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Planetary Stand Mixer
The rotary egg beater already published spins two blades on fixed axes - so the cook must keep moving it, and a stiff dough stalls it. Herbert Johnston, an engineer at Hobart, watched a baker turning dough with a spoon and built the next rung: the beater turns on its own axis while a carrier walks it round the bowl, so the blade sweeps everywhere without the bowl or the beater being moved by hand.
**US 1,264,128**, "Mixing-machine", Johnston and Rataiczak, assigned to Hobart Manufacturing, filed 1. March 1915, granted 23. April 1918. Hobart's big bakery machines came first; the domestic KitchenAid followed in 1919.
**You build the motion, not the appliance**: a planetary gear set with a pen for a blade, drawing its own path on paper, and a coverage measurement against a fixed-axis beater.
Intermediate
3 hours
Instructions
1
1
Read the gear set
Read the gear set
Count the teeth on the ring and on one planet. Measure the ring's inside diameter and a planet's outside diameter with the caliper; the pitch radii are close to half of each.
Materials for this step:
Planetary Gear Set (Steel)1 setTools needed:
Digital Caliper 6-Inch2
2
Mount it over paper
Mount it over paper
Screw the ring gear flat to a plywood board. Tape graph paper under it, centred. Fit one planet so it rolls inside the ring.
Materials for this step:
Plywood Sheet1 piece
Graph Paper1 sheet
Masking Tape1 rollTools needed:
Hand Saw
Cordless Drill3
3
Give the planet a blade
Give the planet a blade
Glue a short dowel upright in a hole in the planet, four-fifths of the way out from its centre, and tape a marker to it so the tip just touches the paper.
Materials for this step:
Dowel Rod1 piece
Permanent Marker1 pieceTools needed:
Hot Glue Gun4
4
Walk it round
Walk it round
Push the planet slowly round the inside of the ring, letting it roll rather than slide, until the drawn pattern closes on itself. Then draw, for comparison, the circle the same blade makes when the planet is held in one place and simply spun.
Tools needed:
Steel Ruler5
5
The same in dough
The same in dough
Optional but convincing: put 200 g of flour and 120 ml of water in a bowl and stir with a fixed-axis beater without moving it. Note the untouched ring of dry flour at the wall - the reason for the carrier.
Materials for this step:
Plain Flour200 gTools needed:
Large Mixing Bowl (Glass)
Digital Kitchen Scale6
6
Path, coverage and gear ratio
Path, coverage and gear ratio
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History & Context
History & Context
**What the patent specifies:** a mixing machine in which the beater rotates about its own axis while being carried bodily around the bowl. **Modern build (derived):** a planetary gear set and a pen, which draws the path the blade takes.
The 20-gallon Hobart was standard in large bakeries by 1915; the domestic version arrived in 1919 and the layout has not changed since. Its limits: the gearbox must take dough loads, the bowl must match the beater's reach, and a blade that reaches the wall will also scrape a bowl that is out of true.
Materials
7- Placeholder
- 1 piecePlaceholder
- 1 sheetPlaceholder
- 1 rollPlaceholder
- 1 piecePlaceholder
- 1 piecePlaceholder
- 200 gPlaceholder
Tools Required
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