Xem Studiomeasured geometry

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Pinion between a fixed and a free rack (travel doubler)

How does a pinion between two racks double a stroke? · Hardware · basis: Xem Studio design following Brown No. 118 (1868)

Also called: rack doubler, pinion between two racks, stroke doubling rack, piñón entre cremallera fija y móvil, Ritzel zwischen fester und loser Zahnstange

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

sizes
4 in table

Notes

  • A pinion turns on an axle carried by a rod. Below it is a fixed rack, above it a rack free to slide. Moving the axle a distance d rolls the pinion on the fixed rack, and its top, moving at twice the axle's speed, carries the free rack 2d: the stroke is doubled with no gearing ratio.
  • Module 1, 20-tooth pinion, racks with pitch lines 20 mm apart (one pitch diameter); drawn with the axle 6.28 mm (two pitches) along and the free rack 12.57 mm along. The free rack's own guide is not drawn.
  • Brown's No. 118 (pinion on the connecting rod between a fixed and a movable rack).
  • Parts (each has its own page): gear-rack-m1-120-full-depth, spur-gears-module-1, pinion-carrier-rod-100-bore6, dowel-pins-metric.
  • Brown's movement No. 118 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

Pinion between a fixed and a free rack size chart

parametervalue
pinion20 T, module 1
racks2 × 120 mm, pitch lines 20 mm apart
ratiofree rack = 2 × axle travel
rod100 mm

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. 118: 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

pinion-between-racks-doubler-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-between-racks-doubler-mechanism

Pinion between a fixed and a free rack (travel doubler), isometric render of a generated part
Render of pinion-between-racks-doubler-mechanism-assembly from the free STEP; not to scale.

Fits with

Gear rack, module 1, 120 mm, full-depth 20° teeth, isometric render of a generated part
Gear rack, module 1, 120 mm, full-depth 20° teeth120.0×11.0×8.0 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
Pinion carrier rod, 100 mm, Ø6 axle hole and Ø3 end hole, isometric render of a generated part
Pinion carrier rod, 100 mm, Ø6 axle hole and Ø3 end hole110.0×10.0×5.0 mm★ 1 file
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

Questions

How does a pinion between two racks double a stroke?

A pinion turns on an axle carried by a rod. Below it is a fixed rack, above it a rack free to slide. Moving the axle a distance d rolls the pinion on the fixed rack, and its top, moving at twice the axle's speed, carries the free rack 2d: the stroke is doubled with no gearing ratio.