Just the Facts: Weight and Weight Distribution

General Yo-Yo
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Yo I’m making another one of these to get my facts straight. It seemed impossible to talk about weight without talking about weight distribution so I’m going to include both of them here. Let’s start with talking about weight in general and then weight distribution. Might as well make a general note about distribution because it is confusing. For calculating the MMOI (Mass Moment of Inertia), the energy gifted to the yo as it hits the end of the string, weight distribution is all about where the weight is concentrated in relation to the central axle like it matters if the weight is concentrated away from the axle but not away from the gap ie.weight distribution distance from the gap of the yoyo (width) doesn’t play into these equations for MMOI. Weight distribution closer to the gap does help balance the yo and adds stability. (How easy it wants to stay how it is vs get knocked off plane).

Please correct me if I am wrong. I studied the arts and was terrible at science but I really like yoyos and want to make sure I understand them correctly. I read Don Watsons YoYo Physics 1-5 and learned a ton which allows me to say a couple things and know that they have been tested and proven but there are also more things relevant to actually playing with heavier yo-yos that not brought up in Watson’s essays like heavier=more dangerous so we should have a list that includes real world things also besides just like pure spin time and we should include notes on how the physics apply to actually playing Yoyo.

Shoutout to @Philip for this post which sparked my interest in this and covers a lot of what I want to talk about. I understand information best when it is clearly listed out so that’s what I want to make.

Also, I’m just trying to find out the facts, I don’t really care about “feel” because it is so relative like one persons sluggish is another’s too zippy. I don’t really want this to get derailed by people stating their preferences either but feel free to share them. I do want some real world applications though, let’s just try to stay away from more ethereal descriptors like “floaty” and try to focus on more quantifiable descriptors like control or stability (ability to stay spinning on plane).

Also I’m going to use heavier to describe a difference. That could be 60g to 63g or 63g to 100g. The math should hold up either way. It just seems easier to use heavier or lighter as a way to compare different weights. I’m using imaginary yo-yos to make these comparisons and all other factors should be considered even.

There are a lot of factors that affect how a Yoyo plays and feels and I would like to eventually understand all of them. I’m making this topic to try to just understand weight and weight distribution.

Facts about Weight
-As weight increases, so does spin time.
-As weight increases, more energy is required to move the Yoyo equal distances (real world this can be good or bad, depends on skill level and preference, I find lighter yo-yos harder to control because they require less force to move and I have a poor Yoyo finesse score)
-As weight increases, so does the amount of damage they can do. (More real world factors to consider like material, shape, etc…)
-As weight increases, so does stability (not sure if this is the right way to describe this but I want to get across the idea that heavier yo-yos care less if you accidentally bump them wrong with your hand while playing.)
-Heavier yoyos can make you more tired to play with over a long play session.

Facts about weight distribution
-As weight moves away from center axle (more rim weighted), spin time increases vs same weight with a more even distribution of weight.
-As weight moves away from center axle (more rim weighted), it becomes harder and harder to reacher higher RPMs vs same weight with a more even distribution of weight.
-As weight moves away from center axle (rim weight), stability increases.
-The rim weight can be shifted closer in the width direction (to the gap), to help balance a yoyo and add stability. The MMIO is still calculated the same.

I think this covers almost everything! Thank you @hsb @MarioMaker17 @Jeaves @YoyoGeezer for helping fill this out and if anyone else thinks of anything to add or edit, holler!

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I’m not sure that it is as simple as that. Shape also matters, e.g. a blade vs. a rod vs. the flat part of a sheet of the same weight. It really depends on the shape of the part of the yoyo that is making contact. That’s probably the rim, where there is a lot of variation in profiles.

Materials also make a difference here.

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Yeah absolutely but consider two yo-yos that are the exact same one is 40g and one is 100g which would you rather smash you in the nose

Edit well…I guess they couldn’t be the exact same and be the same material you’re right…hmmmm

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40g. But if both are 60-70g shape would be the deciding factor.

Also, per your other points, during an accident in normal play that 40g yoyo is probably going to be traveling quite a bit faster.

It’s also more likely to get out of control in the first place. A 5000g (playable) yoyo probably isn’t getting anywhere near your nose by accident.

