Here's another drawing showing a boiler with a crown bar:
Note that it is not a locomotive, but a portable boiler.
And, changing the subject, a French 4-4-6 cab forward:
Ed
RRR_BethBr At the risk of re-resurrecting an old thread - I think you're both correct. According to toot-toot, crown bar construction was an earlier/different method of boiler construction than what your cross-section depicts, which is the typical stay bolt method. By definition, the boiler you posted wouldn't need crown bars, because it was designed not to have them. According to my research, crown bars would have been found either a) spanning top sheet b) underneath the roof sheet, or c) both places, and attached/stayed to each other by metal supports I've seen called "sling stays". In either case, the crown bars would still be bolted to whatever structure they were supporting (the roof or top sheets). Think of the roof bracing of a cathedral, and you'll have some idea of how a crown-bar firebox would look (though not exactly, of course).
At the risk of re-resurrecting an old thread - I think you're both correct. According to toot-toot, crown bar construction was an earlier/different method of boiler construction than what your cross-section depicts, which is the typical stay bolt method. By definition, the boiler you posted wouldn't need crown bars, because it was designed not to have them.
According to my research, crown bars would have been found either a) spanning top sheet b) underneath the roof sheet, or c) both places, and attached/stayed to each other by metal supports I've seen called "sling stays". In either case, the crown bars would still be bolted to whatever structure they were supporting (the roof or top sheets). Think of the roof bracing of a cathedral, and you'll have some idea of how a crown-bar firebox would look (though not exactly, of course).
I had the impression that crown bars were designed so that the stay bolts could pass through both the crown sheet and roof sheet at approximately 90 degrees. That would be something automatically taken care of with a Belpaire--hence no need for crown bars. However, the below source takes a different view:
The 1916 "Locomotive Dictionary" defines "crown bar":
"A beam extending across the water space above the crown sheet of wagon top boilers to support the stay bolts holding up the crown sheet where the opening for the steam dome prevents staying the crown sheet to the roof sheet. They are usually supported at the ends by castings resting on the top edges of the side sheets of the firebox and by sling stays from the roof sheet or dome shell. Thimbles on the crown sheet stay bolts maintain the proper spacing between the crown sheet and the crown bars. Not in general use now."
Note that toot toot mentions crown bars as being on Belpaire fireboxes.
I am not finding any photos of Belpaire fireboxes with a steam dome above the firebox. In particular, on the PRR.
I did find a cross-section drawing of a firebox (anthracite burning, it looks like) with a crown bar and sling stays:
I would think the left side would represent a section looking backwards--hence the big round hole for inserting coal. There are three pipe-looking things above the crown sheet, two of which present at an angle. I think these go from the roof sheet back to the rear sheet for the purpose of staying that large expanse of sheet metal above the height of the crown sheet.
And the right side is looking forward, showing the boiler tubes. Note also the small round "circle" up towards the top of the steam space that represents the pipe containing the throttle linkage.
It looks to me that wagon-top boilers would have to have the steam dome opened to clean the top of the crown sheet, because the crown bars were indeed in the way. On a wagon-top boiler. Of which it does not appear there were any Belpaires.
7j43kSince the stay bolts of a Belpaire firebox, by definition, already intersect those two sheets at a right angle, I don't see the point of crown bars. But if you examine the cross-section of a Belpaire firebox below:
But if you examine the cross-section of a Belpaire firebox below:
I think it was a worthwhile resurrection.
The posts that say "me too" after 10 years or answer a question from someone who hasn't posted in the forum for a decade are decidedly less useful.
Henry
COB Potomac & Northern
Shenandoah Valley
Think nothing of it, Dave.
It IS a curious thing about "old posts". There is certainly no reason not to add a further bit of information to a post, no matter how old it is. And, if one has reason to "resurrect" a post for further discussion--why not?
But I do understand how a funny feeling can happen to a person when an old post suddenly appears.
It's a-weird.
