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    Discussion in 'The main mechanical design forum' started by cosmarchy, Mar 17, 2013.

    1. cosmarchy

      cosmarchy New Member

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      Hi,

      Does anyone know of what kind of gearbox to use where the forward and reverse ratios are the same. Ideally I'm looking for an inline simple design. I initially thought of a planetary design but I'm not sure you can get the same ratio for both directions.

      Any help is appreciated.

      Thanks
       
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    3. vdjelle

      vdjelle New Member

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      Hi cosmarchy,
      Don't understand actually your questions. A gearbox with a ratio of for example 3, has an input that turns 3 times so the output has 1 turn. if you turn the output 1 turn the input will turn 3 times.
      With a transmission you'll be able to change this fix ratio of a gearbox. (for example the ZF transmissions)

      Best regards,
       
    4. cosmarchy

      cosmarchy New Member

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      :eek: OMG!! in my haste I missed out some critical info :eek:

      The input will always rotate in the same direction but I need to be able to change the direction of the output. I need the ratio of the input to output shaft to be 1:1

      Sorry for the confusion
       
    5. mayvamecha

      mayvamecha New Member

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      You should use idle gear for same direction of input and output. When you desire reverse rotation of output you should decouple the input gear and couple your motor shaft with idle gear. Your idle gear should have same dia with input and output gears as well. (Note that this is the same principle with car motor gearbox system eg: switch to rear gear)
       
    6. PierArg

      PierArg Well-Known Member

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      Hi cosmarchy,

      I'm curious to know what is the application!

      I think you need to use a transmission type similar to the automotive gearboxes with an idle gear and a selector.
       
    7. cosmarchy

      cosmarchy New Member

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      The application is a bit of an odd one really. Its to replace a gearbox on a really old machine but as usual its not a simple case of copying the existing one :eek: it is similar to a lathe but an ancient thing which probably predates christ by the looks of it.
       
    8. Paul_Sterling

      Paul_Sterling New Member

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      A marine type gearbox is probably what you need, those are usually equal ratio forward and reverse, and single speed boxes are available.

      Cheers.
      PS.
       
    9. KrzLeo

      KrzLeo New Member

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      You can try this layout. red gears are bevel gears and blue are spur gears. When bevel gears are engaged using top bevel idler, output direction is reversed and when bottom spur idler is engaged, you get same direction. [​IMG]
       
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