Ch9 Gears

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Ch9 Gears
2011-05-10 02:04:45

Mechanisms Final
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  1. Epicyclic or Planetary Gears
    • annulus: outer ring gear which meshes with the planet gears
    • carrier: movable arm
    • 2 DOF
    • system requires control of 2 inputs to produce 1 output
    • high torque output
    • load shared equally across planet gears means longer life for each
    • total motion of any gear is sum of motion of arm and motion of gear with respect to arm
    • if arm were stationary would get a simple gear train
    • => all motion relative to arm is analyzed as simple gear train
  2. Differential Mechanism
    • receives 1 input and produces 2 outputs
    • designed to drive a pair of wheels with equal torque while allowing them to rotate at different speeds
    • a vehicles wheels rotate at different speeds especially when turning corners
    • when turning outside wheel rotates faster and inside wheel rotates slower
  3. Fundamental Law of Gearing
    • The angular velocity ratio mv is constant at all positions
    • The torque ratio mT is constant at all positions
    • Gear tooth contours on mating teeth must be conjugates (involute curve)
  4. Involute Curve
    size of teeth must be the same for gears to mesh