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 apo
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.
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.
But if you examine the cross-section of a Belpaire firebox below:
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
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.
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.
No offense intended Ed. I was speaking more generally about how some Forum members react when a very old post suddenly gets new responses. And I myself have accidentally replied to (and thus “resurrected”) an old post because I failed to note the original posting dates.
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).
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 genera
