\fdO'^ - Old Forge Coal Mines

230 STRENGTH OP MATERIALS.
(609) The key has a shearing stress exerted on two
sections; hence, each section must withstand a stress of
10,000 pounds.
20,000 ,^^^^ ,
—^^r =
2
Using formula 65, with a factor of safety of 10,
r, AS^ . 10 P 10X10,000
Let d = width of key ;
/ = thickness.
Then, ^ / = ^ = 2 sq. in. But,
problem,
Hence, di = ^d' = '-Z; d' = 8; b = 2.828'
from the conditions of the
^ Ans.
(610) From formula 75, the deflection S = a-^ry,
and, from the table of Bending Moments, the coefficient a for
the beam in question
is --.
48
JV= 30 tons = GO, 000 lb. ; /=
/ = 64
54 inches; £ = 30,000,000;
Tj c IX 60,000 X 54» ^_, .
=-0064 m.
48 X 30,000,000 X ,, Ans.
d4
Hence, 5 = o .^.q ^ .o^
(611) {a) The circumference of a 7-strand rope is 3
times the diameter; hence, C = 1^ x 3 = 3|'.
Using formula 86, /"= 1,000 T" = 1,000 X (3i)' =
14,062.5 1b. Ans.
(d) Using formula 84,
P=100C%orC=/^- = i/^-^^j^=5.9r. Ans.