Da Vinci's Ball Bearing Puzzle

Leonardo Da Vinci Ball Bearing puzzle is part of the Professor Puzzle's Great Minds range of unique puzzles. 

Leonardo Da Vinci conceptualised the first helicopter. He knew that the propeller on his helicopter design would need to rotate extremely fast for lift off. And that he would have to find a solution the friction problem. Ball bearings, together with a lubricant, would significantly reduce friction, greately increasing the propeller's speed. Although the use of ball bearings was known to the Romans, it is Leonardo Da Vinci who is generally credited with their invention.

Aim: Can you make the ball bearings sit at the opposite ends of the puzzle?

Difficulty level  : 3 (1 - the easiest, 5 - the hardest)

Measures 9 x 6.5 x 5.5cm.