< Outer Boiler >

Barrel from a sheet
2.5mm copper sheet is annealed and rolled on a steel pipe as a guide. Note a steel bar is used to fix the sheet square to the tube.

Rolled sheet is riveted with a strap and silver soldered. I used firebricks to keep the job warm. It saves much time and gas.

truing up
Square the barrel ends to the exact length.

Inner and outer firebox are designed with CAD.
This is a design of special jig to mill the formers with a rotary table. The jig is just a 100*100mm square plate with holes at the center of each arc around both inner and outer formers.
Special Jig

Cutting formerFormers
Formers are made from 9mm mild steel sheet, cut with hacksaw and shaped with miller. Rotary table is regarded as a lavish option for amateur, however it is very useful in many cases.

The pads are made from 15mm cherry wood.

Flanged plates before flanging.

Eye glass for punching work. High intensity light is necessary for the work.

Annealing and flanging a plate. Wood or plastic hammer is suitable for flanging.

Flanged plates

Open out a hole for the doom bush with a small drill and a metal fretsaw.

Doom bush is turned from a gunmetal casting.

The bush is silver soldered to the barrel. Note four small pins secure the bush.

I always put enough solder onto the joint before heating. This method needs no skill. You may be relaxed and just wait for the solder melts. Also you can save solder. You have to heat the job slowly at start to avoid the short wires of solder fall down by vapor of moisture in flux. Once the moisture comes out, sticky flux catches the solder firmly.

For scribing vertical lines, the flanged plate should be laid truly.

Interchanging the job with the cutting tool because the backhead is too big to turn. Note a DTI is used to check the radius of the tool.

Flanged plate is machined to ensure a nice fit to the barrel and the wrappers.

Backhead and throat plate

Outer wrapper is bent with various bars and tubes as guides. Diameter of tube can be adjusted with a sheaf of paper.

Bent outer wrapper with the backhead. Gaps between the parts should be less than 0.1mm to avoid leakage. In a dark room you can inspect the gap with a small lamp in the firebox.

Boring for bushes of safety valves and turret. Don't bore them before bending the sheet, otherwise you will have oval hole after bending.

Barrel with straps to catch the outer wrapper and the throat plate.

Throat plate is fixed to the barrel with brass screws before soldering.

Assembled outer boiler with revets. Note a small "fork" to close a gap between barrel, wrapper and throat plate.

The whole job is silver soldered and pickled.

Finished outer boiler: 350mm length, 100mm diameter