Pretty much anything not covered by the topics above. Short lived production bikes or vehicles, Electrical, Tires, Paint, Brakes, etc. Use this for tech questions, and "Shoot the Bull" for general conversation, no tech.
I doubt machinery was part of the tooling used. To me it looks like the skills of an early watch maker, furniture maker, and an extremely talented engineer. Amazing piece of work and art. And fully functional to boot.