A simple manually operated gyroscopic power ball.
Based on the hugely popular power balls that were a big craze 10 to 15 years ago, this stripped down version is simple to operate and gives a fascinating insight into the dynamics of gyroscopes.
At the heart of the device is a heavy spinning disk that exhibits gyroscopic behaviour; It will want to remain pointing in the same direction, but if it is tilted on certain axes it will provide a force perpendicular to that being applied. What really makes this interesting is the fact the shaft is loosely connected to an outer ring. The shaft will be slipping on what is effectively a clutch. But if a twisting force is applied the shaft gains grip on the outer ring which twists the disk around. Holding the whole thing and moving with a stirring motion, you are utilising the gyroscopic forces to hold the shaft against the outer ring and gain traction. With the right rhythm and slowly increasing the speed of the stirring motion you actually speed up the disks rpm.
The Hand Spinner is simple to operate, you grip the rim between four fingers and roll the rotor along a tabletop to start it spinning. When the rotor is spinning, a firm stirring motion with the rim held horizontally will cause the rotor to steadily increase in speed. Speeds of over 8000pm can be achieved with the correct technique.
As the speed steadily increases it will become more and more difficult to perform the stirring action due to the strong gyroscopic forces. If the speed is allowed to decrease some simple tricks can be performed, one of which is to hold the rim at 45° and observe the rotor direction. Then flip the rim so that the angle is in the opposite 45° direction and the rotor will flip accordingly.
The Hand Spinner comes with a display stand and is supplied in a sturdy protective cardboard tube.
The principle behind the idea comes from a product released in 1973 called the dynabee. You can find out more information about it any the many clones on this wiki page about Gyroscopic exercise tools and there is also a better version of the page on the German wiki.