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Piston-Float Air Churn: Hollow Floats With Pistons Worked by a Fixed Eccentric
D. N. Egbert, Hudson, Ohio · Public domain (expired patent)
Emma

Created by

Emma

6. October 2026SE
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Piston-Float Air Churn: Hollow Floats With Pistons Worked by a Fixed Eccentric

Egbert wanted the air "forcibly discharged in small jets at the very point where it is most required, viz, the moving surface of the dasher." D. N. Egbert of Hudson, Ohio, received US 6,727, dated 18 September 1849, for a rotary churn-dasher in a case with a zinc bottom: two sets of arms joined by hollow floats whose sides are pierced with small holes, each fitted with a piston. Connecting rods join the pistons to an eccentric ring running on an eccentric fixed to the end piece, so each float fills with air as it ascends and discharges it as it descends. A strap from a large pulley on the crank shaft to a small one on the dasher's shaft turns it fast. This rung works out the air each float pumps, then prints the floats, pistons, eccentric and arms, builds them over a stainless bottom, and makes butter.
Advanced
About 6 hours, plus printing

Instructions

1

Air per float

Loading Jupyter Notebook...
2

A dasher that is also an air pump before it

The embedded blueprint pumps air with a tube over a loose plunger. Egbert builds the pump into each float of a rotary dasher.
3

Read US 6,727

"It will now be perceived that as the floats ascend above their horizontal position by the revolution of the dasher, each piston is in turn withdrawn in its appropriate float and the hollow cavity filled with air; as the floats descend below their horizontal position this air is forcibly discharged through the perforations of the floats, below the surface of the liquid."
4

Print the parts

Print two hollow floats (/uploads/blueprints/piston-float-air-churn-hollow-float.stl) and two pistons (/uploads/blueprints/piston-float-air-churn-piston.stl), the fixed eccentric (/uploads/blueprints/piston-float-air-churn-eccentric.stl) and its ring (/uploads/blueprints/piston-float-air-churn-eccentric-ring.stl), two arm sets (/uploads/blueprints/piston-float-air-churn-arms.stl) and the crank arm (/uploads/blueprints/piston-float-air-churn-crank-arm.stl). Print in PETG at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.

Materials for this step:

PETG FilamentPETG Filament1 piece

Tools needed:

FDM 3D PrinterFDM 3D Printer
5

The case

Make two plywood end pieces with a 90 mm radius half circle grooved in each, and bend a 0.5 mm stainless sheet into the bottom, seated in the grooves with silicone, as his zinc bottom. Screw the eccentric to the inside of one end on the axis, offset upward as printed.

Materials for this step:

Plywood SheetPlywood Sheet1 piece
Stainless Steel Sheet - 304Stainless Steel Sheet - 3041 piece
Silicone SealantSilicone Sealant1 piece
#8 x 1" Wood Screw#8 x 1" Wood Screw1 piece

Tools needed:

Coping SawCoping Saw
Tin SnipsTin Snips
Deburring ToolDeburring Tool
Rubber MalletRubber Mallet
Screwdriver SetScrewdriver Set
6

Dasher, pistons and rods

Slide the two arm sets onto a 10 mm square hardwood shaft and screw a float to the ends of each pair of arms, holes outward. Fit a piston in each float. Fit the ring over the eccentric and join each piston to the ring with two thin pine rods on M3 screws, so the ring is carried round by the arms. Pass the shaft through the other end and glue the crank arm and handle on.

Materials for this step:

Hardwood DowelsHardwood Dowels1 piece
Pine BoardPine Board1 piece
Machine ScrewsMachine Screws1 piece
Hex NutHex Nut1 piece
Wood GlueWood Glue1 piece

Tools needed:

Hand SawHand Saw
Cordless DrillCordless Drill
Drill Bit SetDrill Bit Set
Screwdriver SetScrewdriver Set
7

The patent drawing

US 6,727 drawing sheet, public domain (expired patent).
Step 7 - Image 1
8

Crank and make butter

Let the heavy cream stand until it reaches about 15 °C, checked with the thermometer. Pour in 1.5 litres. Crank steadily and watch for jets of bubbles as each float goes down; 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.

Materials for this step:

Heavy CreamHeavy Cream1500 ml
Coarse Sea SaltCoarse Sea Salt1 piece
WaterWater1 piece

Tools needed:

Leave-In Probe ThermometerLeave-In Probe Thermometer
StopwatchStopwatch
Digital Kitchen ScaleDigital Kitchen Scale
Stainless Steel Mixing Bowl (Large)Stainless Steel Mixing Bowl (Large)
9

Pistons that stick, no jets

Piston-float air churn troubleshooting.

Flow

Loading...
10

History and honest limits

**D. N. Egbert** of Hudson, Summit County, Ohio, received US 6,727, dated 18 September 1849. A tightening pulley on a spring lever kept the strap taut. He claimed the combination of the pistons moved by stationary eccentrics with the floats of a revolving dasher. **Honest limits.** Our crank turns the shaft directly, without his strap and pulleys; stainless sheet and printed parts stand in for his zinc and wooden floats. The notebook gives an upper bound. 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

13

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CC0 Public Domain

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