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ME321 Kinematics and Dynamics of Machines

ME321 Kinematics and Dynamics of Machines. Steve Lambert Mechanical Engineering, U of Waterloo. Gears. Spur Gears - Parallel shafts and ‘straight’ teeth. Gears . Example internal spur gear. Example rack and pinion. Helical Gears.

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ME321 Kinematics and Dynamics of Machines

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  1. ME321 Kinematics and Dynamics of Machines Steve Lambert Mechanical Engineering, U of Waterloo

  2. Gears Spur Gears - Parallel shafts and ‘straight’ teeth

  3. Gears Example internal spur gear Example rack and pinion

  4. Helical Gears Helical gears are smoother and quieter than spur gears, but are more expensive, are not easily engaged, and they generate a thrust load

  5. Bevel Gears Straight bevel gears Skew bevel gears

  6. Hypoid and Worm Gears Hypoid gear Worm gear

  7. Fundamental Law of Gearing We require a constant velocity ratio. For this to be possible, the common normal of the contacting tooth flanks must always pass through the pitch point.

  8. Involute Action Imagine that the gears are replaced by two cylinders connected by a string This system will satisfy our fundamental law The path traced by Q will represent our tooth profile

  9. Involute Action These are equivalent. Path traced by point Q is an Involute.

  10. Gear Tooth Nomenclature

  11. Gear Nomenclature Pitch Circle Circular Pitch Addendum Dedendum Clearance Diametral Pitch: Circular Pitch:

  12. Standard Gears Diametral Pitch:

  13. Interacting Gears • Centre Distance (r2 + r3) • Contact Ratio • Interference

  14. Contact Ratio Contact ratio is the average number of teeth in contact CR = length of line of action / base (circle) pitch CR = l / BP

  15. Contact Ratio CR = l / BP, where: Line of action: l = AC-AP + DB-DP

  16. Interference Interference occurs if point C falls outside point D - contact beyond involute profile occurs if O2C > O2D where:

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