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Spur Gears0 pages
Spur Gear Selection
For a required centre distance and gear ratio a suitable pair of spur
gears can be selected used and assessed by the following procedure.
Select numbers of teeth in gears and module (pitch).
Gear Ratio i = Z2 (Teeth driven gear)
Z1 (Teeth driven gear)
Factors Sb and Sc Gears
Gear Type
Steel Gears and racks
Cast Gears
Table 1 Speed factor for Strength Xb (for 26000 hour rating)
2
2
Sb N/mm
130
52
Sc N/mm
9.65
9.30
Gear Shaft rpm
Daily
Hours
0.1
1
5
10
40
100
150
200
400
500
600
1000
1500
2000
3000
5000
10000
24
12
6
3
1
0.784
0.865
0.970
1.060
1.250
0.640
0.700
0.775
0.864
1.031
0.565
0.623
0.685
0.750
0.880
0.518
0.568
0.628
0.690
0.800
0.435
0.475
0.526
0.580
0.678
0.375
0.420
0.460
0.512
0.596
0.349
0.384
0.426
0.474
0.552
0.330
0.362
0.410
0.448
0.525
0.294
0.321
0.357
0.401
0.465
0.286
0.310
0.342
0.380
0.445
0.274
0.300
0.331
0.368
0.437
0.246
0.268
0.297
0.328
0.385
0.223
0.245
0.272
0.301
0.349
0.211
0.231
0.263
0.286
0.328
0.180
0.198
0.221
0.245
0.286
0.153
0.167
0.186
0.207
0.240
0.122
0.134
0.147
0.164
0.192
Gear Shaft rpm
0.1
1
5
10
40
100
150
200
400
500
600
1000
1500
2000
3000
5000
10000
24
12
6
3
1
1.149
1.448
1.830
2.200
3.320
0.780
0.998
1.258
1.570
2.280
0.564
0.718
0.901
1.168
1.653
0.488
0.625
0.790
0.980
1.440
0.377
0.478
0.607
0.762
1.218
0.320
0.408
0.514
0.650
0.928
0.297
0.372
0.474
0.602
0.862
0.282
0.355
0.455
0.575
0.825
0.250
0.317
0.404
0.508
0.728
0.240
0.304
0.382
0.480
0.700
0.233
0.294
0.370
0.472
0.675
0.209
0.262
0.334
0.425
0.610
0.192
0.240
0.307
0.381
0.551
0.180
0.226
0.287
0.360
0.520
0.157
0.196
0.250
0.308
0.425
0.132
0.165
0.211
0.263
0.390
0.106
0.132
0.167
0.210
0.304
Table 3 Strength Factor Ys
100
80
70
60
50
40
35
30
12
13
14
15
16
17
18
19
20
22
24
26
28
30
35
40
50
60
70
80
100
127
Rack
.658
.679
.700
.714
.729
.740
.750
.760
.770
.786
.800
.813
.828
.838
.862
.876
.900
.913
.923
.928
.931
.930
_
.625
.644
.662
.678
.690
.702
.710
.720
.728
.740
.752
.762
.772
.782
.800
.820
.842
.850
.858
.860
.860
.860
.839
.618
.638
.655
.670
.684
.696
.704
.713
.720
.732
.741
.753
.763
.772
.789
.803
.822
.833
.839
.839
.840
.836
.820
.614
.632
.650
.664
.676
.687
.697
.706
.713
.726
.735
.742
.750
.759
.775
.788
.806
.815
.820
.821
.822
.820
.808
.610
.628
.645
.659
.672
.682
.691
.700
.707
.714
.728
.735
.743
.750
.765
.776
.794
.802
.806
.808
.809
.808
.800
.605
.623
.640
.653
.665
.675
.683
.692
.698
.709
.718
.725
.732
.738
.751
.761
.776
.783
.788
.791
.793
.789
.780
.600
.616
.632
.646
.657
.665
.672
.680
.686
.696
.700
.699
.711
.716
.727
.736
.752
.758
.762
.765
.767
.770
.767
.597
.612
.626
.638
.650
.657
.665
.672
.677
.674
.667
.671
.675
.677
.686
.693
.705
.716
.723
.728
.734
.738
.755
.596
.610
.623
.635
.647
.653
.660
.664
.665
.660
.648
.645
.647
.649
.654
.660
.675
.686
.695
.703
.710
.716
.742
.593
.606
.620
.631
.639
.647
.650
.652
.652
.647
.641
