I gets lots of emails from people who do not own a Rondix tank and who cannot see how the thing works. There are sometimes additional questions, like does the film go in and out of the cassette. To explain the brilliantly simple concept I tried drawing coils of film with the film turning back on itself when the winding direction is reversed. But I could not draw that. The video of the tank in operation does not and cannot show what is happening inside so I decided to build a mechanical model of the tank. I found an old length of film and a 35 mm cassette. I then went into the attic to unearth some 1970s Meccano and even found the sewing box in the house to extract a cotton reel.
The result you can see here and on the Videos Page.
What a crude mechanical model cannot show are the other design features, the ridges in the bottom of the tank and in the lid that prevent the image area coming into contact with the walls of the tank, for example.
The ‘poor man’s Rondinax’ may have been simple but it was a brilliant design. Truly elegant.