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How to Select a Transmission Timing Belt 3

[Step 3] Temporarily Select the Belt Type Using the Selection Guide Table

Select the required belt type from the table below, based on the rotational speed (rpm) of the small pulley and the designed power.

[Step 4] Determine the Number of Teeth for Large and Small Pulleys, Belt Length, and Distance Between Shafts

(1) Select the number of teeth for the large and small pulleys that satisfy the gear ratio already determined.
*Please refer to the following to select timing belts.

(However, for small pulleys, select teeth numbers greater than the allowable minimum number of teeth shown in Table 26.)

Gear Ratio
Table 26. Allowable Minimum Number of Teeth
  Rotational Speed of Small Pulley (rpm)
Belt Type and Minimum Number of Teeth   Up to 900 Over 900
Up to 1,200
Over 1,200
Up to 1,800
Over 1,800
Up to 3,600
Over 3,600
Up to 4,800
Over 4,800
Up to 10,000
MXL 12 15 15 16
XL 11 11 12 16 16
L 14 14 16 19 20
H 16 18 20 24 24
S2M 16 16 18 20 20 20
S3M 16 16 18 20 20 20
S5M 16 20 24 24 24 26
S8M 24 25 28 30 32
S14M 40 48
P2M 14 14 14 16 18 20
P3M 14 14 14 18 20 28
P5M 18 20 24 28 30 40
P8M 22 24 26 28 28
UP5M 18 20 24 28 30 40
UP8M 22 24 26 28 30
MTS8M 24 24 26 28 28
T5 12 14 16 18 18
T10 16 18 20 22 22
2GT 12 14 16 18 20
3GT 14 14 16 20 20
EV5GT 18 20 24 28 30
EV8YU 26 28 32 36

(2) Determine the approximate belt circumference (Lp´) based on the tentative distance between shafts (C´), the diameter of the large pulley (Dp), and the diameter of the small pulley (dp). (Calculate pulley diameter with P.D. dimensions)

Determine the Number of Teeth for Large and Small Pulleys, Belt Length, and Distance Between Shafts_1
: Tentative distance between shafts
Dp
: Pitch diameter of large pulley (mm)
dp
: Pitch diameter of small pulley (mm)
Lp´
: Approximate belt circumference (mm)

(3) Determine a belt circumference (Lp) closest to the approximate belt circumference (Lp´), and calculate the exact distance between shafts using the following formula.
For belts, please refer to the product pages.

Determine the Number of Teeth for Large and Small Pulleys, Belt Length, and Distance Between Shafts_2
Dp
: Pitch diameter of large pulley (mm)
dp
: Pitch diameter of small pulley (mm)
Lp
: Belt Circumference (mm)
C
: Distance between shafts

[Step 5] Determine the Belt Width

(1) Calculate the approximate belt width (Bw′: mm) using the formula below, and select a belt width that is closest to the approximate belt width.

Determine Belt Width_1
Pd
: Designed power
Ps
: Reference transmission capacity…Use the Reference Transmission Capacity Table.
Km
: Mesh correction factor (Table 27)
Wp
: Reference belt width (Table 28)
Table 27. Mesh Correction Factor (Km)
Number of Meshing Teeth Zm 6 or more 5 4 3 2
Km 1.0 0.8 0.6 0.4 0.2
Km *1 1.0 0.7 0.5
Determine Belt Width_2
Zd
: Number of small-pulley teeth
Dp
: Pitch diameter of large pulley (mm)
C
: Distance between shafts (mm)
θ
: Contact angle (°)
dp
: Pitch diameter of small pulley (mm)
Table 28. Reference Belt Width (Wp)
Belt Type MXL XL L H S2M S3M S5M S8M S14M MTS8M P2M P3M P5M P8M T5 T10 2GT 3GT EV5GT EV8YU
Reference 6.4 25.4 25.4 25.4 4 6 10 60 120 60 4 6 10 15 10 10 4 6 15 20

(2) Check if the designed power (Pd) satisfies the following formula.
(If not, re-select a belt width one size larger.)
*For belt types P□M and UP□M, substitute the value of *Km for the mesh correction factor.

  • Pd<Ps ・Km ・Kb

■ For 2GT, 3GT, EV5GT and EV8YU

  • Pd<Ps ・Km ・Kb ・KL
Pd
: Designed power
Km
: Mesh correction factor
KL
: Length correction factor (Table 30)
Ps
: Reference transmission capacity
Kb
: Width correction factor (Table 29)

Table 29. Width Correction Factor (Kb)

Belt Type Belt Width Width Correction Factor
Nominal mm Kb
MXL 019 4.8 0.72
025 6.4 1.00
037 9.5 1.57
050 12.7 2.18
XL 025 6.4 0.15
031 7.9 0.21
037 9.5 0.28
050 12.7 0.42
L 050 12.7 0.42
075 19.1 0.71
100 25.4 1.00
150 38.1 1.56
H 075 19.1 0.71
100 25.4 1.00
150 38.1 1.56
200 50.8 2.14
S2M 040 4 1.00
060 6 1.59
100 10 2.84
S3M 060 6 1.00
100 10 1.79
150 15 2.84
S5M 100 10 1.00
150 15 1.59
250 25 2.84
S8M
MTS8M
150 15 0.21
250 25 0.37
300 30 0.45
400 40 0.63
S14M 400 40 0.29
600 60 0.45
Belt Type Belt Width Width Correction Factor
Nominal mm Kb
P2M 40 4 1.00
60 6 1.59
P3M 100 10 1.78
150 15 2.84
UP5M
P5M
100 10 1.00
150 15 1.59
UP8M
P8M
150 15 1.00
250 25 1.79
T5 100 10 1.00
150 15 1.60
200 20 2.30
250 25 2.90
T10 150 15 1.60
200 20 2.30
250 25 2.90
300 30 3.50
400 40 4.60
500 50 5.80
2GT 4 4 1.00
6 6 1.67
9 9 2.67
3GT 6 6 1.00
9 9 1.66
15 15 2.97
EV5GT 9 9 0.53
12 12 0.76
15 15 1.00
EV5GT 15 15 0.71
20 20 1.00
25 25 1.29
Table 30. Length Correction Factor (KL)
Length correction factor (KL) 0.80 0.90 1.00 1.10 1.20
2GT Belt Length (mm) Up to 130 131~182 183~280 281~419 420 or more
3GT Belt Length (mm) Up to 190 191~260 261~400 401~599 600 or more
EV5GT Belt Length (mm) Up to 440 441~550 551~800 801~1100 1,101 or more
EV8YU Belt Length (mm) Up to 600 601~900 901~1250 1251~1799 1,800 or more

Notes

  • *1 For belt types P□M and UP□M, substitute the value of *Km for the mesh correction factor.

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