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Eccentric sheaves Ø30 at 3, 5 and 8 mm offset

What is the stroke of an eccentric sheave? · Hardware · basis: Disc on a shaft offset e from its centre; stroke = 2e

Long Earth Society build part. Quiet displacer and pump drive used on the LES rigs. The engines

Exact dimensions. Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part. Mating features

sizes
3 in table

Notes

  • A Ø30 × 8 disc with a Ø5 shaft hole offset 3, 5 or 8 mm from its centre: 6, 10 or 16 mm stroke.
  • A radial Ø2.5 hole (M3 tap drill) at mid-thickness locks it to the shaft.
  • It turns inside the Ø30 strap, which carries the load round its whole bore; it sits anywhere along a straight shaft without a crank throw.

Sizes

fileoffset estrokediscshaft
eccentric-d30-e336Ø30 × 85
eccentric-d30-e5510Ø30 × 85
eccentric-d30-e8816Ø30 × 85

Mating features

Drawn at the exact size. Open press, slide, run and socket features by your process's clearance; leave designed gaps and clamp fits as drawn.

featureexactmates withfitfiles
eccentric boreØ5Ø5 shaftslideeccentric-d30-e*
set-screw holeØ2.5M3 tap drilldesignedeccentric-d30-e*

Where the files are

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

WikipediaEccentric (mechanism)webCC BY-SA 4.0 (text)
Long Earth SocietyEngine and rig builds on extrusion framesweb, videoLES site

Free files

★ Free files 3 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

eccentric-d30-e3eccentric Ø30, 3 mm offset (6 mm stroke), Ø5 shaft, Ø2.5 set-screw holeSTEP · STL
eccentric-d30-e5eccentric Ø30, 5 mm offset (10 mm stroke), Ø5 shaft, Ø2.5 set-screw holeSTEP · STL
eccentric-d30-e8eccentric Ø30, 8 mm offset (16 mm stroke), Ø5 shaft, Ø2.5 set-screw holeSTEP · STL

Plain text: sheet.txt · JSON: /api/geometry?object=eccentric-sheaves

Eccentric sheaves Ø30 at 3, 5 and 8 mm offset, isometric render of a generated part
Render of eccentric-d30-e5 from the free STEP; not to scale.

How it fits

Goes in or on

Metric shafts Ø3 to Ø10 with D-flats and clip…Ø5 shaft, M3 grub

Connects to

Split eccentric strap for Ø30 sheaves, 51 mm to…Ø30 disc in the Ø30 strap bore

Alternatives

Crank discs for a Ø5 shaft, 10 to 30 mm strokecrank and con-rodScotch yokesine motion

You might also need

Swash (wobble) plates Ø40 at 10, 15 and 20°, isometric render of a generated part
Swash (wobble) plates Ø40 at 10, 15 and 20°3 sizes★ 3 files

Questions

What is the stroke of an eccentric?

Twice the offset: the 5 mm eccentric gives 10 mm.

Why an eccentric instead of a crank?

It sits anywhere on a straight shaft with no throw, and the strap bears all the way round.