3D Printed Motor/Trans Mock-up

The interface between the motor and the RX8 transmission is the most critical mechanical design of the entire build. I have to ensure that the shafts are aligned within thousands of an inch while rotating at 10,000 rpm and the spacing is perfect to ensure full clutch engagement and disengagement. Unfortunately there are no off-the-shelf parts that I can use for this, it all has to be custom. This means that I have to design it all from my measurements of the old RX8 gas motor, the new electric motor, and the transmission. I would then take all these measurements, create a CAD model of the design, and then send it off to get machined while blindly praying and hoping that I didn’t get anything wrong. Well luckily I have another step here that I can take… 3D Printing.

I decided to take the huge outer adapter and split it up into 3 sections that my printer could handle. I also cranked the printer up to ridiculous part strength mode because I planned to actually use these parts to bolt the motor and transmission together. As you can see below it actually turned out even better than I had expected. I was able to bolt it all up tight together and check the shaft alignment, shaft end-to-end spacing, and even threw on a 3D printed shaft coupler to validate that the clutch could fully engage.

After getting back an outrageously high quote from a machine shop up here, a friend’s dad mentioned that he could help get it machined through his company. This turned out to be a huge benefit not only to cost, but to design improvement as I was able to sit down with him for a few hours over the weekend and talk tolerances and design improvements to ensure a truly professional and bulletproof design. I’ll update the CAD files to reflect our discussions, confirm everything in a full system mock-up, and then send the final designs to start the machining process!