The aluminium tube holds a pen. The pen draws on the paper as the arms rotate. The pink and orange dials control the rotational speed of the pink and orange arms respectively. The dials also control the direction that the arms rotate - either clockwise or anticlockwise. In between the fastest and slowest speeds there is an infinite range, so the relative speeds can produce a huge variety of patterns. There is also a certain amount of slack in the internal workings which results in a uncertain amount of randomness. By changing the pen and the speeds one pattern can be drawn on top of another.