In the following text, main consideration will be given to Nylon MC901 and Duracon M90, However, the basic equations used are applicable to all other plastic materials if the appropriate values for the factors are applied.
18.4.1 Bending Strength of Spur Gears
Nylon MC901
The allowable tangential force F (kgf) at the pitch circle of a Nylon MC9O1 spur gear can be obtained from the Lewis formula.
F = mybsbKv (kgf) (18-1)
where:
m = Module (mm)
y = Form factor at pitch point (see Table 18-15)
b = Teeth width (mm)
sb = Allowable bending stress (kgf/mm²) (see Figure 18-1)
Kv= Speed factor (see Table 18-16)
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Table 18-15 Form Factor, y |
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Table 18-16 Speed Factor, KV |
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The allowable tangential force F (kgf) at pitch circle of a Duracon M90 spur gear can also be obtained from the Lewis formula.
F = mybsb (kgf) (18-2)
where:
m = Module (mm)
y = Form factor at pitch point (see Table 18-15)
b = Teeth width (mm)
sb
= Allowable bending stress (kgf/mm²)
The allowable bending stress can be calculated by Equation (18-3):
where:
sb'
= Maximum allowable bending stress under ideal condition (kgf/mm²) (see Figure
18-2)
Cs = Working factor (see Table 18-17)
Kv = Speed factor (see Figure 18-3)
KT = Temperature factor (see Figure 18-4)
KL = Lubrication factor (see Table 18-18)
KM = Material factor (see Table 18-19)
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| Table 18-18 Lubrication Factor. KL | ||||||
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| Table 18-19 Material Factor, KM | ||||||
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