Powerball (excercise tool)
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Nanosecond Powerball is the successor for the Dynabee gyroscopic grip-strengthening exercise device, which was originally produced by DynaFlex: all major patents for the Powerball, its construction and modern features like rev counter and the light-emitting diodes powered by a little generator embedded in the gyroscope are held by DynaFlex and NanoSecond companies. It is a gyroscopic toy sold commercially as a wrist exerciser device or as powerball. It can be started with a short rip string or by a snap of the thumb. Once the gyroscope inside is going fast enough, a person holding it in his hand can accelerate the gyroscope to incredibly high revs by following a circular wrist motion with the device. Modern devices come with electronic rev counters (current record is 16,317rpm, set by Akis Kritsinelis from Greece Video here or here). He has also set an 90 second strength record of 20,082 revolutions see video.
The most advanced Powerball model for today is a 350Hz Metal - this powerball is made completely of metal and has twice the weight of "regular" powerball models. This powerball is harder to operate, since it could give in about 25kg of torque when internal rotor is rotating at high revs. The current world record for the metal Powerball is 13,731rpm, set by Akis Kristinelis.
Nanosecond's Powerball was the first to feature electronic rev counters, and a generator with some light-emitting diodes, making this toy and training tool more attractive for professional and educational use.
At first sight the physics of this device looks confusing, but is surprisingly simple. It can easily be understood with a little knowledge of gyroscopes. Their striking property is that the axis of a spinning gyroscope will resist a force applied to it and will start rotating perpendicular to the force applied.
The axis of the gyroscope in the gyro powerball is fixed to the spinning mass and it rests in a little groove inside the wrist exerciser device, which almost completely covers the gyroscope inside it, except for a small round opening on top of it, which is where you can manually start the gyroscope. Once the gyro is spinning, tipping the device will cause the gyroscope to start precessing, with its axis slipping around in the groove in a circular fashion. The groove inside the device, is a little wider than the axis, and the gyroscope's evasive action towards the externally applied force will cause one end of the axis to push against the upper rim of the groove, while the other end of the axis pushes against the lower rim of the groove. While the axis is slipping around inside the groove, the friction between the axis and the groove rims will accelerate or brake the spinning gyroscope, with a maximum effect when the axis starts "rolling" inside the groove. Since this friction force is essential for the device's operation, the groove must not be lubricated. The acceleration of the gyroscope is best when the precession of the gyroscope is supported and amplified by wrist motion.
It takes a while until one finds the "rolling" point, but the gyro will also be accelerated to a smaller extent by the slipping friction.
The device is covered by US patents 3,726,146 (1973) and 5,353,655 (1994) by L.A. Mishler and US patent 5,800,311 (1998) by P.S.Chuang and 6,942,601 (2001) by P.S. Chuang
