Kelly,

Is the flaw in the 1361 the same as what sidelined the 7002?

I remember reading that the reason they were parked was that the roof sheet was too thin. Please correct me if I am in error.

JD Johnson, Morehead and North Fork Railroad Historian

I'd also like to thank Mike Tillger and Scott Cessna for their honest appraisals of this situation, and I wish them luck in the future with this project. I myself have been between that proverbial "rock and a hard-place", and it's no fun!

Regards:

Rich O

If by flaw, you mean PRR design standards, then yes, it is the same flaw. If by flaw, you mean did someone approach the boiler with a UT tester, it is a similar flaw. If you mean specific parts, well, yes and no.

To answer the questions on the roof sheet, there are several things to consider.

As far as the K-4 is concerned, we feel pretty confidant we figured out what the Pennsy did. When the earlier Belpare boilers were built, they were designed to have the crown/roof sheet bolts thread through the roof sheet and stick out enough to be able to thread a nut on the ends as well. When you use nuts that bear against the sheet you can use a thinner plate than you can without them. This is because you have not only the threads through the sheet as an attachment, but you also have a nut holding the sheet as well. This type of construction allows for a higher “constant” to be used in the flat stayed surface formulas in the ASME Locomotive Codes. The higher the constant, the thinner the minimum required thickness.

The Pennsy at some point (1940 +/-) eliminated the nuts and went with the bolts threaded into the sheets only method, presumably to save on costs. Everything we’ve seen so far indicates that they kept the same bolt pitches and didn’t make the sheet thicker to make-up for the lower constant. How they got away with it regulatory wise I don’t know, but in actual practice it worked. We went back as far as the 1920s era Locomotive Codes and couldn’t make it work. This particular calculation changed very little up to and including the last Loco Code of 1952.

The K-4 and most other Pennsy engines before the 1940s were built with 3/8” thick roof sheets. With the 5.0625” transverse bolt pitch, and 3/8” thickness, this gives a working pressure of only 175 psi for a 205 psi boiler. This isn’t even considering normal wastage which has made it even thinner. When you use the constant for nutted construction, you get a working pressure of 210 psi. This is one of the “design flaws” that Mike Tillger talked about.

This is where you get to the debate of “it worked before so why mess with it”. The problem is that you have to be able to hang your hat on numbers that support using a given part. If you can’t do that, then it’s all over and you replace the part.

I hope this helps,

R L Musser

Kelly,

I appreciate your answer. I was referring to the design.

Thanks,

JD

Well, the tender has exactly how much original fabric? Anyone really opposed to having a new boiler fabricated using modern engineering and welded construction? We had to do the same with our family's steam traction engine, and I got to tell ya, it still looks, sounds and operates as always, but it is so much easier when the boiler inspector comes to visit.
There are still companies that do this kind of work, at least get a quote, what can that hurt?
http://www.boilersmith.com/custom.html

Makes you wonder about the mythical reputation Pennsy has as an engineering/loco building force and the "Standard Railroad of the World". Maybe back in the day they parlayed that reputation into a level of trust in their designs and construction that wasn't totally deserved.

So, are nuts outside the sheet still a viable option under today's reg.s?

Far be it for me to defend the PRR, but at the time K4’s were designed (1914), they were the primo performance machines in railroading. The boiler was designed to produce the absolute maximum amount of steam for a given weight. Corrosion was not even a consideration. There is no way those boilers were intended to have a 90 plus year life span. In fact, Linn remembers asking some old Pennsy head about firebox life, and got the response, “We got two years out of them, sometimes”.

That higher performance comes with the cost of lower (or no) redundancy, just as a Ferrari doesn’t have the redundancy of a Chevy truck.

As far as the decision to remove the crown bolt nuts in the 40’s, its one of those things that probably just fell through the cracks. New boilers for the Duplexes were being built without the nuts (though with thicker roof sheets to compensate), so it’s easy to see where someone in the engineering department could decide off the cuff to remove them from everything. Just as its easy to see (given the engine’s operational records) that the designers of the PRR’s late steam weren’t equal to their predecessors early in the Century.

Nuts are an option, but if you mean using them on the present sheet you would have to replace all of the bolts so they were long enough for nuts. Also, with the wastage that has occurred, even with nuts, it still won't make 205 psi.
You could go with a new 3/8" roof sheet and use nuts, but as explained before, you would only have a few thousandths cushion. It would be much better to go with a thicker sheet without nuts which would be cheaper and have a good corrosion allowance.

Rick

Well, I had meant on the present sheet, but I see the problem. However, doesn't replacing the sheet mean dealing with those corners?

Anyone for a radial stay K4 with "falsies"?

No need for falsies I don't like them on any girl.

The corners are no big deal as they can be rolled to proper shape.

Rick

Well, that could easily be done in the jacket work, without having to mess with the wrapper sheet. Once the jacket is on, who's to know? Kind of like putting a counterweighted Model B Ford crankshaft into a Model A Ford engine rebuild--- better performance, and it's invisible from the outside. A radial firebox will still make enough steam for present-day purposes, maybe even enough to handle a 9-car "Broadway" at track speed if the need arose.

Some earlier hints remind me:
How often did the PRR plan to replace the boiler (or the sheets in question) , and how often did they actually replace them?

In reply to Mr Mitchell's comments:
I think the hometown people can be very proud of their locomotive, it was consumed by the very purpose it was built for and lasted in service far longer than expected and the basic design was copied by many other railroads. One or two flaws does not discredit an entire fleet from being one of the outstanding icons of the iron horse era! A newly built replacement boiler would be just a routine item if steam would have remained in service.

In reply to M Austin's question:
I no longer have direct acess to the boiler drawings or notes , and my memory is not the best with numbers, but I would guess that the pitch on the crown sheet was in the vicinity of 4 3/8 X 4 3/8 inches

In reply to Dennis Storzek's question:
Joe Michaels did the calculations for the welded flush patch 3rd course repair, which has yet to receive a written final approval from the FRA. That issue has nothing to do with the roof sheet issue.

Let's all wait for the final boiler engineering report before any decision making, if we don't, we have not learned anything from the past failures of this project.

I too, must publicly thank the team of workers and volunteers who contributed their time and effort into this project and lets not forget Steamtown National Historic Site and its staff for providing the facility. I had the pleasure of working with contractors Bob Yuill, of Historic Machinery Services and his staff, Kelly Anderson, from the Strasburg Railroad, and his staff, and Nathan Mutchler of Mechanical Services, I very highly reccommend all of these companies if you are looking for contractors or consultants for your next project.

Mike Tillger