Big Boy boiler pressure...

F

frogpipe

Yesterdayz Trainz Member
So I've been mucking about with the UP Big Boy, seeing all the news about 4014 lately, and after letting it sit on a spur for about 1/2 hour...

frogpipe_20130725_0000_zps134eadd3.jpg


This is the beginning of my run, with the boiler at 500+ psi - headed to Tehachapi from Cable (up hill) I hit 130+ mph before it derailed just past Tehachapi.

I'm thinkun' this don't conform to prototype...

:D
 
Good Morning Wkwood
Just out of curiosity, which build are you running the BigBoy in? Pre SP1 there was a bug that created 'free energy' in the boiler, which caused this issue, however this should now be fixed. It's possible there's an issue in the Espec itself though that might be causing this, it only received a basic upgrade to the Espec so there may still be some bugs.

Regards
 
The e-spec appears to be TC3 '2.8' I'm looking at it now and looks like cylinder clearance is the culprit here, looks large to me, bigger cylinder clearance is more speed, smaller cylinder clearance is less speed, I use 1.3inches for e-specs and it's rather hard to exceed 80mph with 300 tons on a large loco, if you use a 4inch cylinder clearance you reach 100mph with the same loads, the big boy one looks like it's about 2 or maybe 3 inches.

Hence why I said it has warp engines, it was set up for speed by N3V, lol, the high boiler pressure seems to be from the high pressure valve venting very low volume of steam, I'd use 3kg/s for a boiler of that size, N3V set it up to 0.8kg/s.

Cheers.
 
ZecMurphy said:
Good Morning Wkwood
Just out of curiosity, which build are you running the BigBoy in?

Regards
Click to expand...

Uh Zec, I didn't ask the question but now I'm interested... :D

I have been running the Big Boy with 3000 ton consists on UMR-2012 and boiler pressure is still bad, Sure I can get up speed but even with 70% coal and 70% water I drop with a 10% regulator and a 6% forward and it still hovers at 140 to 150 PSI. Considering the firebox this thing has, that's way low even at 60MPH. The only way I can get pressure to rise is if I drop the regulator below 10%, say 6% and that's not enough to keep it moving on level terrain.

For Me, I'm in SP1, HF3 (58414). I've never monkeyed with an Engine Spec, is there a tutorial somewhere?
 
My apologies, that should have been 'frogpipe'. I do apologise to both members, it wasn't intentional. I guess I must have flipped between a few tabs before replying.

My question does still stand, but is directed at Frogpipe :)

Regards
 
ZecMurphy said:
Good Morning [frogpipe]
Just out of curiosity, which build are you running the BigBoy in? Pre SP1 there was a bug that created 'free energy' in the boiler, which caused this issue, however this should now be fixed. It's possible there's an issue in the Espec itself though that might be causing this, it only received a basic upgrade to the Espec so there may still be some bugs.

Regards
Click to expand...

This is the latest greatest TS12, 58414. I find it disappointing that

it only received a basic upgrade to the Espec
Click to expand...

don't you (as in N3V as a whole) think that as a built in locomotive it deserves to have a full and proper update? Especially since it's not "crowd sourced" but authored by "Auran"?

Either that, or it shouldn't have been included with that game.


EDIT: I just doubled checked, to be sure nothing had been noodled with, and it's using Big Boy Enginespec,<kuid2:523:51469:7> which is NOT locally modified.
 
Last edited:
Hi guys, may I please ask something here for interests sake and excuse me if I am being blonde and missed points somewhere.
I have done no updates - still with build 49922 - and Big Boy has no problem when I place it for example on Mojave.
The safety valve blows at 299psi and it seems operate normally with loads as well.
 
Azervich said:
The e-spec appears to be TC3 '2.8' I'm looking at it now and looks like cylinder clearance is the culprit here, looks large to me, bigger cylinder clearance is more speed, smaller cylinder clearance is less speed
Click to expand...

Actually, bigger cylinder clearance is less efficiency -- and therefore higher steam usage for similar output. You might be able to wind it up to higher speed, but that's definitely a secondary effect.

Too small a cylinder clearance volume will give a loco that runs too efficiently, can produce too much excess steam, and has too low a water consumption.

the high boiler pressure seems to be from the high pressure valve venting very low volume of steam, I'd use 3kg/s for a boiler of that size, N3V set it up to 0.8kg/s.
Click to expand...

That might be worth a tweak -- but watch out for a sawtooth pressure problem where the valve keeps turning on and off. Properly proportioned locos don't run hard against the safety valves for long periods of time.
If you were looking at doing an upgrade on this enginespec, you might be better off tweaking the efficiency values for the boiler, or the boiler-heat-loss tag. This would be a better way to keep that excess heat (and thus steam) under control than just boosting the safety valve flow.
 
bendorsey said:
According to the Model Railroader Cyclopedia boiler pressure was 300 psi.

Ben
Click to expand...

I guess that would add another dimension to the Game aspect of Trainz, too much boiler pressure and boom. Much like the MSTS guys have with crashing their simulations. We need a Gomez Addams mode!
 
Okay I've been tweaking the Engine Specs for the Auran DLS Big Boy. <kuid2:5233:51469:7>

Here's what I've added / changed.

tractive-effort-constant 0.708 // Weight on Drivers/Locomotive Weight Ratio (wasn't in spec, added it)
firebox-heating-surface-area 67 // Was 40, most references indicate this as 67 (Wikipedia for example) This seems to have helped boiler pressure recovery the most.
steam-chest-volume 1.3884 // 4 times cylinder volume was .5
piston-volume-max 0.3471 // 32 inch stroke * piston Area + .4 (min volume) * piston area.
piston-area 0.2861 // (23 3/4in / 2) ^2 * pi M^2
number-cylinders 4 // was missing
number-power-strokes 2 // was missing

After making these changes boiler pressure can be sustained at cruise (<15% cutoff and below 30% regulator) and you can accelerate like it used to in TRS2006 and 009. I also don't get the runaway boiler pressure. I can also now get wheel spin with a heavy load (3000T coal train) necessitating a little bit of cutoff and throttle control like it used to be.. ;-)

The numbers I am using are based on info out on the Internet. The strange thing now is that the locomotive above 10mph sounds like a model T so setting the cylinder count must have affected the sound? Is there a way to turn that back so it sounds more like a lumbering locomotive?

Also, coal burn rate is way too low and even with the coal turned all the way up it's not filling up the coal level, also on a long run with 3000T, it's barely empyting the tender, so somehow I need to turn up the coal feed rate. That's always been a problem, but figuring a 3000T load and 50 miles at least half of the coal (or more) should be gone. Does anybody have any hints on that? I see shovel-coal-mass and burn-rate so I presume
adjusting those two values may help?

Overall I'm much happier with how the locomotive performs just on these tweaks alone, I'm trying to fine the other
parameters, boiler volume, and actual steam-chest-volume etc. Since I have 4018 not too far from me, maybe I should take
a tape measure over? :o
 
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