[steamer_ctn]

 scottb613, on 23 January 2021 - 05:17 AM, said:

My own preference would be for the ORTS steam code to provide more tunable variables - more of the MSTS approach - providing greater flexibility - and putting proper performance back on the shoulders of the modeler.

I don't want to return to the MSTS days where a lot of cutting and pasting was done in ENG files, and the end result was that we sometimes had very inconsistent physics performances in MSTS. Part of the challenge is that detailed information is not always easily obtainable.

So the balance that I have worked to is to make parameters "visible" where it is likely that good detailed information broadly exists, and /or the parameters will have a significant impact on the performance of the locomotive. So in short I am open to making more parameters visible, but don't give me a list now, and expect it to happen. Instead they will be added, as appropriate, when different areas are investigated and possibly coded.

 darwins, on 23 January 2021 - 03:33 AM, said:

What I am noticing here is that having a good AI fireman actually depends a lot on having a good model of manual firing. So if we want to improve the AI fireman, I think we need to start by reconvening the now defunct "manual firing" sub-group.

I don't think that it as simple as saying that we just need to get manual firing working and then AI firing falls in place on top of it.

The steam locomotive is a "heat engine", ie it burns coal to generate heat energy which is then converted to mechanical energy by using the resulting steam. So the heat in the boiler is the the key determining factor, boiler pressure is an indication of the amount of heat in the boiler, and in the steam era, it was the easiest performance measure. So the key parameters to watch during any detailed firing testing are in the Heat line, in particular the In and Out figures.

In effect the AI fireman watches the In/Out heat values and attempts to "balance" these values so that the boiler heat is maintained at a neutral point, and hence boiler pressure is also maintained. Typically a real fireman "learns the route", and gets to know how to fire the locomotive to the route conditions ahead. So for example, if he knows that he is approaching a gradient, he will start to bank the fire up so that he can maintain boiler pressure for the grade.The approaching gradient length and steepness will determine how much and how soon he needs to build up his fire. Thus the challenge for the AI fireman is that he would firstly need to identify any approaching Issues, and then the potential impact, so that he can determine how to respond. Naturally we are talking about hundreds of different possible outcomes, and responses.

In manual mode, the player provides this ability to identify these approaching issues, and then from learned experience can determine an appropriate response to how the fire should be set up. This eliminates a whole lot of code complexity in OR.

As he is incapable of looking ahead, the AI fireman just tries to ensure that the player has sufficient steam to operate the locomotive. Given that the AI fireman does not "think" in the same way as a real fireman, I don't think that some of the manual firing components are readily translatable into the AI fireman mode. I think that it is wiser to consider the two as completely separate logic streams.

The hybrid approach of providing some override controls for the AI fireman was an attempt to provide a means of allowing a "look ahead" approach for the AI fireman.

It may however be possible to add some features to the AI fireman to give him a more "realistic" appearance. For example, somebody suggested turning off the AI stoker when stationary, etc, so perhaps these types of things might be an easy possibility. Though at the end of day he will always try to maintain the heat levels in the boiler.

So moving forward, I would suggest that perhaps some of these types of features could be considered. If we start making changes, I would like to see a single set of test stock (ideally from the CTN site), and test scenario used to ensure that we are all seeing the same results, and outcomes. The final results can then be tried on other units as required. I would also like to see a separate thread set up that focuses purely on the feature that we are looking at rather then being used for general discussions, and information sharing.

As a bit of background, it might be good to run the run Tutorial activity #2 of the Zig Zag Railway. This type of scenario would be the most challenging for the AI fireman to cope with, as there are frequent stops, and starting on gradients. This type of scenario could be considered as a test scenario. Longs runs are not as challenging for the AI fireman.

[darwins]

Heat Out - is fairly clear.

Heat In - could have two meanings in OR - please can you clarify which one is in the HuD. It could mean "Heat" which is transferred from the fire into the boiler or it could mean "Energy" contained in the coal or wood that is shovelled into the firebox.

Heat In to the boiler (from the fire) immediately does work, converting water to steam or increasing the temperature or pressure of the steam (in other words the reverse of the effect of heat out).

If the "Heat In" figure in the HuD refers to the energy content of the coal shovelled in, that is a whole different ball game - it is not "Heat" at all until the coal begins to burn.

