFiremanMaxPossibleFiringRate( 3500lb/h )
SteamFiremanIsMechanicalStoker ( 0 )
ORTSBurnRate( 1000 8500 3000 18000 4000 24500 5000 25500 )

Most variations of the improved boilers seem to work reasonably well, though some more testing is in order. The other 'good' versions are listed at the bottom of this page, for anyone that wants to review them. Data from a loco that was sent to the test plant at Rugby informed some of the adjustments. The test results gave a maximum sustained output of 20760lb/h requiring 3324lb/hr of coal. (Although firebox and heating surface could evaporate more, the actual evaporation was limited by the original draughting and single chimney - not to mention how fast the fireman could shovel.) As the maximum evaporation figures in the HuD for different boilers were between 22000 and 26000 for various boilers, I used the ORTSBoilerEvaporationRate to limit this.

ORTSBoilerEvaporationRate = MaxEvaporation in HuD / Measured Max Evaporation * 15.0

The more interesting boiler was the original low superheat design. My ORTS model reads like this:

Comment ( boiler and firebox represent straight throatplate with 160 small and 14 large tubes )
Comment ( original Jubillee boiler 20 locos with this arrangement @ July 1938 )

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( 383ft^3 )
ORTSEvaporationArea ( 1625ft^2 )
MaxBoilerPressure ( 225psi )
ORTSSuperheatArea ( 228ft^2 )
MaxSteamHeatingPressure ( 80psi )
ORTSBoilerEfficiency( 0 1.0 160 0.3 )
ORTSBoilerEvaporationRate ( 13.60 ) Comment ( Evaporation limited by draughting/exhaust )
SafetyValvePressureDifference( 5 )

Comment ( *** Fire *** )
ORTSGrateArea ( 29.5ft^2 )
ORTSFuelCalorific ( 13200btu/lb )
ORTSSteamFiremanMaxPossibleFiringRate( 3500lb/h )
SteamFiremanIsMechanicalStoker ( 0 )
ORTSBurnRate( 1000 8000 3000 17000 4000 24000 5000 25000 )
Comment ( Low burn rate due to poor draughting )

Perhaps it proves that quality of the ORTS model that this boiler is something of a disaster in the simulator - much as it was in real life. However there were a few drivers who managed to get some very reasonable performances out of these. I am not sure if I can work out a way to reproduce them. Perhaps this boiler model needs more tweaking... Perhaps not, I am very pleased that it is relatively easy to model a poor design in ORTS, this was very difficult to achieve in MSTS.

For anyone interested the other 'good' boilers are:

Comment ( boiler and firebox represent straight throatplate with 130 small and 21 large tubes )
Comment ( 5 locos with this arrangement @ July 1938 including 5552 )

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( 378ft^3 )
ORTSEvaporationArea ( 1534ft^2 )
MaxBoilerPressure ( 225psi )
ORTSSuperheatArea ( 256ft^2 )
MaxSteamHeatingPressure ( 80psi )
ORTSBoilerEfficiency( 0 1.0 160 0.4 )
ORTSBoilerEvaporationRate ( 13.95 ) Comment ( Evaporation limited by draughting/exhaust )
SafetyValvePressureDifference( 5 )

Comment ( *** Fire *** )
ORTSGrateArea ( 29.5ft^2 )
ORTSFuelCalorific ( 13200btu/lb )
ORTSSteamFiremanMaxPossibleFiringRate( 3500lb/h )
SteamFiremanIsMechanicalStoker ( 0 )
ORTSBurnRate( 1000 8500 3000 18000 4000 24500 5000 25500 )


Comment ( boiler and firebox represent straight throatplate with 168 small and 21 large tubes )
Comment ( unique boiler fitted to 5607 @ July 1938 )

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( 366ft^3 )
ORTSEvaporationArea ( 1656ft^2 )
MaxBoilerPressure ( 225psi )
ORTSSuperheatArea ( 290ft^2 )
MaxSteamHeatingPressure ( 80psi )
ORTSBoilerEfficiency( 0 1.0 160 0.4 )
ORTSBoilerEvaporationRate ( 13.5 )
SafetyValvePressureDifference( 5 )

Comment ( *** Fire *** )
ORTSGrateArea ( 29.5ft^2 )
ORTSFuelCalorific ( 13200btu/lb )
ORTSSteamFiremanMaxPossibleFiringRate( 3500lb/h )
SteamFiremanIsMechanicalStoker ( 0 )
ORTSBurnRate( 1000 8500 3000 18000 4000 24500 5000 25500 )

