# Flat disc Ø72 × 6 with a Ø2 rod bore

> What thin disc fits a 76 mm chamber on a 2 mm rod?

- Category: Hardware › Pistons, cylinders & rods
- Kind: Hardware
- Basis: 2 mm radial gap to the Ø76 chamber like the LTD kit; swept volume at 15 mm stroke 61.1 mL
- Page: https://xemstudio.com/objects/flat-disc-72-rod-bore/ · JSON: https://xemstudio.com/api/geometry?object=flat-disc-72-rod-bore · Plain text: https://xemstudio.com/objects/flat-disc-72-rod-bore/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**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

- Ø72 × 6 with a Ø2 bore for the rod (pressed through, flush at the bottom). Swept volume 61.1 mL against the 5 mL glass piston's 1.87 mL: ratio 33.
- 2 mm radial gap to the chamber wall (designed); 1 mm end gaps at the ends of travel.

## 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 |
|---|---|---|---|---|
| rod bore | Ø2 | Ø2 displacer rod | press | all |
| outside | Ø72 in a Ø76 bore | chamber ring (2 radial gap) | designed | all |

## Sizes

| feature | value |
|---|---|
| displacer | Ø72 × 6 |
| stroke | 15 |
| swept volume | 61.1 mL |
| volume ratio | 33 |

## Where the files are

- Atlanta Vinyl Store: [Premium 11 oz sublimation mug: 3.75 in H × 3.25 in D](https://atlantavinylstore.com/products/premium-11oz-sublimation-mugs) — web — listing (verify at link)
- James R. Senft: [An Introduction to Low Temperature Differential Stirling Engines](https://www.stirlingengine.com/) — book — Moriya Press (verify at link)
- Wikipedia: [Stirling engine](https://en.wikipedia.org/wiki/Stirling_engine) — web — CC BY-SA 4.0 (text)
- Long Earth Society: [Engine builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/flat-disc-72-rod-bore/index.json

- mug-ltd-displacer-72x6: [STEP](https://xemstudio.com/files/hardware/flat-disc-72-rod-bore/mug-ltd-displacer-72x6.step) · [STL](https://xemstudio.com/files/hardware/flat-disc-72-rod-bore/mug-ltd-displacer-72x6.stl) — displacer Ø72 × 6, Ø2 rod bore (2 mm radial gap to the Ø76 chamber: designed; 1 mm end gaps at the ends of its 15 mm stroke)

## Questions

**What is the displacer to piston volume ratio of the mug LTD?**

About 33: 61.1 mL displacer sweep to 1.87 mL of 5 mL glass syringe, both at 15 mm stroke.

## Fits with

- [Bottom plates Ø120 and Ø170](https://xemstudio.com/objects/round-bottom-plates-120-170/)
- [Top plates Ø120 and Ø170 with a syringe socket](https://xemstudio.com/objects/round-top-plates-syringe-socket/)
- [Glass syringes 1–50 mL (all-glass, ground-glass plunger): barrel and plunger](https://xemstudio.com/objects/glass-syringes/)