One reason to get oil burning working is that these two values are basically the same thing for oil burning. Not having a delay in releasing heat from the fuel would allow us to look at boiler behaviour independently of fire behaviour.


Although the AI fireman can not (easily) be pro-active, he can be reactive in more realistic ways.

In the LMS firing video there is a simple explanation given that when the driver adjusts the controls to use more steam, then more coal will be needed on the fire.

Stop putting coal on when the loco is stationary is a good rule. I think it might be put better as stop firing when the regulator is closed.

Something similar could be done with injectors - MSTS went to one extreme on turned both injectors on full - OR seems to have gone to the other extreme of having them very finely adjusted. Possibly we could look at having the No 2 injector turn on 50% or 100% depending on water level. With the No 1 injector only being used if water continued to fall.

Quote

It may however be possible to add some features to the AI fireman to give him a more "realistic" appearance. For example, somebody suggested turning off the AI stoker when stationary, etc, so perhaps these types of things might be an easy possibility. Though at the end of day he will always try to maintain the heat levels in the boiler.

There perhaps needs to be thought about when to reduce heat levels as well as when to increase them.

Looking at "stored energy" might give a more realistic way to prevent the safety valves lifting. Something like if stored energy > 90% max stored energy stop firing. If stored energy > 95% and water level < 95% then put No 2 injector on full.

[ATSF3751]

Here are a few more videos on how we fire steam locomotives over here in the US. A Lot of very good info in these videos along with showing many aspects of firing and operations of steam locomotives over here in the USA. The locomotives are both mainline and tourist steam locomotives. These videos also show and explain how the engineer and fireman need to work together as a team.

For instance the Milwaukee Road 261 a 4-8-4 wheel arrangement, while running at 60 MPH the locomotive will burn through about 3 LBS of coal a second and evaporate 2 Gallons of water a second just to give you a rough estimate on the kind of fuel and water a coal burner goes though at speed on the American Mainlines. Our fuel and water capacity is quite a bit higher then of those in the UK. The Milwaukee Road 261 for instance carries 35 Tons of coal and 20,000 Gallons of water. On longer trips we also carry along a water tender that has an extra 20,000 Gallons of water carrying capacity.

One thought I had was would it be possible to have the stoker be off and then not turn on until you hit a specific speed and have the locomotives be hand fired before that point when it comes to coal?

Brandon

Union Pacific 844 4-8-4- Oil
https://www.youtube....vogL3LL8Q&t=11s

Southern Pacific 2472 4-6-2- Oil
https://www.youtube....h?v=QPfPznzL1OM

Nickel Plate Road 765 2-8-4- Coal
https://www.youtube....h?v=ZK5YrXvX0F0

FRISCO 1630 2-10-0- Coal
https://www.youtube....h?v=R2GrcYoW80E

https://www.youtube....h?v=5W7495NZ_l8

Reading Blue Mountain and Northern 425 4-6-2- Coal
https://www.youtube....h?v=QIIzazAqc3M

Western Maryland 734 2-8-0- Coal
https://www.youtube....h?v=wCunwwpMoBQ

Virginia & Truckee #22 Inyo 4-4-0- Wood
https://www.youtube....h?v=6QCiE3LX1bE

[darwins]

Using the OR heat model the following figures are given in the HuD:

Heat In = I am assuming this to be the total amount of heat transferred from the fire to the boiler

Heat Out = I am assuming this to be the total amount of heat being lost from the boiler

Rad = Heat lost from the boiler through the boiler cladding by radiation etc. (This is generally a small number and I assume this is included in the total 'Heat Out'.

Stored = Heat stored in the boiler (In other words the temperature and pressure of all of the water and steam in the boiler). Given that temperature is not going to vary enormously in the range of working pressure then, this should be more or less analgous to the pressure we see on the pressure gauge. (It is also going to be affected by the relative proportions of water and steam in the boiler as steam is much less dense than water.)

Max = ? possibly the maximum amount of heat that can be stored in the boiler - OR gives this as a fixed value for any particular locomotive - although as noted for stored energy it would vary depending on the relative proportions of water and steam.

Safety = ? again a fixed value for a particular loco - is this the amount of stored heat that causes the safety valves to lift - - slightly higher than Max - why is this a different value to Max? Surely exceeding the maximum capacity should lift the safety valves? (Or does it represent the amount of heat that safety valves can dissipate in a given time?)

