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Question: How is boiler volume defined?
If it is provided by the railroad, fine, use that.
If it's just a rough calculation of the boiler as kinda-like a cylinder then it does not take into consideration the volume of the tubes that are inside of it -- you have to subtract the volume (using the OD) of all of them from the volume of the boiler cylinder to get the value for this parameter (overstated by a bit since the boiler is never 100% full of water).
Steam Physics - Maybe It's a Bug ?
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Posted 27 March 2019 - 11:43 AM
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Posted 27 March 2019 - 12:30 PM
Hi Dave,
In my test case - I obtained the boiler volume from a calculator on Peter’s website - there was also a note on the site that stated Boiler Volume has little affect on the ORTS Steam model... That seems to be the case from my testing - as I tried extremes and the effect didn’t seem too substantial... I think many of us probably use “steamlocomotive.com” for our source data and they don’t include boiler volume in their standard definitions... Previously - on my last locomotive for MSTS - I just took basic measurements of the model for a rough calculation... With only six locomotives of this type built - finding additional real world data seems unlikely...
Regards,
Scott
In my test case - I obtained the boiler volume from a calculator on Peter’s website - there was also a note on the site that stated Boiler Volume has little affect on the ORTS Steam model... That seems to be the case from my testing - as I tried extremes and the effect didn’t seem too substantial... I think many of us probably use “steamlocomotive.com” for our source data and they don’t include boiler volume in their standard definitions... Previously - on my last locomotive for MSTS - I just took basic measurements of the model for a rough calculation... With only six locomotives of this type built - finding additional real world data seems unlikely...
Regards,
Scott
#33
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Posted 27 March 2019 - 01:57 PM
Scott
You asked for an example of the ORTSBoilerEfficiency curve. I have been working with a medium sized UK mixed traffic loco, the 49xx Hall class, experimenting with how the curve actually works. It has a BP of 220 and a grate area of 27 sq.ft.
What the curve does is place a limit on how much fuel can be fed to the fire to generate steam with increasing amounts of fuel leading to a descrease in efficiency. In other words the more coal you pile on, the less steam will be produced per pound of fuel. The more aggressive this curve is the lower the grate limit becomes. The grate limit is the point at which more fuel will not make more steam, and if you are driving with a heavy hand, you begin to run out of steam and pressure begins to drop.
If you look at the locomotive page of the HUD and then at the Fire section, you will see the ideal firemass. Run along that line and you will then see burn rate, this goes up and down as conditions require but normally should never exceed maximum firing rate, and almost at the end of the line there is an item labelled GrLimit. This is the Grate Limit and can be varied by the type of curve you develop.
Curve A ORTSBoilerEfficiency ( 0.0 0.98 20.0 0.75 40.0 0.65 60.0 0.49 80.0 0.34 100.0 0.27 120.0 0.20 140.0 0.15 110.0 0.25 )
This is an example of a curve that will limit the engine to low speeds and a low grate limit. This makes it much harder to drive
Curve B ORTSBoilerEfficiency ( 0.0 0.98 24.0 0.95 36.0 0.85 48.0 0.80 62.0 0.70 74.0 0.60 86.0 0.50 98.0 0.40 110.0 0.30 )
This example gives more flexibility allowing for higher speeds and a higher grate limit. It gives about 2250LB/Hr firing rate and a train speed on the level of about 80 mph. It needs a bit more work to get a higher speed and higher maximum burnrate
.
To find out what the theoretical grate limit is for your loco, take the figure for max firing rate and divide it by the grate area which will give you the maximum amount of fuel that can be put on the fire per sq ft (GrLimit), and still generate steam. Then by making a curve and fiddling with it, you can move that GrLimit lower until you get to see the reduction of steam as more fuel is added, but no more steam is made as the loco hauls its load up the grade. Boiler pressure should slowly begin to drop and will continue to drop until remedial action is taken. In the UK this was known as" mortgaging the boiler", using the steam on the climb then recovering on the level or downhill stretch.
You asked for an example of the ORTSBoilerEfficiency curve. I have been working with a medium sized UK mixed traffic loco, the 49xx Hall class, experimenting with how the curve actually works. It has a BP of 220 and a grate area of 27 sq.ft.