Comment ( boiler and firebox represent straight throatplate with 159 small and 24 large tubes )
Comment ( fitted to 80 locos @ July 1938 - standard straight throatplate version )

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( 369ft^3 )
ORTSEvaporationArea ( 1730ft^2 )
MaxBoilerPressure ( 225psi )
ORTSSuperheatArea ( 331ft^2 )
MaxSteamHeatingPressure ( 80psi )
ORTSBoilerEfficiency( 0 1.0 160 0.4 )
ORTSBoilerEvaporationRate ( 11.97 ) Comment ( Evaporation limited by draughting/exhaust )
SafetyValvePressureDifference( 5 )

Comment ( *** Fire *** )
ORTSGrateArea ( 29.5ft^2 )
ORTSFuelCalorific ( 13200btu/lb )
ORTSSteamFiremanMaxPossibleFiringRate( 3500lb/h )
SteamFiremanIsMechanicalStoker ( 0 )
ORTSBurnRate( 1000 9000 3000 19000 4000 25000 5000 26000 )


Comment ( boiler and firebox represent sloping throatplate with 132 small and 24 large tubes )
Comment ( standard sloping throatplate boiler fitted to 44 locos @ July 1938 )

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( 382ft^3 )
ORTSEvaporationArea ( 1640ft^2 )
MaxBoilerPressure ( 225psi )
ORTSSuperheatArea ( 307ft^2 )
MaxSteamHeatingPressure ( 80psi )
ORTSBoilerEfficiency( 0.0 1.0 160 0.48 )
ORTSBoilerEvaporationRate ( 12.62 ) Comment ( Evaporation limited by draughting/exhaust )
SafetyValvePressureDifference( 5 )

Comment ( *** Fire *** )
ORTSGrateArea ( 31ft^2 )
ORTSFuelCalorific ( 13200btu/lb )
ORTSSteamFiremanMaxPossibleFiringRate( 3500lb/h )
SteamFiremanIsMechanicalStoker ( 0 )
ORTSBurnRate( 1000 9000 3000 19000 4000 25000 5000 26000 )


Comment ( boiler and firebox represent sloping throatplate with 105 small and 28 large tubes )
Comment ( unique boiler fitted to 5677 @ July 1938 )

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( 378ft^3 )
ORTSEvaporationArea ( 1651ft^2 )
MaxBoilerPressure ( 225psi )
ORTSSuperheatArea ( 312ft^2 )
MaxSteamHeatingPressure ( 80psi )
ORTSBoilerEfficiency( 0.0 1.0 160 0.46 )
ORTSBoilerEvaporationRate ( 12.53 ) Comment ( Evaporation limited by draughting/exhaust )
SafetyValvePressureDifference( 5 )

Comment ( *** Fire *** )
ORTSGrateArea ( 31ft^2 )
ORTSFuelCalorific ( 13200btu/lb )
ORTSSteamFiremanMaxPossibleFiringRate( 3500lb/h )
SteamFiremanIsMechanicalStoker ( 0 )
ORTSBurnRate( 1000 9000 3000 19000 4000 25000 5000 26000 )

Comment ( boiler and firebox represent sloping throatplate with 132 small and 24 large tubes )
Comment ( boiler fitted to 5731 with different superheater @ July 1938 )

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( 382ft^3 )
ORTSEvaporationArea ( 1640ft^2 )
MaxBoilerPressure ( 225psi )
ORTSSuperheatArea ( 357ft^2 )
MaxSteamHeatingPressure ( 80psi )
ORTSBoilerEfficiency( 0.0 1.0 160 0.48 )
ORTSBoilerEvaporationRate ( 12.62 ) Comment ( Evaporation limited by draughting/exhaust )
SafetyValvePressureDifference( 5 )

Comment ( *** Fire *** )
ORTSGrateArea ( 31ft^2 )
ORTSFuelCalorific ( 13200btu/lb )
ORTSSteamFiremanMaxPossibleFiringRate( 3500lb/h )
SteamFiremanIsMechanicalStoker ( 0 )
ORTSBurnRate( 1000 9000 3000 19000 4000 25000 5000 26000 )

[DarwinS]

Is there one compound model that is representative of all British models?

