Steam & Excursion > SP Cab Forward 4294, Sacramento

As a kid in the 50’s, I played on SP ‘cab forward’ 4294 at Sacramento, the only cab forward preserved. Here are two pics from that period and one as it is now at the CSRM museum, Sac. I also rode the ‘City of San Francisco’ from Sac to Iowa several times, all inspiring my rail interest.

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sort of off topic question, I wonder how many gallons of water would be in the boiler of the cab forward loco under normal operating conditon. Curious about the boiler capacity on a big boy or challenger under operation.
Doug

Fascinating locos which handled most SP freight and passenger service between LA and Bakersfield in the '40s and up to when the diesels arrived.

Bill Deaver
Tehachapi, CA

hoggerdoug Wrote:
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> sort of off topic question, I wonder how many
> gallons of water would be in the boiler of the cab
> forward loco under normal operating conditon.
> Curious about the boiler capacity on a big boy or
> challenger under operation.
> Doug

"Cab Forward 4294 - Souhern Pacific Railroad's Sigature Locomotive" by Anderson, Cipolla, and O'Day, p. 20, lists the boiler water capacity as 10,935 gallons.

However, when I take the weight of the locomotive with boiler filled with water, subtract the empty boiler weight (giving me the weight of the water) and divide by the accepted density of water (8.3 lbs/gal), I come up with 9,771 gallons. Due to thermal expansion, density of water decreases as temperature rises, which may account for the discrepancy between the listed capacity, and my calculated value.

Corrections welcome!




 

Arved Grass
Fleming Island, FL

What does 'filled' with water mean?

Starting with 'cold' water, you'd want the water level in the sight glass
to be in the lower 10% ( of the visible portion of the glass)

Upon sufficient heating of the boiler water, it will expand to reach
95% of the height in the visible glass.

So, is the volume of the water space a simple calculation of the interior 
volume, and what that volume equates as the calculations of the interior 
physical volume.

Then, there's  what the water level is at about the 25% level,in the glass,
stationary and quiescent.   Upon opening the throttle, the water level raises
in the glass account of submerged steam bubbles ...the submerged bubbles
displace water, thus raising the water level in the glass to about the 50% level.

So you've got many choices to pick from when discussing a boiler "filled with water".
What specifically is the level that you're tryin to compare?  And at what temperature.
Also you could specify the capacity by the weight of a gallon of heat-expanded water.
That 8,6 gallons, by weight, could be a 20% increase in volume when heated,
but still the same weight ...8.6 lbs.

​W.


 

From Bessemer & Lake Erie RR diagram book dated 1/6/1944, Page 46 for B&LE 2-10-4 #643, now owned by the Age of Steam Roundhouse Museum of Sugarcreek, Ohio
Water in boiler, 2 gauges, 406° F -- Weight 41,937 pounds, 20.97 tons, Capacity 5,890 gallons
I hope this helps. Be Safe.

John B. Corns
Age of Steam Roundhouse Museum
213 Smokey Lane Road SW
Sugarcreek, OH 44681
330/852-4676
https://www.ageofsteamroundhouse.org
 

That level of Specificity is always appreciated..

​WHY IS BOILER WATER LEVEL SO SIGNIFICANT???

When running, beginning a trip with 'two gauges of water' is a risky way to start out.
With the throttle open, that water level will rise up to nearly a full glass.
That's not a good water level to operate at.

But, some engineers preferred to run with boiler water at high levels in the glass.
IIRC, the E-L RR had an engineer ( 1970's HICO fan trips) who's last name 
was Hofer --- his nickname was "Highwater-Hofer"... always wanted the sight glass
better than half-full.  But he managed to make that work.

At the other extreme, I've seen engineers that ran with low water in the glass,
so that when they closed the throttle, the water would disappear out the bottom !!!
Makes everybody in the cab "go to full clench" ...'til they see the water Bob-up
in the glass --- using both the pump and the injector to get the water level up.

That's hard on the firemyn, 'cause that much added water really depresses the
boiler water temp.   So, that calls for adding more fuel.  
With coal burners, you have a long delay waiting for the whole firebed to get
up to 3,000 F .  That's hard to do, with little or no draft up the stack.

With oil burners, all you gotta do is widen on the oil delivery valve..... and if you've got a
good draft up the stack---- you can keep up the pressure.
 BUT, with low draft, like the train slowing way down, widening on the oil feed-rate turns the 
exhaust smoke into dense clouds of carbon, and the added fuel cools-off the flame 
temperatures  ...Coating the boiler tubes with layers of gooey, black un-burned carbon.

That added carbon layer deposited in the boiler heating surfaces is an insulating event
of high proportions... and you don't want a layer of 'insulation' when you're trying to boil
water at high temperatures ..

A good firemyn knows the hilly territory, knows the train's mass behind the tender,
knows the schedule, and has an engineer that communicates frequently about imminent
changes they'll be making to the throttle and valve gear settings.  
That level of subtle cab teamwork in action is a great thing to observe & exciting to watch.

Because of the delay in controlling the boiler water temperatures, the firemyn has to have 
the current firing conditions, and water levels, about 5-minutes ahead of when the actual
changes in drafting will be taking place.  You'll be making adjustments well ahead of 
when the change in 'firebox state' is actually needed....injectors are not instantaneous
in changing water levels, and the firebox brick-work changes it's temperatures very
gradually.. .whether heating-up or cooling down.

 ( That's why, as a firemyn, it's good to be very familiar with the territory being covered and
have a deep understanding of the expected firing demands...this is especially important
in night running...where you can't clearly see the route ahead).

