[steamer_ctn]

Unfortunately due to conflicts created by another PR I have withdrawn the Duplex Steam engine feature from the Unstable version.

I will attempt a rebuild of the PR and reintroduce it when I have some time.

[darwins]

Traindude, on 08 July 2023 - 06:15 PM, said:

I think it would be a better time than ever for me to share my ideas for implementing articulation into the "multiple steam engines on one locomotive" functionality. Please let me know what you guys think!

An excellent paper. The ideas for including lights, special effects and freight anims with the different sections are essential. (Some might also apply to some old time articulated diesel and electric locos!)
I hope the coders find a way to make these work.

Interestingly up until now we have only been allowed one ORTSFreightAnims ( ) block in one eng file - the possibility of more than one block might allow separation of things that belong to a loco (change in mass etc) from things that can change (removable lamps).

[Traindude]

darwins, on 10 July 2023 - 09:34 PM, said:

An excellent paper. The ideas for including lights, special effects and freight anims with the different sections are essential. (Some might also apply to some old time articulated diesel and electric locos!)
I hope the coders find a way to make these work.

Interestingly up until now we have only been allowed one ORTSFreightAnims ( ) block in one eng file - the possibility of more than one block might allow separation of things that belong to a loco (change in mass etc) from things that can change (removable lamps).

Thank you darwins! You're right, there are articulated diesel and electric locomotives that have a combination of driving and idler wheels (before "power trucks" became a thing--the Milwaukee Road's old Boxcab locomotives on the electrified sections of the Pacific Extension come to mind).

I think once we get it working for steam locomotives, then the articulation parameters can be easily adapted to diesel and electric locomotives as well. Cesarbl's recent discussion on grouping wheels for independent wheelslip (see page 7 of the thread) seems to be a step in the right direction. I'm still unsure as to whether the lights, FX, and freight animation information should stay where they currently are within an *.eng file or be included in the ORTSSteamEngines groupings. I'm hoping the coders can use my proposal as a jumping-off point, though...

[Jonatan]

I don't know what all this means but I'll recite the old saying: "they were too busy with the question wether they could, to ask the question wether they should".

It sounds nice, but every new feature or redesign of systems has to be implemented in such a way it won't require rewriting the thousands of existing .engs and .wags we have in our collections.

[Traindude]

Jonatan, on 13 July 2023 - 12:41 PM, said:

I don't know what all this means but I'll recite the old saying: "they were too busy with the question wether they could, to ask the question wether they should".

It sounds nice, but every new feature or redesign of systems has to be implemented in such a way it won't require rewriting the thousands of existing .engs and .wags we have in our collections.

FYI, darwins and I were talking about my proposal for adding new parameters to add articulation to the whole "multiple engines on one locomotive" concept--so no more two-plus-piece models for one locomotive! (See page 8 of this thread for a *.pdf download of my proposal.)

Believe me, I agree that the addition of new features does have the inconvenience of having to edit and re-edit all of our *.eng and *.wag files, but if we're moving toward more realism and doing away with the constraints of MSTS, it's well worth the effort in the long run!

[steamer_ctn]

steamer_ctn, on 09 July 2023 - 06:49 PM, said:

Unfortunately due to conflicts created by another PR I have withdrawn the Duplex Steam engine feature from the Unstable version.

I will attempt a rebuild of the PR and reintroduce it when I have some time.

I have now attempted to re-introduce this feature into the latest Unstable version. It should appear shortly.

There has been significant changes to the code, so if you identify any steam locomotive features that used to work, and now don't please let me know. If you can reference any issues against a CTN locomotive, this will enable me to experience the same issue that you are reporting.

Thanks

[Laci1959]

Hello.

