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Fairlie Merddin Emrys

6.3 Boiler

Making the boiler presented an unexpected challenge in terms of time. So far everything in the kit had an excellent fit and working on parts to make them fit was very limited. This applies much less so to the boiler centre section. In terms of size the rolled boiler centre (100) is okay, no problem with that, but mine was rolled irregularly and too narrow. The instructions say that pressing the parts together will take considerable force, but if I had done it that way I would simply have crushed the lower firebox. It took me several hours of patient working on the metal sheet of the boiler centre to make it fit on the lower firebox. This is by no means criticism on the kit. The boiler centre is simply a difficult part to roll so I understand it is impossible to supply it with even so much as a close fit.

Lower firebox

First job is to assemble the lower firebox alias foundation ring (101). Nothing much to be said about that. If you have progressed to this stage there should no surprise in that.

Boiler centre


As said the boiler centre was rolled far from perfect so it needs considerable adjustment. As the assembly is initially too narrow I first carefully bent the sides outwards only to get the lower firebox in the tab slots of the centre boiler.

The light peeping through from behind the shows the remaining issues. The light showed up directly beside the top tab so you need to go working from there.

I worked the metal on a  steel bar that I clamped in my vise. Note that I marked the fireman's side F on the lower firebox assembly. Really there is not fireman's side BUT this ensures you use the same side over and over again when trail fitting.


Is said, start forming from the top a test fit after small adjustments. Work a little at a time rather then taking big steps.

Considerable progress. As you can the tab slots on the side will not match the tabs yet. This fit will only come if the match between the two parts is prefect. Resist the temptation to file in the tabs or the tab holes to "solve" that problem. The tabs and the tab slots are signalling the size of the remaining issues you have.

After almost two hours of careful working I found the fit be close enough. Two tabs clicked in by themselves and the other were off by just a few tenths of a mil. It was then, and only then, that I decided to file a little on the tab slots.
Also take care that the boiler centre does not skew. The bottom edge should be parallel. On this photo it still a little adjustment.

The instruction manual does not mention anything about bending the lower angle but there etch line on the inside.

Bending the angles is difficult because the metal strip is only a millimetre or so. I tried in many ways to bend with a vise or other means to bend it in one go. I gave up on that and finally bent it with a pair of pliers, taking care to bend it over in steps to avoid creasing of the material.


There won't be a perfect result. Mirror light on it and you will see small bumps. But it is good enough foremost because the larger part of the edge won't be visible.

The horizontal space between the tabs slots was about a millimetre shorter then the horizontal distance between the tabs. So I file the tab slot about 0.5 mm deeper.


Check if the the protruding ends of the boiler centre are in line with the firebox centre. They should also be equally wide throughout (22.3 mm wide)


Boiler ends


If you got the boiler ends right the boiler connecting plates (114) will snap into position in their respective tabs with a positive, audible click.

So much so that they stay in place without soldering.

Check if the connecting plates are straight and both vertically and horizontally aligned.

The manual almost casually says to leave as much material as possible form the diagonal feeds.
So I snipped away the other parts and pulled out my Proxxon table saw and cut straight through the sprue.
Not that the clack valves are not mirrored but identical and give the corresponding holes in the taper sections are off centre.
This should be the end result (parts held together with blue tack for the sake of the photo)
The valve's sprue is file thin to form a thin foot to stand on. This gives the solder more tack.

You need to position the valve in five dimensions

  • no tilt forward or backward
  • no lean left or right
  • and perpendicular to the length of the boiler
  • precisely positioned in longitudinal direction
  • precisely positioned in lateral direction

Hold it there and then solder it with your other hand. Easy, nah? Well no. It proved impossible so I drew my self-closing tweezers to help. Clamping the valve in the tweezers I kept adjusting the valve until it sat correctly. Then I dabbed it with flux and let a big blob solder flow to it without touching the valve.

and check

At this stage I could not resist making a photo with the boiler in the tank-apron assembly. I puzzled how to get it in until it occurred to me that is should be inserted from the bottom (duhuh).


Now the fabrication of the smokeboxes is due. Soldering the smokebox inner (133) is easy. Just ensure (check, check, check) that everything is square and true.
As per instruction [140] the bottom end smokebox has a small hole for the ejector pipe on the drive's side. To avoid any error I marked that part.



