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One pinion driving an internal and a spur gear on one axis (two speeds)

How can one pinion drive two gears at different speeds on the same axis? · Hardware · basis: Xem Studio design following Brown No. 55 (1868)

Also called: two speed gear, star gear, internal and external gear, piñón con engranaje interior y exterior, Ritzel mit Hohlrad und Stirnrad

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

sizes
5 in table

Notes

  • A pinion sits between a ring gear and a spur gear that share an axis: it drives the ring the same way at 20/60 of its speed and the spur gear the opposite way at 20/20 — two speeds and two directions from one pinion.
  • The tooth counts must satisfy N_ring = N_spur + 2·N_pinion (60 = 20 + 2 × 20) so both meshes sit at the same 20 mm centre distance.
  • It is the fixed-carrier (star) form of an epicyclic train; Brown's No. 55 draws it with the two driven gears on one shaft.
  • Parts (each has its own page): internal-ring-gear-m1-60t, spur-gears-module-1.
  • Brown's movement No. 55 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

One pinion driving an internal and a spur gear on one axis size chart

parametervalue
ring60 T internal
spur gear20 T
pinion20 T
centre distance20 mm
speeds (pinion = 1)ring 1/3 same way; spur 1 opposite

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. 55: figure, his text and an animationwebPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

pinion-driving-internal-and-spur-gear-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.
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Plain text: sheet.txt · JSON: /api/geometry?object=pinion-driving-internal-and-spur-gear-mechanism

One pinion driving an internal and a spur gear on one axis (two speeds), isometric render of a generated part
Render of pinion-driving-internal-and-spur-gear-mechanism-assembly from the free STEP; not to scale.

Fits with

Internal (ring) gear, module 1, 60 teeth, Ø80, isometric render of a generated part
Internal (ring) gear, module 1, 60 teeth, Ø8080.0×80.0×8.0 mm★ 1 file
Spur gears, module 1: 10 to 80 teeth (20° involute), isometric render of a generated part
Spur gears, module 1: 10 to 80 teeth (20° involute)26 sizes★ 26 files

Questions

How can one pinion drive two gears at different speeds on the same axis?

A pinion sits between a ring gear and a spur gear that share an axis: it drives the ring the same way at 20/60 of its speed and the spur gear the opposite way at 20/20 — two speeds and two directions from one pinion.