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13G MOLESWORTHS PoOKST-BOOK
Cranes.
Ordinary height of handle above ground, 3 feet
Diameter of circle described by handle, 32 inches.
Angle of jib = 45°.
Each man worliing at the handle of a crane
imparts a pressure of about 15 to 20 lbs.
W = Weight to be raised by crane in lbs.
P = Power applied to the handle in lb«.
D = Diameter of circle described by handle in
inches. __
n = Number of revolutions of handle to one
of barrel. •
B = Diameter of barrel in inches.
D x P X n _ W X B
B ~ W ’ ~ P X n '
WxB WxB
n ~ D x P ' ~ n X D ’
P X D X n
Power gained by Blocks.
Let N = number of cords or chains leading to or from the
movable block, the power gained will = N.
Stiffness of Ropes. t
R ± Stiffness of ropes in lbs. avoirdupois, or excess of ten-
sion at the leading side of the rope.
d = Diameter of rope, in inches.
n =; 48 for white rope — 35 eft for tarred rope.
r = Effective radius of pulley in inches.
T — Tension in lbs. avoirdupois.
R = - (’0012 + -OOlOSen + ’0012 T) for white rope.
= - ('006 + ‘00139211 + -00168 T) for tarred rope.