Smokebox and chimney

The construction of the boiler is progressing well, but to determine its exact position on the frame, it’s useful for the smokebox to be completed first. From there, the exact height and location on the frame can be measured.

Unlike my other locomotives, this smokebox is not made from a steel tube, but is constructed from sheet material. This is because this smokebox does not have a separate smokebox saddle; instead, the smokebox and the saddle form a single unit.

The fronts are shaped from 2 mm copper sheet, and the outer shell is bent from 1.5 mm brass sheet. The whole assembly is riveted with copper rivets.

The original Y14 locos featured several types of smokeboxes, all made from sheet steel. These were initially riveted with flush rivets, later with snaphead rivets, and on the preserved locomotive, the construction is even welded. 

Over the locomotive’s lifespan, various types of chimneys were used. The Great Eastern Railway applied the so-called stovepipe chimneys, while the London and North Eastern Railway mostly used a cast chimney with their standard shape and a lip at the top.

The smokebox

First step: from 10 mm aluminium a former plate was milled

The contour is milled using light cuts. Two bolts hold the plate directly onto the milling bed.

Two millimeter copper sheet is annealed so that it can be formed around the aluminium plate.

Chain drilling to create the large hole for the boiler barrel (114.5 mm or 4.5 inches)—in hindsight, it turned out to be a lot of work…

.....So for the second hole for the smokebox door, the rotary table was setup. 

The small cutout at the bottom is filed by hand according to the drawing’s dimensions. This defines the height of the boiler.

The smokebox wrapper plate is centered and drilled for rivets. 

Bending is carried out using the roller bending machine.

The ends are bent outwards over a piece of round bar. It involves a bit of guesswork, with the rivet holes providing some indication of the bend’s position.

The brass plate is annealed only once, before riveting it to the front smokebox door plate.

Held in position with two small clamps, the holes from the brass plate are transferred onto the front side—starting at the center, then placing one rivet to the left and one to the right each time. 

The smokebox is temporarily fitted to the frame to check alignment and positioning.

Because the smoke box is made of sheet metal and only riveted, it had to be carefully clamped before boring the 28 mm hole for the chimney. That’s why only small cuts were made each time.

The chimney

The base is cut from solid brass, which is easier to work with than steel. This is particularly useful when it comes to filing and final finishing.

The first profile was created using a radius tool. Because the tool’s radius was undersized, the shape was formed by carefully maneuvering both the X and Z cross slides. The finished dimensions were checked with a small gauge plate.

A general overview: the base has a diameter of 58 mm.

By soldering the base to a bar, it could be securely held in the milling machine vice for the next operation.

The boring head was now used to machine the large radius at the bottom of the chimney base.

This is where craftsmanship comes into play. Using a coarse half-round file, the second radius is shaped by eye. It takes a relatively long time and requires close attention to where material needs to be removed.

But with a bit of patience, you can get quite far.

The surface is finished with a smooth file and emery cloth to give it a clean and neat appearance.

Holes are drilled to fit the bolts that will attach the chimney to the smoke box.

The 'stove pipe' was turned from a solid bar. I had a piece of scrap brass that was nearly the correct diameter—I needed 41 mm, but settled for a 40 mm piece. Once the chimney is mounted on the locomotive, I doubt the difference will be noticeable.

After turning the outer surface to a 1.8-degree taper, the interior was drilled using the largest bit I have—21.5 mm

The inside was bored to a 2.75-degree taper using a large cutting tool. 

With that complete, the base and stack are prepared for soldering.

Silver-tin alloy solder was used. 

A final cleaning operation in the lathe.

The chimney, finished in the style of the Great Eastern Railway, is fitted onto the locomotive.

A general view of the locomotive, which already captures the character of a 

Great Eastern Railway Y14 class.

The progress on the boiler

Further progress on the boiler. Alas, no more vacation, but some work could still be done over the weekends.

Finding the correct position for the girder plates (also known as crown stays). By adjusting their placement outward or inward, the height of the inner firebox relative to the outer shell can be modified. The central crown stay, positioned in the middle, serves as the reference plane.

I've designed the boiler with a height of 43 mm between the two, measured at the center.

At the same time, care must be taken to ensure that the firebox is positioned centrally within the boiler. The known dimension for this is 8 mm, so two strips, each 8 mm thick, are used to hold the assembly together.

A final check from the smokebox side. 

Once everything is in place, the girders are drilled and riveted.

Silver soldering requires more focused heat. Therefore, in addition to the propane torch, an oxy-acetylene set was used. The firebox doorplate was soldered during the same operation. We began with the girders on top and worked our way down to the firebox doorplate. In this position, both could be soldered without the need to move anything.

Cleaning up in the pickle bath. 

There is a problem with the size—either the coal shovel is too big, or the boiler is too small.😃

After cleaning, a visual inspection is done to ensure everything is in order. If not, reheating and resoldering can be performed—this step is easy now but impossible later.

The shaping machine was put to use for making the firebox foundation ring parts

The strip we used was wide enough to use it to wrap around the corners. 

It requires some extra machining to achieve this design, but corners are usually a common source of leakage. This approach makes soldering much easier, and the seam can be checked before soldering the rest.

The foundation ring is complete. A small step (recess) was added to simplify the positioning of the long sides.

A recess has also been milled for the blowdown bush, ensuring that the center of the blowdown valve aligns with the bottom of the foundation ring. This allows the boiler to be fully blown down after a run, preventing any water or dirt from remaining inside.

The inner and outer sections of the boiler.

Holes have been drilled in the backhead for the regulator bush, water gauge, and other fittings.

Roughening the backhead girder surface before riveting ensures that the silver solder flows properly between the riveted seam.

Again, the visual inspection confirms that the silver solder has fully penetrated the seam.

After soldering, the bushes for the water gauge and regulator are drilled and tapped. A small steel rod serves as a guide for the tap. This process is done manually to ensure maximum control while tapping with the small M2 tap—I definitely don't want to break a tap here!

Determining the recess that needs to be filed away to create space for the top bushes. 

In Solidwork an easy cut-extrude command; here a lot of work.

Drilling holes for 3mm rivets, which will secure the firebox, foundation ring, and outer boiler in place during soldering.

Once again, the surface is roughened to ensure proper penetration of the silver solder.

A simple soldering setup ensures maximum control of the heat. One propane burner and the oxy-acetylene burner are used, allowing precise monitoring throughout the soldering process.

The two boilers are a step further in construction.

Chain drilling the fire door hole in the backkead.

Through repeated filing and measuring, the hole's position is precisely aligned with the boiler assembly. In this boiler, the fire door location is 0.3 mm off-center—not a significant issue and difficult to avoid in this type of metal sheet work. However, the hole in the backhead must be precise, as a soldering seam with a 0.3 mm gap is quite large for silver soldering. A fire door that is 0.3 mm off-center is barely noticeable and functions perfectly fine.

Test-fitting the backhead. To maximize the firebox length, only a few millimeters of space have been left between the back of the boiler and the hornblocks. As a result, the boiler must be manufactured to precise tolerances.

A view of the future cab.

There's still a long way to go, but another step forward has been taken.