I'm trying to apply the characteristics of Peter's PRR_T1_6111 steam locomotive with the correct proportioning to a simple small locomotive.
I got stuck at the Weight ( ) line. My question is what mass is this.
1. The mass of a railway bicycle (ie an axle with two wheels pressed on it)?
2 The mass of a railway bicycle (i.e. an axle with two wheels pressed onto it), plus the corresponding part of the mass of the connecting rod (RODxA, RODxD)? To me, this seems the most logical because the NumberWheelsetAxles ( ) line is below it, and only a simple multiplication is required.
3. The total mass of the elements listed in the AnimatedParts ( ) line?
Current code:

	ORTSAdhesion (
		Wheelset (
			ORTSCurtius_Kniffler ( 7.5 44 0.17 0.7 )
			Axle (
				ORTSInertia ( 2342 )
				ORTSRadius ( 0.375m )
				AnimatedParts ( "WHEELS1, WHEELS2, WHEELS3, Rod01, Rod02,  Rod11, Rod12,  Rod21, Rod22, WHEELS4" )
				NumberWheelsetAxles ( 4 )
				Weight ( Xkg )
			)
		)
	)

Does OR recognize metric units (kilograms or tons) in this line?

Sincerely, Laci1959

[darwins]

For a steam locomotive the weight is the adhesive weight on an axle or group of coupled driving axles. So neither 1 or 2 or 3, but rather the total adhesive mass on that engine. OR should recognise kg or t in that line. For a locomotive with only one engine the equivalent is ORTSDriveWheelWeight ( x ) but for a locomotive with more than one engine you use Axle ( Weight ( x ) ) for each engine.

[Laci1959]

darwins, on 22 April 2024 - 10:29 AM, said:

For a steam locomotive the weight is the adhesive weight on an axle or group of coupled driving axles. So neither 1 or 2 or 3, but rather the total adhesive mass on that engine. OR should recognise kg or t in that line. For a locomotive with only one engine the equivalent is ORTSDriveWheelWeight ( x ) but for a locomotive with more than one engine you use Axle ( Weight ( x ) ) for each engine.

https://kephost.net/p/MTE5NTc5Ng.png

Just to make sure. Are the parts marked in the picture?
IF the wheel is solid, then its total mass?

[darwins]

That locomotive has only one engine. You should not use

       ORTSAdhesion (
                Wheelset (
                        Axle (
                                Weight ( Xkg )
                        )

Just use ORTSDriveWheelWeight ( x ) in the eng section.

[Laci1959]

darwins, on 22 April 2024 - 11:24 AM, said:

That locomotive has only one engine. You should not use

That's for sure?
Then the devil took it away. It's a waste.
It would have been good because the rotation of the two front wheels is unrealistic when slipping. I thought this was a solution to a ten-year-old problem.

[darwins]

https://i.imgur.com/9Rjssyn.jpeg

For this loco with only one engine 22.0 + 22.0 + 22.0 = 66.0 so we use

  ORTSDriveWheelWeight ( 66.0t-uk )

https://i.imgur.com/Tj06T98.jpeg

For this loco for the front engine 20.0 + 20.0 + 19.95 = 59.95 and for the rear engine 20.65 + 21.0 + 21.0 = 62.65 so we use

ORTSAdhesion (
  Wheelset (
 	Axle (
  	Weight ( 59.95t-uk )
      	)
 	Axle (
  	Weight ( 62.65t-uk )
      	) ) )

[Traindude]

I touched on this a while back in a private convo with some of the big steam guys on this forum, but I think that it would be beneficial to map any steam exhaust emissions and sounds (pulse-based) to the crankpin position.

Here's what the exhaust pattern for a two- or four-cylinder (non-articulated/non-duplex) locomotive looks like...:


NOTE: The numbers on the driving wheel are to help people locate the crankpin positions by imagining the face of the wheel as a clock face. Sometimes it's more helpful than "Forward Dead Center", "Top Quarter", etc.

