Picture of Educational Gyroscope for Blind Children
 A number of years ago for one of my design courses at Otago University, we were instructed to design and build a toy for visually impaired children. We had a speaker come in and tell us all about the different aspects of assisted learning for kids with visual impairments. One thing that is very important in their development are toys that stimulate wrist rotation. This assists with motor development and strengthens muscles that would normally be exercised through hand-eye coordinated movements.  What I came up with was an encased gyroscope. It allows the holder to turn their wrist only on a single axis, and also makes a neat whirring noise and slight vibration that might intrigue someone who couldn't see it. The gyro is easiest to describe as a yo-yo encased in a pair of clamshell-like covers. 

The prototype I turned on a metal lathe, using brass for the flywheels, and aluminium for the clamshells. The clamshells are attached by a single shaft through the middle, and can't rotate independently of one another. The two flywheels are attached by a tube, and the clamshell shaft passes through this tube. The inside and outside are only connected by a pair of bearings which allows the internal flywheels to spin while the outer shell remains stationary. 
In order to use the gyro, you wind a cord around the middle like a yo-yo and pull it out like a ripcord to start the wheels spinning.

Since completing the project I learned of a product called the NSD Powerball which operates on basically the same principal, but has a dynamic gyroscope axis, rather than a fixed one like in my design. 
rimar20003 years ago
What a good work!
Kiteman3 years ago
OK, dopey question - how does a visually-impaired child thread the string through and wind it up?

andrew.spencer.2 (author)  Kiteman3 years ago
no, good question actually, sorry I should have elaborated on that. It's quite simple to do, but tricky to explain. You hold the tip of the string near the edge of the crack and just begin winding it around as if you were winding up a yo-yo. After you have a few turns on, you can let the tip go and continue winding until you have used up all the string. Hope that helps
OK. I wonder if the end of the string could be modified in some way, maybe dipped or coated in something to make it grip the shaft?