I think a few of these phenomena become less true as you move away from hypothetical"'all else being equal" comparisons to actual implementations. Still fun to think about.

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Yeah you’re right because I do think that heavier is easier to control I just tried this 80g guy and was like ooo I better be careful but it feels less dangerous because it’s so much easier to control and I wanted to get that across but it is pretty complicated…I tried to use do damage and instead of dangerous I just know if I hit myself wrong it will be bad

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Great post!
Mind if I add to the conversation?

This is true but it also depends on the location of the weight. The Shutter is heavier than the Shutter Wide Angle but the Wide Angle is more stable and tends to spin longer because it has more weight pushed away from the center of the yoyo.

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essentially for any yoyo there’s a number called the mass moment of inertia (about the axis of the axle) , the MMOI along with how fast its spinning combine to create angular momentum, this is what providees spintime, while friction of course reduces it,

the best yoyo designs balance, ergonomics, MMOI and friction, as design factors to produce a long spinning yoyo

essentially the further you put mass (and the more mass) from the axis about which it spins the more “power” it has, but in doing so it also becomes harder to reach higher rpms (because the throw also needs to input more energy, to be converted to angular momentum via the pads)

if you want elaboration let me know (educated quite fully in physics)

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No I definitely don’t mind and thank you! I forgot to put a line about how people should help me fill the in and share their experiences and I’ll update the OP in a sec w that and this post because I hadn’t even thought about that and this format worked well for the bearing discussion like I just copy pasted stuff and now it’s like all the info people could need to go from beginner not knowing much about bearing shape to okay now I know too much

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Can you frame it in like one sentence like as balance leans away from equal to rim weighted the effect on rpms is … and this affects binds …?
Mmoi is just so far away from easy to understand because it affects so many things vs like rpm which is like one thing

Or wait I get it now but I think we need to define power

Is this right”the more rim weighted a Yoyo is, the harder it is to reach higher and higher rpms”?

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This is good information. Never thought about how rim weighted yoyos take more energy to get up to higher RPMs

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Yo-yo physics is very complicated. Without understanding calculus; the specifics will be difficult to grasp. But the simple way to understand is the angular-momentum of a disc:

j = 1/2 * (mass * Radius^2)

for a ring:

j = mass * Radius^2

Put simply; a ring has twice the angular momentum of a disc with the same mass. If you think of a yo-yo half as a series of slices starting with the bearing-hub (disc) and then is a series of rings of increasing diameter until the largest being the outermost rim (ok not Noctu).

You can see then that by putting the largest mass on the outer rim with the largest diameter; we can create the most angular momentum. This is why bi-metals have such power when compared with most mono-metals.

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I would definitely read the post where @Jeaves elaborates on Moment of Inertia.

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I basically want to say that but using Yoyo terms like weight instead of mass and axle instead of axis because it’s more real world and easier to grasp

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yeah this is about right as a summary
for equal mass
rim weighted = power

but only if you have enough grip in the response pads (and a good throw) to get the rpm up

it get even more complicated of you consider different response pad diameters (so lets not go there and pretend its all 19mm)

this is probably why some people prefer less powerful throws, it feels easier to throw and bind

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so many factors is why i tend to trust reviews, you cant really tell how it will play from specs alone
as there are lots of tradeoffs, even things like string length and thickness affect “power” as percieved

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Moment is what I think most refer to as “feel”. This is where understanding calculus is important. This physical property of a complex, solid body like a yo-yo in motion is hard to explain - let alone understand; without using integral-calculus.

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I don’t want to require a complex explanation (though that is probably exactly what I am doing)… But can you describe how grip from response pads influences the RPM?

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just if its not grippy enough, some of the energy you put in will be lost when it slips sooner than the end of the string

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Updated the OP to include what I think is correct but let me know if i got it wrong…I will have to do more topics about all the yoyo stuff because I just want to understand it…not sure if spintime and rpms needs it or tightness of binds because its basically you want it bound up as tight as possible…I don’t know the only other topic I was curious about was just the facts about string length like does a longer string let you have to adjust tension less often?

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equally binds may end up less tight, causing the same thing

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