It could be possible to map the exhaust emissions and sound to the crankpins if the shape file's animation keyframes on which each crankpin hits a "dead center" is known. (For pre-existing models, you may have to uncompress the shape file to find this information.) Here's how it can potentially be coded into an *.eng file (two-cylinder with 16 driving wheel keyframes assumed):

ORTSWheelCrankAngleDifference ( 0deg 90deg )
ORTSWheelCrankDeadCenterKeyFrames(
Comment ( *** Left Cylinder *** ) 
    Cylinder1 ( 
        Forward ( 0 ) 
        Back ( 8 )
    )
Comment ( *** Right Cylinder *** ) 
    Cylinder2 (
        Forward ( 4 )  
        Back ( 12 )
    ) 
)

Here's what a four-cylinder locomotive (GWR Castle, Balanced Compound, etc.) would be coded (again, assuming there are 16 driving wheel keyframes total):

ORTSWheelCrankAngleDifference ( 0deg 180deg 270deg 90deg )
ORTSWheelCrankDeadCenterKeyFrames(
Comment ( *** Left Outer Cylinder *** ) 
    Cylinder1 ( 
        Forward ( 0 ) 
        Back ( 8 )
    )
Comment ( *** Left Inner Cylinder *** ) 
    Cylinder2 ( 
        Forward ( 8 ) 
        Back ( 0 )
    )
Comment ( *** Right Inner Cylinder *** ) 
    Cylinder3 (
        Forward ( 12 )  
        Back ( 4 )
    ) 
Comment ( *** Right Outer Cylinder *** ) 
    Cylinder4 (
        Forward ( 4 )  
        Back ( 12 )
    ) 
)

For 3-cylinder locomotives (Flying Scotsman, Union Pacific 9000), the exhaust pattern would look like this:


Even though there are 6 puffs/chuffs per driving wheel rotation, the driving wheel animation is still divided into 8 or 16 keyframes. Since 4 is not divisible by 3, it becomes necessary to specify non-integer values for the dead center keyframes (again, 16 keyframes assumed):

ORTSWheelCrankAngleDifference ( 0deg 120deg 240deg )
ORTSWheelCrankDeadCenterKeyFrames(
Comment ( *** Left Cylinder *** ) 
    Cylinder1 ( 
        Forward ( 0 ) 
        Back ( 8 )
    )
Comment ( *** Center Cylinder *** ) 
    Cylinder2 ( 
        Forward ( 2.667 ) 
        Back ( 10.667 )
    )
Comment ( *** Right Cylinder *** ) 
    Cylinder3 (
        Forward ( 5.33 )  
        Back ( 13.33 )
    ) 
)

In the case of articulated (Big Boy, Challenger, etc.) or divided-drive (PRR T1, Q2, etc.) locomotives, these parameters would fall within each ORTSSteamEngines grouping (one-piece model with 16 keyframes assumed):

ORTSSteamEngines ( 2
        Steam (
                Comment ( Front Steam Engine )
                NumCylinders ( 2 )
                CylinderStroke ( 32.0in )
                CylinderDiameter ( 23.0in )
                AttachedAxle( 0 )
                ExcessRodBalance ( 100lb )
                ORTSWheelCrankAngleDifference ( 0deg 90deg )
                ORTSWheelCrankDeadCenterKeyFrames(
                Comment ( *** Left Cylinder *** ) 
                    Cylinder1 ( 
                        Forward ( 0 ) 
                        Back ( 8 )
                     )
                Comment ( *** Right Cylinder *** ) 
                    Cylinder2 (
                        Forward ( 4 )  
                        Back ( 12 )
                    ) 
                )
              )
        Steam (
                Comment ( Rear Steam Engine )
                NumCylinders ( 2 )
                CylinderStroke ( 32.0in )
                CylinderDiameter ( 23.0in )
                AttachedAxle( 1 )
                ExcessRodBalance ( 100lb )
                ORTSWheelCrankAngleDifference ( 0deg 90deg )
                ORTSWheelCrankDeadCenterKeyFrames(
                Comment ( *** Left Cylinder *** ) 
                    Cylinder1 ( 
                        Forward ( 0 ) 
                        Back ( 8 )
                     )
                Comment ( *** Right Cylinder *** ) 
                    Cylinder2 (
                        Forward ( 4 )  
                        Back ( 12 )
                    ) 
                )
               )                
    )

For geared locomotives (Heisler, Shay, Climax), the gear reduction complicates the calculation of the dead centers, as these dead centers would be located relative to the crankshaft instead of the wheels, even though the wheels are animated "conventionally."

