Section 17 Strength and Durability of Gears - SDP/SI

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ELEMENTS OF METRIC GEAR TECHNOLOGY where: b b = tan –1 (tan β cos α t ) PHONE: 516.328.3300 • FAX: 516.326.8827 • WWW.SDP-SI.COM The zone factors are presented in Figure 17-2 for tooth profiles per JIS B 1701, specified in terms of profile shift coefficients x 1 and x 2 , numbers of teeth z 1 and z 2 and helix angle β. The "+" symbol in Figure 17-2 applies to external gear meshes, whereas the "–" is used for internal gear and ex ternal gear meshes. 3.0 Metric 0 10 I R T 1 2 ––––––– = – 0.02 (x1 ± x 2 ) (z1 ± z 2 ) 2.9 2.8 – 0.015 3 2.7 – 0.01 4 2.6 – 0.005 5 – 0.0025 2.5 0 + 0.0025 6 Zone Factor ZH 2.4 2.3 2.2 2.1 2.0 + 0.025 + 0.04 + 0.06 + 0.005 + 0.01 + 0.015 + 0.02 + 0.03 + 0.05 7 8 9 10 1.9 1.8 + 0.08 + 0.1 + 0.09 + 0.07 11 12 1.7 1.6 1.5 0° 5° 10° 15° 20° 25° 30° 35° 40° 45° Helix Angle on Standard Pitch Cylinder β Fig. 17-2 Zone Factor Z H T-161 13 14 15 A
I R T 1 2 ELEMENTS OF METRIC GEAR TECHNOLOGY PHONE: 516.328.3300 • FAX: 516.326.8827 • WWW.SDP-SI.COM 17.2.3.C Material Factor, Z M –––––––––––––––––––– –––––––––––––––––––– 1 2 2 Z M = 1 – ν 1 1 – ν 2 (17-16) π (––––––– + –––––––) E 1 E 2 where: ν = Poisson's Ratio, and E = Young's Modulus Table 17-9 contains several combinations of material and their material factor. 0 10 3 4 5 6 7 8 9 10 11 12 13 14 15 A Material Structural Steel Cast Steel Ductile Cast Iron Gray Cast Iron T-162 Symbol * SC FCD FC Gear E Young's Modulus kgf/mm 2 21000 20500 17600 12000 Table 17-9 Material Factor, Z M Poisson's Ratio 0.3 Material Structural Steel Cast Steel Ductile Cast Iron Gray Cast Iron Cast Steel Ductile Cast Iron Gray Cast Iron Ductile Cast Iron Gray Cast Iron Gray Cast Iron *NOTE: Structural steels are S…C, SNC, SNCM, SCr, SCM, etc. 17.2.4 Contact Ratio Factor, Z ε This factor is fixed at 1.0 for spur gears. For helical gear meshes, Z ε is calculated as follows: Meshing Gear Symbol * SC FCD FC SC FCD FC FCD FC FC E Young's Modulus kgf/mm 2 21000 20500 17600 12000 20500 17600 12000 17600 12000 12000 Helical gear: When ε β ≤ 1, ––––––––– ⎫ ε β Z ε = 1 – ε β + ––– ε α ⎪ When ε β > 1, ⎬ (17-17) –– 1 Z ε = –– ⎪ ⎭ ε α Metric where: ε α = Radial contact ratio = Overlap ratio ε β Poisson's Ratio 0.3 Material Factor Z M (kgf/mm 2 ) 0.5 60.6 60.2 57.9 51.7 59.9 57.6 51.5 55.5 50.0 45.8
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Section 17 Strength and Durability of Gears - SDP/SI

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