There is not. But there is one compound model that will keep most UK train simmers happy - the Smith-Wordsell model. This was first tried on the North Eastern Railway in the early 20th century but not widely used. It was then adopted by the Midland Railway. On the first locos there were two regulators to allow starting as a simple locomotive before later working as a compound, and separate valve gear and cut off settings for high pressure and low pressure cylinders. This was later simplified to have just one cut off setting and one regulator. Drivers were supposed to open the regulator only to the first setting when starting - in this position the regulator admitted steam to the two low pressure cylinders and the loco starter as a two cylinder simple. When on the move the regulator could then be fully opened and steam would be admitted directly only to the high pressure cylinder. (I am not sure if the reverse process happened on closing the regulator, but suspect that it remained in compound working until the regulator was fully closed... Midland and LMS regulators were a bit strange in that worked differently on opening and closing.) In the 1920s the LMS built many more Compounds more or less to the Midland design. These remained in service until the 1950s.

The Great Northern Railway (Ireland) compounds were I believe on the same system. (Can anyone confirm this?)

Apart from that very many compounds were tried in the UK, particularly in the 19th century on the LNWR designed by Webb. However most of these can be described as any or all of not successful, not numerous and not long lived. So I doubt if any trainsimmer will be in a hurry to use any other compound system for a British locomotive.

France is another matter with Andre Chapelon's masterpieces.... but we had best save that for another day.

[systema]

I have now looked at the CTN resistance set page. Since it doesn't go into detail on calculating Davis figures it is relatively straight forward and appears OK to me. Here is an example of my LMS Carriage Resistance figures.

ORTSBearingType ( Roller )

Comment( Assumptions for FCalc - Standard Roller, 4 axles, frontal area - 8.3m2, Wagon Weight - 33.51 ton (metric))
ORTSDavis_A ( 729.55 )
ORTSDavis_B ( 11.0265 )
ORTSDavis_C ( 0.678562 )

Comment(Curve Resistance and SuperElevation)
CentreOfGravity ( 0m 1.9m 0m )
ORTSTrackGauge ( 4ft 8.5in )
ORTSRigidWheelbase ( 0ft 56in ) ORTSUnbalancedSuperelevation ( 6in )

I do have one question though. Since Fcalc outputs the same for friction and roller bearings for a carriage does it make any difference what ORTSBearingType ( Roller, Friction or Low ) is defined?

Mick Clarke
MEP

[csantucci]

I have checked in the OR code.
The three types of bearing are used to determine the StartFriction under snow and in normal weather conditions. "Low" has the lowest value, "Roller" has an intermediate value and "Friction" has the highest value.

[systema]

The Train Resistance page might be improved by the following. The original resistance as lbs per ton is more difficult to understand than the straightforward statement of resistance as R= Coeff A+Coeff B x W (tons) x V + Coeff C x AREA x V^2

The Table should be designated for Friction Bearings and contain the following information

Wagon Type/Coefficent A/Coefficent B/CoefficientC/Frontal Area
UK Steam Loco/1.3 X W (tons)+29 x N (number of axles)/0.03 x W/0.0024 X Frontal Area/97 sq ft
UK Passenger Car/1.3 X W (tons)+29 x N (number of axles)/0.03 x W/0.00034 X Frontal Area/90 sq ft

etc etc

For steam locos an addional factor of 20 x Weight on Driver in tons must be added to allow for internal running gear friction.
This could be modifed slightly down for modern Steam locos or maybe even Atlatics with only 4 driving wheels. This would have to be calculated outside of Fcalc.

Ideally Frontal Areas should be estimated for each item of stock

Similar tables should be included for Roller Bearings and Low Torque Bearings.

It should then be clearly stated that Coefficients produced in imperial units need to be modified to metric as per the resistance set page or better still just use Fcalc to output in metric units.

A simple spread sheet could be produced to allow input from UK tons or US tons to convert to metric tons and square feet to square meters.

Regarding the typical Rigid Wheel Base values, I don't understand how typical values from the table are supposed to be inputted into the wagon file. This is not explained.

I hope this all makes sense.

Mick Clarke
MEP

[systema]

I have checked in the OR code.
The three types of bearing are used to determine the StartFriction under snow and in normal weather conditions. "Low" has the lowest value, "Roller" has an intermediate value and "Friction" has the highest value.

So the OR bearing type is only relevant for starting conditions in different weather and the Resistance is only derived from the Davis Coefficients?

Mick Clarke
MEP

[steamer1960]

Regarding the new Physics fcalc page, I have studied this. I have also looked at the 5AT website many times on this topic and always end up confused. I do not find the various formulas on 5AT very helpful as they are all in different units and tend to generalise inputs such as a carriage or freight car with no reference to area or bearing types etc.

