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Test-tube marble engine rocker: tube and glass-syringe rings on a pivot
How do I hold the test tube of a marble Stirling engine so it rocks? · Hardware · basis: My geometry: Ø25 ring at the 25 × 150 tube's OD (DURAN / KIMBLE 25 × 150), Ø15.40 ring at the 5 mL glass barrel's published OD (KD Scientific); tube and syringe on one axis so the transfer line never bends
Long Earth Society build part. Rocker of the test-tube marble engine. 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
- 5 in table
Notes
- The tube (hot end out, stopper toward the pivot) and the 5 mL glass syringe (tip toward the stopper) sit on one axis 18 above the pivot; the 4 mm tube through the stopper and a 50 mm silicone tube join them in a straight line, so nothing flexes as it rocks.
- Pivot: Ø3 bore for a dowel-3x30 through two beam-pivot-post-60 posts (hub 10 wide between them). Lever pin Ø3 at (35, −45) from the pivot for the 170 mm rocking link; with a 7.5 mm crank throw the rocker swings -7.9° to +7.9°.
- Rings: Ø25 × 12 for the tube, Ø15.40 × 12 for the syringe barrel, each with an M3 grub (set-m3x4, Ø2.5 tapped) that reaches the glass.
Sizes
| feature | value |
|---|---|
| tube ring | Ø25 × 12 |
| syringe ring | Ø15.40 × 12 |
| axis above pivot | 18 |
| lever pin | (35, −45), Ø3 |
| swing | -7.9..7.9° |
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 |
|---|---|---|---|---|
| tube ring | Ø25 × 12 | 25 × 150 test tube OD | socket | all |
| syringe ring | Ø15.40 × 12 | 5 mL glass syringe barrel | socket | all |
| pivot bore | Ø3 | dowel-3x30 pivot pin (turns in it) | run | all |
| lever pin bore | Ø3 | dowel-3x12 | press | all |
| grub holes | Ø2.5 (M3 tapped) | set-m3x4 | designed | all |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| DWK / DURAN (via Parkes Scientific) | DURAN test tubes 26 130: 25 × 150 mm, 55 mL, wall 1.0–1.2 mm (cat. 261303308) | web | listing verify |
| DWK Life Sciences | KIMBLE reusable culture tube 25 × 150 mm, 55 mL (45048-25150) | web | manufacturer page verify |
| KD Scientific | Full Line of Glass Syringes, rev. A (order codes 78-0871 to 78-0880): piston OD, barrel OD D1, barrel collar D2, piston collar D3, length L | manufacturer datasheet verify | |
| Wikipedia | Stirling engine | web | CC BY-SA 4.0 (text) |
| 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
| marble-engine-rocker-25x150-glass5 | rocker: Ø25 ring for the 25 × 150 test tube and Ø15.40 ring for the 5 mL glass barrel on one axis 18 above the Ø3 pivot bore, beam 216 long, lever pin (Ø3) 45 below and 35 beside the pivot at the end of an arm reaching to y −72.5, 2 × M3 tapped (Ø2.5) grubs | STEP · STL |
Plain text: sheet.txt · JSON: /api/geometry?object=marble-engine-rocker
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Questions
How far does the tube of a marble engine rock?
About ±8° here: enough for the marbles to roll end to end each half turn.