Surface Strength Of Bevel Gears
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17.3.4 Examples of Bevel Gear Bending Strength Calculations Table 17-24A 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 26.56505º 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 More than 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 Table 17-24B Bending Strength Factors for Gleason Straight Bevel Gear No. Item Symbol Unit Pinion Gear 1 Central Spiral Angle bm degree 0º 2 Allowable Bending Stress at Root sFlim kgf/mm² 42.5 42.5 3 Module m mm 2 4 Tooth Width b 15 5 Cone Distance Re 44.721 6 Tooth Profile Factor YF 2.369 2.387 7 Load Distribution Factor Ye 0.613 8 Spiral Angle Factor Yb 1.0 9 Cutter Diameter Effect Factor YC 1.15 10 Life Factor KL 1.0 11 Dimension Factor KFX 1.0 12 Tooth Flank Load Distribution Factor KM 1.8 1.8 13 Dynamic Load Factor KV 1.4 14 Overload Factor KO 1.0 15 Reliability Factor KR 1.2 16 Allowable Tangential Force at Central Pitch Circle Ftlim kgf 178.6 177.3 17.4 Surface Strength Of Bevel Gears This information is valid for bevel gears which are used in power transmission in general industrial machines. The applicable ranges are: Radial Module: Pitch Diameter: Linear Speed: Rotating Speed: md v n 1.5 to 25mm Straight bevel gear under 1600 mm Spiral bevel gear under 1000 mm less than 25 m/sec less than 3600 rpm 17.4.1 Basic Conversion Formulas The same formulas of SECTION 17.3 apply. (See page 84). 17.4.2 Surface Strength Equations In order to obtain a proper surface strength, the tangential force at the central pitch circle, Ftm, must remain below the allowable tangential force at the central pitch circle, Ftmlim, based on the allowable Hertz stress sHlim. Ftm £ Ftmlim (17-37) Alternately, the Hertz stress sH, which is derived from the tangential force at the central pitch circle must be smaller than the allowable Hertz stress sHlim. sH £ sHlim (17-38) The allowable tangential force at the central pitch circle, Ftmlim, in kgf can be calculated from Equation (17-39). (17-39) 416