Overlap ratio or axial contact ratio in helical gears

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SUMMARY

The discussion centers on the Overlap Ratio (OR) and axial contact ratio of helical gear pairs. An OR of exactly 1 indicates optimal engagement between gear teeth, while a value less than 1 suggests insufficient contact, potentially leading to increased wear and reduced load capacity. The user seeks a physical understanding of OR, particularly in scenarios where the transverse contact ratio exceeds 1. References to specific literature, including QTC's "Elements of Metric Gear Technology" and KHK Gear Technology, are provided for further exploration.

PREREQUISITES
  • Understanding of helical gear geometry
  • Familiarity with contact ratios in gear design
  • Knowledge of gear load capacity and wear mechanisms
  • Access to gear technology literature, such as QTC and KHK references
NEXT STEPS
  • Study the physical implications of Overlap Ratio in helical gears
  • Examine the relationship between transverse and axial contact ratios
  • Review sections 8.4, 11.4, 17.2.3, 17.4.3, and 21 of QTC's "Elements of Metric Gear Technology"
  • Explore KHK Gear Technology resources for advanced gear design principles
USEFUL FOR

Mechanical engineers, gear designers, and students studying gear technology who seek to deepen their understanding of helical gear performance and design considerations.

k.udhay
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Hi,

I am trying to understand the Overlap Ratio (OR) / axial contact ratio of a helical gear pair. Unlike transverse contact ratio, I am unable to understand OR so easily.
What does it mean if the OR is exactly 1? What will happen practically when it goes less than one? Thanks.
 
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Thanks. But this book again tells the OR as a mathematical relation whereas I want to understand it physically. I assume a case where the transverse contact ratio is more than 1 already and want to know the effect when OR is less that one.
 
Do you have a pdf copy of the QTC "elements of metric gear technology"
http://www.qtcgears.com/Q420%20PDF%20Files/Tech.pdf
See sections 8.4, 11.4, 17.2.3, 17.4.3 and 21.

KHK have Gear Technology References.
http://www.khkgears.co.jp/en/gear_technology/guide_info.html
 
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