I think the idea was to avoid excavating all the ground in the middle. You just cut around the circumference of the piston and along the bottom. The thing I nev

I think the idea was to avoid excavating all the ground in the middle. You just cut around the circumference of the piston and along the bottom. The thing I never could understand was how they’d seal the walls of the cylinder against the bore so that water doesn’t fill that space and gush right out the top!