120 6x9 cartridge for Polaroid pack cameras

thingiverse

This is a cartridge and back which fits onto/into a Polaroid pack film camera (models 100-455) so it can use 120 film in 6x9 format. This is quite a bit more complex than the 6x6 version because of the path that the film takes. The main cartridge has two free rolling rollers which greatly reduce the friction which was a problem with the previous version. Print all the pieces with supports, with 3 or 4 bottom/top layers and 25% or so infill. The roller ends were made slightly too large. File them down evenly until the roller fits in the indents in the sides of the cartridge and spins freely. A little resistance is acceptable. Insert the drive gear in the upper left--it'll install with a gentle snap. Mount the thumb gear in the two holes to the right of the drive gear with a small screw and be sure it turns the drive gear easily. IMPORTANT: mark the top of the drive gear (white paint) when the drive tab is vertical. This mark will be used to remove the film spool. Sand down the cartridge base surfaces and glue down the cartridge base to the base of the cartridge, placing the longer end toward the gear end of the cartridge and the indents down. This emulates the original pack film cartridge and helps keep out light. To help light from being transmitted through the film counter hole, sand down and paint the bottom of the pressure plate and paint with matt black paint. To use, align the drive gear tab so it is vertical, then place an end cap on an empty spool and insert the take-up spool by placing it onto the drive spool tab and swinging the spool down until it is sitting in the bottom spool guide. Feed the leader of a roll of 120 film face down underneath the left roller, being sure it is between the guides on the roller, until it appears out under the roller. Grab the leader and feed it across the cartridge, then under the right roller (between the guides) until it appears above the roller. Install the pressure plate, verifying that the upper left drive spool tab slips between the slot in the pressure plate. Place 2 end caps onto the left (full) spool and swing the roll of film over the left roller into the spool guides. Place the left cover on. Insert the end of the leader into the take-up spool and wind the thumb gear until the leader is on the take-up spool. Install the right cover, then insert the cartridge into the camera. Close the door and advance the film to the first frame. Cover the film counter hole with black tape (or a red filter) or use the included film counter hole door and uncover only to advance the film. To remove the film, be sure you advance the film until all the remaining backing paper is rolled onto the take-up spool, then align the drive gear so the mark is facing up, then grab the full spool at the bottom and swing it out bottom first.