This is a similar conversion as 6x6, except that there isn't enough clearance with a standard Polaroid back to fit the film capsules. 3d printing a back is your only option. Even so, this is the easiest roll film conversion to do.
Download the 3D files here and print one of each part and 2 top spools. The knob and drive spool should be printed with 100% infill for strength, and the back should be printed with supports everywhere. You will need to sand down the spools and receptors to 600 grit to reduce friction, as well as any place the film slides along. The film pack is designed at 89.5mm, but printers will often add .5 or so mm to the print job and it won't fit until it's 89.5mm wide. Same with the pressure plate. Be sure all parts fit OK without forcing them. The hinges and latching hooks on the back will need filing to fit properly, and the drive shaft hole in the side of the pack will also probably need filing so the shaft fits.
|Insert the 35mm film pack and line up the drive hole with the edge of the camera, file a U shape where it lines up to give clearance for the drive knob|
|Install the back with the hinge pin and be sure it seats correctly with minimal stress when closed. This back has been tested and if the sides are seated against the back the whole length of the back, there won't be any light leaks.|
|Place some hockey or gaffer's tape over the gaps between the edges and the film retainer to prevent any light coming in along the edges.|
An empty 35mm canister is used to takeup the film instead of rewinding it back into the original cartridge. The alleviates the need for a rewind knob.
|To make most use of the film, tape around 5 cm of leader to the film spool that will be loaded with new film. Then, tape the new film end from the bulk loader to the leader with one piece of masking tape on one side only, not folded over the edge. This is so it will release and untape so the end of the roll can be rolled into the take up cartridge. Load it with the bulk loader with 26 turns, which will give you 12 exposures. Alternately, you can just use a new roll of film and cut off the swooped part of the leader.|
|Tape 20 cm of leader to the take up spool and tape this to the loaded film end using 2 pieces of transparent tape, one on each side, not folding it over (as in the pic!) since that causes undue friction. You'll waste 2 frames if you don't use the leader.|
|The film is laid out across the cardridge emulsion side down.|
|The pressure plate is put into place, being sure to line up the film with the edges of the drums on each end.|
|The spool ends are put on and the spools are flipped into their slots and the knob is installed. Install the covers to help prevent light leaks. Note that there are 2 different sizes for each end.|
|Put the film pack into the camera and take up the slack. Close the door and be sure there is no undue stress on the door hinges or locking tabs. Advance the film 4 turns. If there's undue friction in the pack, unload the film and rewind it back into the cartridge and diagnose where the friction is happening.|
|A rudimentary film counter is made with a piece of paper and numbered tabs, so I can keep track of how many times I wind the knob with each photo. The wind ratio chart is included as well.|
The following chart can be copied as a guide for advancing the film:
|Exposure||Number of Winds|
At the end of the roll, if you are using bulk film and attached the new film to the leader with a single piece of masking tape, try winding the film all the way into the takeup canister. The masking tape should break away from the leader. If you are using a commercially loaded roll of film, the film will need to be unloaded in a dark bag and rewound back into the film capsule in order not to lose the last 2 frames.
Feel free to contact me with any questions or news about your build!