I'm building a motion picture film scanner. It will have a simple transport from the feed to the takeup reels that looks similar to this design being used by the Kinograph project: https://www.youtube.com/watch?v=6DtXLO2K-Uw
However, rather than using spring loaded tension hubs as kinograph does, I'd like to use a single roller on a linear actuator, that adjusts position dynamically based on the tension on the film itself. Something like what the MWA Spinner scanner uses: https://www.youtube.com/watch?v=NugH6zdXVmw
I'm doing this because my scanner needs be able to work with multiple gauges of film, and each has different tension requirements. In order for the kinograph design to work with multiple gauges, you'd need to physically swap out the springs with each format change. I don't want to have to do that. Also, film with lots of splices in it sometimes requires less tension, so I want to be able to control that from software as needed.
In this video of the MWA scanner, it's a roller on the lower left side of the scanner deck that's got about a foot of travel. I don't know what the mechanism is that they're using, but I'm guessing it's more sophisticated than a simple spring - some kind of load cell to read the tension and then something to adjust the roller position up and down as needed
Question is - can I buy something like this pre-made? Mine is a one-off scanner so I'm willing to spend a little money on it since it'll save a ton of time in trying to engineer it myself (my background is in film, and while I've built a scanner or two, they've mostly been modifications of existing machines so I didn't have to do this kind of mechanical engineering from scratch).