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    Discussion in 'The main mechanical design forum' started by Camaro51, Jan 25, 2013.

    1. Dana

      Dana Well-Known Member

      Sep 2010
      Likes Received:
      The first step in any kind of design is to clearly define the problem. Some questions would be:

      • How fast does it need to move up and down?
      • How rigidly does it need to be supported when up (against rocking of the boat, pushing buttons on the device, etc.)?
      • Do you need a fail-safe to get it up or down if the mechanism fails?
      • What about water intrusion and its effect on the components? Corrosion is likely to be a problem, especially if you're on salt water.
      • Is there room for mechanism below, or on the sides, or both?
      • Is there a magnetic compass nearby (could be affected by electromagnetic fields of the motors, or steel components)?
      • Have other people done this before? If so, how? If not, why not?

      Next, break down the mechanism into separate functions:

      • Linear guiding
      • Driving up and down
      • End stops

      Once you have clearly defined the problem, the solution often becomes obvious.

      The suggestion of a car window actuator and gas springs (gas spring to lift it slowly, perhaps a small motor winch to pull it down) are good ones. A scissors mechanism is good when you need it to be very compact when collapsed, but linear bearings alongside or below, while less compact, are much more rigid and smoother operating.
    3. Dave B

      Dave B Active Member

      Jan 2012
      Likes Received:

      I like Dana's last comment to look at existing devices for inspiration.
      An old VCR tape deck has a motor and caddy with gear train moving a rack in and out.
      His car window mechanism or a electric seat mechanism are excellent ideas to get you started.

      I often tear down items from a store to begin a test bed utilizing aspects of the device to get started.

      You mentioned you were not very mechanically inclined and the problem you were wanting to solve was a 1 up device for you boat.
      The discussion of how to limit the forces to lift the box using springs is desirable. weights on cables is not since the motion on a boat is unpredictable causing weights and cables to derail etc.


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