[pschlik]

Our local simulated hyacinth macaw's latest Derail Valley video covered a mod which changes the steam loco's throttle/steam chest behavior to what the steam expert considers significantly more accurate. Instead of the throttle setting a target pressure for the steam chest, the throttle controls the flow rate into the steam chest, which will eventually achieve boiler pressure regardless of how little the throttle is opened (assuming no steam is consumed). This changes the driving methodology as at low speeds the throttle cannot control tractive effort directly. In fact, most throttle settings will get the steam chest right up to full pressure unless the cylinder cocks are open to let steam out. Closing the throttle doesn't immediately reduce the steam chest pressure as the steam in there sticks around until it's consumed by the cylinders. At low speeds, most of the throttle is a deadzone where applying more throttle doesn't actually give more steam, but at high speeds the entire throttle is useful. Because the throttle controls flow rate, the average chest pressure at a given throttle and speed will depend on steam outflow, so lower cutoff settings give higher chest pressure as steam will be consumed slower. Lots of interesting stuff, more involved than "50% throttle = 50% chest pressure".

However, this can be compared to Open Rails, which is still using the old MSTS-level understanding (one of many many things MSTS got wrong that leeched into the 'common sense' of simmers despite being utterly wrong) of the throttle that the throttle directly sets the chest pressure instantly. It would be interesting for OR to simulate the more accurate, but more challenging, behavior. This would require some estimation though (how much steam flow does the throttle allow? what's the effective volume of the steam chest? if the locomotive is superheated, is the throttle before or after the superheater?) as I doubt every detail of the throttle response is well documented. Still, I'd like to see it done.

[Traindude]

pschlik, on 24 May 2024 - 06:58 PM, said:

Our local simulated hyacinth macaw's latest Derail Valley video covered a mod which changes the steam loco's throttle/steam chest behavior to what the steam expert considers significantly more accurate. Instead of the throttle setting a target pressure for the steam chest, the throttle controls the flow rate into the steam chest, which will eventually achieve boiler pressure regardless of how little the throttle is opened (assuming no steam is consumed). This changes the driving methodology as at low speeds the throttle cannot control tractive effort directly. In fact, most throttle settings will get the steam chest right up to full pressure unless the cylinder cocks are open to let steam out. Closing the throttle doesn't immediately reduce the steam chest pressure as the steam in there sticks around until it's consumed by the cylinders. At low speeds, most of the throttle is a deadzone where applying more throttle doesn't actually give more steam, but at high speeds the entire throttle is useful. Because the throttle controls flow rate, the average chest pressure at a given throttle and speed will depend on steam outflow, so lower cutoff settings give higher chest pressure as steam will be consumed slower. Lots of interesting stuff, more involved than "50% throttle = 50% chest pressure".

However, this can be compared to Open Rails, which is still using the old MSTS-level understanding (one of many many things MSTS got wrong that leeched into the 'common sense' of simmers despite being utterly wrong) of the throttle that the throttle directly sets the chest pressure instantly. It would be interesting for OR to simulate the more accurate, but more challenging, behavior. This would require some estimation though (how much steam flow does the throttle allow? what's the effective volume of the steam chest? if the locomotive is superheated, is the throttle before or after the superheater?) as I doubt every detail of the throttle response is well documented. Still, I'd like to see it done.

I totally agree, and I've previously discussed this possibility of adding throttle response lag a few years ago.

Also, keep in mind that in the case of compound locomotives, any changes made to the throttle settings won't be reflected at the low-pressure cylinders until the driving wheels turn far enough to let the high-pressure cylinders exhaust some.