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  1. #1
    Join Date
    Aug 2019
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    Default Need ideas for a quick change shaft coupler

    I'm doing another odd job; modifying a chicken rotisserie for cooking lamb. The existing rods at 12mm were too weak and they were flexing the gears out of alignment, so...


    Someone has built new rods. 20mm stainless. And a new gear rack system with chain drive pinions. The issue now is how to attach the rods to the drive system. At the moment there are flat discs on each. About 70mm diameter:
    IMG_3089.jpg

    The rods are lifted into finger slots at each end, that will locate their discs beside the driven discs. I need a way for the operator to couple the discs so that A rotates B.

    My first thought was a pin welded to the edge of one disc, driving a slot in the other disc, but my review committee (!!!) says that is too hard to use. Remember that a lamb plus rod would be over 30kg. Maybe 40kg.
    Lifting that into the finger slots is hard enough, let alone having to remember to stop the driving disc in a suitable position (so that the pin is inline with the finger).


    The review committee thinks something that allows the rod to be loaded while the drive system is turning would be best. Maybe that has a spring clamp/lock that only starts driving the rod when it rotates to a particular point?
    They also want something that is simple, that will not jam, that is easy to clean. et c.
    And maybe allows unloading of one cooked rod while more is still on the other slot or slots
    (I can see why things are not designed by committee )



    The only idea I have so far is an axial pin (welded perpendicular on edge of one disc), and a radial pin on the other (welded from centre out past edge of disc). That way, operator just has to wait for one pin to be at back of driving disc, and they can drop the rod & meat into the finger slots. Driving disc will eventually turn around and hit the radial pin, and start the rod+meat turning.


    Feel free to suggest any crazy ideas, because a search for "shaft coupling images" didn't give me many removable options

  2. #2
    Join Date
    Sep 2012
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    York, North Yorkshire UK
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    Default

    Hi Nigel,

    Dog drives have been in use forever ! I think that your idea of a pair of dogs on each plate 180 degrees apart would do the job. Each pair of dogs would only have to be a thick as the width of the gap.
    Best Regards:
    Baron J.

  3. #3
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    Norwood-ish, Adelaide
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    Default

    We had a Yiros place down the road once (Doner kabab for those in the Eastern states) who did their lamb on a horizontal spit. The method they used I thought was really simple. A pair of skew gears, with the spit shaft being the one on top and the driving shaft coming horizontally away from the wall. A pair of fingers to centralise the spit, but gravity held the gears in contact. To remove, just lift.

    Michael

  4. #4
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    Default

    Quote Originally Posted by Michael G View Post
    We had a Yiros place down the road once (Doner kabab for those in the Eastern states) who did their lamb on a horizontal spit. The method they used I thought was really simple. A pair of skew gears, with the spit shaft being the one on top and the driving shaft coming horizontally away from the wall. A pair of fingers to centralise the spit, but gravity held the gears in contact. To remove, just lift.

    Michael

    Yes, I have seem similar, though not at a Gyros/Yeeros/Yiros vendor. The existing design, that was unreliable and is being replaced, was a vertical driven shaft with worm gears, and a matching single throated helical on the rod. With the weight of the lamb bending the rod, the gear pushed out of the worm.
    Perhaps it should have been modified so that worms turned the other way, but too late now


    This is a lighter-duty version, which I think has sprockets on the rod dropping into the chain:

  5. #5
    Join Date
    Mar 2011
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    Southern Flinders Ranges
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    I repaired one for the local takeaway once, simplest idea I could come up with was very similar to your pin in slot idea except the drive plate on the rod was more of an X shape so there was no real alignment required to get it engaged, just turn it on and the pin will pick up the closest edge when it gets there.

  6. #6
    Join Date
    Nov 2017
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    Geelong, Australia
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    The little drive units for home BBQ rotisserie setups typically just have a square socket that the solid square shaft carrying the meat slides into.

    Personally I’d try and avoid anything in the drive that projects and could grab the operator.
    I know it’s only rotating slowly but the fact that it looks so slow and benign can encourage people to run the drive and eg hold a rag on it for cleaning. Slow typically means a lot of gear reduction and lots of torque.
    From that aspect the square tube type of drive would be probably be safer than an exposed dog style.
    Nothing to stop an operator poking a rag up the rotating drive with their finger, but worst case is probably a bit of a slow pretzel finger, compared to an exposed dog dragging a sleeve/hand in.
    May not be an issue with the overall design, but something to keep in mind. Potentially since there’s likely to be young labour involved with no practical common sense.

    Steve

  7. #7
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    Thanks for all your ideas. In the end, I needed something which could cope with 15mm of play, as the box (oven) that the rods slip into is thin stainless. (i.e. I can push the hanging rails out by that much, and when it heats up, everything probably bends and warps).

    So, I did the dual pin driving dog system:
    Screen Shot 2022-09-14 at 7.33.40 am.jpg


    https://share.icloud.com/photos/050m...4lIHdlNJ7OoTuA

  8. #8
    Join Date
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    Murray Bridge S Aust.
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    Default

    Thanks for letting us know how you solved the problem.
    Kryn
    To grow old is mandatory, growing up is optional.

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