# Mug LTD chamber ring Ø76 × 23

> How tall should the chamber of a small LTD Stirling engine be?

- Category: Hardware › Stirling & thermoacoustic
- Kind: Hardware
- Basis: 7 mm wall so the Ø5 syringe port at x 35 still opens into the chamber; 23 tall so a 6 mm displacer travels 15 with 1 mm at each end
- Page: https://xemstudio.com/objects/mug-ltd-chamber-ring/ · JSON: https://xemstudio.com/api/geometry?object=mug-ltd-chamber-ring · Plain text: https://xemstudio.com/objects/mug-ltd-chamber-ring/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

- Ø76 bore, Ø90 outside (7 wall), 23 tall; 5 × Ø3.4 for the chamber screws on R41 and 2 × M3 tapped 2 deep in the top face at (35.5, ±20.5) for the crank pedestal's foot.
- Chamber 23 − displacer 6 = 17 free; the 15 mm stroke leaves 1 mm at the top and bottom of travel. 15 mm (7.5 throw) is the shortest stroke in the Ø3-bore crank discs whose con-rod eye (R4) clears a Ø3 shaft.

## 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 |
|---|---|---|---|---|
| bore | Ø76 | displacer Ø72 (2 radial gap) | designed | all |
| screw holes | Ø3.4, 5 on R41 | M3 clearance | designed | all |
| pedestal holes | Ø2.5 × 2 deep (M3 tapped), at (35.5, ±20.5) | shcs-m3x8 through the pedestal foot | designed | all |
| faces | flat | bottom and top plates (static seal) | clamp | all |

## Sizes

| feature | size_mm |
|---|---|
| bore × height | 76 × 23 |
| outside | Ø90 |
| displacer gap | 2 radial, 1 at each end of stroke |

## 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/mug-ltd-chamber-ring/index.json

- mug-ltd-chamber-ring-76-h23: [STEP](https://xemstudio.com/files/hardware/mug-ltd-chamber-ring/mug-ltd-chamber-ring-76-h23.step) · [STL](https://xemstudio.com/files/hardware/mug-ltd-chamber-ring/mug-ltd-chamber-ring-76-h23.stl) — chamber ring Ø76 bore × 23, Ø90 outside (7 wall), 5 × Ø3.4 (M3 clearance) on R41, 2 × M3 tapped (Ø2.5) 2 deep in the top face at (35.5, ±20.5) for the crank pedestal

## Questions

**What chamber height suits a 6 mm displacer with a 15 mm stroke?**

23 mm: 17 free, 1 mm left at each end.

## Fits with

- [Build list: Mug LTD (sits on a coffee mug)](https://xemstudio.com/objects/list-ltd-mug/)
- [LTD Stirling bottom plate, Ø120 and Ø170](https://xemstudio.com/objects/ltd-bottom-plate/)
- [LTD Stirling top plate with syringe socket, Ø120 and Ø170](https://xemstudio.com/objects/ltd-top-plate/)
- [Glass syringes 1–50 mL (all-glass, ground-glass plunger): barrel and plunger](https://xemstudio.com/objects/glass-syringes/)