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DIY 3d printed ball swivel

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  • DIY 3d printed ball swivel

    Hi,

    Having first punched a speed bag last week and with my shoulders not being in the best of health, I spent some indoor time over the weekend trying to make myself a ball swivel. I made this mainly as an exercise in design and prototyping - the process might be of interest, so here it is. This first post covers inception to the second working prototype (#7).

    It's certainly not intended to be a clone, but does bear obvious similarities in design and construction to the ARC which I've seen and read about. Ultimately, I will likely end up buying something (Thrasher EVO 13 has been mentioned twice to me), but nevertheless I thought there would be some mileage in having a go at making one for fun.


    I started with a few initial design constraints:
    • 25.4mm nylon ball (influenced by the ARC)
    • 69mm BCD bolt pattern seemed to be the "standard"
    • "as much of a swing" as possible (ball protruding as much as possible)
    • clearance around the mouth for the eye bolt, clip etc.
    I used OpenSCAD to come up with a design... first time I'd ever done roundovers, fillets and countersinks.

    Click image for larger version

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    I printed a few protoypes in PLA (using up old filament).

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    The nylon balls hadn't been delivered yet, so I used the time to iterate on the design looking at things such as:
    • dimensions: thickness, height, hole diameter
    • shape: support surfaces, strength, etc.
    • surface finish: printer settings
    Click image for larger version

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    I didn't like the wide, flat flange of #1-#3, so I made the fillet asymmetrical so it extended to the bolt holes to cover it a bit, and also modified the shape of the "mouth" to give the bolt a bit of support as it hits at the extent of the swing. Comparison of #1 and #5 below...

    Click image for larger version

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    Final (current) design in OpenSCAD looks like this:

    Click image for larger version

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    I had prototype #6 installed last night, and after one more print this morning to tighten up the tolerance around the ball socket, I currently have prototype #7 installed with a 4mm welded eye bolt (counterbored lock nut on the back side of the ball):

    Click image for larger version

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    It is a bit "sticky" in use... when it slows down, the ball judders in the socket. Weak drywall screws are NOT ideal to mount this with, nor is the use of a mini-alloy carabiner. But the way I hit, neither is likely to be a problem short-term.

    I might try a different ball (stainless finial ball??), a different filament in the printer, or perhaps I should quit now and just buy one.


    Hope that's interesting to someone.
    Matt.

  • #2
    Really interesting process, the only thing "I" would advise is never use a wood or drywall screw when you can use a machine screw. A machine screw with flat washer and a lock washer in "my opinion" is the best way to go. Also not a fan of a carabiner's.

    Comment


    • #3
      I believe the ARC has an acetal ball.

      Comment


      • #4
        paranday, thanks. I'll look into that.

        dad, agreed, my shortcuts here are not ideal.

        Comment


        • #5
          How about an Octagon shape like the Everlast swivels, My favorite swivels

          Comment


          • #6
            Originally posted by ventanakaz View Post
            How about an Octagon shape like the Everlast swivels, My favorite swivels
            Octagons are ok, I guess...

            For now, I've picked an "equilateral curve heptagon" just to be different.

            Click image for larger version

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            • #7
              Originally posted by paranday View Post
              I believe the ARC has an acetal ball.
              Replacement balls arrived today, sold as "POM". Currently running one in #5 and what a massive difference for me over nylon in terms of smoothness and noise. I'll print a new shape #8 later, with a few more adjustments.

              Thanks again for the tip!

              Comment


              • #8
                Originally posted by Sambista View Post

                Replacement balls arrived today, sold as "POM". Currently running one in #5 and what a massive difference for me over nylon in terms of smoothness and noise. I'll print a new shape #8 later, with a few more adjustments.

                Thanks again for the tip!
                That's good to hear. Slippery stuff it is.

                Comment


                • #9
                  very interesting stuff!
                  Art of the Bag - A Speed Bag Story
                  http://www.artofthebag.com

                  Comment


                  • #10
                    Interesting to read through your process of creation! Keep going!

                    Comment


                    • #11
                      Thanks, zaza/DizzyD! Glad it was of interest.


                      I guess I'm actually finished... kind of all of sudden. Here's a few photos to wrap up...


                      Photo of prototype #9 installed:

                      Click image for larger version

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                      Router-trimming one of the boards (old chipboard door):

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                      A stack of two chipboard and one solid elm board, ready for roundovers and paint;

                      Click image for larger version

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                      Putting it all together, I have my current setup:

                      Click image for larger version

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                      • #12
                        Sambista, thank you so much for taking us on a wonderful journey through your project. You are very talented in may areas and I enjoyed watching you workout the process. Great job on the project and even better job on the post. Now is when someone of your knowledge of making things starts to feel the withdrawal effects because the journey is always so much more fun than the destination. Wonderful job.

                        Comment


                        • #13
                          I don't get onto this forum much. This is the first time I have logged on in 4 or 5 months. That being said...
                          Sambista you are on the correct tract so far. You have to prototype and test, then prototype then test, then prototype then test, etc. ad nauseum.

                          I read the first couple of comments and the ball I use is Delrin, not Nylon. The secret is you have to match the materials that form the bearing surface. It can be metal-on-metal, metal-on-plastic, plastic-on-metal, plastic-on-plastic etc. And in each case the best solution is different. And that solution may have criteria based on your business model. Performance vs wear, strength vs failure mode. The list is endless.

                          I may not get on here for another few months, or never at all, who knows. But I just wanted to say cheers to all who strive to make a better swivel!
                          -ArcSwivel, aka rdshackleford, aka Tom
                          @ArcSwivel
                          #ArcSwivel sigpic

                          Comment


                          • #14
                            Hi, Tom. Thanks for your comments.


                            Originally posted by rdshackleford View Post
                            The list is endless.
                            I've settled on POM and PLA for now. I might tweak the "insertion depth" of the ball, as I call it, but thankfully I'm not designing for manufacture. Perhaps I'll learn or appreciate more about my swivel as I learn to bag... I'm certainly missing any direct bagging experience with which to evaluate prototypes... "it swings and it's quiet-ish" is a triumph for me.

                            I'm sure I don't appreciate even half how much work you and others will put in to producing something that takes all of those additional criteria and constraints into account, that you can stand behind and give back to others who share the hobby!


                            Originally posted by dad View Post
                            ... the journey is always so much more fun than the destination.
                            You're right, dad... and there's more...

                            I've enjoyed making the swivel. And the new board. And it forced me to tidy a corner of my garage so I could install the board somewhere that made more sense. Which in turn has motivated me to clear more of the rest of the workshop and get it back to operation. Which will help to make making more things easier. And I've still to learn to bag and hopefully find some flow, and a release, and some shoulder rehab, and all of that.

                            So hopefully not withdrawl effects, just enabling the next thing...

                            Best wishes,
                            Matt.


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                            • #15
                              I have to ask, are you a wood worker? Is that a universal bench or a larger router table?

                              Comment

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