< Inner Boiler >
Inner tubeplate and backplate bored in the lathe.
Tubes and flues. Note the front end of them is a little tapered to ease assembly into the smokebox tubeplate.
For firehole ring, copper sheet is rolled and silver soldered with a short strap. The left is a failed one and the right is a recover.
A wood mandrel supports the firehole ring during the operation in the lathe.
Inner backplate with the firehole ring.
The sheet for inner wrapper is cut by a hacksaw and straightened with a file over a steel bar as a guide.
A cylindrical pan had ideal radius for the inner wrapper's round top.
Again many of guides are used to bend the inner wrapper.
Inner wrapper with the firebox tubeplate. The steel screws will be replaced with the copper rivets just before soldering.
To fit crownstay to the firebox round top, the foot of them were pressed onto a large steel pipe.
Small areas between the tube holes should be prortected from overheat during soldering operation.
Tubes and flues are silver soldered to the inner firebox . 1mm solder wire is coiled twice around each tubes and flues. Note the smokebox tubeplate is used as a jig to stand the tubes parallel.
Finished inner boiler