It'd be a nice thing, I think, if some forum program writer would have it put in a flag to show that the last previous entry was kinda old--maybe a parchmenty color tone or something. While there's no reason not to re-open an old topic, neither is there any reason not to make known the fact that it IS old.
Ah, well. The subject, in this case, is well worth continued pondering. At least for those of us who have Belpaire-boilered locos scampering around (think SP&S, for one).
7j43k Dave, I was NOT making fun of anyone when I made my comment. Nor was I ridiculing anyone. Nor putting them down. .... I do object to your use of the term "resurrect". .... Ed
Dave,
I was NOT making fun of anyone when I made my comment. Nor was I ridiculing anyone. Nor putting them down. .... I do object to your use of the term "resurrect". ....
An article about the double Belpaire is included here:
http://www.rypn.org/forums/viewtopic.php?f=1&t=36360
Way way back in this thread, the proposed Lima double Belpaire boiler was mentioned, and Chuck said a 1/6 scale model had been built by the Lima shop forces. This is reputedly true, and I understand the model boiler was donated to the Museum of Transport in St. Louis. I presume that organization still has it, but I don't know whether the model boiler is available for viewing by the Public.
Tom
To expand on Ed's explanation and excellent cross-section photograph— you can see the distinct differences of the angles needed for the radial stays compared to the relatively parrallel Belpaire stays in these diagrams.
Note the necessity for many more flexible staybolts which both add initial cost and increase maintenance cost over the years, each one requiring a gasket.
The simplicity of design and lower maintenance was probably what the PRR favored in the Belpaire.
Staybolts were a necessary evil in the support of all the flat surfaces of the firebox and required a great deal of care in their testing and replacement. In areas of high stress frequent replacement of staybolts could make for considerable down-time and loss of revenue.
Of course the whole reason for all those stays and bracing is to keep the relatively flat sheets of the firebox from buckling under the stress of the steam pressure. If that crown sheet overheats and gets soft the result is catastrophic.
Regards, Ed
Toot Toot spoke earlier about the inconvenience of crown bars on a Belpaire firebox. I do question useage of the term. In his earlier description, he describes it as being sort of an adaptor-plate, so that the stay bolts can intersect the crown sheet and the boiler wall at a right angle.
Since the stay bolts of a Belpaire firebox, by definition, already intersect those two sheets at a right angle, I don't see the point of crown bars.
those things with the 2.2 on them would seem to be in a similar position to what Toot Toot calls crown bars. To me, those are also stay bolts. They appear, again to me, to perform the same function.
stay bolt: a bolt or short rod commonly threaded throughout its length and used as a stay to connect opposite plates (as in a steam boiler) that are subjected to a pressure tending to force them apart
And, since the topic is "resurrected", I'll also comment on Tom's GN P-series comment: While the P-2 was, as Roy pointed out, non-Belpaire, the P-1 WAS a Belpaire boilered locomotive.
According to Middleton and Priebe in their book "Steam Locomotives of the Great Northern Railway" (which was not out in 2008), GN made the P-2 a non-Belpaire to save weight.
They also attribute the Belpaire-ness of the S-1's (yes) and S-2's (no) to the same reason.
dknelson In the "you can't win" department, either people resurrect old threads and run the risk of being made fun of, or they start new ones and are chastised because "there is already a thread" on that topic.
In the "you can't win" department, either people resurrect old threads and run the risk of being made fun of, or they start new ones and are chastised because "there is already a thread" on that topic.
I was NOT making fun of anyone when I made my comment. Nor was I ridiculing anyone. Nor putting them down.
I was marveling at the eight year span between posts. ESPECIALLY when the title includes the declarative "Today's..."
I do object to your use of the term "resurrect". I think if Roy meant to do that, he would have made some mention of doing so, and a reason why he thought it a good idea. Roy's post appears to me to be a simple linear response--he equally well could have made it in 2008.
I do admit I do not actually know Roy's internal intentions. Or how he happened on an eight year old topic. Or decided to comment. His point is well made and appropriate, though.
