We never usually see how the Rondinax or Rondinax-type tank fills the spiral reel either from a cassette (35U) or light-tight container (60) because the lid is closed. I have used an old length of film to show how the spiral reel is filled from the inside out. This invention was a key feature of the Rondinax tanks in the 1930s and is described in detail in the two patents.

The video is included in the Video page above but you can also see it here: