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Refining Steam Locomotive Code

#1 User is offline   steamer_ctn 

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Posted 10 April 2017 - 09:13 PM

As a result of some questions raised by some British OR users, a series of performance tests have been undertaken of a Superheated locomotive. The test results have been compared to a BR test report, and some discrepancies have been identified.

The thread created by the BR testers is located here.

As a consequence of the test results, it is proposed to make some modifications to the OR Steam model code to bring its performance into closer alignment with the test report. A blueprint has been created to cover the proposed work (as it is currently understood).

If there are any American modellers who are interested in participating in a similar testing program as has been established in the UKTrainSim thread above, please let me know as I would be happy to have the assistance of some testers.

#2 User is offline   steamer_ctn 

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Posted 14 April 2017 - 02:31 AM

I am wanting to setup and host some rolling stock for testing and demonstration purposes.

I want to set up the PRR H21 hopper.

I am wondering if anybody can point me to some rolling stock that I could use, and has a close resemblance to the H21.

Thanks

#3 User is offline   Fleegle411 

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Posted 14 April 2017 - 05:59 AM

Broadway Limited Locomotive works has freeware H21 models on their website

http://www.bllw.net/

#4 User is offline   steamer_ctn 

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Posted 14 April 2017 - 01:45 PM

View PostFleegle411, on 14 April 2017 - 05:59 AM, said:

Broadway Limited Locomotive works has freeware H21 models on their website

Thanks for that.

#5 User is offline   ATSF3751 

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Posted 19 April 2017 - 06:46 AM

Most of the mainline steam locomotives that run here on the mainline in the US are super heated so it would be a great idea to have some US Steam incorporated in the test as well. I am currently myself finishing up Milwaukee Road 261 4-8-4 locomotive that is specifically for Open Rails that is a super heated locomotive. I also know quite a bit of specs on the locomotive as well as I am affiliated with the group who maintains and operates it. I do have to admit that steam locomotives in Open Rails still has a very long ways to go until its good but this may be a start in the right direction.

Brandon

#6 User is offline   copperpen 

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Posted 19 April 2017 - 10:21 AM

WRT physics the OR steam locomotive, apart from articulated, is fairly close to where it should be. Effects wise there is still a way to go though.

#7 User is offline   steamer_ctn 

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Posted 20 April 2017 - 01:38 PM

View PostATSF3751, on 19 April 2017 - 06:46 AM, said:

so it would be a great idea to have some US Steam incorporated in the test as well.

I am happy to include US locomotives, are you happy to become a tester?

I would want to start with locomotives which have detailed test reports, and then look at locomotives that don't have as much info available.

#8 User is offline   Jean-Paul 

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Posted 14 May 2017 - 04:41 AM

