Philip,

It looks like that cap stack drawing shows the cap as formed sheet material rather than a casting. I wonder if it was typical to not use a casting for the cap on these earlier tall stacks. I also wonder how they manufactured that formed steel/iron cap.

Yes, I agree the drawing seems to suggest that the cap stack is all formed from sheet metal, which I found puzzling, since a casting would make more sense. The part in question, labelled number 4 in the drawing, is identified simply as the stack "top" (cable code word "Eingesehen" if you needed to order a replacement from BLW). The catalog doesn't go into any detail about how the three stack designs were actually fabricated (and why would it?), so I will have to defer to the expertise of others who have actually handled Baldwin cap stacks and say the cap is a casting and not made of sheet metal.

-Philip Marshall

Export locomotives I know of built by Baldwin generally had copper caps. I think the sheet material aspect quickly becomes a reasonable idea! The little round bulge in the drawing is likely a rivet or screw holding the cap in place

That's not a rivet or screw...it's a decorative ring around the cap (in cross section).

Regarding the material of which the capped was formed:

J.G.A. Meyer included the attached drawing of a capped stack in his Modern Locomotive Construction of 1892. He stated: "The cast-iron top consists of three pieces, namely the ring C, the flare B, and the cap A. The ring C rests on top of the outer shell, the flare rests on this ring, and the cap A is placed on the top of the flare; these are not riveted nor bolted together, but they are firmly held together by expanding the top of the inner shell over the flange on the cap A."

DJS

It seems with all these potentially loose pieces up there, it lends some credence to the term, "blowing one's stack."

I'm inspired by the sharp reverse curve (drip lip) where the cap and flare come together on Meyer's drawing to wonder if the design originated as a means of limiting condensate running down and streaking the stack.

In looking at the drawing posted on the previous page by Philip Marshall, the cross section indicates a relatively thin wall that might be sheet material. But the bumps that suggest a continuous ring shown in cross section suggest that it may be showing the cap as a casting. But even if that were the case, one might expect that bump to be cored out on the inside like an open “U” shape.

Now in the drawing above, posted by D. J. Sullivan, I see that the cap is a casting, and the open “U” is exactly how the circular external ring is made. Particularly in considering the cap as a sheet iron part, I was wondering if it might be made as an assembly of a few individual parts in order to make the whole cap easy to manufacture. Now I see that is what they did in the drawing above.

I suppose there could have been a lot of variation in the manufacture of caps throughout their era.

If they did make the cap as an assembly of 2-3 parts, the question is how to attach them to each other and to the stack. On all of the caps I have been looking at in photographs, I have not found any with the appearance of rivet or bolt heads around the base of the cap. Apparently, they want to replicate the look of the tops of the old style dome casings with the ornate tops used before the hemispherical dome tops that came into use around 1900. None of those show any fasteners either.

In wondering how they might have held an assembly of cap parts together, I had not considered the amazing approach shown in the above drawing posted above. It looks like the stack is two walls with the inner wall (called a “shell”) extending all the way to the top, and then rolled over the top like rolling a tube over a tube sheet. That would capture the three parts of the cap and the outer shell with its bottom resting on the casting that bolts to the casting that mounts the stack assembly to the smokebox. But what I do not understand is what fastens the inner shell to that stack bottom casting that bolts to the smokebox mount. It looks like the inner shell just telescopes into the upper bore of the stack bottom casting. How would they secure that telescoping fit? If that lets go, the remaining four parts could freely separate from each other.

Looking at John White’s book, AMERICAN LOCOMOTIVES An Engineering History, 1830-1880:

Page 409, fig. 209. Builder’s photo of New Jersey Railroad and Transportation Co. locomotive #36 built by Rogers in 1863.

The photo shows a 2-6-0 with a relatively tall, narrow shotgun stack with a very small lip around the top opening. The stack appears to be approximately 14” dia. with a smokebox mounting casting suitable for that stack diameter.

Page 410, Fig. 210 shows the same locomotive in service with “Hudson’s coal-burning Stack.”

I assume this is a stack designed to burn anthracite coal supplied by Hudson Coal Co. This stack is also a straight pipe like the original shotgun stack, but it is larger diameter and has a large cap at the top opening identical to what we regard as a “cap stack.” This larger stack appears to be 18” dia., but is still mounted on the same smokebox mounting casting that was used with the 14” dia. shotgun stack.

So, the Hudson stack is a relatively wider stack mounted on a smaller neck of the original smokebox stack base mounting. I wonder what the reason was for increasing the stack diameter above the smokebox outlet for the Hudson coal-burning stack.

Also:

Page 493, Fig. 262 shows L&N 4-6-0 designed by Thatcher Perkins and built in 1871. A section view drawing shows a cap stack with the same thin-walled cap casting with the stack tube passing completely though it as shown in the drawing posted above. The text says the following: “The plan shown here represents the conventional practices of the time. The boldly moulded cap stack gives the engine a distinctive look but not entirely a new one, for Perkins had used the design while still with the Baltimore and Ohio.”

To me, the descriptions "boldly moulded" and "distinctive" all allude to the design being decorative, and nothing more.

OK, well, I don't think this is too far OT for this thread.

Everything I'm looking at here looks like a standard - and permanent - fixture of the stack design, and particularly for woodburners, indicative of a great deal of concern over setting fires from stack sparks. Baffles, traps, all manner of engineering.

