Documentation/Modules/Timing Belt Drive

Timing Belt Drive

Toothed belt pitch, teeth, power and axis loads

Standards catalog

Validation: indicative · Method band: formula

Open calculator

Indicative method: Pitch geometry, center distance, and power utilization screening

Assumptions

  • Linear elastic material behavior unless noted otherwise.
  • User is responsible for load combinations and load factors per the selected design code.
  • Design standard (US/EU/ISO) sets unit defaults and screening check labels — not a full code worksheet.

Limitations

  • Tooth shear / cord strength catalogs are not full manufacturer worksheets.
  • Professional screening — verify critical synchronous drives with OEM selection tools.

Engineering checks

CheckINDUSEUISO
Power capacity utilizationimplemented——implemented
Shaft radial load estimateimplemented———

Timing Belt Drive (timing-belts)

Purpose

Size synchronous (toothed) belt drives by computing pitch length, number of teeth, belt speed, transmitted power, and shaft loads. Positive engagement eliminates slip, making timing belts suitable for positioning and high-ratio compact drives.

Physics & theory

Timing belts mesh with pulley teeth at a defined pitch . Pitch diameter relates to tooth count: . Belt length for two pulleys includes tooth engagement arcs plus tangent spans. Unlike friction belts, power capacity is limited by tooth shear, belt tensile strength, and pulley tooth bending — the module applies manufacturer-style screening factors.

Speed ratio is exact (no slip). Radial load on shafts combines belt tension from power transmission and centrifugal effects at high speed. Pretension must prevent tooth jump under peak torque while limiting bearing loads.

Power transmission elements operate under cyclic tension, bending, and contact stresses. Service factors account for driver type (motor vs engine), daily operating hours, and shock loading. Belt slip occurs when required friction capacity exceeds available wrap; chain drives depend on proper lubrication and sprocket tooth count for rated life.

Center distance adjustment affects belt length and wrap angle simultaneously — the solver uses the standard open-drive length formula assuming coplanar shafts and parallel pulley grooves.

Governing equations

Numerical method

Closed-form geometry and power screening per timing belt check templates. Tooth count and pitch determine pulley diameters; belt length rounded to whole tooth pitches. Power utilization compared against rated power adjusted by service, width, and speed factors.

Inputs

ParameterDescription
Pitch / tooth countBelt pitch and pulley teeth
centerDistanceShaft spacing
speedDriver, powerOperating speed and power
Belt width, materialWidth factor and rating
Service factorApplication derating

Outputs

  • Pitch length, tooth count, pulley diameters, belt speed, power utilization, estimated belt tension, shaft load components.

Design codes & checks

  • Indicative: Power capacity and tension screening
  • ISO: ISO 5296 synchronous belt drives (reference pitch systems)

Assumptions & limitations

  • Two-pulley layout; no idler pulleys or back-side wrap.
  • Screening-level rating — not a substitute for manufacturer software (Gates, Conti).
  • Neglects belt stiffness dynamics and resonance at high speed.
  • Standard trapezoidal or curvilinear tooth profiles per selected pitch family.

Verification

References

  1. Shigley, J. E., & Budynas, R. G. Mechanical Engineering Design, 11th ed., Ch. 17.
  2. ISO 5296:2012. Synchronous belt drives — Pulleys.
  3. Gates Corporation. Poly Chain GT Carbon Design Manual.
  4. Budynas, R. G., Nisbett, J. K. Shigley's Mechanical Engineering Design, 11th ed.
  5. Beer, F. P., et al. Mechanics of Materials, 8th ed. McGraw-Hill — foundational stress and deformation theory.
Maintainer note: Toothed belt sizing screening.