Ball-bearing yoyo designs

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Mark1D
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Ball-bearing yoyo designs

Postby Mark1D » Tue Jan 05, 2021 10:19 pm

Hello everyone,

I design high-end yoyos, and run a yoyo company as a hobby. I used to use Fusion360 but switched to FreeCAD recently after my free license for Fusion expired.

Most yoyos are pretty simple as far as CAD goes. There's a sketch, and you revolve it to get the body. Some of the dimensions are important (where the bearing sits) and some are very aesthetic in nature, or subject to how you'd like the yoyo to play (powerfully, light, etc).

However, this design is a larger challenge because the body of the yoyo will be constructed from polycarbonate, with steel weight rings on the outside. The hub that holds it together will be aluminum, with a tiny spacer against the inner race of the bearing so that it will spin freely. Furthermore, there will be profile holes cut-out in a cool hexagon pattern. This reduces the mass of the yoyo somewhat, but it's mostly for looks, because they will also cause air turbulence that may negate any performance gains of a design like this.

It's a bit of a pain to iterate on because the hole features are very time consuming to calculate if anything changes. I usually delete the polar array, make changes, then re-add it.

I made an earlier version of this design in Fusion and decided recently to re-make it in FC 0.19.
Here's how it looks in FC:
135339006_245042040329200_8643410830108638031_n.jpg
135339006_245042040329200_8643410830108638031_n.jpg (27.19 KiB) Viewed 1747 times
And in 3D:
134576907_1782763048552928_6105882097726216852_n.jpg
134576907_1782763048552928_6105882097726216852_n.jpg (65.77 KiB) Viewed 1747 times
A design like this will weigh about 63 grams, and it's 57mm in diameter. The steel rings are the bulk of the mass.

Here it is rendered out with Blender:
ice_mode_2.png
ice_mode_2.png (275.73 KiB) Viewed 1747 times
I hope to have prototypes of this ordered later this year after I'm fully happy with the design.
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Mark1D
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Re: Ball-bearing yoyo designs

Postby Mark1D » Sun Feb 14, 2021 7:10 pm

I created a macro to help calculate the density/mass moment of inertia for complicated parts like this:
https://github.com/mdiehr/FCMacros/blob ... fo.FCMacro


I used some portions of the great FCInfo macro to create this.

How it works, is that it looks through all of the objects in the document:

2021-02-14 14_01_27-FreeCAD Link Branch.png
2021-02-14 14_01_27-FreeCAD Link Branch.png (11.75 KiB) Viewed 1093 times

Then, for each part, it pulls the density out of the part label (it has to be exactly at the end of the label), displays the mass of each part, and the overall mass and moment of inertia for the assembled yoyo:

2021-02-14 14_01_58-FreeCAD Link Branch.png
2021-02-14 14_01_58-FreeCAD Link Branch.png (271.15 KiB) Viewed 1093 times

Storing the density in the label is not the best way to do this, but it was easy for me to figure out how to store information there, it's highly visible, and it allows an easy way to include/omit parts that shouldn't be part of the calculations.
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doul
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Re: Ball-bearing yoyo designs

Postby doul » Mon Feb 15, 2021 5:54 pm

Hello, great work. the multi material design is awesome.
FreeCAD is cool 8-)
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Mark1D
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Re: Ball-bearing yoyo designs

Postby Mark1D » Wed Feb 24, 2021 2:45 pm

Black_and_white_POM.jpg
Black_and_white_POM.jpg (113.91 KiB) Viewed 590 times
Here's a render of a new version in POM with chamfers and an internal radius on the cutouts. My machinist told me that polycarbonate probably wouldn't hold up to CNC milling.
montagdude
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Re: Ball-bearing yoyo designs

Postby montagdude » Wed Feb 24, 2021 3:43 pm

Cool! Do you have a website for your yo-yo company, if it's okay to post that here? I am into yo-yos too, and I'd like to see what you have.
galou_breizh
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Re: Ball-bearing yoyo designs

Postby galou_breizh » Wed Feb 24, 2021 6:38 pm

You could use a dynamic property to store the density (https://wiki.freecadweb.org/Release_not ... namespaces).

I guess you can also directly associate a material to a body but I never used this.

Gaël
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Mark1D
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Re: Ball-bearing yoyo designs

Postby Mark1D » Wed Feb 24, 2021 9:00 pm

montagdude wrote:
Wed Feb 24, 2021 3:43 pm
Cool! Do you have a website for your yo-yo company, if it's okay to post that here? I am into yo-yos too, and I'd like to see what you have.
Here it is: https://mk1yoyos.com/
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Mark1D
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Re: Ball-bearing yoyo designs

Postby Mark1D » Wed Feb 24, 2021 9:14 pm

galou_breizh wrote:
Wed Feb 24, 2021 6:38 pm
You could use a dynamic property to store the density (https://wiki.freecadweb.org/Release_not ... namespaces).

I guess you can also directly associate a material to a body but I never used this.

Gaël
I'll try this out, thank you!
oldboffin
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Re: Ball-bearing yoyo designs

Postby oldboffin » Fri Feb 26, 2021 9:59 pm

I think your rendered view is great, what did you use to do it and can you tell us what your computer is. BTW I think you should have no trouble machining polycarbonate.
Great work, thanks for sharing.