COUPLINGS and Clutches Machinery's Handbook, 31st Edition
2528
HP = horsepower transmitted N = revolutions per minute
r = mean radius of friction cone, in inches r 1 = large radius of friction cone, in inches r 2 = small radius of friction cone, in inches R 1 = outside radius of leather band, in inches R 2 = inside radius of leather band, in inches V = velocity of a point at distance r from the center, in feet per minute F = tangential force acting at radius r , in pounds P n = total normal force between cone surfaces, in pounds P s = spring force, in pounds α = angle of clutch surface with axis of shaft = 7 to 13 degrees β = included angle of clutch leather, when developed, in degrees f = coefficient of friction = 0.20 to 0.25 for greasy leather on iron p = allowable pressure per square inch of leather band = 7 to 8 pounds W = width of clutch leather, in inches
W
Development of Clutch Leather
α
r 1
R 2
R 1
r 2
β
1
2
sin R r 2 =
sin sin R r 1 =
α
α
2 +
r r r 1 2 =
V rN 360 12 2 π =
β α =
#
, 33 000
, 63 025 P frN n
HP
W rp P n =
#
F
HP
=
=
2
V
π
For engagement with some slip:
, frN HP 63 025 #
sin
P s
α
P
P s
=
=
sin
α
n
For engagement without slip:
, 63 025
sin cos f +
HP
P s
h
^
α α
#
P
P s
= +
=
sin cos f
frN
n
α α
Angle of Cone.— If the angle of the conical surface of the cone type of clutch is too small, it may be difficult to release the clutch on account of the wedging effect, whereas, if the angle is too large, excessive spring force will be required to prevent slipping. The mini mum angle for a leather-faced cone is about 8 or 9 degrees and the maximum angle about 13 degrees. An angle of 12 1 ⁄ 2 degrees appears to be the most common and is generally
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