Roller-and-Concave Friction Churn: Cream Runs Once Between a Sprung Roller and a Fixed Concave

"The cream only requires to pass between the roller and the concave once in order to produce butter."

Print the frame lying on its cheek, the front cheek, the roller, the shoe, the pinion, the wheel with its crank and the base. The frame, cheek and base need a 240 mm print bed. Print in PETG at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.

Cut a 10 mm dowel 148 mm long as the axle and push it through the roller. Lay the roller in the concave with the axle in the back cheek's slot, and screw the front cheek on with five M4 screws. Lay the shoe over the roller, put a spring on each of two M4 screws, and screw them down through the bridge into the shoe until the springs press the roller into the concave.

Fix the pinion on the axle behind the back cheek with an M3 screw drilled through the dowel. Glue a 10 mm dowel 19 mm long into the back cheek's stud hole, put the wheel on it meshing the pinion, and hold it with an M3 screw and washer through its crank arm into the stud's end. Screw the frame onto the base with four M4 screws and set the base on the container, its opening over the container.

Pour 0.5 litre of heavy cream at about 15 °C, checked with the thermometer, into the hopper and turn the crank steadily, timing it with the stopwatch. The cream runs out under the hopper's front wall, down the apron and between the roller and the concave, and falls with the scraped butter into the container. Gather the butter into a lump with the spatula, 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 20,803, 6 July 1858. His spring plate ran from end to end of the roller, partly encircling it, made yielding by spiral springs, and also scraped the butter off it. He showed a second roller (Fig. 3) and suggested placing it in an ordinary churn box with a concave bottom. His receptacle C had a faucet to let off the buttermilk. He claimed breaking the globules by compression and friction with a roller revolving in, and touching, a stationary concave. Our printed shoe, sizes, gearing and container are ours. FDM prints hold food in their layer lines, so wash well and replace when worn.