Raw = ? not sure what this is ?

The important thing about working with a heat model is that it should not contain any secret sinks or sources. The behaviour of safety valves in OR at present suggests that heat is being created, destroyed or hidden somewhere. This is the description given by an experienced fireman:

Quote

Mostly, when the safety valves lift, you will see the pressure gauge flinch slightly, as the pressure drops initially, then return to normal (pressure reduces, boils faster), followed by a slow reduction in pressure to five or ten pounds below working pressure where they will seat again and the pressure will start to climb. Obviously how slow the pressure change will be depends on how hot your fire is. Some locos the valves will ‘feather’ before blowing properly, others (rarely) will have a very definite open and shut. It’s not uncommon to see the pressure sit at up to three or four pounds above the red line with the safety valves open.

This is the observation from OR with manual firing (Max pressure is 225 psi for this loco)

https://imgur.com/undefinedhttps://imgur.com/8Cq1FN1.png

Safety valves lifted at 225 psi. Pressure continued to rise a little before becoming steady at 232 psi. (Slightly higher above the red line than suggested but, possibly just within acceptable limits. The worrying thing at this point is that Heat In exceeds Heat Out and Stored Heat is continuing to rise. (Suggesting that pressure should also be rising still.) We should expect at this point that heat in and heat out would be equal and that the pressure would remain constant - perhaps somewhere between 225 and 228 psi - until heat in falls below heat out.

There is also a mismatch between the heat energy figures and those for the mass of steam - the HuD tells us that the boiler is evaporating water at the rate of 22k lb/h and that the safety valves are releasing steam at the rate of 32k lb/h - in other words not even an equilibrium - the boiler is losing steam faster than it is being generated and therefore we would expect the pressure to be falling.

A few minutes later we find that Heat Out has now risen far above Heat In

https://imgur.com/9YXcED8.png

It is not clear why there was a delay in heat being lost - as soon as the safety valves opened massive amounts of heat were being wasted. Anyway stored heat is now far above 'Safety'. The loco remains at 232 psi for some further time. Until enough heat has been wasted to let the pressure drop.

https://imgur.com/vRcZF7G.png

We are now back on track, expecting the valves to reseat themselves at perhaps 215 or 220 psi. All well and good, this is what happens.

The valves do indeed reseat themselves and the escape of steam comes to an end.

https://imgur.com/jOGYKfW.png

Although steam usage is less than steam production, heat out is slightly more than heat in. This makes sense as I now have the injector on, adding cold water to the boiler and therefore increasing the heat losses.

Immediately after this the injector was shut off.

What happens after that is surprising. Far from starting to climb again as described above the pressure continues to fall. The pressure falls for a further 5 minutes dropping all the way down to 156 psi (a huge drop of 64 psi after the safety valves had closed)

https://imgur.com/IIWwsaF.png

During all of that time heat in was greater than heat out (and steam production greater than steam usage).
The strange thing is that although heat in is greater than heat out - stored heat continues to drop. Where is that heat going?

This is clearly rather different to what was described for a real locomotive. There also seems to be a naughty gremlin somewhere consuming the heat energy.

My loco is now in a static state with a small fire and at this point would follow the behaviour described here:

Quote

It depends mostly on the state of the fire. If your fire is small, for example sitting on-shed in a morning, they may lift, the pressure will drop back a bit, then they will stop, the pressure begins to creep up again and the valves lift and it gets into a cycle, with the valves lifting for shorter periods each time, staying closed for longer periods.

If we can get safety valves working correctly as described by loco crew, then I think it would be reasonable to let them lift for the AI fireman too.

Here is a static loco left in the care of the AI fireman for 6 hours:

https://imgur.com/hQrgawR.jpg

The AI fireman has kept a good big fire and throughout that time heat in has consistently been greater than heat out.
Stored heat is now bigger than 'Max' and 'Safety' but the safety valves have not lifted. (Rather than a boiler explosion, instead there is extra stored energy available whenever I drive off.) The pressure shown on the gauge is just below the red line.

[ATSF3751]

Now that is very interesting darwins! Thank you for doing that test and very strange with some of the findings! Surely some of the coding must be off by quite a bit and needs some work.

