# Plunger clevis for a glass syringe: cap over the piston collar with a con-rod fork

> How do I connect a crank to a glass syringe plunger?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: My geometry, drawn to the glass syringe's published piston collar (KD Scientific / Tomopal: 5 mL Ø17.25, 10 mL Ø19.95); fork sized for the 5 mm thick pin-end con-rods
- Page: https://xemstudio.com/objects/glass-syringe-plunger-clevis/ · JSON: https://xemstudio.com/api/geometry?object=glass-syringe-plunger-clevis · Plain text: https://xemstudio.com/objects/glass-syringe-plunger-clevis/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**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.

## Notes

- The cap's pocket is the piston collar's published diameter, exactly (5 mL Ø17.25, 10 mL Ø19.95), 3 deep (the collar thickness drawn on the plunger file; the datasheet gives no thickness). One M3 grub (set-m3x3) in a Ø2.5 tapped hole reaches the collar's edge; the cap's top face pushes on the collar.
- Fork: 12 × 12 block, 5 mm slot for a 5 mm con-rod, Ø3 pin hole 12 above the collar underside, for a dowel-3x12 (flush both sides).
- Used on the mug LTD and the test-tube marble engine (5 mL).

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| collar pocket | Ø17.25 × 3 (5 mL) / Ø19.95 × 3 (10 mL) | glass piston collar | slide | plunger-clevis-* |
| grub hole | Ø2.5 (M3 tapped) | set-m3x3 | designed | plunger-clevis-* |
| fork slot | 5 | 5 mm con-rod | run | plunger-clevis-* |
| pin hole | Ø3 | dowel-3x12 | press | plunger-clevis-* |

## Sizes

| part | pocket_mm | body_mm | pin_above_collar_mm | pin |
|---|---|---|---|---|
| plunger-clevis-glass-5ml | 17.25 | 23.25 | 12.0 | Ø3 (dowel-3x12) |
| plunger-clevis-glass-10ml | 19.95 | 25.95 | 12.0 | Ø3 (dowel-3x12) |

## Where the files are

- 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](https://www.kdscientific.com/media/brochures/KDS%20Glass%20Syringe%20Datasheet.pdf) — PDF — manufacturer datasheet (verify at link)
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/glass-syringe-plunger-clevis/index.json

- plunger-clevis-glass-5ml: [STEP](https://xemstudio.com/files/hardware/glass-syringe-plunger-clevis/plunger-clevis-glass-5ml.step) · [STL](https://xemstudio.com/files/hardware/glass-syringe-plunger-clevis/plunger-clevis-glass-5ml.stl) — cap for the 5 mL glass plunger: Ø17.25 × 3 pocket (the piston collar, exact), Ø23.25 body, M3 tapped (Ø2.5) grub to the collar edge, 12 × 12 fork with a 5 mm slot and a Ø3 pin hole 12 above the collar's underside
- plunger-clevis-glass-10ml: [STEP](https://xemstudio.com/files/hardware/glass-syringe-plunger-clevis/plunger-clevis-glass-10ml.step) · [STL](https://xemstudio.com/files/hardware/glass-syringe-plunger-clevis/plunger-clevis-glass-10ml.stl) — cap for the 10 mL glass plunger: Ø19.95 × 3 pocket (the piston collar, exact), Ø25.95 body, M3 tapped (Ø2.5) grub to the collar edge, 12 × 12 fork with a 5 mm slot and a Ø3 pin hole 12 above the collar's underside

## Questions

**How does the con-rod attach to a glass syringe plunger?**

Through this cap: it sits over the plunger's collar (pocket at the collar's exact Ø), an M3 grub holds it, and a Ø3 pin through its fork carries the con-rod's small end.

## Fits with

- [Glass syringes 1–50 mL (all-glass, ground-glass plunger): barrel and plunger](https://xemstudio.com/objects/glass-syringes/)
- [Con-rods with Ø3 pin ends, 45 and 60 mm, 8 × 5](https://xemstudio.com/objects/pin-end-con-rods/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)
- [Set screws (grub screws), M3–M8 (ISO 4026)](https://xemstudio.com/objects/set-screws-metric/)
- [Build list: Mug LTD (sits on a coffee mug)](https://xemstudio.com/objects/list-ltd-mug/)
- [Build list: Test-tube marble engine](https://xemstudio.com/objects/list-test-tube-marble-engine/)