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Linear Actuator (Solenoid pushing a cylindrical magnet)

  1. May 14, 2014 #1
    I am working on a home made electromechanical actuator to replace the vacuum actuator on the front axle of my Jeep Cherokee.

    The vacuum actuator isnt the greatest and I have replaced it and the system lines few times.

    SO I figure, I know what force the vacuum actuator is putting out, I know the stroke length, I have stuff to make this, why not?

    BUT I want to get the physics right in my head first.

    SO, Lets say I have a spring that will push a cylindrical magnet away from the shift fork, and a solenoid made from wiring that push the magnet into the shift fork. Which engages the hubs.

    I already figured out the spring portion and drawn out the magnetic field interaction.

    Does anybody have an equation to get an accurate (or conservative) repelling force for the solenoid and the magnet?

    I havent really found a good source, wiki has some, but I dont trust wikipedia.

  2. jcsd
  3. May 26, 2014 #2


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    Gold Member

    Before you go through the trouble of trying to engineer something from scratch (and something with electrical components for that matter), you might consider just buying something. Take for example the "4x4 Posi-Lok" which is a cable conversion kit for your differential. It will let you maintain the disengaging capability on your axle with a simple cable-actuated solution.

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