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Rhombic drive link, 30 mm centres
How long are the links in a rhombic drive? · Hardware · basis: Rhombic kinematics (tools/rhombic_geom.py): four equal links L = 30 between crank pins at e = 7 on gears 66 apart and yoke pivots at ±12.7
Long Earth Society build part. The balanced beta drive for the 2 in tri-clamp engine; the rhombic frame head in the linkage fittings carries it on the spool. 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
- 4 in table
Notes
- Four identical links join the two crank pins to the two yokes, forming the rhombus. Each is 30 mm between Ø3 holes (fit: run), 38 × 8 × 5 with round ends.
- Two ride each crank pin: the lower link next to the gear, the upper link outside it.
- Link length, gear centres, throw and yoke span together set the phase: here 90.0° with both strokes 20.12 mm.
Sizes
| parameter | value |
|---|---|
| centres | 30.0 |
| outline | 38 × 8 × 5 |
| holes | 2 × Ø3 (run) |
| quantity | 4 |
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 |
|---|---|---|---|---|
| link ends | Ø3 | Ø3 pins (turn on them) | run | link-* |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| Wikipedia | Rhombic drive | web | CC BY-SA 4.0 (text) |
| Wikipedia | Stirling engine | web | CC BY-SA 4.0 (text) |
| Philips Research / Meijer | The Philips Stirling engine (rhombic drive papers, 1958–1965) | web | reference verify |
| Long Earth Society | Engine builds | web, video | LES site |
Free files
★ Free files 1 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json
Plain text: sheet.txt · JSON: /api/geometry?object=rhombic-link
How it fits
Connects to
Rhombic drive crank gear, module 1.5, 44 T, 7 mm…Ø3 hole on the gear's crank pin
Rhombic drive upper yoke, 25.4 mm pivot spanØ3 pin at the yoke's ±12.7 pivots
Rhombic drive lower yoke, 25.4 mm pivot spanØ3 pin at the yoke's ±12.7 pivotsAlso needed
Dowel pins, 2–6 mmØ3 link pinsIn these build lists
Beta Stirling, rhombic drive, 2 in tri-clampDisplacer and piston in one bore, driven by two counter-rotating gears on a rhom…You might also need
Questions
How many links does a rhombic drive need?
Four equal links: two on each crank pin, one to the upper yoke and one to the lower.
What link length goes with this rhombic drive?
30 mm centres, with a 7 mm throw, gears 66 apart and yoke pivots at ±12.7.