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Elliptical gear, module 1.5, 31 teeth, eccentricity 0.5, bore at a focus

How are elliptical gears made? · Modern device · basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance

Also called: elliptical gear, oval gear, non circular gear, engranaje elíptico, elliptisches Zahnrad

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

length
52.67 mm
width
46.09 mm
height
12.0 mm

Notes

  • Pitch curve an ellipse with semi-axes 24.89 × 21.55 mm (eccentricity 0.5, perimeter 31 × π × 1.5 = 146.08 mm), the Ø8 bore at a focus; teeth generated by a 20° basic rack rolled round the pitch curve without slip (addendum m, dedendum 1.25 m), so any two such gears mesh. Outline: every tooth flank and fillet is a spline fitted to the generated curve within 0.008 mm.
  • 31 teeth (odd): a pair pivoted at their foci 49.77 mm apart (the major axis) meets tooth-to-space at both ends of the major axis. 12 mm face.
  • Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

Elliptical gear, module 1.5, 31 teeth, eccentricity 0.5, bore at a… size chart

dimensionvalue
module1.5
teeth31
pitch ellipse49.77 × 43.11 mm
eccentricity0.5
boreØ8 at a focus
face12 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. 33: figure, his text and an animationwebPublisher's page; dimensions are facts
Xem StudiodrawingwebPublisher'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

elliptical-gear-m1-5-31t-e0-5-focus-boregear, bore (focus) on the Z axis, near vertex on +X, z 0..12STEP · 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=elliptical-gear-m1-5-31t-e0-5-focus-bore

Elliptical gear, module 1.5, 31 teeth, eccentricity 0.5, bore at a focus, isometric render of a generated part
Render of elliptical-gear-m1-5-31t-e0-5-focus-bore from the free STEP; not to scale.

Fits with

Elliptical gears turning about their foci (speed ratio 0.33 – 3), isometric render of a generated part
Elliptical gears turning about their foci (speed ratio 0.33 – 3)4 sizes★ 1 file

Questions

How are elliptical gears made?

Pitch curve an ellipse with semi-axes 24.89 × 21.55 mm (eccentricity 0.5, perimeter 31 × π × 1.5 = 146.08 mm), the Ø8 bore at a focus; teeth generated by a 20° basic rack rolled round the pitch curve without slip (addendum m, dedendum 1.25 m), so any two such gears mesh. Outline: every tooth flank and fillet is a spline fitted to the generated curve within 0.008 mm.