Steam & Excursion > Just some musings

I believe that 4014’s flues and tubes are approximately 20-feet long;  so, presuming the the front tube sheet is located at the same plane as the front-end band of the sheet metal jacket, where Would Be the approximate location of the rear tube sheet?
( external marker).

Maybe under the safety valves?
The front of the rear sandbox?
Between the two sandboxes ?

​W.

Interesting. . . if the Big Boy flues are twenty feet long, than they are about the same length -- perhaps slightly shorter -- the the flue pipes on the venerable 4-4-2 "Atlantic" EB-6 locomotives. 

I believe that back in the day (like 110 years ago) there was some test stand studies done that established that about 20-22 feet was the optimal length for flue pipes in a locomotive. 
 

It looks like for this drawing (grabbed off the internet, so I don't know if it's accurate or not) that the firebox extends to about the rear of the posterior sand box, and the smokebox starts about the area of the anterior sand box. . .
 



Edited 1 time(s). Last edit at 05/18/19 07:29 by Narniaman.

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So the unknown here is how far forward of the front of the firebox is the rear flue sheet?  I don't know how long the combustion chamber is and it would extend from the front of the firebox to the rear flue sheet.  Probably 5-6' as a WAG

Yes, the so-called ‘combustion chamber’ is a large, cave-like, circular extension of the firebox, extending from the throat sheet, forward.

On the above drawing, the visible, exposed area of the firebox sheets represents the region adjacent to what had been the grate bar, side supports.  The crown sheet forms the ‘roof’ of the furnace inside the boiler, and it extends, along with the
‘combustion chamber’,   to well under the rear sand box..

​W.

(The above drawing appears to be a rendition of a toy [Kadee couplers?].  The gap between the engine and tender is wayyy to wide..😆)



Edited 3 time(s). Last edit at 05/18/19 08:58 by wcamp1472.

>
> (The above drawing appears to be a rendition of a
> toy .  The gap between the engine and tender is
> wayyy to wide..😆)
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Pretty sure you're correct. 

There don't seem to be a whole lot of actual cross sectional drawings of a Big Boy. . .at least on the internet! 
 

UP Big Boy drawing shown below.

For comparison with other large engines.  Flue lengths.

UP   4-8-8-4  22' 0"
C&O  2-6-6-6  23' 0"
PRR  6-4-4-6  22' 0"
NP   2-8-8-4  22' 0"
WM   4-6-6-4  23' 0"
DRGW 4-6-6-4  22' 0"

UP   4-8-4    20' 6"  (800 series)
SP   4-8-4    21' 6"  (GS2)
NP   4-8-4    19' 6"  (A-2)
C&O  4-8-4    21' 0"
NYC  4-6-4    19' 0"  (J3a)

ATSF 2-10-4   21' 0"

-Larry Doyle



Edited 1 time(s). Last edit at 05/18/19 07:51 by LarryDoyle.

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Train Shed Cyc 47 has the RME drawing -- rear tube sheet is a few inches ahead of the front end of the rear sandbox.

NICE!

Many thanks...

​W.
 

On the side view there is a line of washout plugs (round dots) just below the handrail, starting above the #5 driving wheel and spaced evenly the length of the firebox and combustion chamber.  The leading washout plug in this group is just forward of the rear flue sheet.
- Doug Debs

“The leading washout plug in this group is just
> forward of the rear flue sheet.”

Please clarify. 
.
Which way is ‘forward’ in your reference?  ( towards the smoke box, or towards the ‘door sheet’?)
What is purpose of calling attention to the washout plugs’ locations?

W.

Interesting to compare the tube lengths given above with those of some engines built about 20 years earlier.

USRA light and heavy 2-8-2's  19' 0"
ATSF 2-10-2  24" 0"
B&O 2-8-8-0  24' 0"
USRA light and heavy 4-8-2   20' 6"
ERIE 2-8-8-8-2  24' 0"

And, with some from about 20 years before that

UP 4-4-0   11' 6 1/2"
ATSF 2-8-0   13' 9" 
PRR 2-8-0  13' 8 1/2"

-LD

Once you break up the hot-gas stream into 150+ smaller  gas streams, surrounded by cold water,  it’s a wonder that there’s any conductible heat remaining in the flow, after about 8 to 9 feet of travel.

The reason for the term ‘cold’ is the relative temperatures reaching above 3000 deg. F. Compared to the boiler water in the
400 deg. range.  The colder water surrounding the tubes is very thirsty for heat— so the gasses enterin smoke box will be nearly the same temp as the water at the front tube sheet...... nowhere near boiling under pressure...

I’d guess there were flue-gas temp readings at the smoke box end of the flues, that showed a beneficial contribution of heat....but that would only be occurring at excessively high firing rates...

The 4000 class drawing shows the circulator tubes in the firebox, supporting an array of arch bricks, fir coal use—- that’s a very long flame path directly under the crown sheet.  I suspect that the arch bricks are eliminated in the oil-burner  configuration.

it’’ll  be interesting to see how the conversion works-out..... 
The success will only be told, if put to work against a real “drawbar challenge.”
Oh, well...

​W.



Edited 1 time(s). Last edit at 05/18/19 16:28 by wcamp1472.

Frisco1522 Wrote:
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> So the unknown here is how far forward of the
> front of the firebox is the rear flue sheet?  I
> don't know how long the combustion chamber is and
> it would extend from the front of the firebox to
> the rear flue sheet.  Probably 5-6' as a WAG

It's 112 inches.

-LD

Very little boiling takes place around the boiler tubes, past the first several feet.
In a superpower locomotive with such a big firebox and long combustion chamber, the forward tube area acts more like a feedwater preheater than a boiler.

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