[copperpen]

There is an eng file parameter called ORTSCylinderEfficiencyRate ( x ) where x is currently a value between 0.6 and 1.2. I wanted this to be a range of 0.1 to 1.7 but Peter felt this was too wide a range. The description for this parameter is Multiplication factor for steam cylinder (force) output, these values working in conjunction with the force factor tables do give reasonably good results. If this parameter is not present a default is used.

[Lindsayts]

 copperpen, on 16 June 2014 - 01:54 PM, said:

There is an eng file parameter called ORTSCylinderEfficiencyRate ( x ) where x is currently a value between 0.6 and 1.2. I wanted this to be a range of 0.1 to 1.7 but Peter felt this was too wide a range. The description for this parameter is Multiplication factor for steam cylinder (force) output, these values working in conjunction with the force factor tables do give reasonably good results. If this parameter is not present a default is used.

Yes, I saw this, I believe Peter is incorrect here, a reasonable range for the OR steam code at its present state would be 0.5 to 1.7.
To some extent the code is inconsistent here, why go to all the bother of trying to calculate pressure drops and cylinder effective pressures then throw in an overall factor. I personally would be quite happy just to have ORTSCylinderEfficiencyRate and forget about the rest. For most of the time steamers where produced they were almost always constructed by rules of thumb. As I have already said Chapelon appears to have been the first railway engineer to start looking at pressure drops and gas flows, he appears to have gone to great lengths to understand the limitations.

In the end for the code to work on pressure drops and such goes against the way steamers were designed for much of the time they were being used. The major problem with the code trying to be a true simulation of the machine is that there is almost no information about exactly what happens in the individual parts of a steamer. Even Chapelon most of time only giving overall performance figures. Only mentioning almost in passing the effects of passage sizes and problems caused by the valve gear.

Thinking on this, I personaly believe that ORTSCylinderEfficiencyRate should range from 0.5 to 1.7 this would give the range of control that would allow one to easily get the performance one required.

Note, as far as I am concerned OR is a train simulator its not really required to be an accurate engine physics simulator all it has to do is SIMULATE the locos real performance. Although I can easily see the attraction that a good steamer physics simulator can have. I already having done a couple of them myself.

A slight gotcha here is that I would not die of shock if some errors are still in a code base so complex as that that exists in MSTSSteamLocomtive.cs

Lindsay

[cjakeman]

Some good points being made here. Don't want you to think they are being ignored, but I've been busy with the new website and I know Peter has also been working hard on improving our documentation - which has also been a concern.

 Lindsayts, on 16 June 2014 - 03:15 PM, said:

Note, as far as I am concerned OR is a train simulator its not really required to be an accurate engine physics simulator all it has to do is SIMULATE the locos real performance. Although I can easily see the attraction that a good steamer physics simulator can have.

Perhaps we could have a simple max power-speed curve definable in the ENG file. If present, this would bypass any modelling of the firebox, boiler and cylinders and would assume that the fireman can always deliver as much steam as is needed.

Is that what you mean?

[Genma Saotome]

I know what would help me: Having an Excel spreadsheet that mimics what OR is doing, where I could enter the parameter values from locomotives whose performance I understand and then examine & compare the results.

For instance, I have very good data on the WP 2-8-8-2 locomotives... I'd start there and eventually plug in data for a variety of other locomotives that I understand. If the results are fundamentally different from the expected I might be able to drill in and figure out why.

[Lindsayts]

 cjakeman, on 24 June 2014 - 06:41 AM, said:

Some good points being made here. Don't want you to think they are being ignored, but I've been busy with the new website and I know Peter has also been working hard on improving our documentation - which has also been a concern.


Perhaps we could have a simple max power-speed curve definable in the ENG file. If present, this would bypass any modelling of the firebox, boiler and cylinders and would assume that the fireman can always deliver as much steam as is needed.

Is that what you mean?

Many thanks for the reply, I was not sure I had been heard but one must __ALWAYS__ remember OR is being developed by volunteers that do have other lives.

That would be ideal, but really we do not at this stage need anything even that complex. As stated all thats really needed is to have the parameter ORTSCylinderEfficiencyRate ( x ).capable of being varied ove a wider range 0.5 to around 1.7 would be reasonable.

As I have previously mentioned and this needs to be clearly understood steamers were ___VERY ___ variable machines even within the one class. Steam loco's were NEVER mass produced (Note 1) all machines being individually built so they were all a bit different. Beyer Peacock the builders of the Garrat locomotives at least in the early days (1920's) stamped all there parts with the locos class number, the stamp include the items position. For instance a coupling rod would be stamp G42 LR for the rod on the rear engine unit left side.
Old drivers will clearly state different locos in a class had differing personalities, this being one of steamers attractions.

Note 1: Some companies, two being the American Locomotive works and particularly Heisler Locomotive works did make some parts on jigs so they were interchangable, Heisler being the only company as far as I know that advertised you did not need a machine shop to own there loco's. All normal running parts being availible as off the shelf spares.

Lindsay

[Lindsayts]

Oops, a correction to the previous post, its the American Locomotive Company.

Lindsay

[Genma Saotome]

As an aside and follow up to Lindsay's comments, most people today are ignorant of the fact that truly interchangeable parts are a relatively modern creation. For most countries the need for interchangeable parts was largely a military requirement, one not meet outside of the U.S. until almost the start of the 20th century. Interchangeable parts for industry always followed later.

There is an interesting anecdote of King Edward (of the U.K.) that makes this point: On visiting an International Fair held in London the King marveled at an exhibit where parts on a machine could be swapped out w/ no loss of efficiency or function. This in spite of the fact that British Scientists were already making machines that measured one millionth of an inch... the problem was very low acceptance by industry -- all across Europe. Things did change somewhat in the run up to the Great War and certainly afterwards. In the U.S. the story was different... once the interchangeable concept was meeting the military's needs (2nd half of the 19th century) Industry, across the board, was pretty quick to adopt it.

We all know the railroad industry is perhaps the acme of being hidebound... here in the U.S., in the early 60's, some roads were still using straight pins to hold several sheets of paper together... those mechanical staplers were too newfangled to be trusted I guess. So it should not be a surprise that steam locomotives -- universally mechanical with 20, 30, 40, even 50 years of service & repairs -- did not perform uniformly.