Hello everybody I am in need of some help. I am conducting an experiment on the effects of weight distribution on the spin time and stability of a yoyo. I am still in the research phases of the project and I have come across some troubles. It seems as though I can not find any reliable sources on the physics of a sleeping yoyo. I have found some information on responsive yoyos, but none on the modern counterparts. If anybody knows anything about the physics of a sleeping yoyo and a source for the information it would be greatly appreciated. Also any knowledge on the “moment of inertia” and how it relates would be helpful.
Thank you for any help you might give.
Contact a manufacturer or pro. They’ll tell ya.
Sort of doubt a) most of them even know the answer or physics behind yoyo design, or b) they have the time and energy to educate on the topic.
There’s gotta be a body of work on gyroscopes and/or the gyroscopic effect. Not a bad place to start, I wouldn’t think.
Moment of Inertia is the rotational version of mass. Just like things with large masses take large forces to change their motion, things with large moments of inertia take larger torques to change their angular motion. The moment of inertia is larger when more mass is concentrated farther from the axis of rotation. The gyroscopic effects occur when the string isn’t perfectly centered since this makes the string tension and gravity forces cause a torque and lead to precession.
I could go on and on since I’m a college junior in physics, but I don’t wanna math up the place 
haha.
Anyway, a simple article on rotational dynamics will get you a good intuitive understanding depending on your background in physics.
MIT did this study in 1974 and their paper on the subject can be easily found.
1 Like
Physics texts can give you a great start. There are many websites also.
You will be interested in the physics of a rotating mass and rotational momentum. The physics of a sleeping yoyo, however, is much simpler than that of one being used for a complex trick; such as one moving in multiple dimensions while rotating at the end of a string.
As simple as they appear, yo-yo physics are actually rather complex, and a cursory look at rotational inertia only gives part of the story. Once you learn a little about that topic, here’s a link below to some additional yo-yo physics regarding small bearing versus large bearing for your reading pleasure. You may learn something there…
Also, you may want to offer up to your audience here the motivation behind your yoyo study. Is it for a junior high or high school science project? A college term paper? With this information we may be able to offer up technical information at a level commensurate with your knowledge and requirements.
db
1 Like
I found that if you put as much weigh as possible on the most outside of the diamiter, the more inertia, and spin time I would get. I did a simple experiment putting as much mass as possible to the center.
1/3 the spin time accured, with the stability being even less. Also, making the object spinning less wide in increments would increase the spin time by 3% if you divided the increments into 10ths for the first 5. And then in increasing it up to 10% the thinner it got. If I had te means of monitoring it, I’m sure a bell chart would have been more descriptive.
This was done at an extremely hard throw achieving 1200 rpm, measured by a strobe.
In more practical terms for my modern designs, my weight (hump) you see in my designs is carefully widened, I.D. Is increased, or decreased to get the result I am looking for.
Vibe, or wobble plays a part in the object spinning, as the harmonics of a vibe will fight against the overall spin time.
Not sure if any of this was found helpful, but cutting shaped on a lathe, with a second hand on my watch gave me the basics to start my hobby.
FYI, the torent was an experiment trying to achive as much rim weight as possible on a yoyo with the walls being as thin as possible, still making it possible to manufacture. It was never designed with intent to be sold on the market. That happened by mistake.
4 Likes
Thank you very much! Would it be ok if I quoted you on some of this as a yoyo manufacturer?
Sure.
To make my statement very basic,
The more narrow a spinning object is with the weight on the outer most part of the diameter has the most inertia.
The wider the object with the weight towards the center has less.
Which is more stable? Wide or thin?
It depends on where the weight placement is. Rim heavy, wide, yoyos are stability beasts. Narrow throws can be also.
Define “stable” ?
For a yoyo?
How about: The tendency of the yoyo to not deviate from the axis of revolution.
Think of an imaginary yoyo only 1/4" wide, but 2" in diameter.
Even as it stopped spinning, it wouldn’t have anywhere to tilt off its axis.
Go take the front wheel off your bicycle and spin it real fast, (its weight is on the OUTSIDE)
then hold it by each side of the axle with each hand.
Try tilting it off the axis, and feel the resistance.
Now, go find something wide, that has equal mass, and do the same thing. (two wheels far apart side by side)
There is close to zero resistance.
Don Watson wrote 5 books on the subject… I -HIGHLY- suggest you start there as they are quite comprehensive. If you want to go further than that, I’d be happy to help once you have that much down
Kyle
Theoretically, the most stable would be thin with most weight on the rim since the weight will be more concentrated to the rim instead of the wall. The wider the yoyo, the more materials should be transferred to build the wall instead.
#see image attached
BUT, when you make a yoyo too narrow, you will have less moving area for the string since it will be closer to rub the wall and ultimately the rim than a wide yoyo, say, even if the inner wall were in the same diameter… Therefore thin yoyos are only stable for long sleeper kinda thing, but suffers a lot on normal play where the string will actually rub the wall much more. With wide yoyos, the string must be tilted far enough before actually touching the rims, with narrow yoyos it’s closer and less forgiving.
Also inner wall (the flat area around the response system) plays a big role to stability. The less diameter of the inner wall (like most yoyorecreations), the less likely for the yoyo to tilt when the string rubs the wall, why? because the inner wall has smaller diameter it’s far away compared to the diameter of the rim, therefore less effect on the spinning direction. Unless the string is tilted so far away that it touches the rim, when the spinning direction will suddenly change.
With wide inner wall (like duncan fhz shape), the string will rub the wider area of the yoyo, which means closer diameter to the rim, therefore it will reduce spin time more and will be more “tilty”. Keep in mind that different materials also have different effect, aluminum has less friction than polycarb plastic, and so on.
Now to answer the question, the most stable yoyo will have less diameter for the inner wall, more diameter for the yoyo, more rim weight, and a compromise between wide (slightly less rim weight but more freedom for string movement) and narrow (more rim weight but less freedom for string movement).
But there is one thing with too stable yoyos, they are actually less maneuverable since it have too much tendency to stay in one direction, that will give a sense of less control… feels like riding a bike that wants to keep itself straight. Also more rim weight means the yoyo will actually be awkward to throw since it will be like it don’t wanna spin right away when thrown, if you compromise with bigger bearing or narrower gap, you will have to compromise the less potential rpm. More stable is not always a good thing. That’s why the best yoyo don’t and cannot exist, because it’s not “a” best combination of these parameters, but “a range” of what is optimum for yoyo designs, and it depends on the player himself to decide which yoyo works the best for him…
Sorry if I derailed the thread a bit…
1 Like
Take a look a newtons laws all of them are in effect in when you look at it also something about friction.