Rocking-Chair Crossed-Groove Churn: Rocking a Seat Turns a Wheel That Gives the Dasher Two Strokes a Turn

"This movement of the chair vibrates the treadle E which in consequence of its connection with the shaft F, by means of the rod (d) and crank, rotates said shaft F, and wheel G, the latter in consequence of the guides (f), (f), of the rod or bar H, fitting in the grooves (e), (e), giving, through the medium of the rod or bar H, and lever I, the dash rod K, a reciprocating motion, two complete strokes being given said rod at every revolution of the shaft F, and wheel G."

Print the grooved wheel (/uploads/blueprints/rocking-chair-crossed-groove-churn-grooved-wheel.stl) and two guides (/uploads/blueprints/rocking-chair-crossed-groove-churn-guide.stl). Print in PETG at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.

Build a pine frame about 600 × 300 mm on 160 mm legs. Hang a small seat on two pendants from a rod across uprights, so it rocks; link its front by a rod to a treadle hinged low on the frame, and the treadle by a rod to a crank on a 10 mm square shaft across one end. Fix the wheel on the shaft outside the frame.

Bolt the guides 70 mm apart on a pine bar so both slide in the grooves. Pivot the bar's top on a lever whose fulcrum stands on a post, and hang the dash rod from its other end into a food-grade container on a shelf at the far end.

Let the heavy cream stand until it reaches about 15 °C, checked with the thermometer. Pour in 1.5 litres. Rock the seat steadily by hand; the dasher strokes twice for each turn of the wheel. 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.

**H. D. Baker** of Pittstown Corners, Rensselaer County, New York, US 19,334, 16 February 1858. His operator sat in the chair, one foot on the treadle and one on the platform. He claimed the whole combination, not any part alone. He wrote that a crank in place of the wheel would need multiplying gearing for the same speed. Ours is tabletop size and rocked by hand; sizes are ours. FDM prints hold food in their layer lines, so wash well and replace when worn.