This is modeled after BNSF ES44C4. There is an engine with my logo and without, which just has flat sides. Choose between solid or spoked wheels or mix and match.
Truck pivot bolt = M5 10mm x 2
Truck post = M3 8mm x 2
Wheel bolt = M3 12mm x 8
I printed the engine at 200 microns and the wheels and trucks at 400 microns. Choose from solid or spoked wheels.
The trucks pivot on the center hole using the M5 bolt. Don't tighten this bolt all the way down. The trucks should be able to spin and rock. The trucks are kept from spinning freely by the M3 8mm bolts.
Use M3 12mm for the wheels.
I am still working on a solution for magnetic buffers.