If the tubes are set 7/8 inch apart,
centre to centre, instead of 1-1/4 inches, the heating surface will be
greatly increased and the furnace casing better protected.
Assembling.--When all necessary holes have been made and are of the
correct size, begin by riveting and silver-soldering in the ends of the
drums. Next fix the cross tubes, E, taking care that they and B and C form
rectangles. Then slip the F, G, and H tubes half an inch into the main
drum, and support A, by means of strips passed between the G and H tubes,
in its correct position relatively to B and C. The E tubes can now be
pushed into B and C and silver-soldered. The supports may then be removed,
and the a and H tubes be got into position and secured. Drum D then demands
attention. The connecting tubes, KK, should be silver-soldered in, as the
boiler, if properly made, can be worked at pressures up to 100 lbs. per
square inch.
The casing is of 1/20-inch sheet iron, and in five parts. The back end must
be holed to allow A, B, and C to project 1 inch, and have a furnace-door
opening, and an airway at the bottom, 5 inches wide and 1 inch deep, cut in
it.
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