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Thread: Inside a dish positioner jack and how to open it

  1. #1
    Junior Member hca's Avatar
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    Default Inside a dish positioner jack and how to open it

    In this case it was jammed and the motor free spinning till the limit switches but no extension or retaction.

    Basically the plastic nut had jammed up with surface rust on the shaft and the traveling tube had stripped off.

    here it is opened up and how I got into it.

    To do that I drilled out the first 4 dimples that retain the bearing from being pushed out of the tube at an angle, idea being to remove the dimple and leave a burr free hole.

    2 options to open it

    1 - If the tube is still securely threaded on the plastic nut, drill out the dimples securing the swivel eye and remove it from the tube.

    2- else clamp the drive pin in the vice and unscrew the traveling tube from the plastic nut, it might take to force if its not striped as there are locking 4 dimples.

    Next secure the outer tube upright in a vice so the tube end sits on the traveler with clearance for the shaft and nut, drive out the bearing and thread with a piece of steel rod or big pin punch till the bearing clears the drilled holes. It should just push out the rest of the way.


    Last edited by hca; 27-05-20 at 05:49 AM. Reason: typos, read it with glasses on!

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    Junior Member hca's Avatar
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    Default putting it back together

    To put it back together.

    If you removed the banjo eye from the inner tube skip a few steps, else if its still attached to the inner tube as was my case.

    I am not sure whats best to lube the drive thread but as the nut is plastic maybe molykote or similar silicon grease might be best.

    First put the plastic tube guide over the thread till it sits behind the bearing, make sure its right way around, then attach the inner tube to the plastic nut.

    As I don't know of any glue the will bond to the plastic nut and steel, I considered epoxy which might physically fill the gap but decided to build up the thread on the plastic nut with teflon pipe tape till the tube screwed on tightly and made the original dimples deeper with a center punch.

    Remove the remaining dimples at the motor end of outer tube with a rat tail file so the bearing can pass from the bottom, and lube the tube inner with some oil.

    Introduce the bearing into the tube from the bottom then seat the plastic guide, continue until the inner tube enters the plastic guide and on till the bearing is just past where it sits. Somehow this reminds me of household upper management.

    Re centre punch the dimples behind the bearing.

    If you had the banjo off just slide the inner tube and shaft in from the top.

    Either way now knock it back in till the bearing firmly seated on the rear dimples.

    There are some options to secure the bearing, but the easiest is just make new dimples with the centre punch. Which ever way remember any movement in the bearing will translate into play on the dish positioning.

    Next set the limit switches.

    Screw in the tube till its about 2 turns from fully in. Run the motor till it stops at the fully in limit switch.


    Line up the tongue and reattach the motor. Run it end to end to check the limit switches.

    Finally I don't know why this failure occurred, The surface rust that jammed up the nut could be just be from humidly or possibly wash down water entry, this jack is not out on a dish, it is used to lift the reflux stack off the top of my still, so its indoors and the weight is not excessive.

    The controller stops with an error if the shaft does not rotate and stalls the motor thus no pulses from the counter reed switch. So I am not sure why it stripped the plastic nut.

    The was another image below but It seems not to work.??


    Last edited by hca; 29-05-20 at 06:00 AM.

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