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Table 17-26B Surface Strength Factor of Gleason Straight Bevel Gear

No. Item Symbol Unit Pinion Gear 1 Allowable Hertz Stress sHlim kgf/mm² 164 2 Pinion's Pitch Diameter d1 mm 40.000 3 Pinion's Pitch Cone Angle d1 degree 26.56505º 4 Cone Distance Re mm 44.721 5 Tooth Width b 15 6 Number of Teeth Ratio z2/z1 u   2 7 Zone Factor ZH 2.495 8 Material Factor ZM (kgf/mm²) 60.6 9 Contact Ratio Ze   1.0 10 Spiral Angle Factor Zb 1.0 11 Life Factor kHL 1.0 12 Lubricant Factor ZL 1.0 13 Surface Roughness Factor ZR 0.90 14 Sliding Speed Factor ZV 0.97 15 Hardness Ratio Factor ZW 1.0 16 Dimension Factor of Root Stress kHX 1.0 17 Load Distribution Factor kHb 2.1 18 Dynamic Load Factor kV 1.4 19 Overload Factor  KO 1.0 20 Reliability Factor CR 1.15 21 Allowable Tangential Force on Central Pitch Circle Ftlim kgf 103.0 103.0

17.5 Strength Of Worm Gearing       This information is applicable for worm gear drives that are used to transmit power in general industrial machines with the following parameters: Axial Module: Pitch Diameter of Worm Gear: Sliding Speed:  Rotating Speed, Worm Gear:  m d2   v5 n2   1 to 25 mm less than 900mm     less than 30m/sec less than 600 rpm    17.5.1 Basic Formulas:      Sliding Speed, vs (m/s)        Vs =     d1n1                              (17-48)               19100cosg 17.5.2 Torque, Tangential Force and Efficiency    (1) Worm as Driver Gear (Speed Reducing) where: T2 = Nominal torque of worm gear (kgf.m)            T1 = Nominal torque of worm (kgf.m)

Ft = Nominal tangential force on worm gear's pitch circle (kgf) d2 = Pitch diameter of worm gear (mm) u = Teeth number ratio = z2 / zw   hR= Transmission efficiency, worm driving (not including bearing loss, lubricant agitation loss, etc.) m = Friction coefficient (2) Worm Gear as Driver Gear (Speed Increasing) where: h1 = Transmission efficiency, worm gear driving (not including bearing loss, lubricant agitation loss, etc.) 17.5.3 Friction Coefficient, m     The friction factor varies as sliding speed changes. The combination of materials is important. For the case of a worm that is carburized and ground, and mated with a phosphorous bronze worm gear, see Figure 17-12. For some other materials, see Table 17-27.     For lack of data, friction coefficient of materials not listed in Table 17-27 are very difficult to obtain. H.E. Merritt has offered some further information on this topic. See Reference 9.

Table 17-27   Combinations of Materials and Their Coefficient of Friction, m

Combination of Materials m Cast Iron and Phosphor Bronze Cast Iron and Cast Iron Quenched Steel and Aluminum Alloy Steel and Steel m in Figure 17-12 times 1.15 m in Figure 17-12 times 1.33 m in Figure 17-12 times 1.33 m in Figure 17-12 times 2.00

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