What the curve does is place a limit on how much fuel can be fed to the fire to generate steam with increasing amounts of fuel leading to a descrease in efficiency. In other words the more coal you pile on, the less steam will be produced per pound of fuel. The more aggressive this curve is the lower the grate limit becomes. The grate limit is the point at which more fuel will not make more steam, and if you are driving with a heavy hand, you begin to run out of steam and pressure begins to drop.
If you look at the locomotive page of the HUD and then at the Fire section, you will see the ideal firemass. Run along that line and you will then see burn rate, this goes up and down as conditions require but normally should never exceed maximum firing rate, and almost at the end of the line there is an item labelled GrLimit. This is the Grate Limit and can be varied by the type of curve you develop.
Curve A ORTSBoilerEfficiency ( 0.0 0.98 20.0 0.75 40.0 0.65 60.0 0.49 80.0 0.34 100.0 0.27 120.0 0.20 140.0 0.15 110.0 0.25 )
This is an example of a curve that will limit the engine to low speeds and a low grate limit. This makes it much harder to drive
Curve B ORTSBoilerEfficiency ( 0.0 0.98 24.0 0.95 36.0 0.85 48.0 0.80 62.0 0.70 74.0 0.60 86.0 0.50 98.0 0.40 110.0 0.30 )
This example gives more flexibility allowing for higher speeds and a higher grate limit. It gives about 2250LB/Hr firing rate and a train speed on the level of about 80 mph. It needs a bit more work to get a higher speed and higher maximum burnrate
.
To find out what the theoretical grate limit is for your loco, take the figure for max firing rate and divide it by the grate area which will give you the maximum amount of fuel that can be put on the fire per sq ft (GrLimit), and still generate steam. Then by making a curve and fiddling with it, you can move that GrLimit lower until you get to see the reduction of steam as more fuel is added, but no more steam is made as the loco hauls its load up the grade. Boiler pressure should slowly begin to drop and will continue to drop until remedial action is taken. In the UK this was known as" mortgaging the boiler", using the steam on the climb then recovering on the level or downhill stretch.
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Posted 27 March 2019 - 09:04 PM
A couple of points.......
Boiler volume
I calculated the true boiler volume of the boiler for Victorian Railways H220 (Heavy Harry) also calculated the volume of just the barrel and found the latter to be reasonably close to the actual true boiler volume. So using the vloume of the barrel is quite reasonable.
The effect of the boiler volume is that if the value is to small, when one suddenly increases steam consumption , say on entering a steep grade. The boiler pressure will drop quicker and recover quicker when the fire gets going, ie the reserve capacity of the boile is lower when boiler volume is to small.
Note; H220 is the loco used in my post on page 1, further details
Wheel arrangement 4-8-4
Loco weight 146 tons
Tender weight 113 tons
Cylinders 3 21.5 x 28in
Boiler
heating surface 4760 sq ft
grate area 68 sqft
super heater around 900sqft
tractive effort 55,000 lbs
drawbar HP (dynometer car) 3300bhp at 47.5mph, peaking at 3600bhp
H220 (Heavy Harry) was built as a express passenger loco, design to pull a 550ton load up a 1 in 48 at 30mph. Sadly it never was used as such as it was built at the start of the WW2 and the line to serviceton was never strenghend to take the H220'sheavy axle load. It spent its time on the Albury line usually pulling fast freights. It ended up a legendary loco capable of outstanding performances. It once was used on the "Spirit of Progress" a heavy Melbourne Sydney express passenger train and inspite of being limited to 60mph arrrived in Albury 300miles from Melbourne 20 minutes quicker than the timetabeled time. On that run it topped the Glenroy bank a 1 in 50 grade at over 50mph pulling a 500ton train.
Lindsay
Boiler volume
I calculated the true boiler volume of the boiler for Victorian Railways H220 (Heavy Harry) also calculated the volume of just the barrel and found the latter to be reasonably close to the actual true boiler volume. So using the vloume of the barrel is quite reasonable.
The effect of the boiler volume is that if the value is to small, when one suddenly increases steam consumption , say on entering a steep grade. The boiler pressure will drop quicker and recover quicker when the fire gets going, ie the reserve capacity of the boile is lower when boiler volume is to small.
