[Lindsayts]

Does anyone, may be Peter (steamer_ctn) have a steamer working well using the new OR parameters. I am unable to make much sense. Everything is being parsed OK but the loco (Victorian Railways H220) is WAY down on power, the model producing just over half the drawbar power as indicated by Dynometer car tests on the real machine. I am wondering therefore what I have incorrect. Being able to have a look at a correctly working loco will be a good start to solving the problem.

Note: I have built up a new eng file from scratch by going through the source and extracting the eng file parameters and the comments indicating what a particular parameter does, so there is a chance I have missed something. I do not think I have though. It took me a while to get around an extra brace in the include files but it appears now to be being parsed correctly.

One symptom is the steam production (from the f5 hud) is always near the boilers maximum production rate no matter what, the ONLY way so far I have been able to get it down is by setting the boiler volume very low. The steam details in the f5 hud indicate the gratearea, evaporation area, superheater and boiler volume are being read in correctly.

Lindsay

[captain_bazza]

Sounds like some of the hard code needs tweaking. As a 'steam' driven man, I'm grateful for the testing you're doing, Lindsay.




Cheers Bazza.

[Lindsayts]

captain_bazza, on 03 June 2014 - 06:19 PM, said:

Sounds like some of the hard code needs tweaking. As a 'steam' driven man, I'm grateful for the testing you're doing, Lindsay.




Cheers Bazza.

It appears its the eng file that requires tweaking, this knowledge though is difficult to get at.

The source code for the steamers appears to be very flexible and its well commented now (thank god) but its also very complex. A facility that that code uses widely is an interpolated look up table that is user defined. Its called in the code an "Interpolator" unfortunately it did not work when I tried it last.

The failure is that if one specifies another set of values in the eng file the results are quite unexpected. Note, there is no docs on the eng file format and I had to guess it based on the source (and I do not read c# well). I have not reported it as a bug as I believe (I could of course be wrong) its VERY likely none of the current developers no anything about this facility of OpenRails. I gained that impression when no one replied from a request for more info, and I do not wish to put more pressure on the developers.

Below is an example of the syntax I believe is required, this is for forcefactor2 this being the positive (ie steam) pressure part of the cycle in the cylinder.

engine(forcefactor2 ( .200 .5 .265 .64 .33 .685 .395 .78 .46 .85 .525 .88 .590 .915 .655 .934 .72 .96 .785 .97 .85 .98 )

The line consists of an even numbered line of values that are in fact paired. The first of the pair being the cuttoff the second part basicly a factor based on the cylinders brake men effective pressure (bmep). For instance the first pair of values 0.200 and 0.5, 0.2 is the cuttoff 0.5 is the bmep ratio. The same for 0.265 and 0.64 and so one down the string. Sadly this produce very odd results.

Note: The interpolator function is NOT part of the steam code but it is a common mathematical function offered by OR for general use around the program.

If this facility worked there would be little one could not do with a steamer in OR.......sigh....... :(.

[copperpen]

Having been the tester for the steam code produced by Peter I can say that as long as the base parameters are correct you will get the right amount of power out. You have no need to consider adding any external factors such as your forcefactor2 line. The Interpolator tables are not user definable, unless you have some definitive data that is better than that already provided. The two essential things the steam code needs to work properly are a grate area and a reasonably sized boiler, If no other ORTS type data is inserted, the program will use the MSTS equivalents from the eng file.

The boiler always producing near maximum all the time is something that still needs to be looked at, but is far better than the original attempt which had steam production running way above the defined maximum. One thing that does affect steam production is the FuelCalorific value, however the downside to reducing this is increased consumption to compensate, another item that needs fine tuning.

[Lindsayts]

copperpen, on 04 June 2014 - 12:48 AM, said:

Having been the tester for the steam code produced by Peter I can say that as long as the base parameters are correct you will get the right amount of power out. You have no need to consider adding any external factors such as your forcefactor2 line. The Interpolator tables are not user definable, unless you have some definitive data that is better than that already provided. The two essential things the steam code needs to work properly are a grate area and a reasonably sized boiler, If no other ORTS type data is inserted, the program will use the MSTS equivalents from the eng file.

The boiler always producing near maximum all the time is something that still needs to be looked at, but is far better than the original attempt which had steam production running way above the defined maximum. One thing that does affect steam production is the FuelCalorific value, however the downside to reducing this is increased consumption to compensate, another item that needs fine tuning.

The base parameters, Grate area 78 sq ft, Boiler Volume 650 cubic ft, Evaporation area 3960 sq ft, Superheater area 800 sq ft and Fuel calorific value ARE all correct (Loco weight is 145 tons, 95 being on the drivers, tender weight loaded was 115 tons). The reason I use this particular loco for testing is that it is one of only 3 steamers that I know that the power as measured by a Dynometer car has been published. This loco H220 a number of times produced a drawbar power of 3600hp at 50mph. OR does not even get close to this no matter what one does.

This is why I asked for a complete eng file that uses the new parameters. As there are no docs on the eng files layout I have had to guess it. Its possible there is an issue I have overlooked.

The power output of steamers has historically been seriously underestimated. A rule of thumb for latter design superheated steamers with radial valve gear is between 50 to 80 ihp at around 70 mph per square ft of grate area. Actual steam consumed for this can vary by a factor of over 2 to 1, British built machines nearly always having the lowest water consumption. The higher power figure given (80ihp/ft^2) being for express passenger loco's.

