The Spinning Lime Tree Seed

 

Hubschraubermuseum Bückeburg
Leonardo de Vinci's Manuel Helicopter

De Vinci worked as a military engineer for the Duke of Milan between 1487 and 1490.  In this time, 450 years before anything actually rose from the ground carrying humans, me made the sketch that the above model replicates, and is to be found in the Helicopter Museum in Buckeburg, Germany.  

Toy bamboo rotors have been found in China dating back to 300BC.  

Modern Japanese flying toys

As I gaze out on my street, the wind blows between the avenue of lime trees, and the seed cases take off, like a science fiction invasion of alien craft.  The seeds are set off a central stem to create a flywheel effect, carrying the rotating kinetic energy into the curved leaf fins.  The seed shoot upwards high above the parent tree.  

The real step forward in flight came when it was realised that the cross-section of the wing must be an aerofoil, not a thin piece of cloth as illustrated by de Vinci.  Flight is all about creating a vacuum above the wing.  The spinning lime tree seed forces air downward.  The weight of the seeds themselves maintain the vertical stability by rotating like a steam engine's 'governor'.

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I have always wondered why Leonardo's design has become so famous.  The most well known of these pictures is to be found in Paris, having been taken there by Napoleon.  I assume the fame is not so much the design, which anyone can see does not have the second screw necessary to stabilise the body of the plane.  Also these principles can easily be observed in nature.  But it is the audacity to also place humans on the machine.  It is not a surprise that the pictures remained in de Vinci's sketchbook.  They were for a different generation.