Gear Ratio
For a spur gear pair the ratio is the ratio of tooth counts. With the module it gives pitch diameters and centre distance; with efficiency, the output torque.
Ratio i = z₂ / z₁3
- Output speed n₂
- 483 rpm
- Output torque T₂
- 145.5 N·m
- Transmitted power
- 7.59 kW
- Pitch diameters d₁ / d₂
- 36.0 / 108.0 mm
- Tip diameters d_a = m(z + 2)
- 40.0 / 112.0 mm
- Centre distance a
- 72 mm
- Pitch-line velocity v
- 2.73 m/s
- z₁ = 18 — undercut limit at 20° pressure angle is 17 teeth
- Tooth counts must be whole numbers
METHOD
How it is calculated
i = z₂ / z₁ n₂ = n₁ / i T₂ = T₁ · i · η d = m · z a = (d₁ + d₂) / 2 v = π · d₁ · n₁ / 60 000
ASSUMPTIONS & NOTES
- Standard 20° pressure angle, no profile shift.
- Tooth root and surface (pitting) strength require ISO 6336 or AGMA 2001.
- For multi-stage reducers, calculate each stage and multiply the ratios.
Results are for preliminary design and checking; base the final design on the governing standard and safety factors.
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