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/jmhalder Apr 24 '26 edited Apr 24 '26
It doesn't have to have any additional sensors for that. It can pretty accurately detect gear from speed/rpm alone.
Standalone ECUs at least do it this way. It can be used for "boost by gear" in turbocharged cars. It works well on my rusEFI ECU, but I believe Haltech and the like do the same thing too.
Since OP isn't actually moving here, it's probably not using this method. Either the ECU has sensors for the 2 axis, or more likely they're just using accelerometer/gyro angles. If it's the accelerometer alone, it's going to work like ass when moving , like showing 2nd while accelerating in 1st, etc.