This Excel-based gear design tool provides a quick and reliable way to calculate critical parameters such as stress numbers, allowable stress limits, geometric factors, and design factors essential for mechanical gear analysis. Users simply need to input application-specific conditions — including operating power, running RPM, number of pinion teeth, diametrical pitch, and material specifications — to generate accurate and consistent design evaluations.
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Bending Stress Number
The bending stress number in gear design quantifies the average tensile stress experienced at the root of a gear tooth as it behaves like a cantilever beam under load during operation. This stress is a primary mode of potential gear tooth failure and is critically analyzed using the following formula:
- st: Bending stress number
- Wt: Transmitted tangential load
- Pd: Diametral pitch
- F: Face width
- J: Geometry factor for bending strength
- Ko: Overload factor
- KB: Size factor
- Kv: Dynamic factor
- Km: Load distribution factor
- Ks: Rim thickness factor
Contact Stress Number
The contact stress number in gear design represents the maximum compressive stress developed at the contact surfaces of mating gear teeth as they roll and slide over each other during operation. This value is crucial for predicting surface-related failures such as pitting or spalling, which can limit gear life. The contact stress number is typically determined using the Hertzian contact theory, factoring in parameters such as the force transmitted, material properties, gear geometry, and the width and curvature of the contact area. The contact stress number quantifies the maximum compressive stress that occurs at the surfaces where gear teeth of mating gears come into contact. The associated formula:
: Contact stress number
: Elastic coefficient (material property for contact)
: Transmitted tangential load
: Overload factor
: Size factor
: Dynamic factor
: Load distribution factor
: Face width
: Pitch diameter
: Geometry (contact) factor
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