The moment of inertia is part of mass calculations and it calculates the amount of angular resistance based on the axis. In regards to yoyo designs it can help determine if something will precede or go off plane and out of control easily as well as how it will play compared to another yoyo with known moi. Speaking of moi calculations I haven’t figured out how to get calculations in fusion for multiple bodies like a bi-metal, I always have to transfer it to solidworks, has anyone else had that issue or figured out how to do it.
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Sorry I phrased my question poorly, I do know what MMOI is. I was curious what the MMOI for the specific yoyo @MarkD was talking about.
As to your problem I’m not sure. In Onshape I select multiple bodies then click the weight tool for MMOI and weight but I haven’t encountered that problem. I know @MarkD used to use Fusion. Maybe he knows?
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20k per half. maybe not too out of the ordinary but it’s higher than any other design i’ve released by a good margin.
in fusion what I used to do is examine each part separately and add them together in a spreadsheet.
I imagine there’s a better way but I’ve been using freecad for years now and I wrote my own plugin for yoyo analysis
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D bearing mini i think you should full send on man it’s an amazing look
You can copy all of the bodies into the bodies folder of a component, and then right click on the root component folder to query the properties of all the bodies combined.
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For printing or other medium?
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Yes. 
Have printed a couple prototypes, but plan to use some other materials once happy with the design.
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I like it. I just designed my second throw with an inner rim for thumb grinds (though it’s been a long time since the last), but it’s an unresponsive.
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Hey there,
I just got to a point in my yoyo design where I needed to add mass to reach my desired weight. From a designers point of view, when looking to add or decrease mass, where would you start first? Thank you in advance for the help 
-DedHed
@DedHed
In crease rim thickness or a very very small change in diameter. Or perhaps change it to a bimetal or you can increase the shape a bit. Example if you have a w shape increase the length of the rim area ever so slightly.
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Generally it depends on where I see the design is lacking.
If I want more mass…
- If it is not powerful enough, I add more rim weight exclusively (usually under the rim)
- If it is not durable enough, I thicken everything or build out a thicker hub
- If it just needs more mass for some other reason (???) I spread it between making it more powerful and more durable.
If I want less mass…
- If I want to maintain the power I thin out things that can take it, especially center weight
- If I want to reduce power, I simply remove mass from under the rim
Other options…
- Tweak shape or dimensions to change weight
- Change material or axle length (has many knock-on effects, can mean a redesign)
- Give up and see if it’s fine how it is through prototyping (costly! $$$)
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Thank you Mark this is absolutely terrific! I really appreciate you taking the time to go over that. I knew there had to be some sort of method to the madness. Thanks again for all the help 
Thank you thank you these are wonderful tips
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Dumb question. The machine shop wants me to provide a dxf with tolerances for the bearing blanks I’m having machined.
am I just supposed to like draw an arrow to a feature lol? ISO 2768-1 Class F or something? ———>
What are you using to generate the dxf? I think I recall that you’re using Fusion for design, in which case it’s an option in the drawing for the dimensions in the sketch. Double click the dimension, open the precision and tolerance tab, choose a tolerance type, and then enter the value (or values).
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Yes using fusion! Thank you!
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Realized I misread the question. Disregard what I previously said
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