Because you have not built the boiler and do not have certification for materials and its construction, I would talk to a boiler inspector befor you proceed any further. It would be a waste of time and money if you cannot get it approved.

Paul.

I am wondering if this is an LBSC design, or at least one influenced by him – the tapped plates for fittings and single hole for top feed are distinctive.

It revisits the dilemma imposed by our boiler rules which are primarily concerned with testing rather than design. If a drawing could be found and the tapped holes for fittings were shown on it then a boiler tester would only need to be interested in their condition and could not fail the boiler for not having bushes – even though this is the far better way of going about things.

However if no drawing is available it needs to be designed (including calculations) and made to best practice as it stands today to pass.

I have before me my copy of the latest edition of The Scriptures (Orange-on-White, a.k.a. The Boiler Test Code 2018)…

This is not verbatim but a précis to suit what we have here. "Shall" is a legal word meaning exactly what it says:

5. Design Verification.

This section clarifies that a boiler not to a recognised design must be accompanied by the relevant drawings and by calculation or well-proven example, evidence of adequate strength of design and materials.

The drawings or accompanying text shall show the Working Pressure – if that is not available it has to be calculated and the calculations verified.

The boiler shall treated as a new design, so given an "Initial hydraulic shell pressure-test", without cladding, to 2 X WP.

===

So in this case, you would need and can only produce, as Paul Kemp says, a drawing of the boiler as it is, and use the regular calculations to assess its own, sensible working-pressure guided by typical for the scale of the locomotive. As its history is unknown it would be treated as a "new" boiler and given the initial 2 X WP hydraulic test – and when the loco is finished, the first regular 1.5 X WP hydraulic, and the steam-accumulation, tests.

Though that section does not say refer to materials, you do not need traceability documents for an owner-built copper boiler's materials.

===

You need to know the boilers Bar.litre capacity – simple enough once you know the working-pressure. Fill the boiler completely using a measuring jug, multiply that amount of water in litres by the WP in Bar.

A boiler also needs an ID number. You can use your own, but the Orange-on-White Book recommends following your Club's federation's system.

#

NB: Club Boiler Inspectors are not duty bound to test a boiler full-stop. They will do their best and a happy boiler admirer is one who has just passed a boiler for service, but the Test Code makes clear that he can, and should, refuse to test a boiler he feels outside of his experience. Obviously he can also fail a boiler even just on dry examination, but has to give the refusal and explanation in writing. There is a space on the Certificate for this, though to be honest if this was a boiler not yet on the books and unlikely to be made serviceable in the near future, I'd probably just apologise and refuse it verbally, though still explain why of course.

I suggest, if you haven't already, obtaining a copy for yourself of The Boiler Test Code 2018 , so you know what is expected, in detail.

It is not the best of technical documents as the applicable clear road ahead is not immediately obvious, but it does contain all the information you and the Boiler Inspector need. Just as well because the Certificates are not the simplest of forms to complete!

You can also follow the instructions to ensure by a preliminary test, the boiler is ready for its official test. If you do I would suggest going to WP only first, hydraulically of course and in gentle stages, and only if that's satisfactory, to 1.5WP maximum. Leave the 2WP to the proper test.

+++

Another thought on the apparent soot. Soot or oxide? I wonder if that is actually from the silver-soldering, not from any firing.

Thank you!

Looking at the photos again, it seems actually well made, but not very well designed, as if by someone not versed in the more subtle aspects of loco boilers.

One puzzle, as you mention, is how the original builder intended to get the steam to the super-heater, which with only one element of a pair of rather small tubes, would act as a pretty efficient restrictor.

Normally there would be 3 or 4 super-heater flues and these are usually above the fire-tubes. Now, there is no intrinsic reason that I know of, why a miniature boiler could not have the super-heater below the other tubes provided there is room behind the chimney and blast-pipe for it, but it's normally at the top to suit the steam-pipe from the regulator in the dome.

Some models do use external regulators, either hidden in the smoke-box or rather inelegantly on the back-head, the latter usually on narrow-gauge locos where bolting bits on the outside is a bit more prototypical.

Yet your boiler shows no sign of any internal steam-pipe, nor of any external regulator mountings. I can only think its designer had an external pipe in mind, difficult to hide on a standard-gauge outline loco in British railway practice, though I suppose it could be hidden under the cladding.

The hole on the lower corner of the back-head: I'd assumed it to be for a blow-down valve, though It could have been intended for a feed clack.

Oh to know what loco is being replicated!

****

I think a lot of club boiler-inspectors would be unhappy to certify this boiler, whose main problem may be that over-high internal fire-box. They may well want at least, the threaded holes fitted with silver-soldered bronze bushes, unless they can accept a design directly comparable to known boilers using direct threads.

Probably, your best course of action if you decide to use it, would be to write down what work needs doing to it, and its working-pressure and the method you used to find that. Then before cutting any metal, show the boiler inspector both the unit itself and that information, and ask his advice.

Note that the initial shell test is just that – the full certification needs it pass a hydraulic test in working condition, and a steam-test to verify the safety-valves, pressure-gauge and feed arrangements.

'

I wonder how many other miniature locomotive boilers there are out there, all forlornly awaiting identifying and pairing with the rest of the intended machine in the hope that the Great God PER will bestow his blessings upon them? Looking at the second-hand traders' exhibition stands I reckon you could almost build a somewhat quirky but effective engine around the once-high hopes languishing in the dream-catcher trays of assorted wheels, possibly-identified boilers, unidentified cylinders, unidentifiable bits, rusty castings and grubby frames..