Note; H220 is the loco used in my post on page 1, further details
Wheel arrangement 4-8-4
Loco weight 146 tons
Tender weight 113 tons
Cylinders 3 21.5 x 28in
Boiler
heating surface 4760 sq ft
grate area 68 sqft
super heater around 900sqft
tractive effort 55,000 lbs
drawbar HP (dynometer car) 3300bhp at 47.5mph, peaking at 3600bhp
H220 (Heavy Harry) was built as a express passenger loco, design to pull a 550ton load up a 1 in 48 at 30mph. Sadly it never was used as such as it was built at the start of the WW2 and the line to serviceton was never strenghend to take the H220'sheavy axle load. It spent its time on the Albury line usually pulling fast freights. It ended up a legendary loco capable of outstanding performances. It once was used on the "Spirit of Progress" a heavy Melbourne Sydney express passenger train and inspite of being limited to 60mph arrrived in Albury 300miles from Melbourne 20 minutes quicker than the timetabeled time. On that run it topped the Glenroy bank a 1 in 50 grade at over 50mph pulling a 500ton train.
Lindsay
#35
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Posted 27 March 2019 - 09:55 PM
Some feedback to some of the points -
I believe that the importance and impact of this parameter is as follows:
The steam locomotive is a heat engine which converts heat energy (produced by the fire/fuel) into mechanical energy (steam / usage causes loss of heat) to drive the wheels. Thus the boiler mass acts as an energy storage medium. The boiler pressure effectively measure the capacity of the boiler to produce the energy required.
A modern analogy for the boiler would be a battery. So the bigger the battery, the longer it lasts, the smaller the battery, the quicker it "dies". Similarly with the boiler the larger its mass, the longer it takes for the boiler pressure to drop, and conversely the smaller it is the quicker that the boiler pressure drops. Ideally a huge boiler would provide a large time before the boiler pressure would drop below a critical level. However the size also impacts the time taken to put the heat back into the boiler, ie the larger that it is, then the longer that it takes to bring it back up to pressure, the smaller it is the quicker that it is bought to pressure. (See Lindsayts example of a locomotive changing grades and the impact of boiler volume)
The boiler volume does not impact the maximum possible boiler pressure, but rather the rate of change in boiler pressure.
Locomotive designers therefore needed to select an appropriate size that provides the "sweet spot" between these two extremes.
As Dave, has suggested wherever possible, for accuracy sake, use real information to calculate the volume. The CTN calculator uses a design rule of thumb calculation for design purposes, and should only be used as a last resort if real information cannot be sourced.
The method suggested by Lindsay and Dave to calculate a cylinder volume, and then subtract the boiler tubes and flues is the best method if the information is available.
I believe that the Steam HUD is still present in MG. At the moment it does not come up by default. I think that you need to navigate to the Locomotive HUD view, and then click on the single locomotive option in the HUD scroll menu.
A steam locomotive is not an instantaneous device (even though OR has reduced the response time to maintain some level of play-ability), and thus I don't think that it needs any higher degree of record points. The steam data collection was not originally added for this type of use, it was mainly added to allow comparison with test reports which followed a more "static" form of locomotive operation in the testing facility. Have a look at some of the test reports to get a sense of the values.
Adding more points would also impact the performance of OR as it would use extra processing capacity, etc.
The data collected by OR can be graphed using an Excel type of program.
This would require some wider discussion. As steam consumption is the major form of heat loss, this gives a better indication that the Boiler Mass is being adversely impacted, and that BP will soon start to be impacted. As described above, depending upon the boiler volume size, by the time the BP reaches a critical level, it could take too long for the fire to be built up and the heat recovered to ensure boiler pressure recovery. This could explain some of the BP "collapses" that you have commented on.
Whilst I know that this measure is not visible to a real crew, I tend to use it more then the BP.
It caps the maximum steam produced by the fire, etc.
Older locomotives tended to work to a maximum of 15, whereas some more modern US locomotives may have figures up to 30.
In OR you can work on the value that OR shows in the HUD. This rarely changes.
This then becomes a question of the test process being used. It would be a lot more complicated to add I think.
Quote
Question: How is boiler volume defined?
The steam locomotive is a heat engine which converts heat energy (produced by the fire/fuel) into mechanical energy (steam / usage causes loss of heat) to drive the wheels. Thus the boiler mass acts as an energy storage medium. The boiler pressure effectively measure the capacity of the boiler to produce the energy required.
