A link to Mid Continents steam status page:

https://www.midcontinent.org/category/cnw-1385/

Ed

Looking good! Congrats to MCRM on the 1385's progress.

Les

Beautiful - I'm interested in the steam dome being bolted with a flanged joint to a saddle on the top of the boiler. Was this and engineering consideration, or a convenience for maintaining the throttle valve and easier access to the boiler interior?

The answer is:
D. All of the above.

Sorry for what is probably a newbie question about a basic issue, but do all steam locomotives (or modern ones anyway) use arch tubes?

Not all used arch tubes. Arch tubes are one of the three most common primary variants of firebox improvements, the other two being thermic siphons and combustion chambers. Arch tubes and siphons combine additional heating surface with added water circulation (also flooding the crown sheet, noted as a safety enhancement) while combustion chambers add heating surface and improve combustion - thereby increasing heat available for transfer. Two other combustion improvements often used in conjunction are above-grate combustion air vents and smoke eaters. Some locos didn't use any improvements. Depended on the RR's mechanical department and more-so what the loco was used for. A yard goat doesn't need the steaming capacity of a 100 MPH passenger engine with a heavy load.

There were plenty of things tried with firebox and boiler design. If you want to lose quite a bit of time you can study the Locomotive Cyclopedias and other materials for days on end.


Also of note with 1385's new boiler - not a single boiler stud installed before tubes installed. Is modern practice now to just outer seal weld - with internal threads exposed to water penetration of the barrel? And drilling/tapping/welding after coating with Apexior?

Some boilers are rebuilt today with hammered and flanged parts, but this one appears to be entirely welded fabrications with very little curved metal. What are the tradeoffs in doing this?

I can't tell from the photos, but I don't see any belly plugs. I'm kind of surprised there aren't washout plugs for the front flue sheet area. Hard to tell looking at the photos.

It is equiped with belly plugs.

-Sam

Thanks for the response, TrainDetainer. I am following a couple of other boiler/firebox rebuilds (e.g., ARR 557) and had not seen arch tubes mentioned in those rebuilds and it occurred to me they might be somewhat rare. They seem to me to be similar to the idea behind water tube boilers but in a form suitable for a steam locomotive. Does anyone know, did C&NW 1385 originally have arch tubes?

There's arch tubes and arch tubes. Most of the arch tubes I've dealt with ran from over the firedoor in the door sheet to under the tube bundle in the rear tube sheet. The arch brick were stacked on top of the arch tubes.

My very little understanding is that the CN&W R-1 boilers were originally soaks and converted to super heat in house by CN&W. They had a pile of these R-1 class locomotives. Unfortunately the conversion was not superior and had some flaws. One was some poor circulation with "cold spots" or at least serious differential going on which caused stress in other parts of the boiler causing some serious cracks in the barrel? The three surviving R-1 locomotives I believe all have belly patches in the same place. This new configuration of ciculators or arch tubes was designed to try to improve the situation. So there was some modifications to address a few other things such as draft on the lower tubes? May seem to be small changes but the idea was to improve the less than stellar super heat conversion. Again my understanding is that many RR had problems when they converted soaks to super heat in the 1920s-30s. I believe M. Austin would have the real and more accurate skinny on this. I have had not one ounce of involvement with this project since 1972-3 when we got her operating again after her deep sleep after 1963 run. So here is my disclaimer that "this is my understanding, not to be confused with absolute truth or facts". I have tried to follow this build over the years but was involved with other projects so didn't always digest all the twists and turns this boiler project had in the last 15+ years. I hope this is a "good build" and wish those responsible for making this happen the best of outcomes.

Regards, John.

Continental fabricators of St Louis also built the new boiler for the Southern Ry 2-8-0 at the Monticello RR Museum and a new water tank for the Lake Street Elevated 0-4-4T at the National Museum of Transportation near St Louis. And boiler courses for the new PRR 4-4-4-4 duplex as well. They are good people to work with.

I would call the tubes in the firebox, circulator tubes not arch tubes. It would be interesting to see a photo after they install the brick arch. The Security Circulators that are in the Big Boy firebox look like upside down T's. I have seen pictures of other locomotives with what I would call homemade circulators like the ones in the 1385, SP4449, maybe the 611. B&O had a Mikado with something similar, that they called a semi-water tube firebox.
Tom Hamilton

I think the specific designation would depend on their primary purpose - to support a brick arch or increase circulation, not that the same things can't do both of course.