Designing a bimetal yoyo for school project

I originally made a post about designing a customisable yoyo for a school project. I have now gone with a similar yet different idea.

I am designing a bimetal yoyo with interchangeable rings for a school design & technology project. The primary aim of this project is to improve the durability of bimetal yoyos.

I have already done a few sketches on some ideas I’ve had about my project. I’m still currently conducting research.

Constructive criticism is appreciated.

More unusual ring design.

Just a pointer…threads and large diameters with thin walls require a master machinist with the proper equipment. This goes both for the the body, which I assume is aluminum, as well as the threaded steel ring. The local deformation of both different materials due to heat generation and cutter loads will result in two piece that will not be necessarily perfectly balanced and circular, once threaded together. I’m not sure how you can thread both of the inside sides of the steel ring slot without an absolutely custom made tool, especially given the small dimensions and the need for a very fine pitch thread.

Anyways, I wish you the best of luck if you try to do this!


A couple of you sketches show threads on both the inside and outside of the body/ring (first sketch in particular). Not a good idea and difficult to do. Perhaps that is what db is referring to here:



it was already produced many years ago by Any-yo was a failure and therefore has not been followed, the main causes were:

  • fragility of the object, (on such large diameters the deep threads can not guarantee strength and solidity to such important masses.
  • ease of disassembly undesired in use due to the rotation (being the opposite cups and rotating in the same direction, one of the two rings would be pushed to screw to the body while the other would be pushed to unscrew)
  • accentuated vibrations due to the necessary thread tolerances.
    the double threading on both edges of the cup and of the ring both to not bring benefits is practically impossible to achieve, when there would be seizure problems.
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I have a new idea for a threaded ring. It would be connected to a threaded hub using spokes.

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Last idea seems most plausible. Side effects have been in use for years, and are a simple proven way to add or subtract weight from a yoyo.

Not to rip off another design but if you were to do some sort of cap, for example the vapor motion or metal skyva, that threads into the hub like a side effect but puts a majority of the added weight out towards the rim that may be a good way to accomplish your goal. Although I don’t think it would work to have the thread on caps form the actual rim of the yoyo, as it would not be worth it from a performance/cost standpoint.

But hey, with a thread on cap rather than spokes you could add fingerspin capability to boot!

Hope my ramblings make sense, sounds like a cool project!

If you ask me, my solution would simply just make four holes to screw the rings in place. It will be easier to machine than threads or spokes.

One more thing about the spokes, they will create aero drag and caused the yoyo spin time to drop. The higher the rpm the quicker it drops. I know because I used to own Adegle Rhong-To.
Not to mention it’s really hazardous, it’s almost like putting your finger on bicycle spokes when it’s spinning.

“The best design is as little design as possible” -some German dude

Dude the steel rings look like fan blades that are gonna slice a finger off!