I saw a mention in an ICS textbook on steam locomotives about using a smokebox cement between the cylinder saddle and smokebox barrel when bolting the two together. Was this a common practice? What did this cement consist of and what was its purpose?

Filling the gap between both surfaces to avoid vacuum leaks. Furnace cement works fine.

Have seen a form of cement/mortar used in the saddle/smokebox connection before and it can be used to patch holes as well as seal new applications. You will curse the SOB who patched the smoke box as it is a dirty thankless job when it comes time to remove the boiler or smoke box from the saddle. If one were to just cut around the saddle and remove the saddle bolts after the boiler or smokebox is free maybe not as bad. But chipping that old cement out of a smokebox makes a crappy job worse. Have only removed saddle bolts on two locomotives and it is right up there with the most pain in the butt jobs. Bucket loads of concrete or mortar makes the job even more fun. Add soot, cinders, rust and a torch blasting back at you and it's magic time followed by Miller time. Hopefully you don't run into the patching and only have minimal amounts used for sealing.

On the Polson #2 the fit was good and we seal welded the smokebox and thicker strengthening plate after everything was in place and ground flush. This was while the boiler was on the ground. I don't recall or wasn't involved if any compound was smoothed over the joint area or not after final fitting was done? My recall was every thing was nice and snug and no need. At this time the smokebox was loosely bolted to the boiler and the final holes were not drilled to size yet. One of many things I learned from this project is when installing the smokebox it is that riveting the smokebox to the boiler is the last thing you do so when it comes time to fit the smokebox to the saddle you can do so. Otherwise you might have a gap to fill with some sort of shims or gasket to seal and proper fit to the saddle. I know the professionals out there already know this and I have "rediscovered the wheel". But a person could go out of sequence with good intentions and not realize the mistake until later and make more work for oneself. I miss working around steam locomotives, it is a great diversion from the rest of the world.

Go Rick Go! thoroughly enjoy on your endeavors with railroad and steel industry adventures. Simply amazing work you do.

Regards, John.

My contention is that the cement has a more utilitarian purpose, that of filling the voids between the cylinder casting and the smokebox barrel. This keeps soot and cinders out of places that are uncleanable, preventing moisture retention, corrosion, etc.......

Of course I have heard legends of cement being used to patch holes in the smokebox, leaking tubes in the front tube sheet and such.....

I've seen a half a foot of it poured into the bottom of the smokebox, but it was a park hulk so no idea why somebody thought that was a good idea. If I had to guess, it would be to prevent the expenditure on a new smokebox bottom patch to last until disposal. Hope it wasn't to close up holes in the tube sheet.

The "saddle" for the 58 is a 1 1/2" plate rolled to the 39" OD of the smokebox shell. Originally this plate mated up tight against the boiler shell. Now, with the corrosion that has taken place, there will be a gap of up to 1/4 to 3/8" in places where the new smokebox bottom will mate with the saddle. So, when I read of smokebox cement it occurred to me that I could use this material to fill in that gap. As Matt noted, my intent is to fill the void to prevent corrosion from occurring.

Furnace cement is readily available and if it will do the job then I'll just use that.