Examples of Bevel Gear Surface Strength Calculations
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17.4.3.L Tooth Flank Load Distribution Factor, KHb Factors are listed in Tables 17-25 and 17-26. If the gear and pinion are unhardened, the factors are to be reduced to 90% of the values in the table. Table 17-25 Tooth Flank Load Distribution Factor for Spiral Bevel Gears, Zerol Bevel Gears and Straight Bevel Gears with Crownina. KHb Stiffness of Shaft, Gear Box, etc. Both Gears Supported On Two Sides One Gear Supported on One End Both Gears Supported on One End Very Stiff 1.3 1.5 1.7 Average 1.6 1.85 2.1 Somewhat Weak 1.75 2.1 2.5 Table 17-26 Tooth Flank Load Distribution Factor for Straight Bevel Gear without Crownina. KHb Stiffness of Shaft, Gear Box, etc. Both Gears Supported On Two Sides One Gear Supported on One End Both Gears Supported on One End Very Stiff 1.3 1.5 1.7 Average 1.85 2.1 2.6 somewhat Weak 2.8 3.3 3.8 17.4.3.M Dynamic Load Factor, Kv The dynamic load factor can be obtained from Table 17-24. 17.4.3.N Overload Factor, KO The overload factor can be computed by Equation 17-11 or found in Table 17-4. 17.4.3.O Reliability Factor, CR The general practice is to assume CR to be at least 1.15. 17.4.3.P Allowable Hertz Stress, sHlim The values of allowable Hertz stress are given in Tables 17-12 through 17-16. 17.4.4 Examples of Bevel Gear Surface Strength Calculation Tables 17-26A and 17-26B give the calculations of surface strength factors of Gleason straight bevel gears. Table 17-26A Gleason Straight Bevel Gear Design Details No. Item Symbol Unit Pinion Gear 1 Shaft Angle S degree 90º 2 Module m mm 2 3 Pressure Angle a degree 20º 4 Central Spiral Angle bm 0º 5 Number of Teeth z 20 40 6 Pitch Circle Diameter d mm 40.000 80.000 7 Pitch Cone Angle d degree 26.565.5º 63.43495º 8 Cone Distance Re mm 44.721 9 Tooth Width b 15 10 Central Pitch Circle Diameter dm 33.292 66.584 11 Precision Grade JIS 3 JIS 3 12 Manufacturing Method Gleason No. 104 13 Surface Roughness 12.5 mm 12.5 mm 14 Revolutions per Minute n rpm 1500 750 15 Linear Speed v m/s 3.142 16 Direction of Load Unidirectional 17 Duty Cycle cycle Over 107 cycles 18 Material SCM 415 19 Heat Treatment Carburized 20 Surface Hardness HV 600 ... 640 21 Core Hardness HB 260 ... 280 22 Effective Carburized Depth mm 0.3 ... 0.5 418