Three-Stroke Swing Churn: An Undulating Slot Gives the Dasher Three Strokes Each Swing

"The lid being pressed down, motion is given to the swing frame E, by means of the handle I, and as the frame swings the cross bar with the friction rollers plays in the slots D, and F, giving three distinct motions to the dasher, thereby causing a greater amount of agitation to the milk at each swing or oscillation of the cream vessel than is performed by any other machine of the same kind."

Print two slot plates (/uploads/blueprints/three-stroke-swing-churn-slot-plate.stl), the roller bar (/uploads/blueprints/three-stroke-swing-churn-roller-bar.stl) and two rollers (/uploads/blueprints/three-stroke-swing-churn-roller.stl). Print in PETG at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.

Build a pine A-frame about 520 mm high, two legs each side, and hang a swing frame of two pine uprights and a floor board from a 10 mm rod at the top, with a pine handle out from its floor. Bolt a slot plate inside each pair of legs so its slot's centre is 300 mm below the pivot.

Stand a food-grade container on the swing's floor. Push a 10 mm dowel dasher rod through slots in the swing's uprights into the roller bar's socket, the rollers on its stub axles in the slot plates, and fix a perforated pine dasher on its foot inside the container.

Let the heavy cream stand until it reaches about 15 °C, checked with the thermometer. Pour in 1.5 litres and fit the lid. Swing the frame steadily by the handle; the dasher strokes three times each way. Time until the butter comes. 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.

**Charles H. Dana** of West Lebanon, Grafton County, New Hampshire, US 17,781, 14 July 1857. He did not claim an oscillating churn, nor more than one stroke per swing as such; he claimed the irregular curved pieces forming the undulating slot with the slotted swing frame and roller cross bar. Our slot's waves and sizes are ours; his drawing gives none. FDM prints hold food in their layer lines, so wash well and replace when worn.