Here are some universal linears that use the Tower Pro MG90S mini servos. Liner has .825" of travel 0-180 degrees of servo movement. There are left and right to fit your project. Use Dog Bone arm to move things with 1/4" diameter hole, .400" outside diameter and 1/8" (.125") thick. Use small flat washer and 4x1/4 screw for rack to hold arm. If you need some assorted length arm bones, let me know.Raft and support for the top part. The bottom part and rest will print without raft or support. Use #4 sheet metal screws to put cases together. Ears for mounting to your project. The pinion gear you will have to push on the servo. I drilled it out to .180" and pushed it on making ribs. It is hard to push on but stays. Didn't need a screw to hold gear on servo. Drill .120 hole for #4 screw to go through and .089"-.093" where it threads.