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Four-bar links: flat links with 20 to 100 mm hole centres
Where can I get 3D printable linkage bars for a four-bar mechanism? · Hardware · basis: Flat links 10 wide × 5 thick, Ø3 holes at exact centres from 20 to 100 mm
Long Earth Society build part. Linkage bars for 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
- 7 in table
Notes
- Seven lengths: 20, 30, 40, 50, 60, 80 and 100 mm between hole centres.
- Ø3 holes at both ends for Ø3 pins, so links pin to each other, to the bell cranks and to the Scotch yoke rod.
- Builds crank-rockers, parallel motions, rocking beams and the Ross yoke linkage.
Sizes
| centres | width × thickness | holes |
|---|---|---|
| 20 mm | 10 × 5 | Ø3 |
| 30 mm | 10 × 5 | Ø3 |
| 40 mm | 10 × 5 | Ø3 |
| 50 mm | 10 × 5 | Ø3 |
| 60 mm | 10 × 5 | Ø3 |
| 80 mm | 10 × 5 | Ø3 |
| 100 mm | 10 × 5 | Ø3 |
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.
| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| end holes | Ø3 | Ø3 pins (turn in them) | run | all |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| Wikipedia | Four-bar linkage | web | CC BY-SA 4.0 (text) |
| Long Earth Society | Engine and rig builds on extrusion frames | web, video | LES site |
Free files
★ Free files 7 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json
| link-20 | four-bar / rocker link, 20 mm centres, Ø3 holes, 10 wide × 5 thick | STEP · STL |
| link-30 | four-bar / rocker link, 30 mm centres, Ø3 holes, 10 wide × 5 thick | STEP · STL |
| link-40 | four-bar / rocker link, 40 mm centres, Ø3 holes, 10 wide × 5 thick | STEP · STL |
| link-50 | four-bar / rocker link, 50 mm centres, Ø3 holes, 10 wide × 5 thick | STEP · STL |
| link-60 | four-bar / rocker link, 60 mm centres, Ø3 holes, 10 wide × 5 thick | STEP · STL |
| link-80 | four-bar / rocker link, 80 mm centres, Ø3 holes, 10 wide × 5 thick | STEP · STL |
| link-100 | four-bar / rocker link, 100 mm centres, Ø3 holes, 10 wide × 5 thick | STEP · STL |
Plain text: sheet.txt · JSON: /api/geometry?object=four-bar-links
How it fits
Connects to
Bell cranksØ3 arm holes
Scotch yokeØ3 rod-end hole
Eccentric and strapØ3 strap eyeAlternatives
Ross yoke alpha for two parallel 10 mL syringessolved Ross linkage for an alphaAlso needed
Dowel pins, 2–6 mmØ3 pins through the jointsYou might also need
Questions
Which lengths make a crank-rocker?
Grashof: shortest + longest ≤ the sum of the other two, with the shortest as the crank. For example a 20 crank, 60 coupler, 50 rocker and 60 ground.
What pins go through the holes?
Ø3 pins, dowels or shafts; the holes are Ø3 exactly, so apply your fit to them.