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stepper motor fix

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  • stepper motor fix

    had this car problem

    I had no idle for weeks ..stepper reset would not reset it (there is a procedure where you push the throttle down ten times and it resets)

    anyway took it apart today

    and it appears that the pinion gear has come loose on the stepper shaft - the shaft no longer turns the gear

    I'm going to try and glue it on with retainer glue - obviously all will be cleaned before i do it - opinions?

    Click image for larger version

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    all the best....mark

  • #2
    If the torque loading is low, you have nothing to lose. Make sure the parts are as clean and degreased as you can manage.


    • #3
      The torque loading is high for such a thin shaft, two strong springs each side of the butterfly. I've greased the snail cam and plunger lightly.
      on advice from friend I wheeled the shaft between two files to raise knurls ...then added the high strength glue .and pushed it on - I could feel a bit more resistance as I pushed it on
      Now I wait for 24 hours, before putting it back together ..crossed fingers , arms , legs etc

      all the best..mark


      • #4
        Yeah, that's a bugger. Consider how you might create some splines in the shaft by displacing metal. So not cutting them, but raising the splines. I once saw a machine in an auction that made knurls that way, by rolling the shaft across a flat die. I think the key is to have those splines be parallel to the shaft, so when you press the gear on, it cuts a nice straight 'keyway' into the gear.

        How hard is that shaft? Since this is HSM, I suppose you could use any number of machines to cut a small flat toothed die, with tight spline spacing. You would then need to somehow roll the shaft across that die. That'd be kinda neat, but probably very difficult with the motor intact.

        Of course you might just pinch the shaft in some pliers. Maybe even pound on the plier jaws a bit to really set the splies.

        Another thought is to make a relief in the plastic, so there can be some mechanical engagement of your adhesive. Though I'm not sure that approach works with the retaining compound you plan to use. Depends on the shear strength vs. strength when filling a void.

        I recall another thread very much like this one a few months ago. The OP realized that the reason he was having so much trouble was because the gear was actually cracked. So be sure that isn't your case before you spend too much time.

        Maybe someone here can 3d print you a gear

        Edit - while composing I see the OP updated. Thanks for the update! Often we don't even get that. Two files is a great idea. And using the edges, instead of the face, would get you parallel splines. Hmm.
        Last edited by Glug; 03-26-2020, 12:46 PM.


        • #5
          Loctite will work. You could just install a roll pin.


          • #6
            Roll pin - Don't know about that, the shaft is only about 3mm in diameter
            Anyway ..tested and its working - for how long - I don't know.


            • #7
              video showing it working after fix