In this next part of the quiz, we move up from the running gear and into the heart of the locomotive: the firebox and boiler.
We all know that the firebox is the core of any steam engine, but do you know all the various parts that make up a firebox? They are a bit more complicated than they appear!
1.: What are the “Backhead”, “Mudring”, “Crownsheet” and “Neck”, and where are they located in the firebox?
2.: What is a “Syphon” and a “Circulator”? How do they work, and how do they differ?
3.: What exactly are grates? What do they look like and how do they work?
4.: What 3 functions does the “Brick Arch” in a firebox perform?
5.: How are oil burning fireboxes different from coal burning fireboxes?
6.: What are “Watertube Boilers”?
Bonus: We tend to think that the various auxiliary parts of a locomotive were all made by the main builder of the engine (BLW, ALCO, Lima), but this isn’t actually the case. Scores of small specialized companies developed and manufactured many of the smaller components of a locomotive (actually not just the small parts, but almost everything except for the cab and boiler shell!). One good example is the automatic coal stokers. There were a couple of competeing manufactures who built and sold their own brand of stoker. Can you name them?
That’s it for this part of the quiz right now. I got a lot mre to add to it though, and I’ll add more questions as these get answered. (I told you the firebox was a lot more complicated than it appears to be! Just wait until I get to boilers and front end arrangements!!!)
Good Luck!
Matthew Imbrogno
-Mechanical Vollenteer, Arizona Railway Museum www.azrymuseum.org
I almost forgot to toss my ante into the fire! It aint fair if I make you answer all these questions if I don’t give one myself! I won’t answer one of your’s though, I don’t want to take your fun away!
The subject is Staybolts: Staybolts are the houndreds of bolts that hold the inner firebox and the boiler shell together. Because a waterspace has to exist around the firebox, between it and the outer boiler shell, some sort of spacer is needed to keep everything together in proper alignment. Also, because of the pressure in a boiler, and because the firebox plate needs to be as thin as possible to conduct heat to the water efficently, the firebox needs to be supported and held against the pressure to keep from buckling inward. Staybolts act like a suspension system, litereally ‘hanging’ the firebox from the boiler shell. When you view the outside of a firebox, and see all those bolts and nuts on the side, those are the crownbolts. They pass through holes drilled through the boiler shell and firebox.
Staybolts have two or three parts: a seat in the boilershell which is custom fitted to the contour of the plate, a threaded rod or “bolt”, and another seat on the inside of the firebox. The seats are specially drilled and tapped into the plates to ensure a pressure-tight seal. Many of the later staybolts have sealed caps with bolt ends fully contained inside them, so that there is no gap or crack to let steam escape. Some staybolts have only one cap or seat, with the other end of the bolt being riveted straight to the boiler plate. These are prone to leakage however, and fell out of favor in the thirtys.
There are two types of staybolts: Static and flexible or Radial-Stayed bolts. Static bolts are generally used on the lower part of the firebox, where the firebox and boiler shell plates are perfectly parallel and not subject to much flexing or sheer. Flexible staybolts are used on the upper, curved sections of the fir
Ok now! SDR_North knows a lot about fireboxes! There are still a few openings for the rest of you though!
SDR_North got #1 absolutly right, and #2 half right; we’re still looking for the definition of a “Circulator”. Thank’s also for your very thorough description of Grates, although I’d like to add a little to that.
Grates are not only triangular, but they can also be eliptical or flat rectangular. Grates are hollow on the inside, and have slits in the top to let air through. They were more like a grid mesh, literally a “grate” or “grating”.
For #4, Deflecting heat is only one job that the brick arch does. What are the other two?
Number 5 and 6 are both good answers, but a little elaboration on the arrangment of a watertube boiler could be usefull.
Now for some additional questions:
#7: what are “Drop Plugs”, How do they work?
#8: The accumulation of soot and ash is not a critical problem, but it plagues engines by blocking the transfer of heat from the fire to the water. How do crews clean the soot off of a boiler while on the road? While in the shop?
#9 What are you doing if you are “Wabashing” an engine?
And another bonus: For those of you who have read “Rio Grande Glory Days”, what happons if you try to burn Gilsonite in a locomotive? I’ve also read about burning tires and other non-standard fuels in an engine during an emergancy. Have you heard of any similar experiances?
Feel free to add any questions you’d like to if you have any! I’ve been looking for a real stumper!
Matthew Imbrogno
-Mechanical Vollenteer, Arizona Railway Museum www.azrymuseum.org
On the MILW Idaho Division, where they had oil-fired steamers, one time at least two engines got a load of road tar instead of Bunker C. One engine had enough steam to complete its run, account of heavy sanding to keep the tar from sticking. The other fireman didn’t know, or realize he had road tar instead of fuel oil. Both engines needed shoppping to chisel off the tar from inside.
We had several good swings at #4, and we got some of it, but let me fill in what else I was looking for. In addition to difflecting the heat and spreading it more evenly around the firebox, the brick arch acts as a bottleneck, forcing the draft into a smaller opening, and accelorating the smoke and used air off of the fire. That helps boost the draft volume and hence the fire temperature. Another, more subtle thing that the brick arch does is it helps control cinders and ash. After the air passes through the narrow opening at the rear of the firebox, it enters the larger space in the upper forward part as it passes through the neck and enters the tubes. Because the arch is built on a downward sloping angle, the heavier cinders and ash fall into the bottom front corner of the firebox, where it is collected and removed. That helps to reduce the amount of wear on the tubes and flues.