Reading what Peter had to say in his last post I do agree with him to a point. I do agree that we do not want to go backwards with the Eng files but I do feel the need to have US and UK Steam fired a little differently as there some differences in how UK and US steam locomotives are fired in the real world. Yes I do understand this would make things more complicated and maybe what would be best is to have a so called "Basic" Idea of how a steam locomotive should be fired and then eventually we can modify the locomotives in the Eng files depending on how that country fires there steam locomotives. Even the United States and Canada have different rules and regulations regarding how to operate a steam locomotive so it varies from country to country.

I feel that is what Scott was trying to get at when he was talking about the Eng files. For instance if you were to try and run an American Steam Locomotive in the UK with how they are fired over there yes it would work but I do not feel they would get the proper steaming capabilities that they need over here in the United States and vice versa. Try running a Steam Locomotive from the UK on United States tracks the way we run our steam locomotives over here. Just something to put into consideration.

Yes the general idea of how to fire a steam locomotive is the same but there are just too many differences that I see between the two that we need to figure out the best way to compensate it. I do think Peter has a good idea of how the coding should work and we do need to follow his guidance as well and what he has to say.

I also like his thought of making a new thread for every specific aspect of firing we are currently working on at that time. I also like the idea of us all using the same locomotive at first and then eventually using different locomotives once we get all of the tweaks figured out with the coding. We need to take one step at a time and figure this out piece by piece. Work together to accomplish this goal we all have but also try to have fun with it.

The end result will be much more satisfactory and fulfilling once things are squared away but I think we have a good base to work with and some great ideas. So guys what should we tackle first?

Brandon

[darwins]

I don't think there is actually a huge difference between US firing and UK firing. The big point of difference is between stoker firing and hand firing. At the moment all engines large and small are basically following a stoker fired algorithm. (Just that the hand fired ones do not use any steam for the stoker!) I don't think there is a problem with starting from there and figuring out the hand firing algorithm later. In fact it may be worth setting up oil firing if we can. To me it seems logical to start with oil firing as energy in the fuel is converted directly to energy in the boiler without a significant difference between feed rate, burn rate and combustion rate. This would allow us to concentrate on boiler behaviour, without getting too bogged down in the complex behaviour of solid fuel fires. If we are happy with boiler - evaporation, pressure, safety valves, blower, injectors, heat in, heat out then we could then move on to the behaviour of the coal fire with a stoker. If that works well then look at hand firing, with the added complexity of putting fuel on in rounds and not putting fuel on at all in certain situations.

[ATSF3751]

Very good idea! I second that motion to go forward with that approach! There are many steam locomotives over here in the US that are oil fired. I think if we all work together on this we can figure this out step by step.

Brandon

[scottb613]

Hi Folks,

All sounds good - I still think my very old suggestion - to capture all that great HUD information that required many screenshots to relay - in a black box (really orange) style debugger - would make talking about physics so much easier. Simply capturing every 5MPH or 10MPH delta that's available now doesn't seem to give us enough data.

:whistling:

Regards,
Scott

[Traindude]

Not sure whether this is relevant specifically to this discussion, but I'd like to see dimmable headlights on steam locos, rather than simply on/off. If diesels and electrics have them, why can't steam engines?

Something I also discovered relates to steam engine air compressor governors. Instead of the governor completely shutting off steam to the compressor when maximum pressure is reached, the governor always allowed a small "trickle" of steam to flow to the compressor, causing the compressor pistons to slowly "creep". This accomplished 3 things: 1) Making sure lubrication is still flowing to the compressor steam cylinders, 2) preventing condensation from accumulating in the steam side cylinders, and 3) preventing the pistons from seizing up. This is why you sometimes hear an occasional "thump" from the compressor even though the air pressure is at max. However, the speed of the compressor is so low--maybe no more than 15 strokes per minute--that it doesn't significantly increase main reservoir pressure.

In other words, instead of the compressor steam usage dropping to zero when the main reservoir pressure reaches maximum pressure, the steam usage should be about one-tenth or so of full steam usage.

[ATSF3751]

I agree with you on both of those. The Milwaukee Road 261 does have a dimming feature on the headlight along with turning the class lights on and off independently. I know the UP 844, UP 3985, UP 4014 and many other steam locomotives are like this as well. SP 4449 also has those features as well along with having its mars light independent from the headlight as well. I believe many other US Steam Locomotives are also in this same category when it comes to lighting.

Brandon