#video by #Practical-Engineering on #building #tunnels #underground. Almost entirely talking-head filler and stock footage, though there’s a chart plotting unsupported roof span against “stand up time” at 10'17", with “competent rock” of high rock mass rating being able to stand up without support for a long time, not even rock bolts (anchors), much less more advanced supports. #digging
on 02026-02-18#video by #Practical-Engineering on "pulser pump" water pumping #mechanisms with no moving parts that we believe existed at the Alhambra until the 18th century, recreated by Cáceres in the 20th. The YouTuber here recreated it using acrylic “sheet goods” cut by his friend’s service bureau. He entrains air in the downward flow of water, as in a trompe, and separates the air out of the water at a lower elevation, also as in a trompe. But then he lets the compressed air out of a long riser pipe, and it hasn’t completely separated, so some water is still entrained in it, but less than on its downward trip, so it can raise the water above its initial level. Basically it’s a trompe connected to an #airlift-pump. As with a geyser pump or a #hydraulic-ram pump (also depicted), only a small fraction of the water is pumped upwards. Dean Millar’s paper calls trompes “hydraulic air compressors (HACs)”.
on 02026-01-06#video #toread by #Practical-Engineering predicting electric grid collapse aftermath
on 02024-11-05