Gravity is Optional

A rattleback is an object that rotates in only one direction. If you try to rotate it in the "wrong" direction, it stops and begins rotating in the other direction. There are no internal parts .. no mechanism .. to produce the effect. Rattlebacks can be made from wood, stone, bone, spoons, chewing gum, or any ridgid object. The toy version is made from clear plastic.

These objects have been found in Celtic archelogical sites.

The "trick" is that

Another type of rattleback works by having off-axis weights. In this case

For a rattleback to work, the point that touches the surface when it is not spinning is different from the point touching the surface when it is spinning.

There are 2 basic ways to make rattlebacks

If you tap the end of a rattleback, it will start rotation in one direction. If you tap it in the middle, it rotates in the other direction.

By the way, some rattlebacks will change directions several times.

Using Gum

Ok - this guy makes a rattleback from chewing gum (still wrapped, not used).

Author: Robert Clemenzi
URL: http:// / Rattleback.html