# Can a yoyo spin like spintop while flying around the air?

1. Mar 28, 2012

### tomyu169

modern metal yoyo with ball bearing works totally different with the old. it can spin about 5mins within one throw for some reason. and can it spin about 1min if I throw it horizontally? you may wonder about what is a horizontal throw. then see the video post below.

https://vimeo.com/39247415

To my disappointment, a yoyo that can spin more than 5mins vertically cannot even spin for 5 seconds horizontally? What leads the depressing result? Can someone give me a force analysis? I guess the tension and gravity is the key while it spin horizontally.

I think the yoyo spinning horizontally just like a spintop while flying around the air. And it do precession once we throw it because of the unbalance. So the way to keep longer spin time during horizontal condition is to reduce the precession speed.

According to the w(precession)=mgr/Iw
m -------mass
r -------- distance between original center of rotation and the center of mass
I ---------- moment of inertia
w ----------- the rotation speed of object

L=Iw means with a given throw the Iw is constant.

So the only way we can do is to decrease the yoyo’s mass and shorten the string?

2. Mar 28, 2012

### sophiecentaur

Is this not just a matter friction of the string on the sides? When the yoyo is hanging down, the string is well clear of the cheeks and stable. The ball bearings are the only source of friction. But, when you are whirling it around, it only needs a small change in angle for the string to touch the sides and then friction brakes the yoyo.

3. Mar 29, 2012

### tomyu169

Thank you for the suggestion, so how should i improve the horizontal spin?

to shorten the string or tie a pipe-like thing to change the position of fulcrum and shorten the "r" in the equation?

to reduce the area of the wall which would cause friction? (like the gear-kind thing near the bearing which will leave the string away from the outer wall)

to make some hole on the inner side around gear like the picture showing, and let the air push through it to provide some lift?

or...? i really want to get a fantastic as well as practical idea to get it work!