Here we are in the future, thinking we’re so fancy and cutting edge with mega-scale 3D printers that can extrude complete, ready-to-occupy buildings, only to find out that some clever inventor came up with essentially the same idea back in the 1930s.
The inventor in question, one [William E. Urschel] of Valparaiso, Indiana, really seemed to be onto something with his “Machine for Building Walls,” as his 1941 patent describes the idea. The first video below gives a good overview of the contraption, which consists of an “extruder” mounted on the end of a counterweighted boom, the length of which determines the radius of the circular structure produced. The boom swivels on a central mast, and is cranked up manually for each course extruded. The business end has a small hopper for what appears to be an exceptionally dry concrete or mortar mix. The hopper has a bunch of cam-driven spades that drive down into the material to push it out of the hopper; the mix is constrained between two rotating disks that trowel the sides smooth and drive the extruder forward.
The device has a ravenous appetite for material, as witnessed by the hustle the workers show keeping the machine fed. Window and door openings are handled with a little manual work, and the openings are topped with lintels to support the concrete. Clever tools are used to cut pockets for roof rafters, and the finished structure, complete with faux crenellations and a coat of stucco, looks pretty decent.
But [Mr. Urschel] wasn’t one to rest on his laurels, for as retrotechtacular printed buildings 1930s style
