Excavator

Ok, super half baked, but what the hell.

Drop

The digger consists of two sharp steel plates with a slight bend to them - like the head of a shovel only a bit wider. The curve is also a lot shallower. The two halves come together and over lap just as far as that curve. The whole thing is hoisted into the air and dropped, the weight of the mechanism driving it into the ground. The hoist mechanism and the weights works together to push the jaws closed. The whole thing operates on two sliding rails so it can be moved over a bucket and unloaded.

Bike

Digs a long straight, wide trench. 4 wheels, no steering. Right behind the front wheels is a set of spinning blades like a tiller. Behind that is a ramp and behind that is the bucket. Then the back wheels. Front wheels are 1ft higher than everything else. They ride on top of what is about to be dug.

Pedaling spins the blades. A very high reduction can also transfer that from the blade to the back wheels. To use it, you'd have to manually dig out an area to set it down. Then start pedaling to get the tiller up to speed, then engage the wheels.

Ideally, the back section would be a square so that I could dig a starter, then use it to dig a trench, then go perpendicular to the trench.

Block

More of process and one that requires several machines, but each is simpler.

The initial "block" would be dug by hand. Then one device would cut down defining two opposing edges. The third edge would be cut then a grate would be inserted. Pointed rods (probably just rebar) can be driven from the starter hole. These engage the grate. A small manual crane can then lift the entire block.

Rail Buckets

The real challenge is less about digging and more about moving it to a location for Soil Processing. I think I could easily move a cubic foot per minute, and I could probably do that 2 hours a day. So 120 cubic feet a day. If that is 40% clay and I'm 80% efficient in extracting it, that's about 38 cubic feet per day. Enough for about 85 bricks. That would cost about $200. So as long as the processing is automated, a shovel might be doable.

So what I need is a modular system that can transfer a bucket. Honestly, just a platform on wheels with a rope would probably work fine. The top would have a cradle with an arm to lift and dump the dirt.