Question about Big Boys

[dtrainBNSF1]

Hi all!

Since finishing the SP&S 700 power upgrade and the NKP upgrade I've been looking through other steam locomotive files just to see how they're rated. Today I took a peek at the Big Boy's simulation file and compared it to figures from steamlocomotive.com.

For maxforce in the simulation file I found 4000Kw (=5364hp)
For maxpower I found 190Kn (=42750lbf)

Now on the site it says that Big Boys developed 6000hp @45mph. That would equal 4474.27293063877Kn.
The site also states that Big Boys had 135375lbf. Now this is what I'm posting about. If I've done my math right, that would be 601.66-repeating Kn! That's unbelievable for me! I mean I've gotten Big Boy to pull 150 doublestacks, an equipment car (baggage car) and a caboose up to Dale Junction at 40mph on track 3 without doing anything to it!

I haven't done anything to the simulation file, but I was wondering if anybody could check my math. According to the dev docs 1Kw=1.341hp and 1Kn=225lbf.

[Kali]

One of the steam engine blueprint figures doesn't do anything - I can't remember which one right now! steam engine power is usually measured via the boiler, as that's the limiting factor in how much work it can do ( you can exceed a steam engine's constant power rating by running the boiler out of steam, etc ).

Anyway try setting both those numbers to zero, see if it moves, if it doesn't then set one to a figure and then swap that for the other one. The graphs matter a lot for RW steam engines - and note given power is a factor of steam production, the boiler graphs matter an awful lot.

[Ericmopar]

You also have to be careful when dealing with a Big Boy or Challenger as the two separate engine sets have their own settings for power and traction.
The forward engine is treated as a separate engine, kinda like a multiple unit diesel lashup.

I was reading something not to long ago, that said Big Boys may have developed more than twice the rated power for short periods.
Challenger 3985 pulled 143 double stacks up Archer Hill unassisted at about 35mph.

[dtrainBNSF1]

Yeah I remember that video. That's why I attempted running 150 double stacks up Sherman Hill to see how a Big Boy would cope with it. I did it with the automatic fireman then, but ever since I've been manual firing. Wonder how well I'd get up Sherman while manual firing...

So each part of the Big Boy is treated like it's own unit...I was wondering about that, but I can't find anything like "BigBoy_a" or anything like that. I'll take another look around. Would that mean theoretically that each part should get half the power then?

[Ericmopar]

Yeah I remember that video. That's why I attempted running 150 double stacks up Sherman Hill to see how a Big Boy would cope with it. I did it with the automatic fireman then, but ever since I've been manual firing. Wonder how well I'd get up Sherman while manual firing...

So each part of the Big Boy is treated like it's own unit...I was wondering about that, but I can't find anything like "BigBoy_a" or anything like that. I'll take another look around. Would that mean theoretically that each part should get half the power then?

Yes half the power. It's kinda funny to take a Big Boy or Challenger rear section and drive that without a front.
It's also a game engine bug that I discovered. When the Challenger is saved, the game will frequently forget the front half! Or at least it loses half the power and traction, so I'm pretty sure it forgets the front.

If you didn't know about the sections being treated different on those locos, you may want to know that you can double click on the main loco, front section and tenders, to change the numbers to match. I'm trying to remember if the Challenger front section is actually with the rolling stock, not the engine itself.

Oh yeah... There are three types of Challenger, and the tenders and front sections have to match the main engine, or you may find your steam dying.

[dtrainBNSF1]

Yeah, I at least knew about the numbering thing (found that out pretty quick after making a scenario and both Big Boy sections were numbered differently).

I've done more "snooping" and found what I needed: the engine blueprints for each part in the "Engine" file. It looks like it refers directly to the simulation file, so now I'll tinker around with it. I'll halve the figures I found earlier and enter them into the simulation file and see what happens.

the tenders and front sections have to match the main engine, or you may find your steam dying.

Really? I thought that was more for aesthetics. When I did my 150-car haul over track 3 I modeled the Big Boy after 4014 which will not have a coal tender but an oil tender. I used the tender from the "Challenger Black" variant to make it look like it was an oil burner.

The graphs matter a lot for RW steam engines - and note given power is a factor of steam production, the boiler graphs matter an awful lot.

