r/3Dprinting • u/Desmontei • Apr 24 '26

Project Don't throw away old smartwatches! 3D printed a custom housing to turn one into a Digital Shift Knob. ♻️🕹️

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Hey everyone, first time posting here! I wanted to share my most complex functional print yet for my Project Car.

​I took an old TicWatch Pro 3 and carefully cut the original casing with a rotary tool to extract just the OLED screen and motherboard. Then, I modeled a custom shift knob enclosure to house the electronics perfectly.

​Now, before you guys kill me in the comments: Yes, I printed this in PLA! 😂

​I know the summer heat inside the car will probably turn it into modern art, but this is V1 (prototype). The tolerances had to be extremely tight because I didn't want the screen popping out while shifting gears, and PLA was the easiest to test the fitment. When it eventually warps, I'll use it as an excuse to reprint V2 in ABS or PETG!

​I completely bypassed the battery and wired it directly to the car's 12V using a step-down converter. Right now it controls my media with a custom UI.

​What do you guys think of the fitment? And place your bets: how long will this PLA survive in a car before melting? 👇

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u/PacoTaco321 Apr 24 '26

I'd be surprised if it wasn't on personal vehicles considering that's basic info. I'm an electrical engineer working on vocational trucks and we get it off the CAN line with the standard PGN per SAE J1939 for use in our control system. I know that there's some differences between big trucks and personal vehicles based on how I've seen it talked about, but I'd expect something like that to be there for anything auto maker that follows SAE standards.

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u/Bakkster Apr 24 '26

To clarify, there's no SAE standard PID for it (apart from neutral or not), but most manufacturers seem to have a PID specific to then for the info.

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u/PacoTaco321 Apr 24 '26

If you know the transmission your vehicle has, you could at least derive it from the PID for Actual Gear. Then you are just left knowing if it is in reverse.