If you do not have the necessary skills for live steam boilers please have someone with the relevant experience help you, as Tony did.

THIS IS NOT the treatise of an expert, but the account of a novice building his first live steam locomotive boiler, written in the hope that it will help other newcomers to Live Steam.

Fortunately, 1½in outside diameter copper tubing just fitted inside the 0.3 mm tinplate casing of the model, but the 1/16in wall thickness of available tubing is excessive, so it was turned down in the lathe to 0.8mm wall thickness, leaving just a short ring of 1½in diameter at the front to support the outer casing. The tube was held in the three-jaw chuck, with a hardwood plug to prevent crushing. The other end was closed by a more precise plug running on the tailstock centre. Cutting fluid (available in aerosol cans) was brushed on often to prevent the tool from jamming, and two cuts were taken at medium speed, using the self-feed. (Figure 4).

Flanging the front tube-plate was also done in the lathe, using a home-made roller in the tool-post. A roughly cut disk of 1.2mm copper sheet, first annealed by heating red hot, was pressed against a lump of steel of appropriate diameter held in the chuck, the pressure being applied by the tail-stock. With the work turning at medium speed the roller was advanced to form the flange (Figure 5). The flange was then trimmed to fit the barrel precisely (Figure 6), and bored for the flue (Figure 7).

Figure 8 shows the boiler parts prior to assembly. The rear tube plate was bored in the lathe before being cut to shape, the piece of copper being screwed to a bit of wood held in the 3-jaw chuck. A wooden former was used to bend the annealed copper firebox wrapper, then to support it while it was being drilled for the 4mm transverse water-tubes. The back-head plate, also 1.2mm copper, was shaped to support the Belpaire part of the boiler casing. It has a door-hole, holes for the steam pipes and bushes, and also holes for 1.2mm brass pins to precisely locate the firebox and barrel during subsequent silver-soldering.

After soldering and while still hot, it was dipped in diluted sulphuric acid for 30 seconds to remove the hardened flux, then rinsed in water. Sulphuric acid is now difficult to obtain, but I believe that citric acid can be used for the same purpose. (Sulphuric acid is hazardous, even in dilute form, which is one reason why it is not readily available. Powdered citric acid is easily found in your local pharmacy but wear eye protection against it spitting while hot). The finished firebox can now be used as a template for cutting out the bottom of the boiler barrel to accommodate it, as the cut-out must be a close fit on the firebox.

The flue-tube is 18mm outside diameter 1mm copper tube, which is a standard plumbing size here in France. It has seven vertical water tubes of 4mm diameter. I know that Eddie Cooke, in his Gazette articles, shows the tubes staggered rather than in-line, but keeping them in line leaves more room for the super-heater elements, and I doubt that the difference in efficiency is perceptible. The higher-temperature 45% silver solder was used for the flue assembly. Figure 10 shows the set of sub-assembled parts.

The flue was now tested for leaks, because if leaking water-tube joints are discovered later on in the assembled boiler they will be impossible to repair. For the test, the ends were closed by metal plates and rubber gaskets, retained by external tie-rods (Figure 11). The whole was pressurised with compressed air and immersed in a bucket of water. In this case, all was well – no bubbles.

The next step was to assemble the firebox to the copper back-head, together with the steam pipes and tapped bushes (Figure 12), using four brass pins in the back-head to ensure correct positioning of the firebox. This time the lower-temperature 55% silver-solder was used. Now the flue was silver-soldered to the firebox, using nails and supports to maintain correct alignment (Figure 13). The brazing hearth is three lightweight building blocks from a local builders’ merchant. Nails can be knocked into this material to hold even small parts while brazing.

And now to the final assembly of the boiler – Figure 14.

This is where it started to go wrong! I had failed to notice (on my own drawing!) that where the main steam pipe emerged from the back-head, it fouled the boiler barrel. Even after filing away as much of the pipe and the barrel as I dared the result was that the barrel is pushed slightly off-centre. My alignment pins had served for nothing. To move the steam pipe would have meant scrapping the already-made regulator-blower-valve unit. I couldn’t face starting again, so the error had to stay.

While the DIY blowlamp had easily coped with all the silver-soldering so far, it just couldn’t produce enough heat to make the joint between the barrel and the firebox/back-head – too much mass of copper. So, I splashed out on a bottle of propane, regulator and industrial blowtorch, nearly £100. This did the job, but perhaps a cheaper solution would have been a second DIY blowlamp to be held by a (trustworthy) assistant to heat the rest of the boiler while the final joint was being silver-soldered.

The next thing to go wrong was that I somehow managed to block the blower pipe with silver solder. An attempt to drill it out punctured the wall of the internal pipe, so it had to be sealed off and abandoned. In its place, the blower is now supplied by the external ‘vacuum ejector’ pipe, which is probably a more elegant solution.

After pickling in acid and washing, the finished boiler was ready for hydraulic test. This was done with a home-made water pump of the type commonly fitted in a tender. As the working pressure was to be 4-5 bar, it was pressure-tested to 11 bar (160psi in Old English), the maximum my gauge can read (Figure 15).

The central position of the vertical water-tubes in the boiler flue made it possible to install a twin-element superheater. The tubes are 2.5mm outside diameter, 0.5mm wall copper refrigeration tubing (an eBay purchase), and the darts are copper cut from an old soldering iron. Because the elements project into the fire, I was afraid that silver-solder might melt, so the darts were brazed. Brazing alloy melts at more than 800ºC (Figure 16). The other end, remote from the fire, was silver-soldered (Figure 17).

And so, fitted into its tinplate casing, and with the smokebox attached, that is the boiler finished. Luckily, it works. There are twin safety-valves as the prototype, a filling plug under the lift-off dome, and a drain plug below. The latter would have been quite useful. In fact it came just above the crank-axle, and so is inaccessible and useless.

In all, the boiler, casing and smokebox took about a month to make. In building the rest of the locomotive, many unforeseen problems were encountered, and it wasn’t completed until many months later. Without much useful advice and encouragement from the renowned Rafe Shirley, I doubt that it would have been finished at all. But it is finished, and it works.

And so, fitted into its tinplate casing, and with the smokebox attached, that is the boiler finished. Luckily, it works. There are twin safety-valves as the prototype, a filling plug under the lift-off dome, and a drain plug below. The latter would have been quite useful. In fact it came just above the crank-axle, and so is inaccessible and useless.

In all, the boiler, casing and smokebox took about a month to make. In building the rest of the locomotive, many unforeseen problems were encountered, and it wasn’t completed until many months later. Without much useful advice and encouragement from the renowned Rafe Shirley, I doubt that it would have been finished at all. But it is finished, and it works.

The French O gauge association, Cercle du Zéro, asked me to exhibit at Quai Zéro, part of a big Euromodels show at Châtellerault. There were three halls, one of which was devoted to trains, mainly O gauge.

Below are are two photos of my exhibit. The upper part of my stand was a model of the train which took me to school in High Wycombe 1955-59 – except that I kept it in the original LNER livery, with (real) teak coaches, rather than the 1950s grubby red. The front articulated pair were built in 1960/61 when I was still at school. The loco body was made from cocoa tins in 1963, but I couldn’t then afford wheels and motor. It was finally finished in 2016.

The lower part of my exhibit was mainly live steam, my completed ex-GCR A5 4-6-2 tank, built last year, and an ex-GCR D11 4-4-0 under construction. They were the only examples of live steam at the show. On the Sunday afternoon I ran the A5 up and down a short length of track.