Wheely Chair Arm Offset.

Discussion in 'Hobby Engineering' started by Butcher9_9, Sep 21, 2019.

  1. Butcher9_9

    Butcher9_9 Member

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    I bought a new chair not that long ago and one thing that annoyed me about it was that the arms did not go far enough back.

    Long story short it was a good excuse to use my CNC machine.

    Made a few basic parts in Fusion and printed a test part for fitment.
    [​IMG]
    [​IMG]

    Tested it for strength and lets just say that I'm glad I have some thick Aluminum on hand. (3D print was only 2 walls so not that strong)
    [​IMG]

    Cut out of the final version 6mm Alu. Tapped ans installed.
    [​IMG]
    [​IMG]
     
    Deano_20802 and mtma like this.
  2. mtma

    mtma Member

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    Always handy to have some metal!

    This is how I would have envisaged it if you needed to take print to the next level (counterbores and stuff could be on the wrong faces it was just a rough).

    Part1.jpg

    The idea is simply to get the slicer to put material where it counts. You could probably also ask that autodesk generative thing for its opinon if it's still there in Fusion 360.

    Could also sneak a top plate in as any depth of section you add is beneficial to reduce the absolute value of stresses due to bending.
     
  3. OP
    OP
    Butcher9_9

    Butcher9_9 Member

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    The 3D Printed part was designed to match the thickness of the Alu Stock I had on hand, Rather that to be a strong part itself. Just to test hold alignment and offsets ect. I did need to adjust the final model and to be honest i should have printed a second test part as it was still not perfect (Makers Muse's rule of three would have been correct in this case). Either was its working as intended so op success :)

    I did see a video on that topology optimization which would bee cool but I'm still not sure if I would trust a 3D printed part to take that load as I do have a tendency to lead heavily on my the arms (to pick Cats up ect)
     
  4. philquad

    philquad Member

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    what sorta chair is it butch
    i just got a left side for my mm v6 as im heavy on the left also
    600 bucks it was
    lucky im getting a new 1 soon but ill still have the same prob
     
  5. mtma

    mtma Member

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    There is obviously high strength aluminium - like 7075-T6 - which sends plastics packing, but cheaper grades such as 5005 are only around the 110MPa ultimate tensile mark which means with some design work products printed with PLA at around 50MPa approaches pissing distance. PETG and ABS are weaker at around 30MPa typical, whereas exotics such as XT-CF20 and PA-CF are 110 and 70 MPa respectively.

    What is a little peachy with the garden variety printed plastics are aging and fatigue limits particularly of the interlayer fracture variety. I have had a lot of variation between plastics manufacturers (some manufacturers even started to embrittle on the roll!).
     
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    Butcher9_9

    Butcher9_9 Member

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    One of these , have a mate who used to work at PLE so got a good price (Cheapest I could find a goodish leather chair )
    https://www.ple.com.au/Products/630752/BattleBull-Rider-Gaming-Chair-Black-Leather

    Yeah but not when you are talking about FFF (FDM) printing you lose a lot of strength in one direction and at least some in every direction. Not to mention that most 3D prints are not solid so absolute maternal strength is not really comparable.

    As you mentioned PLA is very strong its buts also brittle (When my part broken to did so in an explosion fashion) where as ABS/PETG have a bit more ductility. Not to mention that you dont have to worry about plasticizer loss or material break down (PLA is bio degradable, some plastics are UV sensitive ect.
     
  7. philquad

    philquad Member

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  8. OP
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    Butcher9_9

    Butcher9_9 Member

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    Yeah totally has the "Y" in the title :).

    Gaming Wheely Chair, though I'm sure you could do the same thing for a Wheel chair depending on how the arms are attached.
     

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