Page 78 - Mechanical Engineer's Data Handbook
P. 78
APPLIED MECHANICS 67
2.2.2 Winches and pulleys Block and tackle
Winch Velocity ratio VR = n
R where: n=number of ropes between the sets of
Velocity ratio VR=- pulleys (= 5 in figure).
r
W
W Wr Force to raise load F = q-
Force to raise load F=-- n
VR -‘R
where: q =efficiency.
F
Pulleys
Velocity ratio VR-2
W
Force to raise load F = q -
2
Differential pulley
F
7 Velocity ratio VR=- 2
W
Force to raise load F = q -
VR
