Tag Archives: backhead

Early August 2019 Boiler Progress

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August has arrived and with it is a new update on 1385’s boiler as it progresses toward becoming a finished vessel.

The fire door ring has been fitted to the firebox and backhead sheets and will be welded in place.  The firemans’ shovel will pass through this opening many, many times feeding the fire that will keep 1385 running.

fire door

Looking at the other end of the firebox we can see where the rear tubesheet braces will be installed.  Those are the wider-spaced holes below the field of closely spaced 2” tube holes.  The braces are necessary because the holes in the tubesheet are above the top of the throat sheet so the braces are welded to the inside of the belly of the boiler.  The braces are shaped like an elongated and squished “Z” so they can enter the hole in the tubesheet at a right angle and also lay flat on the boiler shell belly as they are welded in place.

The shot of the top of the boiler shows that just a ‘few’ stays need finish welding.  You can also see that the steam dome base has been finished. The holes that do not have stays inserted are going to be some of the flexible stays and are awaiting the installation of the sleeves on the outside of the shell before the bolt itself can be applied and welded in place.

We do not have an anticipated return-to-service date for the 1385 but every weld is one step closer. Stay tuned to this webpage or our official Facebook and Instagram pages to keep up with most up-to-date information on 1385’s progress.

We appreciate the public’s enthusiasm to see the 1385’s progress first-hand; however, the contractor shops where the #1385 work is taking place are not open to the public. Anyone showing up at our contractor’s locations requesting to see the locomotive will be turned away. Please help #1385 return to operation as expeditiously as possible by respecting our contractors’ wishes.

Early-May 2019 Boiler Progress

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Since we have a new month and new Monday we also have a new update! Tom G. from Continental Fabricators writes:

Here is the latest update..
All but 22 backhead stays are installed, most of them have the root pass in and  working on completing the welding.

The side sheet stays are also moving along.
Throat sheet flexible stay installation to start this week…

Included with the update was two photos.

Late-April 2019 Boiler Progress

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Continental Fabricators’ Tom G. supplied Mid-Continent Railway Museum with another new photo and a brief progress update on April 29th. Continental Fabricators is the shop hired to construct a brand new welded boiler for Mid-Continent’s Chicago & North Western #1385 steam locomotive.

“Most of the backhead stays are fit as of this morning and they are beginning to weld. Stays in the sidesheets will be fit this week. The barrel is 60% welded.”

View of 1385 boiler backhead with most stays installed and ready for welding. The backhead is the portion of the boiler that extends into the locomotive cab. The large round hole in the center is where coal is shoveled into the firebox. Photo courtesy Continental Fabricators.

Preparing for Backhead Stay Installation

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During the last week of January Continental Fabricators began installation of the 1385’s backhead diagonal braces. The backhead is the end of the boiler located within the cab and is a large, flat plate or sheet of steel that has been flanged and then welded to the wrapper sheet.  Flanging is the process of very carefully curling the edges of a sheet to meet the next piece it will be mated to.  The flanging process has been covered in previous update posts.

Much of the boiler is round, a naturally strong shape.  With areas that are flat or nearly flat the forces of nature (including steam pressure) are constantly trying to force them round and thus they require support or “staying”. Staybolts, or “stays” and braces are thus used to reinforce the area and prevent the backhead as well as the other flat areas from bowing outward when the boiler is under pressure.

firebox diagram

While installing these braces, crews at Continental Fabricators flipped the wrapper sheet/backhead assembly upside-down to facilitate easier working conditions. The first photo below shows the assembly as of the last week of January 2019 as the braces are being fitted and tack welded in place.  The tack welds are just enough to hold the braces in place so this assembly can be righted and lowered onto the firebox/mud ring assembly to check for proper clearance between the braces and the firebox.  Once Continental is satisfied with the fit-up between the pieces the wrapper assembly will once again be pulled off the firebox, inverted and the braces will receive the final welds.

upside-down wrapper sheet and backhead

Much of the backhead will be supported via staybolts connected between it and the firebox door sheet. The pictured diagonal braces are used to support the part of the backhead that does not line up with the door sheet and is instead connected to the wrapper sheet for support. This picture was taken during the last week of Jan. 2019. Photo courtesy Continental Fabricators.

A few days later during this the first full week of February, Continental’s crews had flipped the backhead/wrapper sheet assembly right-side-up again and placed it over top the firebox/mud ring assembly. The purpose of doing this is to test fit for any contact between the backhead braces and the firebox crown sheet before final welding of the braces and before the wrapper sheet/backhead assembly is welded to the firebox/mud ring assembly.  Once the two assemblies become one the installation of the staybolts can begin.

Bending Steel Part 2: Forming the Throat Sheet

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Gary Bensman and his team continued work flanging various sheets for the C&NW 1385’s firebox during the first half of April. Recent tasks included work on the 1385’s throat sheet and backhead.

This drawing of an Omaha Road Class I-1 boiler, a sister engine to the R-1 class #1385, identifies the location of the firebox, throat sheet and boiler barrel.

The backhead forms the rear end of the firebox and is located inside the cab. The fireman shovels coal into the firebox via a small door which will be cut into the backhead.

The already flanged (curved) sheet is the C&NW 1385’s new backhead. The backhead forms the end of the firebox inside the cab. Gary Bensman photo.

The throat sheet serves to connect the round boiler barrel with the firebox’s square-ish lower half. Such a transition requires the throat sheet to be a more complex shape. Where much of the bending of the steel sheets thus far could be accomplished via “cold flanging” by bending on a pneumatically-powered McCabe Flanger at room temperature, the throat sheet’s complex curves require a more hands-on approach. The “hot flanging” or “heat and beat” method involves heating the metal to make it more malleable and then using sledgehammers to pound it into the desired shape. The photo gallery below shows the throat sheet at various stages of progress.