84), or even trebled, the heating surface may be
increased to 180-200 square inches. With a powerful blow-lamp this boiler
raises a lot of steam.
Tubing the Furnace Flue.--Before any of the holes are made, the lines on
which the centres lie must be scored from end to end of the flue on the
outside. The positions of these lines are quickly found as follows:--Cut
out a strip of paper exactly as long as the circumference of the tube, and
plot the centre lines on it. The paper is then applied to the tube again,
and poppet marks made with a centre punch opposite to or through the marks
on the paper. Drive a wire-nail through a piece of square wood and sharpen
the point. Lay the flue on a flat surface, apply the end of the nail to one
of the poppet marks, and draw it along the flue, which must be held quite
firmly. When all the lines have been scored, the centring of the water
tubes is a very easy matter.
[Illustration: FIG. 83.-End of horizontal boiler, showing position of holes
for stays and fittings.]
The two holes for any one tube should be bored independently, with a drill
somewhat smaller than the tube, and be opened to a good fit with a reamer
or broach passed through both holes to ensure their sides being in line.
Pages:
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176