Hi, engineers !
May I do a suggestion before you begin your tests ?
There is an important parameter in OR, which must not be forsaken :
ORTSBoilerEvaporationRate
Multiplied by evaporation area, it determinates maximal production of steam by the boiler. In OR, its maximal value is 15 lb/h/ft^2, i.e. 73.24 kg/h/m^2 in metric units.
If we look our sources in term of real tests of performances, it's better to know there are two "schools" :
- An anglo-german one, in which IHP and DBHP are related in "normal" conditions of use : for instance, in Germany, IHP and DBHP were usually determinated at an evaporation rate of 57 kg/h/m^2 ( 11.67 lb/h/m^2) before WW II, 65 to 70 kg/h/m^2 after ( 13.31 to 14.34 kg/h/m^2 resp.). Those moderate values were supposed to be representative of a daily use of steam engine, but didn't exclude a more intensive use, for instance to climb a hill or to prevent a delay.
- A franco-american one, in which steam engines were tested (on line, or on a test bench) in maximal conditions. In these cases, for modern engines, evaporation rate could reach values between 85 to 100 kg/h/m^2 ( 17.41 to 20.49 lb/h/ft^2 ). Railway companies knew that in current use, those maximal efforts would be unusual, but also knew by this way the real "continuous" values.
The difference is important. Here is an example : for Deutsche Reichsbahn, maximal IHP of BR44 (a freight-train Decapod) was 1910 HP @ 57 kg/h/m^2 evap. rate. When some of these engines were captured in France post-1945, one was tested on bench in Vitry (F). It appeared that, in "reasonable" (and continuous) conditions, maximal IHP could be estimated at 2500-2700 HP under evaporation rates between 75 and 80 kg/h/m^2, perfectly compatible with boiler construction and evaporating apparatus.
Another one : in France, SNCF-built 241 P are well-known to be able to deliver up to 4000 IHP (many relations of current performances on fast trains). However, when SNCF had to establish scales of equivalence with new Diesel engines, it appeared 241 P were comparable with A1A-A1A 68000, whose Diesel power was 2700 IHP only (i.e. around 2200 HP at rail)... Comparable in daily use (in fact, for an evaporation rate of 60 kg/h/m^2), but probably better in extreme conditions.
So, under ORTS, this parameter is fundamental, but not absolutely "free", because it's not possible to use values > 15 lb/h/ft^2 ( you can write > 15, but without effect...). So, it explains easily why it's impossible, for instance, to get the real 5500 IHP (with a Niagara, for instance) which were effectively obtained, in "continuous" but "maximal" conditions, for an evaporation rate probably between 18-20 lb/h/ft^2. Those 5500 IHP were not an overstatement, but simply an effective "maximal continuous value". Under OR, you won't get more than 4000 IHP, which correspond at a "wise" use of steam engine.
Then, in my sense, first thing to modify in the codes is to liberate this value by allowing more than 15 lb/h/ft. This value is, of course, reasonable, but doesn't correspond with reality of a maximal utilization of a modern steam engine. It was an high value... in 1920, but not in 1940, overall with oil-burning boilers.
And no, there will not be any problems of realism with other parameters of modelization, because to produce more steam needs more heating, and more fuel : in these conditions, boiler efficiency decreases quickly, fixing by this way a strict auto-limitation... Similarly, much more steam significates also more and more problems of condensation in cylinders, more drafting unsufficiencies, and so one... Precisely all these parameters which are cleverly expressed in OR. :)
I presume it would take no more than 5 seconds to remove this limit in codes (and allow calculation of MaxBoilerOutput by simple multiplication regardless of evaporation rate value). It's worth to try, no ?
I would add that if you need informations about some real IHP-DBHP/speed curves, I would be glad to help you.
I apologize for my "frenchie" english !
Cheers !
Jean-Paul

View Poststeamer_ctn, on 20 April 2017 - 01:38 PM, said:

I am happy to include US locomotives, are you happy to become a tester?

I would want to start with locomotives which have detailed test reports, and then look at locomotives that don't have as much info available.


#9 User is offline   steamer_ctn 

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Posted 14 May 2017 - 10:46 PM

View PostJean-Paul, on 14 May 2017 - 04:41 AM, said:

I would add that if you need informations about some real IHP-DBHP/speed curves, I would be glad to help you.

If you have detailed test curves for one of the modern locomotives that you are proposing, then please PM me, or contact me through the CTN site.

Thanks

#10 User is offline   steamer_ctn 

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Posted 23 May 2017 - 12:20 AM

As part of the OR code modifications for the steam model I have now included a default set of cylinder events. The events are the points on the cylinders movement where the various valves open or close as part of the steam cycle.

Typically the events are as follows: Admission, Cutoff, Exhaust and Compression. These events typically change for different cutoff values, and valve gear type, such as Allen , Stephenson, etc.

In OR these are used to more accurately model the steam indicator diagram to calculate Tractive Effort, and steam usage.

I am wondering if there is any interest in "exposing" these parameters so that ENG files could be customised by advanced users with these events, and thus allow for the inclusion of different valve gear. The calculation of these event positions is not a trivial exercise and would require some effort to do so.

So I have two questions:

i) Who is interested in exploring the ability of adding the steam cylinder events for different valve gear?

ii) How would you go about calculating them?

Thanks

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