Note, The wide range of water consumption to produce the power, this is why in the end the steamers in OR must be able to be tuned over a wide area as they varied so much in real life. At the moment the steam code in OR does not appear to give one this wide choice.

The Forcefactor interpolator was tried to see if it would have any effect, the actual values used not being what my technical steam docs say they should be. It did not work, it needs to be looked at really.

IMPORTANT NOTE, I am not trying to be a pain in the neck, OR is a simulation thats meant to be accurate, from my position the steam code is far not holding this reputation. As stated in the past I have put a great deal of effort (and funds) to get a good idea of how steam performed in real life.

Lindsay

[copperpen]

Perhaps you should correspond with Peter as he is the steam code dev.

The code was developed against two known rolling road tests of two different engines, and output was also compared with "anecdotal" evidence of day to day running of different locomotive types. In all cases the power developed matched the published figures. Don't forget controlled testing was always done using a particular grade of fuel which was probably not available every day in traffic.

What you need is a published power curve for that engine and then plot OR output to compare. Only then can a subjective look at the problem be taken.

[Genma Saotome]

Lindsayts, on 04 June 2014 - 08:51 AM, said:

A rule of thumb for latter design superheated steamers with radial valve gear is between 50 to 80 ihp at around 70 mph per square ft of grate area. Actual steam consumed for this can vary by a factor of over 2 to 1, British built machines nearly always having the lowest water consumption. The higher power figure given (80ihp/ft^2) being for express passenger loco's.

Baldwin Locomotive Works used a slightly different method of estimating power at speed: The ratio of evaporation surface to driving wheel diameter. The product of that usually fell in a range between 10 and 18. Locomotives that scored nearer to 10 were high speed; Locomotives scoring nearer to 18 were high power.

Essentially what Baldwin was looking at was the rate of steam production relative to variable consumption where the later was limited to a piston speed of 1100 feet per minute (thought to be a practical upper limit for the mechanical drive). 1100 fpm with a large driving wheel gave you loads of speed. 1100 fpm with a small driving wheel gave you loads of power. To figure out what's going on at other speeds you recalculate by lowering the piston speed.

The final result of their own analysis was a chart of power curves, one line for each integer value of the above ratio, drawn over speed. The vertical axis was percent of cutoff. Pick a ratio, pick a speed, find the data point and run your finger over to cutoff percentage and bingo you have a factor to apply against MEP at 0 mph. IOW you get an estimate of what MEP should be at any given speed.

I put all of this into a spreadsheet and loaded in a couple of dozen locomotives. It does not work that well for modern Superpower locomotives from Lima... they're so much better than what came before. But it does work reasonably well for lots of others (but not all). The WP 2-8-8-2 Mallets come in spot-on: 13mph w/ 4000 trailing tons on a 1% grade; 17 mph w/ 3400 trailing tons -- exactly what the railroad rated.

[Lindsayts]

copperpen, on 05 June 2014 - 12:48 AM, said:

Perhaps you should correspond with Peter as he is the steam code dev.

The code was developed against two known rolling road tests of two different engines, and output was also compared with "anecdotal" evidence of day to day running of different locomotive types. In all cases the power developed matched the published figures. Don't forget controlled testing was always done using a particular grade of fuel which was probably not available every day in traffic.

What you need is a published power curve for that engine and then plot OR output to compare. Only then can a subjective look at the problem be taken.

What were the two locomotives used and can you provide the eng files used so that the tests can be verified. As I SAID theres a distinct possibility that something is not correct in the eng file I am using. There is no docs on the OR parameters so one has to guess how the eng file is laid out. So some example configs would give the rest of us a real good start.

All the same as I have said before Steam loco's are extremely variable machines. One cannot simply specify things such as Grate Area, Heating surface and other general dimensions and expect to get an accurate answer for all machines. Think of the difference between the british A4's, a garrat, a big mallet and a Heisler.

The only criticism I am making of the current position is it appears the developers have assumed they have all knowledge of steamers and the work therefore is beyond complaint. So much knowledge of steam engines has been lost that I certainly believe there is no one currently on this earth not even this writer that can state that.

Work from such engineers as André Chapelon and latter have indicated that steamers were far from being fully developed and could be greatly improved without radical redesign. Chapelon himself NEVER built a new machine all his work was by modifying existing machines.

As stated I am not trying to be a pain in the neck just trying to get the perfect simulation. This means that the developers must assume that more knowledge is availible and the code needs to be more flexible.

Trying to get a steamer to work properly in MSTS is a bit of a pain and this is a serious problem but quite a good representation can be done because the set up is flexible. In the end there is no satisfactory way around these two issues, ie ,If one simplifies it to make it easy flexibilty will suffer and one cannot cover all possibilities. If one makes it very flexible only a handfull of sim uses will be able to produce a good config.

Wishing all well,
LIndsay

[Lindsayts]

Some thoughts related to my previous post............

One cannot be afraid of a complex config, look at the current early work on Timetabling, in the end a decent timetabled "activity" will be a chore to set up but just imagine the possibilties. Particularly when OR gets its own tools and one can set up the signalling correctly.

Lindsay

[Lindsayts]

Pretend I never said anything......................

I decided I have enough to do with the include files (and other things) so I have decided to put this aside.

Lindsay