Spring-Wing Friction Churn: Sprung Wings Rub the Tub and Each Other, Two Plates Rub Below

"The wings serve for causing friction and expressing the cream or milk between themselves and the inner circumference of the churn tub, while the bottom plate H, serves for causing friction and expressing the cream or milk between itself and the bottom of the churn tub."

Print the skeleton (/uploads/blueprints/spring-wing-friction-churn-skeleton.stl), its top ring (/uploads/blueprints/spring-wing-friction-churn-top-ring.stl), four outer wings (/uploads/blueprints/spring-wing-friction-churn-outer-wing.stl), the inner dasher with its tube (/uploads/blueprints/spring-wing-friction-churn-inner-dasher.stl), four inner wings (/uploads/blueprints/spring-wing-friction-churn-inner-wing.stl), pinions D (/uploads/blueprints/spring-wing-friction-churn-pinion-d.stl) and E (/uploads/blueprints/spring-wing-friction-churn-pinion-e.stl), wheel F (/uploads/blueprints/spring-wing-friction-churn-wheel-f.stl), the step (/uploads/blueprints/spring-wing-friction-churn-step.stl), the cover (/uploads/blueprints/spring-wing-friction-churn-cover.stl), the standard (/uploads/blueprints/spring-wing-friction-churn-standard.stl) and the crank (/uploads/blueprints/spring-wing-friction-churn-crank.stl). Print the wings standing up: their 1.2 mm walls are the springs. Print in PETG at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.

Cut a 10 mm square hardwood strip 325 mm long as the solid shaft and sand it. Slide the skeleton on, plate down, its plate 7 mm above the shaft's foot, and fix it with an M3 screw drilled through the boss and the shaft. Screw an outer wing to each standard with two M3 screws, all curving the same way, and an inner wing to each post of the inner dasher, curving the other way.

Set the step in the pot and lower the skeleton in, the shaft's foot in the step and the wings springing against the wall. Lower the inner dasher's tube over the shaft, easing its wings past the standards, and screw the top ring onto the standards with four M3 screws. Lay the cover on with a washer over the tube, slide pinion D onto the tube's flat and fix pinion E on the shaft with an M3 screw drilled through it. Screw the standard to the cover from below with two M4 screws, push a 10 mm dowel through it, press wheel F tight on its inner end to mesh D below and E above, and fix the crank on its outer end with an M3 screw drilled through the dowel.

Pour in 3 litres of heavy cream at about 15 °C, checked with the thermometer. Turn the crank steadily and time it with the stopwatch. When the butter comes, lift out the cover and dashers, pour off the buttermilk, wash the butter in cold water until it runs clear, work in a pinch of salt and weigh it.

**James MacNish** of Berlin, Marquette County, Wisconsin, US 20,804, 6 July 1858, for churns "for making butter by friction". The two shafts and bevel wheels, he wrote, were like churns in common use. He claimed the inner set of tangential spring wings with the outer set, and the friction plates H and J with both sets and the tub. His plate H worked close on the tub's bottom; ours runs 8 mm over it, above a flat step. Our pot, sizes, gear counts and printed spring wings are ours. FDM prints hold food in their layer lines, so wash well and replace when worn.