 If you wait for those throttle changes first, you'll ALWAYS be well behind in regulating the
firebox brickwork heat and water levels ( playing catch-up) ... you'll always be working
extra hard, and you'll have a tiring day at the end of the run

​W.

( A couple of basic,  but relevant facts about water level sight glasses:
  1.  The bottom of the sight-glass MUST be 3-inches , as a minimum,
        above the highest level of the crown sheet --- which slopes upward
         towards the front of the firebox.

  2.   It used to be that, as a back-up in case of a broken sight glass, boilers
        were fitted with a set of 3- 'Try-Cocks', or 'Tri-cocks',  The formal name for these
        3 valves is "Gauge Cocks"  [to visually gauge the boiler's water level].

        The three were set with the lowest tri-cock at the same level as the bottom
         of the water glass.   So, "two gauge cocks" was presumed to be a half-way 
         point of a boiler-full of water.  The top gauge cock was typically set to be at the
         same level as the top of the water glass.  The actual top of the boiler interior 
         may be as much a one or two feet above the level of the top the sight glass.

           I understand that the current FRA practice has made the equipping of boilers
           with  three gauge cocks  is optional, since current regs require two sight glasses
           to be applied to all operational locomotive boilers.  

           It was common on larger locomotives, constructed at the end of  the steam era,
           to be equipped with two sight glasses, as well a set of 3 gauge cocks.
           That remains my personal preference...)
           



Edited 3 time(s). Last edit at 04/08/21 05:15 by wcamp1472.

wcamp1472 Wrote:
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> What does 'filled' with water mean?

Whatever the author meant it to mean.

Wikipedia has the same number, possibly from the same source: 10,935 gallons.

If you've got a better answer, please share. If not, STFU.

Arved Grass
Fleming Island, FL

Arved Wrote:
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> wcamp1472 Wrote:
> --------------------------------------------------
> -----
> > What does 'filled' with water mean?
>
> Whatever the author meant it to mean.
>
> Wikipedia has the same number, possibly from the
> same source: 10,935 gallons.
>
> If you've got a better answer, please share. If
> not, STFU.

WOW!!!!!    And you guys bitch about MY ATTITUDE!  To be clear, the original poster sometimes doesn't have a good track record on TO, and as far as "Wikipedia", I wouldn't trust them either.

HotWater Wrote:
-------------------------------------------------------
> Arved Wrote:
> --------------------------------------------------
> -----
> > wcamp1472 Wrote:
> >
> --------------------------------------------------
>
> > -----
> > > What does 'filled' with water mean?
> >
> > Whatever the author meant it to mean.
> >
> > Wikipedia has the same number, possibly from
> the
> > same source: 10,935 gallons.
> >
> > If you've got a better answer, please share. If
> > not, STFU.
>
> WOW!!!!!    And you guys bitch about MY
> ATTITUDE!  To be clear, the original poster
> sometimes doesn't have a good track record on TO,
> and as far as "Wikipedia", I wouldn't trust them
> either.

Wikipedia is only as good as it's last "edit". It's the classic GIGO, Garbage In, Garbage Out routine.

Arved Wrote:
-------------------------------------------------------
> wcamp1472 Wrote:
> --------------------------------------------------
> -----
> > What does 'filled' with water mean?
>
> Whatever the author meant it to mean.
>
> Wikipedia has the same number, possibly from the
> same source: 10,935 gallons.
>
> If you've got a better answer, please share. If
> not, STFU.

Lighten up, Francis.

The question Wes asked was valid. “Do you mean filled to the top, even though it wouldn’t operate that way?” “Do you mean under typical light operation?” “Do you mean under a heavy load, anticipating a hill ahead, prepped in the roundhouse, or what?”

Wes did have a much better answer, by the way.

We all pay for our TO memberships and a certain right to ask/answer/call out questions. Seeing a member tell someone with the reputation that Wes has to”STFU” is sophomoric, and better left unsaid.

Posted from iPhone

Jared Hamilton
Scott Depot, WV

I guess the answer to this ambiguity of "full"  is the classic wording:
" It depends"

I was simply giving some understanding to the curious, that the  water level in 
a boiler is largely dependent on the boiling temperature , and the fact that hot water
expands by a considerable amount.  

You don't have to get your bowels in an uproar over the realities of the expansion 
 qualities of water temperature in a pressurized vessel.  
Also, that a gallon by volume, varies with the temperature; whereas, a gallon of water
by weight is constant.  ( water is at its most dense state at 39 F;  and ice at 32 F, and lower, 
floats ... because it is less dense than surrounding water ).

Anyone who has observed a locomotive water glass from cold ground water,
to full operating pressure.  You must typically start with the cold water level barely visible
in the bottom of the sight glass .... adding only heat, the volume of that water in the boiler
increases...by temperature alone.  Typically, the hot water level ( at the rated pressure) ,
as read by the height in the sight glass, will rise to about 85% of the full glass.
 
When firing up a "full boiler", starting at ground water temps, has the proper water level at the bottom 
of the glass.  It will grow --- in the glass---to what would satisfy most folks as a 'full boiler'...

Are we saying that the boiler is full at cold water temps,  or water temps around 400 F.
There are confusing aspects to so much of the physics of steam locomotives.
I'm  open to learning more about the myriad of mysteries of these fascinating machines.

Such as:  "how much water is in a full boiler ?"
Answer: It depends.....

W.
( My favorite quote from Voltaire:  " I may disagree vehemently with what you say,
But, I will defend to the death, your right to say it.".).

 



Edited 6 time(s). Last edit at 04/08/21 15:39 by wcamp1472.