Documentation/Modules/Gear Design

Gear Design

Spur and helical gear calculations

Standards catalog

Validation: beta · Method band: formula

Open calculator

Indicative method: Lewis bending + simplified Hertzian contact; ISO 6336 factors where enabled (screening)

Assumptions

  • Uniform load distribution across face width unless noted.
  • ISO 6336 / scuffing / micropitting rows are screening factors, not full worksheet sign-off.

Limitations

  • Full AGMA/ISO 6336 worksheets, micropitting FEA, and dynamic tooth load are out of scope.
  • Professional screening — verify critical gears against code software before release.

Engineering checks

CheckINDUSEUISO
Bending strength safety factorimplementedimplementedimplementedimplemented
Contact (pitting) strength safety factorimplementedimplementedimplementedimplemented
Scuffing safety factorplannedplannedplannedplanned
Bending fatigue safety factorimplementedimplementedimplementedimplemented
Contact fatigue safety factorimplementedimplementedimplementedimplemented
Micropitting safety factorplannedplannedplannedplanned

Gear Design (gears) — beta

Purpose

Design and rate spur and helical gear pairs for bending and contact (pitting) strength. Combines Lewis bending screening with ISO 6336 Method B/C factors including dynamic load , zone factor , elasticity factor , and contact ratio factor .

Physics & theory

Gear teeth convert rotation and torque through involute meshing. Transmitted tangential force at the pitch circle is , where is torque and is pitch diameter. Lewis equation estimates bending stress in a tooth treated as a cantilever: , with module , face width , and form factor .

Contact (Hertzian) stress between mating teeth limits pitting life. ISO 6336 expresses contact stress with factors for load sharing, geometry, lubrication, and material. Scuffing and micropitting are not fully evaluated in indicative mode.

Governing equations

Numerical method

Closed-form ISO 6336 and Lewis screening via solveGearDesign. Input power, speed, module, face width, tooth counts, and material limits feed factor calculations. Results include bending and contact utilization, geometry summary, and pitch-line velocity.

Inputs

ParameterDescription
power, speedTransmitted power (kW), pinion speed (rpm)
module, faceWidthGear geometry
pinionTeeth, gearRatioTooth counts
materialYield, allowable bending/contact stress
Application factors, lubrication, quality grade

Outputs

  • Tangential force, pitch-line velocity, bending stress and utilization, contact stress and utilization, geometry (centers, diameters), factor breakdown.

Design codes & checks

  • Indicative: Lewis bending and simplified Hertzian contact
  • ISO: ISO 6336-1/2/3 Method B/C rating (screening)
  • US: AGMA 2101-D04 (reference context)

Assumptions & limitations

  • External spur/helical pair; no internal gears or planetary sets (see dedicated modules).
  • Indicative scuffing and bending fatigue screening; full AGMA/ISO factor sets not included.
  • Uniform load distribution along face width unless specified.
  • No microgeometry (profile modification) analysis.

Verification

References

  1. ISO 6336-1:2019. Calculation of load capacity of spur and helical gears — Part 1: Basic principles.
  2. ISO 6336-2:2019. Part 2: Calculation of surface durability (pitting).
  3. ISO 6336-3:2019. Part 3: Calculation of tooth bending strength.
  4. Shigley, J. E., & Budynas, R. G. Mechanical Engineering Design, 11th ed., Ch. 13–14.
  5. Beer, F. P., et al. Mechanics of Materials, 8th ed. McGraw-Hill — foundational stress and deformation theory.
Maintainer note: Lewis screening plus ISO 6336 Method B/C bending and pitting rating with KV, ZH, ZE, Yeps factors.