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MOULDING IN GREEN  SAND

121

Fig. 15 is a fusee drum for a derrick crane, having the ratchet cast at one
end. The ratchet is made in a core, the print for which is outlined at A.
Fig. 16 is its mould, cored ready for pouring. Reference to some of its
details will follow presently.

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Fig. 14.—Radial Arm of Drilling Machine
aa shows jointing.    A, A, Prints.    B, B, Loose pieces.

Details of Green-sand Moulds.—Although some details given here
concern moulds made in dried sand and loam, others do not, or only in a
lesser degree, so that the present section is the most suitable for their con-
sideration.

Provisions Made for the Support of Sand.—Owing to the fragile nature

pig> 15>—Section of Fusee Barrel for Derrick Crane
A, Print for ratchet core.
of green sand, abundant support is required. All boxes, except the smallest,
those say of from 12 in. to 15 in. across, are bridged with stays or bars (see
figs 16 and 36), spaced at from 6 in. to 8 in. apart. Those in the bottom
box are flat, since the sand there cannot fall out, being supported by the
floor on which the box rests. Those in the top are vertical, extending down