Custom Shift Knob

I designed and 3D printed a new shift knob for my Miata. The 3D print captures a nut and stack of washers to weigh within 2.5% of what Mazda engineers designed for. I even embedded the LOP logo into the top face.

The History

This was one of the earliest red flags i saw when first looking at this Maita. The second most common touch point in the interior next to the steering wheel was replaced with a faceted crystal?? This should have been a warning about the type of person the previous owner was. After purchasing the vehicle, i knew this was one of the first things that needed to change.

First 3d print

My initial reaction was to see what the internet had readily available to 3D print. I found a file for a spherical shift knob with the Miata logo script embedded into the top face. I downloaded, printed, and installed this knob and went for a drive. Something was off and the shifts felt lifeless.

OE shift knob

Another problem i was facing at the time was that the convertible top was not folding down properly. An investigation revealed that the original OE shift knob was jammed in the hinge mechanism. It was dirty and damaged but it had a nice weight to it. I screwed it on and gave it a test. Shifting felt effortless and so much cleaner than the hollow plastic knob.

Custom solution

When i got home, i put the OE on the scale and weighed it. This was my new mass target because I trust that the Mazda engineers knew what they were doing when designing the shifting mechanism. Afterall that is why the Miata is so famous to begin with: driver feeling.

I liked the spherical shape from the free online model and wondered if I could combine the spherical shape with the weight of the OE knob. I 3D modeled a sphere of the same diameter that was split down the center. I added a recess for a steel nylon lock nut in the top half and a cavity to contain steel washers to add mass. I also added a Mazda themed logo, which I have since changed to the LOP logo, and some counterbore holes to mechanically fasten the two halves together. I printed out my design using PETG on my CR-10s and purchased the necessary hardware. I weighed the assembly of components to get as close to the target mass as possible. I got within 2.5 % of target.

I was so satisfied with the design that I have since reprinted it on my Bambu X1C with the LOP logo.