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Gears & Gear Systems: Manufacturing, Gear Trains, Gear Force Analysis

- - - - Common practice to use one idler only
  - - - NB Image
    - - Some cases, such as automobile transmissions, the
        output shaft is concentric with the input shaft
        
        The design of a reverted compound train is more complicated because of the additional constraint that the centre distances of the stages must be equal
        
        Reverted Gear Train Design
        
        NB Image
    - - In planetary gear trains, some of the gear axes are rotating.
      - Planetary gears always include
        
        A planet carrier or arm
        
        One or more planet gears
        
        A sun gear
      - Planetary gears need two inputs to get a predictable output
        
        The two inputs could be the motion of any two elements in the train
      - Advantages
        
        Compact, Coaxial Input & Output Shaft
        
        Several gears are sharing load – therefore
        smaller gears, lighter weight
        
        Speed ratio and sometimes direction can bechanged without movement of gearssimply by applying a braking torque, easily
        automated.
        
        Gear forces are usually well balanced – no
        free reactions
        
        Allows differential action with one input and
        two outputs
      - Gear Calculations
        
        Tabular Method
        
        Formula Method
        
        nPlanet = nArm + nPlanet on Arm
      - Differential
      - Car Gearbox
      - Synchromesh
      - Contact Ratio
        
        more gradual engagement
        
        less noisy
        
        but cause axial force
        
        unless herring-bone arrangement is used