The TransiDupe project was partially inspired by the Xtend-a-Slide. The Xtend-a-Slide was manufactured by Photosolve. The Xtend-a-Slide is no longer manufactured because Photosolve is out of business.
Originally the Transidupe project was designed around being Xtend-a-Slide accessories. Alternate slide and negative carriers, etc. When the Xtend-a-Slide was not longer being manufactured, I filled out the design to emulate the other portions of the Xtend-a-Slide. As best I could with 3D printing.
The Xtend-a-Slide was mostly CNCed out of solid metal. It consisted of one, or more, lengths of concentric circles of tube that were screwed together, along with a steel front plate for attaching the slide and negative carriers. (The carriers had magnets.) Here is a single section, showing the inner and outer sections.
This is why TransiDupe expresses the length of the tube in sections. Each section corresponds to a single Xtend-a-Slide section. With my crop Canon 60D and 60mm macro lens, I used three Extend-a-Slide sections to produce a slide or negative image that filled the frame.
When I used 110 film (that is much smaller than 35mm film) I needed two Xtend-a-Slide sections to fill the frame on my 60D. With the Xtend-a-Slide I only needed to unscrew a single section. But with the TransiDupe, we'd need to have two versions of the tubes: One three "sections" long and a second set that was two "sections" long.
Or use the PVC version of Transidupe that is designed to use 2" PVC pipe that you cut yourself. In this case you would only need a single set of front and back "tubes" (that are designed to attach to a length of PVC pipe.) Then you'd have cut two lengths of PVC pipe: One for 35mm film and a second shorter one for 110 film. You'd also need 35mm and 110 versions of the negative carriers.
The Xtend-a-Slide slide and negative carriers consisted of a thick transluscent white disk that was used as a light diffuser. The portion that was formed to hold the slide or negative was carved out of thich magnetic rubber (which stuck to the steel front plate.)
I decided that I didn't want the diffuser so close to the slide (or negative), because the diffuser was so close to the film plane, that any dust on the diffuser showed up on the image. At my request, the owner of Photosolve made me a custom version of the slide carrier that was cut out in front of the film. I used an external diffuser that was placed several inches in front of the film.
Transidupe continues this convention. The carriers are cut out in front of the slide/negative and the user is supposed to suspend a diffuser a few inches in front of the film.
As a request to me, the owner also made several modifications of the Xtend-a-Slide negative carrier. I kept wanting to experiment with the negative carrier, which was one of the incentives that started me on TransiDupe project. It is a whole lot more satisfying to be able to generate whatever you dream up! Generate out of thin air! With no sharp tools involved!
Which is why I like that the TransiDupe project be open source so anybody else can make their own modifications. On the off chance that my designs didn't turn out to be the best possible designs of all worlds.
I liked profhankd's slide carrier design (carried over from his DupliHood project) better than anything I could come up with, so the TransiDupe slide carrier is mostly the DupliHood "springpart".
profhankd made the DupliHood be open source so TransiDupe uses the same license. See the TransiDupe source code for the license.