A modern analogy for the boiler would be a battery. So the bigger the battery, the longer it lasts, the smaller the battery, the quicker it "dies". Similarly with the boiler the larger its mass, the longer it takes for the boiler pressure to drop, and conversely the smaller it is the quicker that the boiler pressure drops. Ideally a huge boiler would provide a large time before the boiler pressure would drop below a critical level. However the size also impacts the time taken to put the heat back into the boiler, ie the larger that it is, then the longer that it takes to bring it back up to pressure, the smaller it is the quicker that it is bought to pressure. (See Lindsayts example of a locomotive changing grades and the impact of boiler volume)
The boiler volume does not impact the maximum possible boiler pressure, but rather the rate of change in boiler pressure.
Locomotive designers therefore needed to select an appropriate size that provides the "sweet spot" between these two extremes.
As Dave, has suggested wherever possible, for accuracy sake, use real information to calculate the volume. The CTN calculator uses a design rule of thumb calculation for design purposes, and should only be used as a last resort if real information cannot be sourced.
The method suggested by Lindsay and Dave to calculate a cylinder volume, and then subtract the boiler tubes and flues is the best method if the information is available.
scottb613, on 27 March 2019 - 03:56 AM, said:
First off the "Steam HUD [Shift F5]" is still referenced on your site - I don't think it's actually in the [Shift F5] rotation any longer - I haven't seen it in ages - is it just me - am I blind ? I use the Monogame version of ORTS... Without the HUD it's pretty hard to hand fire...
scottb613, on 27 March 2019 - 03:56 AM, said:
Would you consider changing the steam data collection interval to every minute (or user defined) vs every 5MPH ? Seeing what's happening when I hit grades and over time might prove more beneficial when trying to diagnose issues - it's only 60 log entries in an hour so it shouldn't tax anyone's system or space requirement...
Adding more points would also impact the performance of OR as it would use extra processing capacity, etc.
The data collected by OR can be graphed using an Excel type of program.
scottb613, on 27 March 2019 - 03:56 AM, said:
To be more realistic - I'd like to see the color coded "Steam Usage" removed from the HUD - and have a color coded steam pressure gauge instead (red decreasing - yellow steady - green increasing)... While the crew wouldn't have had color coding - we're usually multitasking (concerned with both driving and the fire) while in the sim so that's a bit more realistic cheat than steam usage... The basic HUD should only provide information that was actually available to the crew...
Whilst I know that this measure is not visible to a real crew, I tend to use it more then the BP.
scottb613, on 27 March 2019 - 03:56 AM, said:
How does the values of [ORTSBoilerEvaporationRate] actually work - is "10" decreasing the evaporation rate - "12.5" does nothing - and "15" is increasing the evaporation rate ?
Older locomotives tended to work to a maximum of 15, whereas some more modern US locomotives may have figures up to 30.
scottb613, on 27 March 2019 - 03:56 AM, said:
While I see the values for steam, fuel, water consumed - I don't see a figure that equates to "steam produced" collected - is it available ?
scottb613, on 27 March 2019 - 03:56 AM, said:
Also if we could add some route info to the data collection - like mileage and/or grade - so we can equate the steam performance to an actual location would be helpful...
#36
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Posted 28 March 2019 - 03:04 AM
Hi Copperpen,
Thanks so much for sharing your work - greatly appreciate having a basic starting point for testing... Hah - I've been "mortgaging the boiler" for years - LOL - never knew that it had a term... As mentioned - my time with the sim is pretty limited so I'll play with this over the weekend when I get in... I'll let you know how I make out... Really - thanks...
Hi Lindsay,
Yeah - when I first started putting this ENG file together - Boiler Volume was one of the first parameters I started playing with...
Anyone know what this value on the "steamlocomotive" site equates to ? Currently - it's not one of the "area" parameters that fit into my engine file calculations... Since this is available - would it be something we should include in our calculations ?
Regards,
Scott
Thanks so much for sharing your work - greatly appreciate having a basic starting point for testing... Hah - I've been "mortgaging the boiler" for years - LOL - never knew that it had a term... As mentioned - my time with the sim is pretty limited so I'll play with this over the weekend when I get in... I'll let you know how I make out... Really - thanks...
