Here is a solid carbon axle for the GT12 Club Race Hero. You will need a ؼ" carbon fiber tube. A 110mm long tube will give a 172mm track, you can cut it a little shorter. To secure the wheel to carbon tube you need a M3 nut and grub/set screw. I haven't tested the spur gear and pinion but they have a 64 pitch. I have used 3d printed gears with a 48 pitch and they work perfect with a 0.4mm nozzle. If you have issue and strip the these gears with a 0.4mm maybe try a 0.2mm nozzle.

On my car using the 3D printed side pods “search my profile” I ended up suing the 6mm. The axle is designed to use symmetrical bushings. The motor clamp is a model from Ken Ausplund and it should be printed out of a high temp material.