I'm not sure if I "chastise" people who start new threads when "there is already a thread". If there was one ongoing at the time, I suppose I might wonder why the person chose to duplicate it, and comment thereon.
But you are probably talking about someone starting a topic that you know has already been resolved earlier. I DO think it irresponsible to do that IF there is a very simple way to do a search. For example, if someone was wondering about the Pendulum cars; I would be "disappointed" if that someone didn't do a search for the term first, and find out about earlier discussions. However, there is not always an obvious search term. And in that case, I see no reason why someone couldn't go ahead and ask. I've done it myself. And if it seems appropriate, I also apologize that I couldn't come up with a search term to do a search.
For myself, if someone has a contribution to make to an old thread I think adding to it is the way to go. I'd rather see one thread be a really complete discussion on a topic (even if the OP long since has become "anonymous") than have to chase down dozens of threads.
Dave Nelson
7j43k "Today's steam question"--- asked 8 years ago. Time flies. Ed
"Today's steam question"---
asked 8 years ago.
Time flies.
I noticed that too. But it's a question that some newer folks may have, and it's not bad to resurrect such things now and then. However, you do make a good point. Sometimes people ask very specific questions about a situation that is important to them at a specific time. A response eight years later isn't much use in those cases.
Quite a few locomotives were built with Belpaire boilers for railroads large and small by Brooks and other Alco plants around the turn of the 20th century. These even included some narrow gauge engines.
While the CNR didn't make a big splash in the Belpaire pool, they did have 75 of these, in three classes:
Built in 1923-24, most of them lasted right to the end of steam.
Wayne
Hi, Tom -
It was the GN P-2 series Mountains, along with the S-2 Northerns. The O-3 Mikes were also exceptions, as were a few smaller engines acquired from other roads, such as the F-12 Consolidations (only 2 on the roster, I believe). Otherwise, use of the Belpaire was pretty much standard GN practice to the end of steam.
One item about the GN's O2 and O3 class Mikes, the O2 was a single locomotive class acquired in a merger. The O3s were USRA lokeys, the only puppys the GN would purchase. If I am not mistaken, the S1 class Northerns outlasted the S2s due to their better pulling ability which was probably the result of the smaller, 72" drivers vs the S2 series 80" drivers, but I certainly am no steam expert by a loooooong shot.....
Dan
to begin at the beginning, the Belpaire firebox was developed in Belgium about 1860 by Alfred Belpaire an engineer seeking to simplify locomotive construction. The firebox technology of the time did not utilise radial staybolts. The crown sheet (roof or top of the firebox) was supported by a series of transverse arches called crown bars. The crown bars sat on the knuckle (curved portions along the sides of the crown sheet where the crown attached to the side sheets) of the firebox. The staybolts threaded into the crown bar and went through the crown sheet at 90*. The outer shell of the boiler was supported by bolts which radiated from the curved top of the crown bar and also passed through the shell at 90*.
Belpaire reasoned that he could do away with all those radial staybolts by making the crown bars a bit taller and then bending and riveting the shell directly to the crown bars. (this gave the outer shell the unique square shoulders look.) As late as the 1930s some small locomotive boilers in the UK (Hudswell and Hunslett if no one else) were built this way. I know, I've worked inside some that were built like this, the construction came as a complete shock to me.
By the early 1900s crown bars fell from favor, so when larger locomotives were built the flat sides allowed staybolts to be run from side to side and up and down maintaining the optimal 90* to the sheets without the crown bars
The technology of the era was flange and rivet. attachment of the Belpaire firebox was no more difficult than the construction of the eccentric course of a wagon top boiler. The Belpaire's shape gave the needed dry steam space without resort to the eccentric course.