I'm not too worried right now about the steam production values. The boiler remains at full pressure most of the time when I'm driving. I REALLY have to be trying to get that steam pressure to drop as/is. Unrealistic? Maybe, but I quote from an account speaking about the Big Boys' steaming ability: "They did sterling service in the Second World War, especially since they proved so easy to fire that even a novice could do a fair job. Since many men who were unsuited to combat service were instead drafted into railroad service to replace crewmen who joined up, this proved essential." Personal translation: New to firing a locomotive? Try a Big Boy!
Although as I recall in-game the max pressure is 280psi. It should be at 300psi.

[dtrainBNSF1]

Just got done with a test run using new figures. I made the consist using the consist editor. According to this chart I found (included as attachment) Big Boys were limited to 3250t. traveling westbound between Cheyenne and Buford. My test consist was as close to this as I could get it. It totaled to 107 default boxcars at approximately 30t. a piece.

I made the climb to Buford and up to the summit at an average of 45mph.

I'm not sure if I'll publish the mods, though because the steam generation bugs me. What bugs me the most is that the safety valves don't lift. Mostly the steam pressure hovers at 280psi. and almost never lowers. Steam generation might be fine but inoperable safety valves are a whole other level of unrealistic.

Any thoughts

[Kali]

Tuning RW steam engines is a bit of a black art, unfortunately - and you really do need to start with the boiler, because that will limit how much continuous TE the engine can put out. Keep the control state dialog window up to make sure the safeties aren't actually lifting & just not doing so audibly, not heared of a boiler reaching a set pressure & staying there like that.

[dtrainBNSF1]

Been a while. I've done some work on the Big Boy. I discovered the reason why the boiler pressure was staying so high: the maximum boiler pressure for a Big Boy is supposed to be 300psi, however the .bin file limits it to 280psi. I tried to raise the max boiler pressure to 300 but ended up with a loco that hovered at 280psi with the safety valves continuously going off. I have since put the psi back to default and it now works normally.

I also discovered that the maximum steam output was WAY too high. After some math I lowered that setting to more realistic measures. Steam pressure still raises quite easily but not as fast as it did before.

After a short talk with Smokebox I've started tinkering around with the .dscv files. Still finding my way there, but I think I've got Big Boy's top speed (80mph) achievable (originally it looks like the loco was set up to only make 69mph - tinkering has made it faster).

I'm doing something similar with the Challenger, but I was wondering if anybody knows what the top speed of a Challenger is? I know that it's been documented that a Challenger with a 20-car passenger train hit 70mph but is it safe to say that a Challenger's max speed is 70mph then?

[mrennie]

Hi all!

Since finishing the SP&S 700 power upgrade and the NKP upgrade I've been looking through other steam locomotive files just to see how they're rated. Today I took a peek at the Big Boy's simulation file and compared it to figures from steamlocomotive.com.

For maxforce in the simulation file I found 4000Kw (=5364hp)
For maxpower I found 190Kn (=42750lbf)

Now on the site it says that Big Boys developed 6000hp @45mph. That would equal 4474.27293063877Kn.
The site also states that Big Boys had 135375lbf. Now this is what I'm posting about. If I've done my math right, that would be 601.66-repeating Kn! That's unbelievable for me! I mean I've gotten Big Boy to pull 150 doublestacks, an equipment car (baggage car) and a caboose up to Dale Junction at 40mph on track 3 without doing anything to it!

I haven't done anything to the simulation file, but I was wondering if anybody could check my math. According to the dev docs 1Kw=1.341hp and 1Kn=225lbf.

There's been a lot of confusion about the units used for "Max force", and much of that comes from a mistake in the dev docs where it says the value is in kN, plus another mistake in the blueprint editor where it says lb/f. After extensive testing by a fellow developer on the beta forum, we've agreed that the units are in fact klbf (which is lucky, because that's what I thought when I did the Connie!).

You did the math correctly, and sure enough, the simulation blueprint is saying that the Big Boy has 190,000 lbf starting t.e., which is still too much! The correct value for "Max force" is 135.375.

As mentioned before, there's another value in the simulation blueprint that is completely ignored by the core code. It's "Max power". You can put 0 and it won't make any difference.

As for the rest of it, it is indeed something of a black art, but there are some handy forumulae:

1 Boiler Horsepower = 34.5 lbs of steam per hour.

Boiler Horsepower = (1/6) grate area (sq. ft.) x boiler pressure (psi)

For example in the case of the Big Boy, the grate area is (only) 150 sq. ft. (quite large really, considering that the FEF-3 has 100sq. ft.).

so, BHP = (100/6)*150 = 2500

The theoretical maximum steaming rate (lbs/hr) = boiler horsepower * 34.5

so, steaming rate for the BB is 2500*34.5 = 86,250 lbs/hr.

