I have created two 3d printed parts with the goal of facilitating long exposures with the Mamiya RB67. The system also has the added benefit of not costing ~80$ USD for the actual dual threaded cable released by Mamiya. My objective was to reduce the vibration risk associated with manually manipulating the timer ring, while also making the single cable release optional if you don’t have one available. Additionally, these models simplify the process of taking long exposures with the “mirror up” mode since the clip part attaches to the lens itself freeing up your hands from having to use a paperclip to trigger the opening of the shutter.
I’m pretty happy with these components and how simple the whole thing is. You can read more/view the video on the project’s home page.
Thingiverse link: https://www.thingiverse.com/thing:4917805