.633
.625
.623
.622
.642
.644
.654
.664
.673
.683
.693
.728
Number of Teeth on Gear being Designed
127
Number Teeth Mating Gear
28
26
24
22
.592
.605
.619
.629
.637
.643
.645
.647
.646
.644
.637
.630
.622
.615
.613
.619
.633
.642
.650
.658
.669
.680
.721
.591
.604
.617
.626
.634
.639
.642
.643
.642
.640
.634
.627
.620
.611
.600
.607
.620
.630
.638
.645
.661
.670
.714
.590
.602
.614
.624
.630
.634
.637
.638
.638
.635
.629
.623
.616
.609
.592
.594
.604
.615
.624
.632
.641
.650
.705
.588
.600
.611
.620
.626
.630
.632
.633
.628
.630
.625
.619
.613
.605
.588
.585
.593
.600
.611
.618
.628
.638
.696
20
19
18
17
16
15
14
13
12
.585
.597
.608
.617
.621
.624
.625
.623
.626
.624
.620
.614
.609
.602
.584
.574
.582
.590
.596
.602
.613
.624
.684
.584
.597
.606
.613
.617
.620
.622
.623
.622
.621
.617
.612
.607
.600
.581
.569
.575
.583
.589
.596
.604
.616
.677
.581
.595
.604
.609
.615
.616
.618
.619
.619
.617
.613
.609
.603
.596
.578
.565
.568
.574
.582
.588
.596
.608
.669
.578
.590
.600
.606
.610
.613
.614
.615
.614
.613
.610
.605
.600
.591
.574
.562
.560
.567
.574
.591
.589
.598
.661
.575
.587
.597
.598
.606
.609
.610
.610
610
.608
.605
.601
.594
.587
.570
.559
.552
.559
.566
.579
.580
.590
.652
.573
.584
.592
.598
.601
.604
.605
.605
.605
.604
.600
.595
.588
.582
.564
.555
.544
.549
.556
.562
.571
.580
.642
.571
.578
.588
.593
.596
.598
.600
.600
.600
.598
.593
.589
.582
.576
.560
.550
.538
.542
.547
.553
.561
.570
.632
.567
.575
.583
.587
.593
.592
.593
.593
.586
.590
.586
.581
.575
.569
.554
.544
.528
.533
.539
.543
.550
.560
.620
.562
.570
.576
.580
.590
.584
.584
.584
.579
.581
.577
.572
.566
.560
.546
.535
.517
.523
.529
.533
.541
.550
.606
Table 4 Zone Factor Yz (Note: factor same for both gears in gearset)
Rack
127
100
80
70
60
50
40
35
30
12
13
14
15
16
17
18
19
20
22
24
26
28
30
35
40
50
60
70
80
100
127
Rack
1.47
1.65
1.75
1.90
2.08
2.20
2.30
2.42
2.55
2.78
3.00
3.20
3.45
3.70
4.30
4.65
5.50
6.50
7.50
8.40
9.70
_
_
1.35
1.47
1.61
1.72
1.84
1.97
2.06
2.16
2.26
2.42
2.59
2.74
2.89
3.03
3.44
3.64
4.07
4.51
4.99
5.31
5.92
6.89
_
1.34
1.46
1.59
1.69
1.80
1.92
2.01
2.10
2.20
2.35
2.50
2.64
2.79
2.90
3.35
3.50
3.84
4.21
4.67
5.00
5.51
5.92
9.70
1.32
1.44
1.55
1.64
1.75
1.86
1.94
2.04
2.12
2.28
2.42
2.53
2.66
2.76
3.00
3.27
3.65
3.89
4.25
4.57
5.00
5.31
8.40
1.30
1.42
1.53
1.61
1.72
1.81
1.89
1.98
2.07
2.22
2.34
2.44
2.56
2.67
2.89
3.11
3.50
3.75
3.97
4.25
4.67
4.99
7.50
1.28
1.39
1.49
1.58
1.67
1.75
1.83
1.92
2.00
2.13
2.25
2.36
2.46
2.54
2.77
2.93
3.28
3.57
3.75
3.89
4.21
4.51
6.50
1.26
1.35
1.45
1.53
1.62
1.68
1.75
1.82
1.89
2.00
2.13
2.23
2.33
2.40
2.60
2.76
3.00
3.28
3.50
3.65
3.84
4.07
5.50
1.25
1.34
1.42
1.48
1.55
1.61
1.66
1.71
1.75
1.88
1.98
2.06
2.15
2.30
2.40
2.53
2.76
2.93
3.11
3.27
3.50
3.64
4.65
1.25
1.32
1.40
1.46
1.53
1.59
1.63
1.68
1.72
1.82
1.90
1.96
2.04
2.11
2.27
2.40
2.60
2.77
2.89
3.00
3.35
3.44
4.30
1.24
1.31
1.38
1.43
1.49
1.55
1.60
1.64
1.68
1.75
1.83
1.88
1.94
1.98
2.11
2.30
