The spiral "guts" of both the late style Radley and Hunter and Rushton stacks were cast; I have seen them both. The Rushton supplanted it at Baldwin because it took less sheet metal work than the R&H due to the cast base and center ring, and was therefore more economically produced.

As to the capped stacks-they were strictly ornamental, at least the ones I have seen. Don't forget, the late, Great Texas and Pacific used a capped stack on some classes of very modern power (most notably their Mountains, Pacifics, and Texas types), as did others, including the Cotton Belt. Baldwin was putting signet stack caps on a lot of their catalog shortline engines up at least through the twenties.

In looking at the drawings that Steve posted, it does appear that the spherical body piece or center ring is sheet steel rather than cast iron. In most of the photos posted in this thread, however, it appears that the center ring is cast. Yet, that one photo showing a Rushton stack broken open also appears to have a center ring that is sheet steel, although it is rather thick (3/8”). I had earlier asked how such a piece could be formed in sheet material.

In thinking about it, I guess it could be rolled in a way that develops the two curvatures simultaneously, with sufficient tooling. So I am guessing that the Rushton stack was manufactured in some cases with that center ring rolled, and in some cases, with it being cast. Perhaps they changed the process at some point during its production period. Apparently, either process was feasible, but the main objective either way was to have substantial thickness to resist the wear imposed by the cinders.

I was the fellow that initially cut the vines away from the Rushton stack remains at the SFHM..the center ring is cast.

Jim,

That sounds like pretty reliable information straight from the source all right. Apparently then all of the center rings on the Rushton stacks were cast. The evidence of the drawing posted by Steve suggested to me that the center ring might be formed plate, but there is no way to positively conclude that from the drawing. So I guess it is cast at 3/8” thick wall. Casting does seem like the most logical way to produce that part.