Is that true? Moment equations depend on mass and raduis. I think people are assuming that the poly body will be made up by a heavier ring. But Aluminum cylinders have a moment also. Since that body will also contribute to the moment - I think it is still debatable as to which would have the higher moment.
The more I think about it; the more confused I get. Yo-yo’s in motion, are very complicated physical objects.
Plenty of yoyos are as good as the Draupnir. What I’m saying is that the Draupnir wouldn’t necessarily be better at what it excels at if it had a slightly thinner wall and slightly thicker rim. The weight distribution can go too far.
Oh okay. Makes sense. Keep up the great work
Perhaps I spoke too soon. Or misspoke. Who knows! I’m not even sure that MOIs are the best way to even talk about yoyos. How does it translate to how a yoyo plays beyond a higher MOI = more energy required to ‘spin-up’?
In any case, it got me curious so instead of doing actual work this morning, I did this instead.
Though I’m not sure I modeled it correctly. I assumed a solid cone and a hoop/hollow cylinder for the body and rings, respectively, and simply changed the densities, assuming the same volume. Of course, they would lead to different overall weights. I think a hollow cone would probably be more appropriate, and I’m not sure if the distance of the hoop makes a difference.
Im pretty sure there’s CAD software that can calculate the MOI - I’m actually fairly certain I’ve seen someone post about it here. Perhaps someone familiar with yoyo design can check.
My results: a 7075 Al body with 316 SS rings will have a higher MOI vs a Delrin body with Grade 6 Ti rings.
I disagree about the Yoyojams. I have dozens of Yoyojam yo-yos and not one of them is cracked.
They just seem to be exhibiting ‘interruptions in the continuity of their molecular integrity’.
A phenomenon that resembles what might be identified as ‘cracking’.
Trust me, I’m a Doctor.
I have an Official Degree from M.Y.O.W.N. institute…
I sort of miss my X-convict now after this thread. Fun yo-yo.
Yes it was!
Moment increases as more weight gets pushed to the extremes of an area (i.e. the rim as opposed to the center)
While you do get some moment for adding weight towards the center, you get a lot more moment by adding weight on the rim.
All of that said, I think moment of inertia isnt super useful/reliable for yoyo design. It’s more like direction on a compass than an actual rule/map for yoyo design
CAD software will give you MOI along all 3 axes, so that’s cool.
As far as the correlation between MOI and performance, the idea is that a higher MOI means the yoyo will resist the forces slowing it down, and so will spin longer.
This answers two of my previous questions. Nice. 
By that same stroke, a yoyo with a higher MOI will require more energy to spin up.
Do two yoyos with different MOIs spin for the same amount of time assuming the energy input is the same? I would think they would, though their RPMs would differ, with the smaller MOI yoyo spinning faster.
My impulse is telling me no, simply because the effects of air resistance and rolling resistance get higher has the RPMs go up, so the lighter, faster-spinning yoyo will suffer from more slowdown at the high RPMs
There’s a bajillion variables and I’m not sure you could realistically design an adequate test setup, but I can see how air and rolling resistance would affect the lower MOI yoyo. But I could also see precession slowing down the higher-MOI, slower-spinnning yoyo.
What was that unwieldly beast that C3 made to shatter the sleeper WR? It was something like 190g and basically a flywheel.
Yes, you can!
This one is “a few” years old…lol
I believe the weight rings are from a company called “Throw Down” (?).
74.2g, “Hybrid” Freehand with custom response. This was during my modding phase so one half is silicone recessed and the other sports, what i think is, a thick Dif pad.
Plays well, a fun throw!
kgb
See above…
kgb
After this first post I found those on Duncan’s website. (btw Thank you for your input!)
omg i havent seen this photo in years.
Source: i took this picture.
LOL I wasn’t even paying attention, if you google image search “yoyoempire o-ting” that’s on the first page of results and it’s the best photo of the bunch by a mile. It’s so weirdly hard to find good profile shots of some yoyos.
It was my old O-Ting. lovely yoyo, im sad i dont own it anymore.
Was just popping back in here to mention the Jade. I’m not sure what yys is, but it fits where I saw it. Looks pretty nice.
