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Ventilating Paddle Rocking Churn: Hinged Paddles That Strike One Way and Slip the Other
George W. Cook, Schenectady, New York · Public domain (expired patent)
Woody

Created by

Woody

6. October 2026NO
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Ventilating Paddle Rocking Churn: Hinged Paddles That Strike One Way and Slip the Other

Cook set out to let "a current of fresh air" into the churn "to hasten the production of the butter and to improve its quality." George W. Cook of Schenectady, New York, received US 3,460, dated 28 February 1844, for "Cook's Ventilating Churn": a semi-cylinder balanced on pivots so it rocks easily, its top closed by thin boards except a narrow opening in the middle. Inside, two frames at about 45° from the vertical, inclined opposite ways, carry perforated paddles hung on gudgeons. As the vessel is canted, one set swings square to its frame and strikes the cream while the other turns flat against its stops. This rung works out how the paddles hang, then prints the ends, frames and paddles, bends a stainless semi-cylinder, and makes butter.
Advanced
About 6 hours, plus printing

Instructions

1

How the paddles hang

Loading Jupyter Notebook...
2

A rocking churn on pivots before it

The embedded blueprint rocks a box on gudgeons with springs to return it. Cook balances his vessel on pivots and puts hinged paddles inside.
3

Read US 3,460

"When the vessel is canted, as represented in Fig. 2 the paddles N drop down or turn on their gudgeons assuming a position nearly at right angles to the sides of the frame of the paddles. At the same time the paddles N2 of the other frame turn until they are in a line parallel with the sides of the frame when they strike against pins or stops O2 inserted into the sides of the frame on the inside thereof."
4

Print the parts

Print two vessel ends flat (/uploads/blueprints/ventilating-paddle-rocking-churn-end.stl), each with its groove, pivot boss and the two ledges for the frames. Print two frames (/uploads/blueprints/ventilating-paddle-rocking-churn-frame.stl) and eight perforated paddles (/uploads/blueprints/ventilating-paddle-rocking-churn-paddle.stl). Print in PLA at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.

Materials for this step:

PLA FilamentPLA Filament1 piece

Tools needed:

FDM 3D PrinterFDM 3D Printer
5

Bend and close the vessel

Cut a 0.5 mm stainless sheet 160 mm wide and about 252 mm long, deburr it, and bend it round a 160 mm form into a half circle. Seat it in both ends' grooves in silicone. Cut two thin plywood boards to close the top, sloping 10–15° down toward the middle and leaving a narrow opening there, as his.

Materials for this step:

Stainless Steel Sheet - 304Stainless Steel Sheet - 3041 piece
Silicone SealantSilicone Sealant1 piece
Plywood SheetPlywood Sheet1 piece

Tools needed:

Tin SnipsTin Snips
Deburring ToolDeburring Tool
Rubber MalletRubber Mallet
ClampsClamps
Coping SawCoping Saw
6

Hang the paddles and the vessel

Hang four paddles in each frame on M3 screws through the frame's sides, so they swing freely and lie against the stops one way. Set the two frames on the ledges inside the vessel, inclined opposite ways. Build a pine stand with two posts and hang the vessel on an M8 bolt through each end's boss, so it is nicely balanced.

Materials for this step:

Machine ScrewsMachine Screws1 piece
Hex NutHex Nut1 piece
Pine BoardPine Board1 piece
#8 x 1" Wood Screw#8 x 1" Wood Screw1 piece
Wood GlueWood Glue1 piece

Tools needed:

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

The build in 3D

FreeCAD model of this build, not of the patent: the semi-cylinder hung on its pivots in a pine stand, one end off to show the two frames of hinged perforated paddles inclined opposite ways, and the top boards.
Design FileBLENDCC0 - Free
Download Model
8

Rock and make butter

Let the heavy cream stand until it reaches about 15 °C, checked with the thermometer. Pour 500 ml through the middle opening. Rock the vessel steadily from side to side; time until the butter comes. Lift out the frames, then 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.
Step 8 - Image 1

Materials for this step:

Heavy CreamHeavy Cream500 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

Paddles that stick, a vessel that tips

Ventilating paddle rocking churn troubleshooting.

Flow

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History and honest limits

**George W. Cook** of Schenectady, New York, received US 3,460, dated 28 February 1844. Blocks on the vessel's convex side met a cross bar of the frame to stop it canting too far; handles in its side rocked it; iron straps strengthened it; a plugged aperture drew off the milk; a button held the two frames in place. He claimed combining with a rocking churn "floats or paddles arranged in and hinged to a frame." **Honest limits.** Stainless sheet, plywood and printed parts stand in for his wooden vessel and frames. FDM prints hold food in their layer lines, so wash well and replace when worn. Your times and weights are the result.

Materials

12

Tools Required

15

Design Files

1

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CC0 Public Domain

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