Tag Archives: backhead

C&NW 1385: Giving it a Try

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The latest accomplishment on the 1385 boiler has been the installation of the Try-Cocks.  That is the proper name of an important set of monitoring and safety devices.  In previous posts the question “What’s the first 3 things to know about any boiler?”, was asked and the answer is still “Where’s your water?“, times three.  It was also shown the highest point of the crown sheet was measured and marked. We are additionally required to install water level indicating devices whose lowest reading shall not be less than 3 inches above the highest point of the crown sheet.          

Close study of the locomotive drawings has shown (Thanks, Ed) that the C&NW standard was to install the indicating devices to show not less than 4 inches of water, giving us an extra inch of safety margin. One of the types of indicating devices is a set of three Try-Cocks, so named because they allow the operator to “Try” the level of the water in the boiler.

Punch marks indicating location of crown sheet are visible just above the blue tape.
Steve R. of SPEC Machine adds punch marks for use with locating the Try-Cock.

In the first picture the punch marks showing the water side of the crown sheet can be seen just above the blue tape.  Steve R. of SPEC Machine works so quickly it is sometimes hard to catch a clear picture as evidenced by the photo of him placing a punch mark to locate the center of one of the Try-Cocks.  A hole is then drilled and threaded to accept the base or “spud” of each Try-Cock. 

Checking the placement and clearance of the throttle and try-cocks.

The above shot shows all three in place along with a temporary placing of the throttle handle to check clearances.  This is part of the 3-D chess necessary to make sure all the components will fit before they are installed.  In the circle is a marking of the water side of the crown sheet so we can be sure the lowest Try-Cock is at the proper level.

C&NW 1385 Try-Cocks. Bonnet and stems (left) are original. Spuds (right) are new.

The Try-Cocks themselves are a mixture of new and old.  As seen here, the bonnets and stems are original to the 1385 but the spuds were machined from a new piece of code-compliant material.  This was necessary because the new boiler has a reinforcing plate applied to the inside of the backhead in order to meet with the strength requirements of the current construction code.  This means the steel in that area is much thicker than the original boiler and in order to properly reach far enough into the water space the spuds needed to be longer.

Each Try-Cock has a drain tube installed in the valve stem to direct the steam and water into the drain cup when the valve is operated to “Try” the water level.  Below is how they look after final installation of the spuds, stems and drain cup.  The drain cup will have a pipe that extends through the cab floor to drain the water out onto the right-of-way.

Final installation of 1385’s Try-Cocks, stems, and drain cup.

In Upcoming Updates: The throttle handle and rod as well as the engine lubricator.

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.