< Outer Boiler >
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.
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.
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
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