Mullet Drivetrain Hack -Mixing ANY Shifter with ANY Derailleur by JulianGoulding
www.thingiverse.com
I wanted to hack together a gravel bike build. Obviously I didn't want to fork out for the dedicated gravel groupset so I went with the mullet drivetrain option intead. I this build you are able to take ANY shifter derailleur combo and make it work. I used Parametric modelling in fusion 360 to make a 3d printed file that can work with everything https://www.youtube.com/watch?v=YeqvTJ-Y22Y

Here’s a vid: https://www.youtube.com/watch?v=YeqvTJ-Y22Y

As the guy notes, these are and have been commerciably available for a long time, but usually one piece to link two specific parts together. This one will basically do whatever you want it to (barring some exceptions where the ratios are too far apart).

I wouldn’t go world touring on it, it seems liable to break or gunk up and you’ll probably increase your consumption of cables, but for throwing together the parts bin special this seems pretty good.