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Centrifugal (fly-ball) governor

How does a fly-ball governor control speed? · Hardware · basis: Xem Studio design following Brown No. 161 (1868)

Also called: flyball governor, centrifugal governor, watt governor, speed governor, regulador centrífugo de bolas, Fliehkraftregler

Exact dimensions. True size, with no printing tolerance added.

sizes
4 in table

Notes

  • Two balls on arms hinged to the head of a spinning spindle fly outward as it turns faster; links from the arms lift a sleeve on the spindle, and the sleeve works the steam throttle (or any regulator), closing it as speed rises. Each ball settles where tan α = ω² r / g: at α = 30° and r = 54 mm the spindle turns 97.8 rpm.
  • Arms 80 mm (Ø24 balls), pivots 14 mm from the axis, links 40 mm from the arms' midpoints to the sleeve; drawn at α = 30°, the sleeve pins 69.28 mm below the arm pivots.
  • Brown's No. 161 (Watt's governor).
  • Parts (each has its own page): governor-arm-80-ball-24, governor-head-16-ears-14, governor-sleeve-16-ears-14, four-bar-links, dowel-pins-metric, linear-shafts-h6.
  • Brown's movement No. 161 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

Centrifugal (fly-ball) governor size chart

parametervalue
arms2 × 80 mm, Ø24 balls
links2 pairs × 40 mm
angle drawn30°
speed at that angle97.8 rpm

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Henry T. Brown (1868, public domain)Five Hundred and Seven Mechanical Movements — scan on archive.orgwebPublisher's page; dimensions are facts
507movements.comBrown's movement No. 161: figure, his text and an animationwebPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Xem Studio design: free to use, print and sell things from; not to be republished as files. Xem Studio Design License. index.json

flyball-governor-mechanism-assemblyAssembled mechanism, all parts placed at one pose (STEP keeps each part separate)STEP · STL
Let your AI pull this. Add https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.
Set it up →

Plain text: sheet.txt · JSON: /api/geometry?object=flyball-governor-mechanism

Centrifugal (fly-ball) governor, isometric render of a generated part
Render of flyball-governor-mechanism-assembly from the free STEP; not to scale.

Fits with

Governor arm 80 mm with a Ø24 ball, Ø3 pivot and link holes, isometric render of a generated part
Governor arm 80 mm with a Ø24 ball, Ø3 pivot and link holes98.0×24.0×24.0 mm★ 1 file
Governor head: Ø16 × 14 collar with forked ears, pivots 28 mm apart, isometric render of a generated part
Governor head: Ø16 × 14 collar with forked ears, pivots 28 mm apart38.0×16.0×14.0 mm★ 1 file
Governor sleeve: Ø16 × 20 sliding collar with ears 14 mm out, isometric render of a generated part
Governor sleeve: Ø16 × 20 sliding collar with ears 14 mm out38.0×16.0×20.0 mm★ 1 file
Four-bar links: flat links with 20 to 100 mm hole centres, isometric render of a generated part
Four-bar links: flat links with 20 to 100 mm hole centres7 sizes★ 7 files
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325), isometric render of a generated part
Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)5 sizes★ 23 files
Linear shafts Ø3 to Ø25 mm (h6), 100 to 1000 mm long, isometric render of a generated part
Linear shafts Ø3 to Ø25 mm (h6), 100 to 1000 mm long10 sizes★ 70 files

Questions

How does a fly-ball governor control speed?

Two balls on arms hinged to the head of a spinning spindle fly outward as it turns faster; links from the arms lift a sleeve on the spindle, and the sleeve works the steam throttle (or any regulator), closing it as speed rises. Each ball settles where tan α = ω² r / g: at α = 30° and r = 54 mm the spindle turns 97.8 rpm.