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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 Cm is a function of the gear ratio, mG.

For 3 ≤ mG ≤ 20

Cm = 0.02 ( -m2G + 40mG - 76)0.5 + 0.46

For 20 < mG ≤ 76

Cm = 0.0107 ( -m2G + 56mG + 5145)0.5

For mG > 76

Cm = 1.1483 - 0.0065m G2


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

For 0 < Vt ≤ 3.556 m/s

Cv = 0.659 e-0.2165Vt

For 3.556 < Vt ≤ 15.24 m/s

Cv = 0.652 Vt-0.571

For Vt > 15.24 m/s

Cv = 1.098 Vt-0.774

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


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

For Vt = 0,

µ = 0.15

For 0 < Vt ≤ 0.0508 m/s

µ = 0.124 e( -2.233z )
where: z = Vt0.645

Vt > 0.0508 m/s

µ = 0.103 e( -1.185z )
where: z = Vt0.45


The materials factor Cs 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:

Cs = 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 dm ≤ 63.5 mm

Cs = 1000

for dm > 63.5 mm

Cs = 1856.104 - 476.5454 log10 dm


For chill cast bronze gears:

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

Cs = 720 + 0.000633C3

for dm ≤ 203.2 mm

Cs = 1000

for dm > 203.2 mm

Cs = 2052.011 - 455.8259 log10 dm

For centrifugally cast gears:

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

Cs = 720 + 0.000633C3

for dm ≤ 635 mm

Cs = 1000

for dm > 635 mm,

Cs = 1503.811 - 179.7503 log10 dm

References:

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

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