Most of these curves were determined by test results, and then a best fit quadratic curve applied. Thus the ABC values are not always related to area, bearing types, etc. (except for the specific train being tested). So unless a specific curve is published for a specific piece of railway stock, I would suggest sticking to the Davis equations, as they seemed to be used in most recent research documents that I have seen, and are still considered valid. This approach would tend to simplify the calculation effort, and "head banging" required to understand the curves.

Please note Fcalc does not distinguish between roller and friction bearings for the Davis Calculation.

Some of the wagon types do have differences between friction and roller bearings (eg Standard Freight Car). Have a look at the accompanying word document for FCalc (Methodology and Theory of FCalc 2) to get an explanation of the rational for the formulas used.

So I have had a look at Wardale's Locomotive resistance formula. This is even more confusing as it does not state what type of loco or what unit of speed the formula is based on. It is however already in Newtons.

Have a look at the links relating to the formula. The design notes referenced (FDC1.1) have a more detaile description of how they have been applied in the 5AT project (lines 24 -30).

Princess corrected. This is what I now have that seems to work (and hopefully will do for a King too!) It was certainly good for a heavy load - 500 tons - so will need also to try it for faster running with a lighter load now.

Thanks for the feedback.

There is not. But there is one compound model that will keep most UK train simmers happy - the Smith-Wordsell model.

Again thanks for the feedback. Do you have a TE formula for this type of locomotive?

The Train Resistance page might be improved by the following. The original resistance as lbs per ton is more difficult to understand than the straightforward statement of resistance as R= Coeff A+Coeff B x W (tons) x V + Coeff C x AREA x V^2

Thanks for the feedback.

I will look at it, and consider the comments that you have suggested (though some I don't quite understand at the moment).

So the OR bearing type is only relevant for starting conditions in different weather and the Resistance is only derived from the Davis Coefficients?

The resistance is calculated in two sections as follows:
0 to approx 5 mph - Starting Resistance Determined by OR Bearing type
5 to ? - Running resistance, as determined by Davis formula, and ABC values entered.

Overall Conclusion: At this stage, I am not convinced that the effort involved in tweaking the Davis formula away from the values provided by FCalc is going produced any better performance results. Unless somebody has a passion to research and investigate alternative Davis equations, I think that the easiest and most consistent approach is to stick with the FCalc values. So hopefully the setting guidelines discussed so far, will provide an easy and accurate configuration.

I will also look at creating a spread sheet to allow easier comparison of curves.

Thanks

[steamer1960]

Princess corrected. This is what I now have that seems to work (and hopefully will do for a King too!) It was certainly good for a heavy load - 500 tons - so will need also to try it for faster running with a lighter load now.

Comment ( *** Cylinders *** )
NumCylinders ( 4 )
CylinderStroke ( 28in )
CylinderDiameter ( 16.25in )
ORTSCylinderPortOpening ( 0.120 )
ORTSCylinderInitialPressureDrop( 0 0.98 50 0.91 100 0.85 150 0.80 200 0.74 250 0.73 300 0.72 350 0.72 )
SteamCylinderCocksOperation ( Manual )

Just out of interest, are you using the Simple model rather then the Compound model to simulate the operation of this locomotive?

If it was a compound locomotive, then it should have the LPCylinders details included.

Thanks

[steamer1960]

The Train Resistance page might be improved by the following. The original resistance as lbs per ton is more difficult to understand than the straightforward statement of resistance as R= Coeff A+Coeff B x W (tons) x V + Coeff C x AREA x V^2

...... SNIP ..............

I think that I have captured the essence of your suggestions.

Thanks for the comments.

A simple spread sheet could be produced to allow input from UK tons or US tons to convert to metric tons and square feet to square meters.

I have added a spreadsheet on the resistance calculation page to allow users to compare different curves to see the differences between them.

{EDIT: Out of interest you may wish to compare the Koffman equation and the relevant Davis equations with it to see how they vary across the speed range}.

In regard to the conversion of imperial to metric units, what did you have in mind?

I already have a Units Conversion (http://ctn.local/physics/conversions/) page. Is this what you were suggesting?