the disadvantage of the Belpaire firebox lay in its rows of cumbersome crown bars which made washing the scale off the crown sheet an incredibly horrid job. (Been there, done that, i can not adequately describe the difficulty of getting the scale off that FLAT surface with all that stuff in the way) Railroads like the Pennsylvania, had early on learned about water treatment and boiler washes and thus were prepared to accept the good with the bad and adopted the Belpaire as standard for its advantages in strength and construction. Other railroads were not willing to make such a comittment to water treatment and maintenance and stayed with the wagon top form eventually eliminating crown bars with radial staybolts
i hope this coherant enough to be understandable. There is an excellent book by Charles Norton called Locomotive Boilers (catchy name huh) which has a chapter on the Belpaire Firebox and its care, inspection and maintenance
I would assume it was ease of maintenance, when you have 10,000 engines to take care of only having to stock one size of staybolt versus all the different sizes you would need with a radial stayed firebox makes sense. Remember the Pennsy was the "Standard Railroad of the World", not that their standards met anybody else's but that everything was standard on their railroad.
Rick
Rule 1: This is my railroad.
Rule 2: I make the rules.
Rule 3: Illuminating discussion of prototype history, equipment and operating practices is always welcome, but in the event of visitor-perceived anacronisms, detail descrepancies or operating errors, consult RULE 1!
twhite and some USRA 2-10-2's for the Pennsy were delivered from Baldwin without them. Tom
and some USRA 2-10-2's for the Pennsy were delivered from Baldwin without them.
Even though the N2's were deilvered with radial stay fireboxes, after the end of the USRA the Pennsy retrofitted the N2's with Belpaire Fireboxes. But they did not change the 5 USRA Mikes used on the GR&I. They also had a few experimentals with radial stay fireboxes such as the K29.
twhiteBut even Great Northern opted for standard fireboxes on their Baldwin built S-2 Northerns and P-series Mountains
Yes this is just pointing out the exceptions. There are always exceptions. The Pennsy & GN archetype steam locomotives have the square hump.
Baldwin built some 2-6-6-4 articulateds for the Pittsburgh and West Virginia with Belpaire fireboxes, and I've seen a photo of an early Northern Pacific 2-6-6-2 Mallet with one, similar to the early GN mallets of the same early 1900's period. But even Great Northern opted for standard fireboxes on their Baldwin built S-2 Northerns and P-series Mountains, and some USRA 2-10-2's for the Pennsy were delivered from Baldwin without them. So even though both US railroads were noted for Belpaire fireboxes, it wasn't universal with all of their steam locos.
Actually, I think that the Belpaire gives a rather distinctive look to a steam locomotive, besides being quite efficient.
Tom View my layout photos! http://s299.photobucket.com/albums/mm310/TWhite-014/Rio%20Grande%20Yuba%20River%20Sub One can NEVER have too many Articulateds!
The PRR really used the Belpaire fireboxes on all of the home made designs. The following quote about the greater surface area is a great advantage, but the work that was being done on the 1361 at Steamtown proved to be extremely difficult because of the shape.
So much for the advantage today.
CZ
It has a greater surface area at the top of the firebox, improving heat transfer and steam production. Its rectangular shape makes attaching the firebox to the boiler more difficult, but this is offset by simpler interior bracing of the firebox.
In addition to having somewhat (but not significantly) larger firebox surfaces for heat transfer, the Belpaire firebox was reputed to place less stress on the staybolts, most of which were a right-angle connection between two flat plates rather than connecting two curved plates (with different radii and centers) at some non-perpendicular angle.
Belpaire fireboxes were common in the UK, and in other places where UK influence was strong. In Japan, where the models followed were mainly German and American, there was no significant use of Belpaire fireboxes.
One of the last developments in steam locomotive technology was Lima's "Double-Belpaire" firebox. which carried the rectangular section through the combustion chamber. IIRC, there was one test boiler built, in 1:6 scale. Then Lima merged with Hamilton and the emphasis shifted to diesels.
Chuck (Modeling Central Japan in September, 1964 - with radially-stayed fireboxes)
Here are some links that mihgt answer some questions.
http://www.google.com/search?hl=en&sa=X&oi=spell&resnum=1&ct=result&cd=1&q=belpaire+firebox&spell=1
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.