Mad Triad

Mad Triad was invented by Heng-Chun Ku. It is becoming very rare. But it at

http://www.biffleys.com/playroom-games/mad-triad.htm
or download the iphone puzzle app version. (See below.)

Note: the physical version of Mad Triad and Handy Mad Triad are a bit fragile. Don't let small children play with it because the twisting knobs will break.