Thanks

[DarwinS]

@steamer1960

The Princess was a simple. (For the compound that I have modelled as a simple, MR/LMS compound, I will give you what information I can find today, but will probably need to wait about 2 weeks until I have time to get into the library/archive at the National Railway Museum or perhaps even the MR archive in Derby, to get any additional technical details. Tractive effort is interesting, as these engines started from rest as 2-cylinder simple locos it looks like the published tractive effort is calculated on that basis.)

MR 4-4-0 Driving wheels 7ft 0in Cylinders 1HP 19in x 26in 2 LP 21in x 26in Boiler pressure 200 psi Published TE: 21840lb
[original locos 195psi, later ones built as 220psi, subsequently all 200psi]
(all built as saturated and later superheated)

LMS 4-4-0 Driving wheels 6ft 9in Cylinders 1HP 19in x 26in 2 LP 21in x 26in Boiler pressure 200 psi Published TE: 22649lb
(The first batch of these were built with Cylinders 19.75in x 26in and 21.75in x 26in, but these were later reduced to the standard size.)

Apparently there are some indicator diagrams for the first locos published in "Engineering" in 1903 (which may be possible to find) - what I am reading says cut offs of 55 to 65 percent used and power output up to 965ihp. Grate area on these was 26sqft at that time, but they were rebuilt to match later locos with 28.4sqft grate area. The original locos at first had an 8.75in piston valve to feed the HP cylinder (subsequently all had 10in piston valves). Steam from the HP cylinder was fed to the LP cylinders via slide valves.

The original examples were built with two sets of reversing gear and two regulators, but later rebuilt identical to the others with one set of reversing gear and one regulator. A note here on the regulator says that when opening, during the first quarter steam from the boiler was admitted directly to both HP steam chests and LP steam chests, with auxilliary pipes delivering steam to both sides of the HP piston so that it did not do any work and the loco started as a two cylinder simple. Further movement of the regulator admitted steam only to the HP steam chest and cut off the supply to the LP steam chest and auxilliary pipes so that the loco worked as a compound. (The two LP cylinder cranks were set at 90 degrees the same as a simple and the HP crank was set at 135 degrees to these.)

Now that I have the friction parameters correct my model does work as a compound with the correct parameters (need to test more):

Comment ( *** Cylinders *** )
NumCylinders ( 1 )
CylinderStroke ( 26in )
CylinderDiameter ( 19in )
LPNumCylinders ( 2 )
LPCylinderStroke ( 26in )
LPCylinderDiameter ( 21in )
SteamCylinderCocksOperation ( Manual )

The version I had working as a simple used:

Comment ( *** Cylinders *** )
NumCylinders ( 2 )
CylinderStroke ( 26in )
CylinderDiameter ( 19in )
ORTSCylinderInitialPressureDrop( 0 0.96 50 0.77 100 0.68 150 0.67 200 0.66 250 0.62 300 0.54 350 0.39 )
SteamCylinderCocksOperation ( Manual )

Which seemed to achieve a satisfactory performance also.

To be prototypical the loco would need to start as:

ORTSSteamLocomotiveType ( Simple )

NumCylinders ( 2 )
CylinderStroke ( 26in )
CylinderDiameter ( 21in )
SteamCylinderCocksOperation ( Manual )

including cylinder cocks operating which does not function on present ORTS compound

...and then after the first quadrant of the regulator change to behave as:

ORTSSteamLocomotiveType ( Compound )

NumCylinders ( 1 )
CylinderStroke ( 26in )
CylinderDiameter ( 19in )
LPNumCylinders ( 2 )
LPCylinderStroke ( 26in )
LPCylinderDiameter ( 21in )
SteamCylinderCocksOperation ( Manual )

That sounds quite challenging

Incidentally the Irish Compounds did work on the same system. Data from Wikipedia

4-4-0 Driving wheels 6ft 7in Cylinders 1HP 17.5in x 26in 2 LP 19in x 26in Boiler pressure 250 psi TE: 23762lb

[systema]

I already have a Units Conversion (http://ctn.local/physics/conversions/) page. Is this what you were suggesting?

My idea is to have a spreadsheet similar to those in FCalc but modified to allow input in Imperial units for Weight, Weight on drivers where applicable and Frontal Area in Square feet. This would show the relevant conversion to US tons and Metric Tons plus Square meters. The calculated Davis Coefficients in both US units and Metric Units would be shown.

This would ensure error free calculations for UK stock which for anything up to British Rail would all be detailed in imperial units. It would also facilitate making metric entries into the eng and wag files for the other relevant parameters.

Hope this is clearer.

Mick Clarke
MEP