The manual recommends bending the wrapper around a 20 mm object. That proved to be way too wide (right). Nickel silver is springy stuff and I still could not fit around the smokebox inner without a lot of strain. 15 mm proved to be a tad too small, so when I found a 17 mm diameter piece of plastic I was a happy boy.

It resulted in an almost fit which needed little persuasion to fit snugly around the inner (left). Take care though that the sheet easily nicks where the holes are etched, so ne thing that can be seen on the right hand sheet (between the yellow lines). Correct it or you will forever see it.

The wrapper is soldered onto the inner structure [137-139]. Note that he the outer full thickness ends have been bent to fit in the corner at the bottom of the smokebox [139].

 Then the pair of liners is inserted into the rear ring of the smokebox and soldered in place [142].

On the photo the boiler front section is fitted into the the rear of the smokebox after the liners have been installed [144]. To make the boiler front fit a little filing may be necessary to make the boiler seam close perfectly.

Once satisfied with the fit of the boiler, file the liners flush with the smokebox wrapper [145]

One last test fit and then the boiler front is soldered into place.

Not the I have scribed the centres of smokebox and boiler with a thin line which makes lining out very easy.

The bottoms of the smokeboxes are filed flat [141]. This also included a mm or so of the underside of the boiler as the boiler falls over the apron just a little bit when the smokeboxes are mounted on the aprons.
The boiler front wrappers are soldered into place [146]

Final assembly

A test fit of the boiler. At first I was quite puzzled how to get the boiler in place until I realised that the only way to do it was from the bottom up. Fitting the boiler between the sides of the main structure was very difficult. So far every single fit that had proved difficult was due to a fault on my side so I knew I had to look into that.


Once more a test fit with the jig on.


I now must confess two errors.

  • The firebox upper sheet extended over the ends of the lower firebox. I thought that it was surplus material and filed it away despite the manual not mentioning that. But the problem is that the manual does not mention the obvious things and this seemed obvious. Once I fitted the boiler in the mainframe I realised I had a visible slot between the frame and the firebox (indicated above).
  • This slot was narrow at the bottom and a about half a mil at the top, indicating the firebox was less true than I thought. This was caused by folding over the bottom edge of the firebox top. The etch had a folding line on the inside so I assumed it need to be bent inwards, again though the manual not explicitly stating so. In the photos on the DVD this etched folding line is visible on the outside, and other photos clearly show that the edge is not bent over, neither inwards nor outward. To aggravate things I forgot to measure carefully before soldering otherwise I would have noticed that the firebox widened towards the bottom. I could have filed a bit to achieve a perfect fit.

How to remedy this? After long consideration I decided to correct the first error. From strip I formed four new extensions and soldered them back on. I filled with Tamiya putty where necessary and sanded it flat. So the ugly slots were gone.

The second error could not be corrected unless I would take the entire assembly apart. Experience taught me that this is a difficult course of action with a high risk of permanent damage. Some more trial fitting showed me that the fit was tight but not too tight to get the boiler where I wanted it. So I decided to leave it and move on. There is no such thing as perfection.


So I went for the giant leap for model mankind and reinserted the boiler and tacked it in place. Within minimal tolerances it was well in place despite the earlier discrepancies.

Smokeboxes were installed.


And the tapered boiler covers were made to fit [152]. They were soldered at the (wide) boiler end ONLY, observing instruction [147 and 154]. Everything is checked and checked again for straightness.


I now trial fitted the cradle as per [155]. I found it wobbled on one point. I carefully observed that and concluded that the firebox at that point sat a tad too low. I filed a few tenths of the mil from that spot and then it fell dead flat in place.

It was then soldered on its four tabs.


Now as per instruction [162]all tacks are soldered into neat seams and then cleaned [163]

Front sheets


Now the boiler has finally landed into its place it is time prepare the front sheets that close the gap between the tank and the boiler. They need to be filed razor sharp from the bottom side so as not to lift the bar connecting the tanks.

After a bout of filing by hand I scuttled to my Proxxon and mounted a grinder. It works very fast so be careful not grind a hole in the part

In place. Soldered on the tank side only. Do NOT solder them to the boiler because the smokeboxes must stay removable for later detailing.

Photo shows that the bar was lifted only a timy bit (a few tenths of a mil)

Tada. Boiler complete!