[Lindsayts]

A small problem of OR's rapid development is the sims reading an interpretation of the ENG files. I wish to ask a number of questions on the way OR handles this.

The following is some extracts of a locos ENG file, this particular loco's behaviour has changed signifcantly in V0.7 and I am trying to correct the situation.

The following values are just put in for show, they do not indicate any kind of problem except how to specify the unit required.

BoilerVolume ( "365*(ft^3)" )

CylinderVolume ( "5.85*(ft^3)" )

If a Voumne is specfied just in a plain number what units does OR assume them to be. the above are in cubic ft if one was
say CylinderVolumne ( "0.75" ) what would this be interpreted as?

On braking, what in steam locos is used for the air compressor power and what units is assumed?
Also for the AirBrakesMainResVolumne what is the units assumed. The extract below is from the SAR 500 class loco, the brakes work OK in V0.62 but not in V0.7 the problem being in the latter version it behaves as the MainRes Value is to low. If one raises it to 20 it fixes the problem. Measuring up some main resviours on real locos gives an aprox size of around 20 cubic ft roughly 0.6 cubic metre. This value needs to be compatiable to the hauled rolling stocks resvior volumne.

AirBrakesAirCompressorPowerRating( 2 )
AirBrakesMainMinResAirPressure( 0 )
AirBrakesMainMaxAirPressure( 110 )
AirBrakesMainResVolume( 2 )
AirBrakesAirCompressorWattage( 19000 )
AirBrakesCompressorRestartPressure( 107 )
AirBrakesAirUsedPerPoundsOfBrakePipePressure( 1 )
AirBrakesHasLowPressureTest( 0 )
AirBrakesIsCompressorElectricOrMechanical( 1 )

Would it also be possible to give at table of the way OR would require a suffix for the various different units to be writen in the ENG file so NO ONE has to assume anything (Note 1). It appears for instance if one puts "DieselUsedPerHourAtMaxPower ( 400L )" in a Diesel loco OR correctly sees that as Litres, this greatly reduces the chance of confusion. This being a real problem in the ENG files.

Note 1: Assumptions in any enginneering work is one of THE greatest causes of problems in THE history of mankind.

Lindsay

[longiron]

Lindsay,
Excellent points. If you have specific MSTS parameters that you would like clarification about the OR "assumed" units, I'd be happy to double check. Open Rails is not going to take on untangling the mess, as you point out, that is the MSTS engine file. We will try to do our best to decipher the commonly used units. We have a different direction to avoid this problem in the future.

[Lindsayts]

I am RRRRRRRRRREEEEEEEEEAAAAAAAAALLLLLLLLL glad that OR is taking a differnt direction here, I must say I am getting really disheartend with the ENG file mess. What I have found so far is with OR one needs most/all of the values to be as close to the real item as possible. This usually gives the most accurate performance. While OR has in my opinion quite some way to go it is currently way ahead of MSTS.

The current problem is NOT how MSTS views the values but how OR views/uses them. The are three values and a question. the question being what in the eng file does OR use for the compressor power rating for a steam loco or does it assume a power, from memory Westinghouse usualy rated there steam compressors in Cubic ft/min, this being the units used in the second parameter below. There are two values in the eng file it could use.......

AirBrakesAirCompressorWattage
AirBrakesAirCompressorPowerRating

It is not clear from testing which if any of these the sim uses.

The Values I would like to know the OR's units if NO suffix is present are ...........

CylinderVolume
AirBrakesMainResVolume
AuxilaryResCapacity (wag file value)


The reason for this is so I KNOW that OR is NOT interpreting the data different to what I am interpreting it as.
I have found some eng files and most wagon files do NOT specify a suffix just a number, this is clearly causing a problem in this release.
In the current situation V0.7 appears to be treating the MainResVolume different to the wagons AuxilaryResCapacity. In both cases no units are specified, In V0.62 it worked OK. I was just wondering what would happen if i specfied the units as this has certainly worked in other cases.

Hmmmmmmmmmmmmmmmmmmm, discussing a problem always helps in trying to find a way forward, just thought of a few more things I can try.
This is MSTS's way of expressing Cubic ft is ( "365*(ft^3)" ) I assume OR would interpret ( "10.34*(M^3)" ) as the same value, 365 cubic ft equaling 10.34 cubic metres. Is this the correct syntax.


Lindsay

[Lindsayts]

On the Westinghouse cross compound compressor ratings, The 1925 edition of the "Locomotive Cyclopedia" states there are two versioms of the 8 1/2 inch compressor, The 150 and the 120, it states the 150 was capable of 150 cubic ft at 200 psi steam pressure and the 120 was 120 cubic ft at 160 psi. It does not give the time period but calculations taking in the air cylinder dimensions and the stroke rate show these figures are cubic ft per minute.

On a slightly different topic I consider a great weakness in the current OR steam "physics" is the lack of "CylinderEffectivity" Currently in OR there is aparently no way to specify the effect of the differences in design and construction of the valve gear and cylinders, Specifying only the cylinder dimensions is not enough. If the "CylinderEffectivty" was effective OR could do a great deal more work on the steam locomotive simulation and not get a great deal more of an improvement in the locomotive peformance. MSTS's great weakness in its steam simulation is the lack of varation in the cylinder effiecency with varyingg cuttoff. It essentially can only be set up for one cuttoff, even so I have found one can get quite accurate performance for a given class of operation, say for instance fast express's. This weakness has been addresssed in OR but without the abilty to vary the effect, this being OR's current weakness.

Lindsay

[longiron]

Lindsayts, on 16 December 2011 - 10:54 AM, said:

I consider a great weakness in the current OR steam "physics" is the lack of "CylinderEffectivity"
Lindsay

Unfortunately, the OR team didn't have time to redo the steam physics as we'd hoped for in v0.7. When done this is set of independant OR steam locomotive configuration parameters you'll be using to set up your physics! Note that UNITS are defined in the parameter name, so there's no confusion.


And thanks for the prototype info, it's always valuable.

[Lindsayts]

Many thanks for the reply "longiron" it was most helpfull. One of the eng files great weakness's was having to specfy powers and forces. To get such information to any great accuracy even for most diesels is no picnick and was largely impossible for nearly all steam locos. From the look of things the new "physics" setup for OR will be something to look forward to.

As you are likely to be aware by now I have a major bee in my bonnet about locomotive peformance at all levels, both power and braking. For all versions of OR will do what I can to get the most accurate performance (as indicated by the performance data I have collected) I can out of the system and will provide feedback in the hope it may be usefull.

Lindsay

[captain_bazza]

I second Lindsay's call for a CylinderEffectivity parameter.

For the reasons he states and also it allows us to factor in a knacked locomotive (steam leaking, etc).

Cheers Bazza