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AGMA WormGear Equations For Rating Factors

Gear Engineering and Design
Mechanics and Machine Design and Engineering

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AGMA Worm and Spur Gear Design Equations and Calculators

AGMA Wormgear Equations For Rating Factors

Values for the ratio correction factor, the velocity factor, and materials factors can be found from tables provided in the ANSI/AGMA 6034-B92 standard. The following equations for the ratio correction factor, the velocity factor, and materials factors provide approximations to the values given in the tables.

The ratio correction factor C_m is a function of the gear ratio, m_G.

For 3 ≤ m_G ≤ 20

C_m = 0.02 ( -m²_G + 40m_G - 76)^0.5 + 0.46

For 20 < m_G ≤ 76

C_m = 0.0107 ( -m²_G + 56m_G + 5145)^0.5

For m_G > 76

C_m = 1.1483 - 0.0065m _G²

 

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Velocity correction factor C_v is a function of the sliding velocity at the mean worm diameter, V_t.

For 0 < V_t ≤ 3.556 m/s

C_v = 0.659 e^-0.2165Vt

For 3.556 < V_t ≤ 15.24 m/s

C_v = 0.652 V_t^-0.571

For V_t > 15.24 m/s

C_v = 1.098 V_t^-0.774

Note: (V_t m/s ) x 196.5 = ( V_t ft/min )

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Friction, µ is a function of the sliding velocity at the mean worm diameter, V_t.

For V_t = 0,

µ = 0.15

For 0 < V_t ≤ 0.0508 m/s

µ = 0.124 e^{( -2.233z )}
where: z = V_t^0.645

V_t > 0.0508 m/s

µ = 0.103 e^{( -1.185z )}
where: z = V_t^0.45

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The materials factor C_s depends on the method of casting.

For Sand Casting

For center distance (Radius) C ≤ 76.2 mm, an initial estimate for the materials factor can be obtained from:

C_s = 720 + 0.000633C³

This value can be compared to the values obtained for the relevant means of casting, as indicated by the following relationships and the smaller value used.

For sand cast gears then:

for d_m ≤ 63.5 mm

C_s = 1000

for d_m > 63.5 mm

C_s = 1856.104 - 476.5454 log₁₀ d_m

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For chill cast bronze gears:

For center distance (Radius) C ≤ 76.2 mm, an initial estimate for the materials factor can be obtained from:

C_s = 720 + 0.000633C³

for d_m ≤ 203.2 mm

C_s = 1000

for d_m > 203.2 mm

C_s = 2052.011 - 455.8259 log₁₀ d_m

For centrifugally cast gears:

For center distance (Radius) C ≤ 76.2 mm, an initial estimate for the materials factor can be obtained from:

C_s = 720 + 0.000633C³

for dm ≤ 635 mm

C_s = 1000

for dm > 635 mm,

C_s = 1503.811 - 179.7503 log₁₀ d_m

References:

ANSI/AGMA 6034-B92, Practice for Enclosed Cylindrical Wormgear Speed Reducers and Gearmotors, Annex C Fomulas for rating factors.