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Trapped-Air Cylinder Dash Churn: A Hollow Dash That Squeezes Air Into the Cream

Charles Murdock, Baltimore, Maryland · Public domain (expired patent)

أنشأه

Emma

6. أكتوبر 2026

Trapped-Air Cylinder Dash Churn: A Hollow Dash That Squeezes Air Into the Cream

Murdock wanted the air carried down through the cream by the common up-and-down dash itself. Charles Murdock of Baltimore, Maryland, received US 6,133, dated 20 February 1849, for "Murdock's Atmospheric Churn": a hollow cylindrical dash, perforated round its lower open end, on the common dash staff, which is bored to slide over a fixed central spindle. The spindle stands in a stationary cylindrical block, smaller than the dash, held to the churn's bottom by a nut. At each stroke the dash fills with air above the cream, carries it down, and when it meets the block the air "is compressed in the cylinder forced radially through the apertures." This rung works out the air squeezed out each stroke, then prints the dash and block, fits them to a churn, and makes butter.

مبتدئ

About 2 hours, plus printing

التعليمات

Air per stroke

جارٍ تحميل دفتر Jupyter…

An air pump in the churn before it

The embedded blueprint puts a pump and a ring dasher in the churn. Murdock makes the dash itself the pump.

Read US 6,133

"The air, however, may be let into the cylinder through a valve in its top or side instead of open end which will do away with the necessity of raising the cylinder above the surface of the cream to receive air. The aperture in the staff must be a little larger than the spindle but must not extend through it nor be intersected by any lateral opening."

Print the dash and block

Print the dash open end up (/uploads/blueprints/trapped-air-cylinder-dash-churn-dash.stl): a 90 mm cylinder with sixteen small holes near its open edge and a socket for the staff. Print the block (/uploads/blueprints/trapped-air-cylinder-dash-churn-block.stl). Print in PETG at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.

المواد لهذه الخطوة:

خيط PETG1 قطعة

الأدوات المطلوبة:

طابعة ثلاثية الأبعاد بالخيط (FDM)

Spindle and block

Drill an 8 mm hole in the centre of a tall food-grade bucket's floor. Pass an M8 threaded rod up through it and the block, with a washer and nut under the floor and silicone round the hole, so the rod stands upright as the spindle.

المواد لهذه الخطوة:

دلو سعة 20 لترًا1 قطعة

قضيب مسنّن1 قطعة

صامولة سداسية1 قطعة

حلقة تثبيت مسطحة1 قطعة

مادة إحكام سيليكونية1 قطعة

الأدوات المطلوبة:

مثقاب لاسلكي

طقم لقم ثقب

مفتاح ربط قابل للضبط

منشار حديد

Staff and lid

Bore a 25 mm hardwood dowel lengthwise, 10 mm, deep enough to slide over the spindle's full height but not through its top, and glue the dash on its foot. Drill the lid for the staff and fit a knob on top.

المواد لهذه الخطوة:

أوتاد من خشب صلب1 قطعة

كتلة خشب صلب1 قطعة

غراء خشب1 قطعة

الأدوات المطلوبة:

مثقاب لاسلكي

طقم لقم ثقب

منشار يدوي

ورق صنفرة

The build in 3D

FreeCAD model of this build, not of the patent: the churn and dash cut away to show the hollow dash with its holes near the open end, the bored staff over the fixed spindle, and the stationary block it closes over.

ملف التصميمBLENDCC0 - Free

تنزيل النموذج

Dash and make butter

Let the heavy cream stand until it reaches about 15 °C, checked with the thermometer. Pour in 1.5 litres. Work the staff up and down, lifting the dash above the cream each time to fill it with air; bubbles burst from the holes at the foot of each stroke. 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.

المواد لهذه الخطوة:

قشدة كاملة الدسم1500 مل

ملح بحري خشن1 قطعة

ماء1 قطعة

الأدوات المطلوبة:

مقياس حرارة بمجس يبقى داخل الطعام

ساعة إيقاف

ميزان مطبخ رقمي

وعاء خلط كبير من فولاذ مقاوم للصدأ

No bubbles, a staff that sticks

Trapped-air cylinder dash churn troubleshooting.

Flow

History and honest limits

**Charles Murdock** of Baltimore, Maryland, received US 6,133, dated 20 February 1849, signed 21 November 1848. The dash could be formed in the underside of the dash block, or as a cylinder fixed to the dash's periphery; in a stone churn the spindle's hole could be drilled and bushed. He claimed the combination of the hollow perforated cylinder dash and the central guide spindle and stationary block with the ordinary upright tub churn. **Honest limits.** A bucket, threaded rod and printed parts stand in for his churn, spindle and dash. FDM prints hold food in their layer lines, so wash well and replace when worn. Your times and weights are the result.