Section 17 Strength and Durability of Gears - SDP/SI

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ELEMENTS OF METRIC GEAR TECHNOLOGY 17.3.3.K Reliability Factor, K R The reliability factor should be assumed to be as follows: 1. General case: K R = 1.2 2. When all other factors can be determined accurately: K R = 1.0 3. When all or some of the factors cannot be known with certainty: K R = 1.4 PHONE: 516.328.3300 • FAX: 516.326.8827 • WWW.SDP-SI.COM 17.3.3.L Allowable Bending Stress at Root, σ F lim The allowable stress at root σ F lim can be obtained from Tables 17-5 through 17-8, similar to the case of spur and helical gears. 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 Σ m degree mm 90° 2 α 20° degree β m 0° z 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Shaft Angle Module Pressure Angle Central Spiral Angle Number of Teeth Pitch Circle Diameter Pitch Cone Angle Cone Distance Tooth Width Central Pitch Circle Diameter Precision Grade Manufacturing Method Surface Roughness Revolutions per Minute Linear Speed Direction of Load Duty Cycle Material Heat Treatment Surface Hardness Core Hardness Effective Carburized Depth d δ Re b d m n v mm degree mm rpm m/s cycle mm 20 40 40.000 80.000 26.56505° 63.43495° 44.721 15 33.292 66.584 JIS 3 JIS 3 Gleason No. 104 12.5 µm 1500 3.142 Unidirectional More than 10 7 cycles SCM 415 Carburized HV 600 … 640 HB 260 … 280 0.3 … 0.5 Metric 0 10 12.5 µm 750 I R T 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 T-179 A
I R T 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ELEMENTS OF METRIC GEAR TECHNOLOGY PHONE: 516.328.3300 • FAX: 516.326.8827 • WWW.SDP-SI.COM Table 17-24B Bending Strength Factors for Gleason Straight Bevel Gear No. Item Symbol Unit Pinion Gear 1 Central Spiral Angle β m degree 0° 2 Allowable Bending Stress at Root σ F lim kgf/mm 2 42.5 42.5 3 Module m 2 4 Tooth Width b mm 15 5 Cone Distance R e 44.721 6 Tooth Profile Factor Y F 2.369 2.387 7 Load Distribution Factor Y ε 0.613 8 Spiral Angle Factor Y β 1.0 9 Cutter Diameter Effect Factor Y C 1.15 10 Life Factor K L 1.0 11 Dimension Factor K FX 1.0 12 Tooth Flank Load Distribution Factor K M 1.8 1.8 13 Dynamic Load Factor K V 1.4 14 Overload Factor K O 1.0 15 Reliability Factor K R 1.2 16 Allowable Tangential Force at Central Pitch Circle F t lim 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: m 1.5 to 25 mm Pitch Diameter: d Straight bevel gear under 1600 mm Spiral bevel gear under 1000 mm Linear Speed: v less than 25 m/sec Rotating Speed: n less than 3600 rpm 17.4.1 Basic Conversion Formulas The same formulas of SECTION 17.3 apply. (See page T-171). 17.4.2 Surface Strength Equations In order to obtain a proper surface strength, the tangential force at the central pitch circle, F tm , must remain below the allowable tangential force at the central pitch circle, F tm lim , based on the allowable Hertz stress σ H lim . F tm ≤ F tm lim (17-37) Alternately, the Hertz stress σ H , which is derived from the tangential force at the central pitch circle must be smaller than the allowable Hertz stress σ H lim. σ H ≤ σ H lim (17-38) 15 A T-180
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Section 17 Strength and Durability of Gears - SDP/SI

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