Spray-Jet Dishwasher Arm

Josephine Cochrane's machine, already published, held the dishes in wire racks and threw water at them from fixed jets while the rack was turned. Robert Tatham's rung makes the water do the moving: jets angled off the radius push the arm round, so a pump and one moving part wash a stationary load from every direction. **US 1,900,529**, "Dishwasher", Robert L. Tatham, filed 29. June 1929, granted 7. March 1933: apparatus for "washing dishes by discharging water with considerable force, in the form of jets or sprays", delivered by a pump. Every domestic dishwasher since has a reaction-driven spray arm. **You build the arm** from PVC pipe on a bearing, fed by a submersible pump, and measure its speed and how much of a dirty plate it actually cleans.