472 Molesworth’s pocket-book
Exhaustive Power of the Blast-pipe in Locomotives.
(Longridge, * Min. Inst. Civ. Eng.,’ vol. Hi.)
d — Diameter of jet or blast-pipe in inches.
I)= Diameter of chimney in inches.
p s= Pressure of steam in lb», per square inch above tbe
atmosphere.
E = Exhaustive power in inches of water.
Increased action obtained by lengthening the chimney is
very .slow when the length exceeds four diameters.
Area of Chimneys.
a — Area of fire-grate in square feet.
F 3= Quantity of coal consumed per hour in lbs.
k = Height of chimney hi feet.
HP = Horse-power of engine (indicated).
A = Area of chimney at top in square inches.
15 F 100 HP 180 a
A = —- = ■ ■ ■ ~ —— •
V h h, V h
Genekal Rules for Brick Chimneys.
Th« diameter at tbe base to ,',th of the height.
Batter of chimneys, 0-3 inch to the foot.
Thickness of brickwork, 1 brick from top to 25 feet from
ditto.
li brick from 25 to 50 feet from the top, increasing by
i brick for each 25 feet from the top.
If the inside diameter at the top exceeds 4 feet 6 inches, the
top length should be It brick thick.
Velocity of Artificial Draught.
H = Height of chimney in feet.
T = Temperature of air supplying the chimney.
t = Temperature of air at top of chimney,
V = Velocity in feet per second.
v = 36-5