Hi Lindsay,
Yeah - when I first started putting this ENG file together - Boiler Volume was one of the first parameters I started playing with...
Anyone know what this value on the "steamlocomotive" site equates to ? Currently - it's not one of the "area" parameters that fit into my engine file calculations... Since this is available - would it be something we should include in our calculations ?
- Evaporative Heating Surface/Cylinder Volume 170.10
Regards,
Scott
#37
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Posted 28 March 2019 - 03:26 AM
Hi Peter,
Thanks so much for taking the time to respond and at least hearing me out on my suggestions...
As for logging performance - shouldn't be much of a concern for performance as the only time it should be on is when needed for evaluation...
I would have thought the steam generated would fluctuate with quality of fire, water level in the boiler, and injector use...
Oh - unless I misunderstood your table entry for ORTSBoilerEvaporationRate - it listed the only acceptable values as being between 10 and 15...
Obviously I need to figure out how to get the Steam HUD working again - before I can talk intelligently on anything steam related - I've seen the scroll menu doohickey using [Shift F5] - haven't figured out how to use it - LOL - it's now a priority since I now know that's where the steam HUD resides...
Anyway - I'll mosey back to my modeling/texturing corner now - I'll leave the steam physics stuff to those of you in the know...
Regards,
Scott
Thanks so much for taking the time to respond and at least hearing me out on my suggestions...
As for logging performance - shouldn't be much of a concern for performance as the only time it should be on is when needed for evaluation...
I would have thought the steam generated would fluctuate with quality of fire, water level in the boiler, and injector use...
Oh - unless I misunderstood your table entry for ORTSBoilerEvaporationRate - it listed the only acceptable values as being between 10 and 15...
Obviously I need to figure out how to get the Steam HUD working again - before I can talk intelligently on anything steam related - I've seen the scroll menu doohickey using [Shift F5] - haven't figured out how to use it - LOL - it's now a priority since I now know that's where the steam HUD resides...
Anyway - I'll mosey back to my modeling/texturing corner now - I'll leave the steam physics stuff to those of you in the know...
Regards,
Scott
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Posted 28 March 2019 - 06:00 AM
This is all very interesting. Is there anywhere, a "library" of modifications of .eng and .wag files, which have been made for use in OR?
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Posted 28 March 2019 - 06:34 AM
dforrest, on 28 March 2019 - 06:00 AM, said:
This is all very interesting. Is there anywhere, a "library" of modifications of .eng and .wag files, which have been made for use in OR?
Hi David,
Check out Peter's fantastic site for everything "ORTS Steam" related - - - he has a library of ORTS steam locomotives hosted there as well...
Link:
Coals to Newcastle
Regards,
Scott
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Posted 28 March 2019 - 10:32 AM
WRT boiler volume, consider the Western Pacific 2-8-8-2.
Tube length = 23ft
Boiler Diameter = 108in
large tube diameter - 5.5in
small tube diameter = 2in
Nbr large tubes = 75
Nbr small tubes = 272
After adjusting units of measure to inches, the volume of the boiler w/o tubes is 2,344,583.164 cu in.
(ditto) the volume of the tubes is 790,288.8378 cu in.
As a percentage, the tubes take up about 1/3 of the total volume of the boiler.
Doing the same calculation for a Southern Pacific Mt-4 (a 4-8-2 passenger locomotive) the tubes take up 49% of the total volume of the boiler.
So there are differences in different locomotives and if these two are not weird outliers then it's safe to say a significant percentage of the total boiler volume is lost to tubes.
Tube length = 23ft
Boiler Diameter = 108in
large tube diameter - 5.5in
small tube diameter = 2in
Nbr large tubes = 75
Nbr small tubes = 272
After adjusting units of measure to inches, the volume of the boiler w/o tubes is 2,344,583.164 cu in.
(ditto) the volume of the tubes is 790,288.8378 cu in.
As a percentage, the tubes take up about 1/3 of the total volume of the boiler.
Doing the same calculation for a Southern Pacific Mt-4 (a 4-8-2 passenger locomotive) the tubes take up 49% of the total volume of the boiler.
So there are differences in different locomotives and if these two are not weird outliers then it's safe to say a significant percentage of the total boiler volume is lost to tubes.