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Self-Closing Float Dasher Churn: Floats That Open to Churn and Close to Gather
Davis wanted one dasher that would churn "in the most effectual manner," then gather the butter and work out the buttermilk.
Robert W. Davis of Rodgersville, New York, received US 7,233, dated 2 April 1850, for self-adjusting rotary churn-dashers. The dasher's fixed slats are set "at such angles as to force the cream toward the center"; movable floats hinged to its sides stand open when turning that way and move it outward, "which various and contrary motions so agitate it, that the butter is soon formed." Turned backward, the floats close on the slats so the outside forms "a uniform curve concentric to the axis," which throws the butter to the sides and bottom and presses it free of milk.
This rung looks at the floats' swing, then prints the sides, slats and floats, assembles the dasher in a box, and makes butter.
Intermediate
About 4 hours, plus printing
Instructions
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The floats' swing
The floats' swing
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A dasher that churns one way and gathers the other before it
A dasher that churns one way and gathers the other before it
The embedded blueprint reverses fixed paired blades to roll the butter up. Davis lets hinged floats change shape by themselves when the crank is reversed.
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Read US 7,233
Read US 7,233
"In order to gather the butter and work it, the dasher is then turned in the contrary direction, and the movable slats then closing the outside of the slats of the dasher form a uniform curve concentric to the axis and moving with the convex side foremost. By a few revolutions of the dasher the butter is thrown from the center to the sides and bottom of the churn box, and these gathered into a roll."
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Print the parts
Print the parts
Print two side pieces (/uploads/blueprints/self-closing-float-dasher-churn-side.stl), four fixed slats (/uploads/blueprints/self-closing-float-dasher-churn-slat.stl), four curved floats with hinge eyes (/uploads/blueprints/self-closing-float-dasher-churn-float.stl) and the crank arm (/uploads/blueprints/self-closing-float-dasher-churn-crank-arm.stl). Print in PLA at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.
Materials for this step:
PLA Filament1 pieceTools needed:
FDM 3D Printer5
5
Assemble the dasher
Assemble the dasher
Slide the two side pieces onto a 10 mm square hardwood shaft 148 mm apart and screw the four slats between them. Hang each float between the arms' knuckles on a 3 mm stainless rod as its hinge, so it swings open one way and lies against its slat the other.
Materials for this step:
Hardwood Dowels1 piece
Mild Steel Rod1 piece
Machine Screws1 piece
Wood Glue1 pieceTools needed:
Hacksaw
Screwdriver Set
Hand Saw6
6
The box
The box
Take a food-safe box about 230 × 190 × 200 mm. Drill both ends on the axis 100 mm up, pass the shaft through with a leather washer at each end, and glue the crank arm and a dowel handle on.
Materials for this step:
Food-Grade Storage Container1 piece
Leather Strip1 piece
Wood Glue1 pieceTools needed:
Cordless Drill
Drill Bit Set7
7
The build in 3D
The build in 3D
FreeCAD model of this build, not of the patent: the box with one side off to show the dasher's side pieces, the fixed slats and the hinged curved floats, and the crank.
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Churn forward, gather backward
Churn forward, gather backward
Let the heavy cream stand until it reaches about 15 °C, checked with the thermometer. Pour in 1.5 litres. Crank forward, floats open; time until the butter comes. Then crank backward so the floats close and the round dasher gathers the butter into a roll; draw off the buttermilk and keep cranking to work it, as he did. 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.

Materials for this step:
Heavy Cream1500 ml
Coarse Sea Salt1 piece
Water1 pieceTools needed:
Leave-In Probe Thermometer
Stopwatch
Digital Kitchen Scale
Stainless Steel Mixing Bowl (Large)9
9
Floats that won't open or close
Floats that won't open or close
Self-closing float dasher troubleshooting.
Flow
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History and honest limits
History and honest limits
**Robert W. Davis** of Rodgersville, Steuben County, New York, received US 7,233, dated 2 April 1850. His drawing shows the dasher in a churn box with slats D strengthening it. He claimed "the self adjusting float or slat (C) which opens when churning the cream and closes of itself when the dasher is turned in the opposite direction to gather the butter."
**Honest limits.** A food-safe box and printed parts stand in for his wooden box and dasher. FDM prints hold food in their layer lines, so wash well and replace when worn. Your times and weights are the result.
Materials
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Tools Required
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Design Files
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CC0 Public Domain
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