Improving the Chikyu Goya (a gyroscope)

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Improving the Chikyu Goya (a gyroscope) (6/17/05)

The Chikyu Goya gyroscope

Chikyu Goya is Japanese for Gyro-Top, which is what we'd call a gyroscope. A fun childhood toy, gyroscopes are used in a number of applications generally to help something achieve a high degree of balance, such as a cruise ship or the Hubble Space Telescope.

The Chikyu Goya gyroscope spinning

The process of starting the tops usually involves an electric motor and the spin is maintained by some very careful management of ball bearings and really good oil, with the occasional touch up by the motors, when necessary. The toy ones need to be started with a string, which can be a little tiring. So I set out to do it with my drill...

A small starter for the gyroscope

I used a drill bit and two washers, held the gyro around it's equator and ran the washers on the axle. While it certainly got the gyro spinning it wasn't enough to maintain balance for long. The string method actually worked better. However, this was a good starting point. I took the diameter of the washers (3/4 of an inch) and multiplied by Pi to get the circumference. Multiplied by 500, the number of revolutions per minute (RPM) the drill is capable of, and the speed could be determined: 1.12 MPH. Piddly.

I could get a faster drill or increase the circumference to spin the gyro faster. The circumference works because we'd be increasing the length of "road" used to run the gyro at the same RPM, which means the effective spead of the gyro would be much faster. Browsing through Home Depot I came across a sanding pad that attaches to a drill via a large rubber pad. The circumference was 14.92 inches! It is made by Saint-Gobain Abrasives under the brand name of Norton and is called a DrillSand.

A larger starter for the gyroscope

End result: 7.07 MPH. Using the gyro uncovered a problem though: it was moving far faster than it was intended to. This was demonstrated by the odd and some what scary noises it was making as it spun. I was curious to find out how much faster it was going than "normal" so I used stopping time to guesstimate how fast the hand started method is. Police use stopping time (braking distance) to determine how fast a car was traveling before an accident so it seemed reasonable. The stopping time was roughly 5 minutes and 24 seconds more than the drill time with the small washers, which works out to about 3.06 MPH. In other words, at 7.07 MPH the gyro was traveling twice as fast as it was intended. It sounds slow but try to imagine something so small flinging by you at the speed of a sprinter. Its doing very well for it's size.

The only thing left to change was the lubricant used in the gyroscope. The designers probably didn't plan on speeds like this so I tried thinking of other mechanical objects operating at high speeds. Engines came to mind pretty quickly, and I happen to have some Valvoline Synpower...

Valvoline Synpower for the gyroscope

To be honest, I didn't have the patience to time how long it would take to stop. I got to 24 minutes and then the cat decided she hated it and attacked it. C'est la vie. Improvements to be made should be obvious, but I've discovered a 6 inch diameter sanding pad (a circumference of 18.85 inches!) and a 4000 RPM drill, which combined should yield a speed of 68.42 MPH. I suspect anyone attempting that should only try that with some serious safety measures in place.