I want to make a tunnel boring machine for digging ~2 meter tall tunnels in sandstone.
Sadly I live in a place with only sand in the underground and that's not suitable for digging tunnels DIY style
We have so much fun with our TBM's in my area. My neighbor, Ralf, built a 3M BEAST! You wouldn't believe the daily progress he makes. It's got integrated support walls and everything. Our club is in a bit of a feud with the hacks 3 subdivisions over. They keep boring too close to our tunnels. Not. Cool. Man.
Anyway, at least you can cut and cover with sand, a perfectly viable tunnelling strategy with lower startup costs.