Outer ring's 2X as big as inner gear. How many full rotations will small gear have for every orbit? Pen's in outermost hole at small circle's perimeter--why does it make a straight line (like a piston)?
Based on 1D distance, it seems it'd make 2 full rotations because inner circumference large circle is 2ce the circumference of the smaller gear circle. So for each 360 degree run, we might expect 2 full rotations based on the 1D ratio of 2:1 in circumference. But, in reality, it makes only one rotation. Since outer ring is 2X inner gear's size, small gear rotates clockwise at same angular speed it orbits counter-clockwise, so horizontal motions cancel out, leaving only vertical motion A piston in a car engine goes straight up and down, but is attached to crankshaft spinning in a circle. The Tusi couple's doing same thing in reverse: a circle spinning inside a circle to for linear piston motion
