Crank-and-Link Double-Dasher Churn: Two Dashers' Cranks Joined by a Curved Link, One Lever Turns or Rocks Both

"The object of my invention is to so arrange the mechanism that by a rectilinear movement of the operator either a vibratory or rotary motion may be given to the dashers."

Make an oval box A whose inside is two 90 mm half rounds 140 mm apart joined by straight sides, 300 deep: a hardwood floor and two straight hardwood sides, with 1.5 mm stainless sheet bent round the ends in grooves, all sealed with silicone. Seal a printed cup for each dasher's foot on the floor at the half rounds' centres. Cut an HDPE cover to the outside with a 27 mm hole over each cup. Screw a hardwood ear C 30 x 60 mm, 140 long, to each end, standing above the box, with a mortise c 24 mm wide and 20 deep near its top.

Turn two hardwood dasher shafts 25 mm across, 320 long, and set a 16 mm stainless rod 80 mm long 20 mm into each top, with a flat filed on its end as the tenon of the coupling f. Mortise four hardwood wings 120 x 120 x 12 mm through each, two crossed at 35 to 155 mm up and two crossed at 160 to 280, turned 45 degrees from the lower pair.

Glue up a hardwood cap D 400 x 120 x 60 mm, cut a recess d 260 x 100 mm, 42 deep, in its underside, and a slot through its front wall for the lever. Glue a tenon b 24 x 20 mm on each end to drop into the ears' mortises, and fit a hook and eye at each end to hold it. Bore it 16.6 mm through over each dasher. Make each crank e of a 16 mm stainless shaft through the cap with a slot in its foot to take the dasher's tenon (the coupling f), and a mild steel flat bar arm, 35 mm throw, with an 8 mm pin. Bend a 6 mm steel rod into a half round joining the two pins, eyes at its ends, and fix a pivot eye at its middle. Pivot a hardwood lever h, 500 long with a handle, on the eye so it comes out through the cap's slot.

Stand the dashers in their cups, pour about 12 litres of heavy cream at about 15 °C, checked with the thermometer, into the box, put on the cover over the shafts, and lower the cap so the cranks' slots take the dashers' tenons and its tenons drop into the ears; hook it. Move the lever's end round in a small circle to turn the dashers, or push it straight to and fro to rock them, timing it. When the butter comes, unhook and lift off the cap, lift out the dashers, take out the butter, pour the buttermilk into a bowl, wash the butter in cold water until it runs clear, salt and weigh it.

**Robert Parker** of North Cohocton, Steuben County, New York, US 33,213, 3 September 1861, "Improved Churn". He claimed "the combination of the cranks, the curved link, and the operating-lever". His box was oval and staved; ours has straight sides and stainless ends. He does not describe the dashers beyond "wing-dashers"; ours follow his Fig. 1. The patent gives no sizes; every size here is ours.