However, for the FEF-3, that works out at about 172,000lbs/hr, but empirical figures published by ALCO show that in reality it's a lot less, around 112,000 lbs/hr. Therefore, I multiply the theoretical by 0.65 and use that for the boiler "Max output". Thus, for the BB, you should set "Max output" to 56062.

After that, it really does turn into a black art. You have to do a lot of testing and tune various parameters. With the FEF-3, to get the maximum steaming rate to match "Max output", one of the most critical parameters was the boiler "Effectiveness" (I ended up with 2.3). Also,to get the boiler pressure to rise and fall at a reasonable rate, you have to experiment with different values for boiler "Volume". If you have it too low, the pressure will drop rapidly as soon as steam usage exceeds steam generation, but conversely, if it's too large, the pressure will stay high for too long. In the end, you settle on a figure that simply feels right. In the FEF-3, I ended up with 1800 cubic feet (which, by the way, is bigger than the space in the boiler, but that just shows that you can't always put in exact real-life figures and expect everything to work prototypically).

Before I forget, another handy formula:

boiler "Superheater" = 1 + (superheater area / Heating surface (tubes and flues))

thus, for the BB, Superheater = 1 + (2043/5375) = 1.38 9that's using the figures found here http://en.wikipedia.org/wiki/Union_Pacific_Big_Boy)

There's a lot more to add, but I need to go and make a coffee ...

[dtrainBNSF1]

Hi all!

Since finishing the SP&S 700 power upgrade and the NKP upgrade I've been looking through other steam locomotive files just to see how they're rated. Today I took a peek at the Big Boy's simulation file and compared it to figures from steamlocomotive.com.

For maxforce in the simulation file I found 4000Kw (=5364hp)
For maxpower I found 190Kn (=42750lbf)

Now on the site it says that Big Boys developed 6000hp @45mph. That would equal 4474.27293063877Kn.
The site also states that Big Boys had 135375lbf. Now this is what I'm posting about. If I've done my math right, that would be 601.66-repeating Kn! That's unbelievable for me! I mean I've gotten Big Boy to pull 150 doublestacks, an equipment car (baggage car) and a caboose up to Dale Junction at 40mph on track 3 without doing anything to it!

I haven't done anything to the simulation file, but I was wondering if anybody could check my math. According to the dev docs 1Kw=1.341hp and 1Kn=225lbf.

There's been a lot of confusion about the units used for "Max force", and much of that comes from a mistake in the dev docs where it says the value is in kN, plus another mistake in the blueprint editor where it says lb/f. After extensive testing by a fellow developer on the beta forum, we've agreed that the units are in fact klbf (which is lucky, because that's what I thought when I did the Connie!).

You did the math correctly, and sure enough, the simulation blueprint is saying that the Big Boy has 190,000 lbf starting t.e., which is still too much! The correct value for "Max force" is 135.375.

As mentioned before, there's another value in the simulation blueprint that is completely ignored by the core code. It's "Max power". You can put 0 and it won't make any difference.

As for the rest of it, it is indeed something of a black art, but there are some handy forumulae:

1 Boiler Horsepower = 34.5 lbs of steam per hour.

Boiler Horsepower = (1/6) grate area (sq. ft.) x boiler pressure (psi)

For example in the case of the Big Boy, the grate area is (only) 150 sq. ft. (quite small really, considering that the FEF-3 has twice that amount, but then again, the FEF-3 was designed for high horsepower).

so, BHP = (100/6)*150 = 2500

The theoretical maximum steaming rate (lbs/hr) = boiler horsepower * 34.5

so, steaming rate for the BB is 2500*34.5 = 86,250 lbs/hr.

However, for the FEF-3, that works out at about 172,000lbs/hr, but empirical figures published by ALCO show that in reality it's a lot less, around 112,000 lbs/hr. Therefore, I multiply the theoretical by 0.65 and use that for the boiler "Max output". Thus, for the BB, you should set "Max output" to 56062.

