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dispositions of the foot may entail coring over it or jointing the pattern at
right angles with the steam-chest face.

In many cases the steam-chest is cast
in one piece with the cylinder body (fig. 40).
Then the interior is produced with a core
for which a print is attached, wide enough
to afford adequate support to the core, and
prints are inserted in the box for the steam
and exhaust passage cores (fig. 41). The
pattern portion for the steam-chest is pre-
pared by boxing-up in order to reduce
shrinkage and to economize timber.

Many cylinders are jacketed. The an-
nular core is made in a box, complete in
all details. All jacketed castings require
especial care in both pattern-shop and
foundry, because the metal is thin and the
risks of displacement of the cores and
obstruction of the vents are very great.
Steam, gas, and petrol cylinders are made
with jackets, and the last named are the
most difficult of all, because of the large
number of cores and their interdependence, Fig> 4I._core BOX for steam-chest Cast
and the very thin walls of metal between                    with Cylinder

them, ranging from about J in. to f in.
When two, three, or four cylinders are cast en bloc the separate cores may

Fig. 42.óCylinder Pattern for Motor-cycle Engine