You guys got #7 dead on. Locomotives usually have 3 to 7 fusable drop plugs running down the middle of the crownsheet. Each successive plug melts at a slightly higher temperature, so that if one plug doesn’t reduce the heat enough, additional plugs will fall out to ensure the boiler won’t fail (hopefully).
On number 8 I’m glad you guys mentioned the locomotive’s soot blower. I don’t know how well known it is, but in the 30’s an automatic soot blower was developed that cleaned the firebox while the engine was on the road. It took the form of an articulated arm with a steam nozzle on the inside of the firebox. It would run back and forth along the sheets, knocking of the soot to keep the boiler in top form.
Wabashing may be a local term, the reference I heard it for was on the Rio Grand Southern.
Now then, I’m glad to get some questions on my side of the fence! The answer for what a pettycoat pipe is the inside part of the smoke stack, which extends down around the exhaust nozzle of the cylinders.
Middleton’s “The Time of the Trolley” mentions work on the soda motors. These relied on the exothermic reaction of adding water to a concentrated sodium hydroxide solution to create heat for the boiler. The intent was to have a fireless steam locomotive to replace horse power for street railway operations. These were being developed about the same time that Sprague was perfecting his system of electric traction and electric operation turned out to be the better ay to go.
As for water tube boilers, the D&H experimentals had a pair of drums on each side of the boiler, the upper one was for collecting steam and the lower was a reservoir for the water tubes. There were two rows of tubes on each side of the firebox, the inside one received most of the radiant heat and thus geneated the steam, the outer ones served as downcomers.
We have an excellent response from Erikem on both Soda motors and D&H’s watertube boilers.
Soda motors were indeed intended for street railway service because they had one very significant feature, they had no exhaust of any kind. As far as operating a Soda motor is concerned, it is just like a fireless steam engine but with a much longer endurance. The “boiler” is really two pressure vessels, one inside the other. The inner tank held pure Sodium Hydroxide, while the outer ‘main’ tank held water and steam. To begin operation, the main tank was charged with superheated water and steam from a stationary boiler. The inner tank was partially filled with ‘dry’ Sodium Hydroxide, also known as "Caustic Soda; hence the name of the engine. As the engine ran and used up the stored steam, the used steam was discharged into the inner vessel filled with the caustic soda. Conventional fireless steam engines on the other hand, simply discharge the used steam into the atmosphere. When the used steam, which by now has cooled to the point where it is only water vapor, meets the soda it causes a chemical reaction in which the soda combines with the water, generating heat. Enough heat is made in the innor tank that it continues to boil the water in the main tank, producing more steam to power the engine. The sodium hydroxide solution also boils at a lower temperature than water, which means that the heat of the reaction won’t generate pressure in the inner tank to counteract the pressure of the main tank at the pistons. The end result is that the engine will keep running as long as there is enough sodium hydroxid left to absorb the water from the exhaust, and it is not solely reliant on the pressure of the initial charge.
More information about Soda Motors can be found on this very informative and fascinating webpage:
The peroxide cycle made use of the exothermic reaction of 2(H2O2) → 2H2O + O2. Additional energy was obtained by burning some diesel oil in the steam-oxygen by-product. These subs were capable of some very impressive underwater speeds, but the hazards of storing concentrated peroxide outweighed the benefits. In addition, a LOT of peroxide was needed to provide useful underwater range.
The Brits built a couple of peroxide subs after WW2, and also came to the conclusion that the problems with peroxide outweighed the benfits. The ultimate answer for submarine propulsion was nuclear.
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I’d also like to mention another famous watertube boiler, the 900psi Babcock & Wilcox water-tube “flash” boiler that was installed in N&W #2300 John Henry in 1954. This was the highest pressure boiler that I can think of being used in a US locomotive. The highest pressure boiler for a conventional steam engine in the US was also a watertube boiler, and a completely welded one at that. Built for D&H by Alco was #1403, the L. F. Loree; a superheated 4 cyli
1.a. mudring…the base to which the inner and outer sheets would be attatched… the “base”
b. backhead… the rear sheets of steel thru which the firebox doors would be as well watercocks and glasses
c. crownsheet…the upper sheets of the firebox where most “radial stays” would be…this area must be covered with water at all times or “boom”…this area also needs protection from the 2000 to 3000 degree temps…see brick arch
d. neck…the front sheets that form the square to round shape of the firebox to boiler transition
2.a. syphon…is a bulbulous area of uppers sheets that are filled with boiler water to increase heating surface
b. circulators…forced air jets above the mudring to increase heating eff.
3 grates…movable pieces of steel that appear “extruded” that allow air to pass thru the firebox and ashes to fall thru to the ashpan
brick arch…protechs the crownsheets from the abrasive nature of cinders…forces circulation of the hotgases and i have to cheat to see the third…
burning oil is the obvious answer…oil burners have no grates…or stokers…most oil burners will have steam lines to the tender to heat the oil
the opposite of firetube…the fire surrounds the tubes which are filled with water
bonus…duplex im sure…the other not so sure…i want to say worthington but…
drop plug…i would guess a fusable plug in a staybolt that would blow steam or water if to high a temp is reached
8…to the tune of “spoonfull of sugar”…a scoop of sand helps the soot go away the soot go away…a shovelfull or 2 of sand in a running engine blasts the soot loose…
i would guess its a wideopen thing…johnson in the corner and notched out as far as she’ll go