Belt Drive
Flat Belt V- Belt
Angle of contact [θ]
1- Open belt drive
The rotation of the driven is the same of the driver
o
θ = 180 ± 2α
o
= 180 ± 2 sin-1 [D-d / 2C]
o
θ1 = 180 - 2 sin-1 [D-d / 2C]
o
θ2 = 180 + 2 sin-1 [D-d / 2C]
The length of belt [L]
L 2C D d π D d 2
2 4C
Requirement 2c>d+D
2- Crossed belt drive
Bigger surface area
The rotation of the driven is the opposite of the driver
o
θ1 = θ2 = 180 + 2α
o
= 180 + 2 sin-1 [D+d / 2C]
The length of belt [L]
2
D d D d
L 2C π
2 4C
I- Flat belt drive
(Neglecting inertia force effect)
F1: Internal force at tight side
F2: Internal force at loose side
F1 > F2
F
1 eμθ
F
2
θ : is the smallest angle of contact = θ1 (rad)
mu :coefficient of friction 0.02=>0.05
Torque = Power / ω = N.m
(Watt)
Torque = 75 x Power / ω = kg.m
(HP)
ω = 2π n / 60
Torque = (F1 – F2) d/2
Normal stress at belt [σ]
F
σ 1
bt
allowable tension =.2 MPa
Consideration
if D/d is very big we should consider bending stress
centrifugal force
II- V-belt drive
(Neglecting inertia force effect)
F1: Internal force at tight side
F2: Internal force at loose side
F1 > F2
F
1 eμ'θ
F
2
Where, μ' = μ/sin β
o o
2β = (34 : 36 ) , Pulley grooved angle
Torque = (F1 – F2) d/2
Number of V- belts [N]
No. of V-belt Transmitted Power Service factor
N PK
P*K K
1 2
Transmitted Power per belt Angular contact factor Pulley diameter ratio factor
Service factor (K):
1.25: Shock free drive …….. [machine tools]
1.40: Moderate shocks …….. [presses – lifts – pumps]
1.50: Heavy shocks ……….. [rolling mills]
2.00: Sudden shocks ………. [cranes]
Angular contact factor (K1)
θ1 180 170 160 150 140 130 120 110 100 90 80 70
K1 1.0 0.98 0.95 0.92 0.89 0.86 0.82 0.78 0.73 0.68 0.63 0.58
Pulley diameter ratio factor (K2)
K2 = d/dm
d : Selected pulley diameter, mm
dm: Minimum pulley diameter, mm
b 5 6 8 10 13 17 20 22 25 32 40 50
h 3 4 5 6 8 11 12.5 14 16 20 25 32
dm 22 32 45 63 90 125 180 212 250 355 500 710
The power transmitted per belt (P*) in Horsepower
Belt width ( b), mm
5 6 8 10 13 17 20 22 25 32 40 50
2 0.024 0.05 0.10 0.19 0.37 0.7 1.0 1.1 1.5 2.4 3.7 6.0
4 0.047 0.10 0.19 0.37 0.74 1.3 1.9 2.3 3.0 4.7 7.4 12
Linear velocity, (v) m/s
6 0.068 0.15 0.28 0.55 1.1 1.9 2.8 3.4 4.4 7 11 18
8 0.086 0.19 0.36 0.72 1.4 2.5 3.7 4.4 5.7 9.2 14 23
10 0.10 0.22 0.43 0.87 1.7 3.1 4.5 5.3 6.9 11.1 17 28
12 0.11 0.25 0.48 1.0 2.0 3.6 5.2 6.1 8.0 12.8 20 32
14 0.11 0.26 0.52 1.1 2.2 4 5.8 7 9.0 14.4 22 36
16 0.11 0.26 0.56 1.2 2.6 4.3 6.3 7.5 9.8 15.7 24 39
18 0.10 0.24 0.54 1.2 2.7 4.6 6.7 8 10.4 16.6 26 42
20 0.08 0.24 0.54 1.3 2.7 4.8 6.9 8.2 10.7 17.1 27 43
22 0.05 0.21 0.49 1.2 2.7 4.8 7.0 8.3 10.9 17.3 27 44
24 - 0.15 0.42 1.1 2.6 4.7 6.8 8.2 10.3 17 26 44
26 - 0.08 0.30 1.0 2.5 4.5 6.5 7.8 10.1 16.1 25 41
28 - - 0.18 0.9 2.3 4.1 6 7.1 9.3 14.8 23 37
30 - - - - 2.0 3.6 5.1 6.2 8.0 13 20 32
The power transmitted per belt (P*) in (KW)
Belt width ( b), mm
5 6 8 10 13 17 20 22 25 32 40 50
2 0.018 0.037 0.074 0.140 0.272 0515 0.736 0.810 1.104 1.766 2.723 4.416
0.035 0.074 0.140 0.272 0.545 0.957 1.398 1.693 2.208 3.459 5.446 8.832
Linear velocity, (v) m/s
4
6 0.050 0.110 0.206 0.405 0.810 1.398 2.061 2.502 3.238 5.152 8.096 13.25
8 0.063 0.140 0.265 0.530 1.030 1.840 2.723 3.238 4.195 6.771 10.30 16.93
10 0.074 0.162 0.316 0.640 1.251 2.282 3.312 3.901 5.078 8.170 12.51 20.61
12 0.081 0.184 0.353 0.736 1.472 2.650 3.827 4.490 5.888 9.421 14.72 23.55
14 0.081 0.191 0.383 0.810 1.619 2.944 4.269 5.152 6.624 10.60 16.19 26.50
16 0.081 0.199 0.412 0.883 1.766 3.165 4.637 5.520 7.213 11.56 17.66 28.70
18 0.074 0.191 0.412 0.883 1.914 3.386 4.931 5.888 7.654 12.22 19.14 30.91
20 0.059 0.177 0.397 0.957 1.987 3.533 5.078 6.035 7.875 12.59 19.87 31.65
22 0.037 0.155 0.361 0.883 1.987 3.533 5.152 6.109 8.022 12.73 19.87 32.38
24 - 0.110 0.309 0.810 1.914 3.459 5.005 6.035 7.581 12.51 19.14 32.38
26 - 0.059 0.221 0.736 1.840 3.312 4.784 5.741 7.434 11.85 18.40 30.18
28 - - 0.132 0.66 1.693 3.018 4.416 5.226 6.845 10.89 16.93 27.23
30 - - - - 1.472 3.650 3.754 4.563 5.888 9.568 14.72 23.55