There was a design on logging locomotives called the "Radley-Hunter" that appears - at least to me - to be a removable design. On my own little specialty, Pennsylvania logging railroads - it was a stock item by Heisler and came on delivery, even of coal-fired locomotives. As-delivered by Heisler in 1917: http://www.randgust.com/wd7.jpg

What's interesting to me is that I've followed the same locomotive over many years of photos and see it delivered with the Radley-Hunter, then it has a straight stack, then a different stack is on, then off, etc. Seems to be a fire-season accessory. Does anybody know if this design was a removable feature over a conventional straight shotgun stack? All this company's locomotives seem to swap and change stacks in every photo I see to the point I've concluded that this design and possibly others must have simply dropped over a conventional stack as needed. And I have no idea what was going on in there as design features compared to the plans and examples already shown here.

Later in-service shot without it: http://www.randgust.com/W&DUPLOGDUMP1.jpg (note the basket spark arrestor)
Prior to sale in 1938 - looks like a slightly different stack back on again: http://www.randgust.com/WD7c.jpg

So....true or false? I have no idea. They also had an 1899 Porter 0-6-0 with what appears to be four different stacks at different times, and a 1897 Lima with three.

Just to show one way our cousins made a capped stack: this from England in a 1946 publication.

The issue with a tapered stack appears to surface in the late 1890s. And, like nearly everything else associated with the front end, it was subject to debate and interpretation.

I don't think so, other than removing the whole stack at the flange. ALL these patented stacks had unique internal "workin's" that made them what they are.

https://books.google.com/books?id=1A4iiGAz628C&pg=PA121&lpg=PA121&dq=radley+%26+hunter+loco+stack&source=bl&ots=pt5sAov2Vp&sig=KOF8S-D75sNpnXdPgTMUyTM1nNQ&hl=en&sa=X&ved=0ahUKEwj7qMaE9YXRAhWDTSYKHfMtDW0Q6AEILzAB#v=onepage&q=radley%20%26%20hunter%20loco%20stack&f=false

Steve,

Here are my thoughts at this point:

There certainly does appear to be intentional style and appearance incorporated into cap stacks. In some cases the revolved shapes of the cap stack on a locomotive nearly repeats those of the dome tops. So cap stack caps are definitely a decorative element. Also, I do not see any obvious operating function in a cap stack such as smoke lifting, or draft modification. They do not appear to have incorporated spark arrestors.

However, I now conclude that there is one principle of cap stacks that does make them functional in addition to being decorative. I believe the cap is a functional element of the stack structure, as I will explain as follows.

What is conspicuously missing on pre-1900 locomotives are cast iron smokestacks. Most stacks were fabricated sheet metal in the stack form of diamond, funnel, or balloon, in a wide range of variations. Their large volumes lent them to sheet metal fabrication to keep the weight down compared to castings, and also to avoid complicated molds needed for castings. Also, the general cone shapes created natural column strength that helped stacks withstand occasional side loading such as hitting snow drifts. These shapes were also often duplicated by interior tubes and cones fastened to the exterior features, thus providing even more strengthening. With all of these stacks, the use of cast iron was only in the base connecting the smokebox barrel to the stack bottom.

There were a few tall, cylindrical stacks in this era, apparently for coal burning locomotives. Most, if not all of these, were straight tubes without any taper, and all of them appear to be made of rolled sheet metal, as opposed to being cast iron. So these were rather thin-walled, “stovepipe” sorts of stacks. Most of these have somewhat of a rolled lip at the top opening, apparently to reinforce the open end of the metal cylinder. Some of these have a very small (in cross section) cast iron ring added to the open, upper end of the stack. These rings are so small and plain that they apparently have no decorative purpose, but rather, are completely functional cylinder reinforcement similar to the rolled bead on some stacks.

However, many of these early straight stacks have the full fancy cap, making them what we would call a “cap stack.” All of these pre-1900 stacks are in the era of ornamentation. So I don’t have any doubt that the full caps of this era were for ornamental purposes. However, I believe they had a second purpose that was indeed completely functional. That was to reinforce the top opening of the thin-walled, rolled sheet metal stack tube. The generously large diameter, ornamental cap also provided the strengthening structure naturally inherent in the diamond stack and its conical relatives. Some of these cap stacks even had a double wall that provided structure by mimicking the combination of interior and exterior shapes of the diamond stack assembly. I can’t think of any purpose for the double wall besides making the stack tube stronger.

This purely functional structural purpose of the cap on tall cap stacks explains why its use continued past the era of ornamentation as the population of straight stacks suddenly boomed by replacing diamond stacks; this occurring during the period when the screens of diamond stacks were typically moved to the smokebox. Although cap stacks retained their ornamentation of the cap form, the cap also had a functional purpose that was structural. Thus it was still needed in this new non-ornamental era.

As all of the diamond stacks turned into vast numbers of straight stacks, this explosive trend began by satisfying the stack demand with the sheet metal cap stacks which had been a conventional design for the previous fifty years. But soon, the need for something simpler spawned the invention of the cast iron shotgun stack, which took over and ended the use of the sheet metal cap stacks.

Ron,

While your logic for using a cap as a strengthening agent is sound, I disagree with you that most stacks were rolled sheet metal. First, we would see a seam, possibly even a riveted one. Second, as with boiler jacketing, I believe locomotive builders would have had no qualms about using brass or Russia iron straps to keep the stacks in shape. Third, to date, we have seen nothing in the written record that indicates any function for the cap.