A new, Self-supporting,Wooden spiral staircase,no column,

When I created my wooden spiral lamp, I was asked how big could I make a spiral, large enough to make a freestanding spiral staircase.

https://photos.google.com/album/AF1QipPIDc3jM8JmOPPyV0RzNwLVtn5NQWGehooLetLN

                                                 

The most famous spiral staircase is in Loretto Chapel,Santa Fe New Mexico,I saw it in 2006.
It was self-supporting,Built in the late 1800s.

This is my version.

A solid wooden 3 foot diameter spiral, if necessary, hollowed out for concrete and steel support.

18 foot tall more or less.10 foot diameter, more are less.