Screw-Lift Churn: An Archimedean Screw Keeps the Whole Body of Cream Moving

"The cream having been admitted into the churn in sufficient quantity, the crank c is turned, which causes the shaft C to revolve, and the cream entering from the larger cylinder A, through the perforations b at the bottom, into the smaller cylinder B, the screw D will consequently raise the cream to the top of the smaller cylinder, and then discharge it again into the larger one, the butter accumulating on the top of the space between the two cylinders."

Print the inner cylinder upright (/uploads/blueprints/screw-lift-churn-inner-cylinder.stl): ten holes near its foot and a flange at 60° round its top. Print the screw upright with supports under the blade (/uploads/blueprints/screw-lift-churn-screw.stl), and the crank arm (/uploads/blueprints/screw-lift-churn-crank-arm.stl). Print in PLA at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.

Stand the inner cylinder in the centre of a stock pot about 240 mm across, its top below the pot's rim, and bed its three feet in silicone. Cut a plywood lid for the pot with a hole at the centre for the shaft, and cut a segment from it as a small lid that lifts off, as his.

Glue the screw on a 10 mm square hardwood shaft so the blade starts just above the floor. Stand the shaft's foot in the hole in the inner cylinder's floor, pass it through the lid, and glue the crank arm and a dowel handle on top.

Let the heavy cream stand until it reaches about 15 °C, checked with the thermometer. Pour in 1.5 litres, enough to stand above the inner cylinder's holes. Fit the lid and crank steadily; time until the butter gathers on top between the cylinders. Pour off the buttermilk, add cold water, churn a little and pour off again until it runs clear; work in a pinch of salt and weigh the butter.

**Thomas Ling** of Portland, Cumberland County, Maine, received US 3,714, dated 21 August 1844. The crank was held on the shaft by a nut or screw on its top; the lids had knobs to lift them. He claimed the large cylinder, the small cylinder with its perforations and flange, and an apparatus for withdrawing, raising and discharging the cream, "not however confining myself to the screw D for that purpose, but substituting any other contrivance, by which the same result can be obtained." **Honest limits.** A stock pot and printed parts stand in for his cylinders and screw. The notebook gives an upper bound, not a measured flow. FDM prints hold food in their layer lines, so wash well and replace when worn. Your times and weights are the result.