After that, it really does turn into a black art. You have to do a lot of testing and tune various parameters. With the FEF-3, to get the maximum steaming rate to match "Max output", one of the most critical parameters was the boiler "Effectiveness" (I ended up with 2.3). Also,to get the boiler pressure to rise and fall at a reasonable rate, you have to experiment with different values for boiler "Volume". If you have it too low, the pressure will drop rapidly as soon as steam usage exceeds steam generation, but conversely, if it's too large, the pressure will stay high for too long. In the end, you settle on a figure that simply feels right. In the FEF-3, I ended up with 1800 cubic feet (which, by the way, is bigger than the space in the boiler, but that just shows that you can't always put in exact real-life figures and expect everything to work prototypically).

Before I forget, another handy formula:

boiler "Superheater" = 1 + (superheater area / Heating surface (tubes and flues))

thus, for the BB, Superheater = 1 + (2043/5375) = 1.38 9that's using the figures found here http://en.wikipedia.org/wiki/Union_Pacific_Big_Boy)

There's a lot more to add, but I need to go and make a coffee ...

Hoo-boy. Thanks for clearing that up for me Mrennie . I was pondering about the power thing all day today after doing several tests with the Big Boy because on a grade of 1.5% with a load of 3250t. according to my formulas (hp/trailing tonnage=hp-per-ton)(hp-per-tonx12/% of grade=estimated max speed) the Big Boy should only be able to crest the hill at 25-or-so miles per hour (tests had me cresting the grade at track speed). But man oh man I had no idea I was that far off. After I get finished with the Big Boy I may need to take another look at the SP&S 700 and NKP 765 because I might have released 2 uber-powered monsters for download.

Just to make sure I understand the formulae: (1/6)150=25x300psi=7500bhp
7500x34.5=258750x.65=168187.5lbs/hr
1+(2043/5035)=1.4(approx.)

It's half past midnight here but I'm still wide awake. Back to work!

[dtrainBNSF1]

There's another thing that bugs me. It's the max boiler pressure. From all sources the Big Boy should have a maximum of 300psi. However when published on steam the locomotive was programmed to produce only 280psi. I've tried to correct this in the .bin file by typing in 300 in the " max pressure" and "pressure for open" lines. The F5 HUD reflects this change but the F4 HUD will only go up to 280psi and it will stay there making it look like it's hovering in place until steam pressure drops below 280. Is there a way to get the F4 HUD to reflect the change?

[mrennie]

There's another thing that bugs me. It's the max boiler pressure. From all sources the Big Boy should have a maximum of 300psi. However when published on steam the locomotive was programmed to produce only 280psi. I've tried to correct this in the .bin file by typing in 300 in the " max pressure" and "pressure for open" lines. The F5 HUD reflects this change but the F4 HUD will only go up to 280psi and it will stay there making it look like it's hovering in place until steam pressure drops below 280. Is there a way to get the F4 HUD to reflect the change?

Before going into that, let me just mention that I had to edit an earlier post ... the FEF-3 has a 100 sq.ft. grate area (not 300, I was confusing it with boiler pressure ).

You interpreted correctly the formulae I gave

That thing with the boiler pressure is annoying. I have the same problem with the FEF-3. I have the "BoilerPressureGaugePSI" controller in the engine blueprint with a range of 0 to 600 (because the dial on the boiler pressure gauge goes up to 600psi - Buzz once explained why that is, something to do with the springs in the gauge). Meanwhile, in the engine simulation blueprint, I've set boiler "Max pressure" to 300psi. There are also three safety valves set to lift at three different pressures (300, 302 and 305). But try as I might, even when the steam generation is way above the steam consumption, I just cannot get the boiler pressure (on either the HUDs or the in-cab gauges) to rise above 300.2psi. I'm going to do some debugging and see what the heck is going on, because it's a bug that's really bugging me.

EDIT: I tried deleting the safety valves entirely from the blueprint and set Max pressure to 600. It didn't make any difference at all. Boiler pressure still wouldn't rise above 300.2psi.

EDIT2: In the BB's engine blueprint, look for the entry for "BoilerPressureGaugePSI". If its max value is only 280 instead of 300, that would explain why the F4 HUD doesn't show more than 280. I haven't got the BB, so I can't check that myself.

[dtrainBNSF1]

Will do

[dtrainBNSF1]

That did it. Where the Big Boy is made of 2 parts I had to change the psi on each part. One thing I'm noticing on my more recent trials is that the boiler is depleting itself of water faster than I can fill it. I lower throttle and reverser settings and end up stalling on the hill. The dev docs make it look like I could possibly increase the size of the cones inside the injectors and feed rate multiplier but wouldn't that also increase how much steam is used in the process?