2.40
2.54
2.67
2.76
2.90
3.03
3.70
Number of Teeth on Gear being Designed
No. Teeth
Number Teeth Mating Gear
28
26
24
22
1.23
1.29
1.37
1.42
1.48
1.54
1.58
1.62
1.66
1.73
1.79
1.84
1.90
1.94
2.04
2.15
2.33
2.46
2.56
2.66
2.79
2.89
3.45
1.22
1.28
1.36
1.41
1.46
1.52
1.56
1.60
1.63
1.70
1.75
1.80
1.84
1.88
1.96
2.06
2.23
2.36
2.44
2.53
2.64
2.74
3.20
1.21
1.26
1.34
1.39
1.45
1.49
1.53
1.57
1.60
1.66
1.71
1.75
1.79
1.83
1.90
1.98
2.13
2.25
2.34
2.42
2.50
2.59
3.00
1.20
1.25
1.32
1.37
1.42
1.47
1.50
1.54
1.56
1.62
1.66
1.70
1.73
1.75
1.82
1.88
2.00
2.13
2.22
2.28
2.35
2.42
2.78
20
19
18
17
16
15
14
13
12
1.19
1.23
1.29
1.34
1.39
1.43
1.46
1.50
1.53
1.56
1.60
1.63
1.66
1.68
1.72
1.75
1.89
2.00
2.07
2.12
2.20
2.26
2.55
1.18
1.20
1.28
1.31
1.36
1.41
1.44
1.47
1.50
1.54
1.57
1.60
1.62
1.64
1.68
1.71
1.82
1.92
1.98
2.04
2.10
2.16
2.42
1.16
1.18
1.25
1.29
1.33
1.38
1.41
1.44
1.46
1.50
1.53
1.56
1.58
1.60
1.63
1.66
1.75
1.83
1.89
1.94
2.01
2.06
2.30
1.14
1.16
1.23
1.27
1.30
1.35
1.38
1.41
1.43
1.47
1.49
1.52
1.54
1.55
1.59
1.61
1.68
1.75
1.81
1.86
1.92
1.97
2.20
1.12
1.14
1.21
1.24
1.28
1.30
1.33
1.36
1.39
1.42
1.45
1.46
1.48
1.49
1.53
1.55
1.62
1.67
1.72
1.75
1.80
1.84
2.08
1.10
1.12
1.18
1.21
1.24
1.27
1.29
1.31
1.34
1.37
1.39
1.41
1.42
1.43
1.46
1.48
1.53
1.58
1.61
1.64
1.69
1.72
1.90
1.07
1.09
1.15
1.18
1.21
1.23
1.25
1.28
1.29
1.32
1.34
1.36
1.37
1.38
1.40
1.42
1.45
1.49
1.53
1.55
1.59
1.61
1.75
1.04
1.06
1.09
1.12
1.14
1.16
1.18
1.20
1.23
1.25
1.26
1.28
1.29
1.31
1.32
1.34
1.35
1.39
1.42
1.44
1.46
1.47
1.65
1.01
1.04
1.07
1.10
1.12
1.14
1.16
1.18
1.19
1.20
1.21
1.22
1.23
1.24
1.25
1.25
1.26
1.28
1.30
1.32
1.34
1.35
1.47
9
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Rack
No. Teeth
+44 121 325 1079
Daily
Hours
Fax
Table 2 Combined Speeed Factor for Wear Xc (for 26000 hour rating)
+44 121 360 0155
Shaft centre distance in mm = 1 /2 sum gear teeth x pitch
= 1 /2 (Z1 + Z2) P
From this initial selection each gear can be assessed for strength
and wear using the following formulae. The least of the four
calculated powers is the capacity of the gear set. The capacity
required is determined by multiplying actual power by a service
factor relative to driver and driven equipment, refer page c2. If
calculated power is below required capacity increase pitch or face
width of gears, adjust teeth sizes accordingly, and reassess drive. If
calculated power is substantially in excess of required capacity a
lower Module could be considered.
Te l
Strength capacity Ps= Xb x Sb x YS x F x N x Z x P2 kw
19,100 x 103
Wear capacity Pw = Xc x Sc x YZ x F x N x Z x P1.8kw
10,000 x 103
Where:- F = Face width mm
N = Gear shaft speed r.p.m.
P = Gear pitch, Module No.
Sb = Bending stress for gear material (see below)
Sc = Surface stress for gear material (see below)
Xb = Speed factor for strength - see table 1
Xc = Speed factor for wear - see table 2
YS = Strength factor - see table 3
YZ = Zone factor - see table 4
