119 OF ENGINEERING FORMULÆ.
Screw Piles.
CAST-IKON SCREW FILE.
Lengths, 9 feet; iiianietef, outside, 2 feet 6 inches; metal
1 inch thick; thread of screw, f at point, 2| at root; pitch of
screw, 7 inches. Flanges If thick, with 10 bolts 1 inch in
diameter. Diameter of screw 4 feet 6 inches, screwed 20 to
45 feet into ground, by 4 levers each 10 feet long, each
lever having 8 bullocks yoked to it.
A more manageable arrangement is a capstan head on the
pile, with rail arms and ropes passing twice round their ends
to a crab-winch.
Weight of bottom length about li ton, intermediate
lengths H ton; bracing per bay, about 0 • 31 tons. A pier of
2 piles 40 feet long with bracing weighs about 16 tons.
Screw Pile Jetties.
SOLID WROUGHT-IKON FILE
Distance of centres apart, 15 feet; diameter of pile, 6 inches;
lengths, 18 to 25 feet; screw, 3 feet 6 inches diameter; 2 feet
6 inches deep; metal at root of blade, 2£ inches thick; dia-
meter of boss, 9i inches; diameter of coupling, 10£ inches;
length of ditto, 21 inches; coupling key, 2 X 1, recessed i inch;
steel pin through coupling li inch diameter, i inch taper;
clips for bracing, 9 inches wide, 10 ihches long, j inch thick.
Pile, -where inserted in shoe, reduced f Inch on two sides
by two flats; bracing of channel iron, 4|" X U" X