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Link webs: a second crank throw on the first crank pin

How do I put two crank pins at different angles on one overhung crank? · Hardware · basis: Design values (pin radii and angles set by the engines' kinematics); Ø3 dowel pins (ISO 8734)

Long Earth Society build part. The second throw on my rolling-diaphragm beta and gamma. 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
2 in table

Notes

  • The web is pressed on crank pin 1 (which is pressed in the crank disc) and carries crank pin 2. The power con-rod runs on pin 1 between the disc and the web; the displacer drive runs on pin 2 outside the web. The shaft ends at the disc, so nothing crosses the con-rods' path.
  • Beta web: pin 2 at the same 10 mm radius, 90° from pin 1. Gamma web: pin 2 at 7 mm, 45° from pin 1; with the bell crank's own lag the displacer leads the power piston's volume by close to a quarter turn.
  • Turn the web over to swap which way pin 2 leads: the web is the same both ways.

Sizes

partpin1_radius_mmpin2_radius_mmangle_degthickness_mm
rd-link-web-r10-9010.010.090.014.0
rd-link-web-r7-4510.07.045.014.0

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
pin holesØ3 (two)Ø3 crank pins (dowels)pressall

Where the files are

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

Long Earth SocietyEngine buildsweb, videoLES site

Free files

★ Free files 2 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

rd-link-web-r10-90link web 14 thick: Ø3 press holes for crank pin 1 (radius 10) and pin 2 (radius 10) 90° apart about the shaft axis, Ø12 endsSTEP · STL
rd-link-web-r7-45link web 14 thick: Ø3 press holes for crank pin 1 (radius 10) and pin 2 (radius 7) 45° apart about the shaft axis, Ø12 endsSTEP · STL

Plain text: sheet.txt · JSON: /api/geometry?object=tri-clamp-rd-link-webs

Link webs: a second crank throw on the first crank pin, isometric render of a generated part
Render of rd-link-web-r7-45 from the free STEP; not to scale.

How it fits

In these build lists

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Questions

Which way does the engine turn?

The way that makes the displacer lead the power piston; turning the web over reverses it.