# LTD Stirling bottom plate, Ø120 and Ø170

> What are the dimensions of the bottom (hot) plate of a coffee-cup Stirling engine?

- Category: Stirling engines › Can & LTD engines
- Kind: Hardware
- Basis: Same outline and M3 hole circle as the LTD top plate and chamber ring; M3 clearance Ø3.4 (ISO 273)
- Page: https://xemstudio.com/objects/ltd-bottom-plate/ · JSON: https://xemstudio.com/api/geometry?object=ltd-bottom-plate · Plain text: https://xemstudio.com/objects/ltd-bottom-plate/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 hot plate of the LTD engine: the cup or the hand warms it and the heat goes through it into the air in the chamber.
- Ø120 × 3 for the 100 chamber, Ø170 × 3 for the 150, with 6 × Ø3.4 on a Ø112 / Ø162 circle (at 30°, 90°, …) matching the chamber ring and top plate; an M3 × 12 from below goes into each tapped ring hole.

## 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 |
|---|---|---|---|---|
| plate screw holes | Ø3.4 | M3 screw clearance (ISO 273) | designed | ltd-100-bottom* |
| plate screw holes | Ø3.4 | M3 screw clearance (ISO 273) | designed | ltd-150-bottom* |

## Sizes

| file | plate | holes | screw circle | centre mark |
|---|---|---|---|---|
| ltd-100-bottom-plate | Ø120 × 3 | 6 × Ø3.4 | 112 | 3.2 |
| ltd-150-bottom-plate | Ø170 × 3 | 6 × Ø3.4 | 162 | 3.2 |

## Where the files are

- Wikipedia: [Stirling engine](https://en.wikipedia.org/wiki/Stirling_engine) — web — CC BY-SA 4.0 (text)
- James R. Senft: [An Introduction to Low Temperature Differential Stirling Engines](https://www.stirlingengine.com/) — book — Moriya Press (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/ltd-bottom-plate/index.json

- ltd-100-bottom-plate: [STEP](https://xemstudio.com/files/hardware/ltd-coffee-cup-engine-kit/ltd-100-bottom-plate.step) · [STL](https://xemstudio.com/files/hardware/ltd-coffee-cup-engine-kit/ltd-100-bottom-plate.stl) — bottom (hot) plate Ø120 × 3, 6 × Ø3.4 (M3 clearance) on a Ø112 circle at 30° + 60° steps
- ltd-150-bottom-plate: [STEP](https://xemstudio.com/files/hardware/ltd-coffee-cup-engine-kit/ltd-150-bottom-plate.step) · [STL](https://xemstudio.com/files/hardware/ltd-coffee-cup-engine-kit/ltd-150-bottom-plate.stl) — bottom (hot) plate Ø170 × 3, 6 × Ø3.4 (M3 clearance) on a Ø162 circle at 30° + 60° steps

## How it fits

### Connects to
- [LTD Stirling chamber ring, Ø100 and Ø150 × 20](https://xemstudio.com/objects/ltd-chamber-ring/): 6 × M3 on the Ø112 / Ø162 circle, ring between the plates
- [LTD Stirling top plate with syringe socket, Ø120 and Ø170](https://xemstudio.com/objects/ltd-top-plate/): same outline and hole circle on the other face of the ring

### Also needed
- [Socket head cap screws, M2–M8 (ISO 4762 / DIN 912)](https://xemstudio.com/objects/socket-head-cap-screws-metric/): 6 × M3 through plate, ring and plate

## Questions

**How big is the bottom plate of a 100 mm LTD Stirling?**

Ø120 × 3 with six Ø3.4 holes on a Ø112 circle.

**Does the bottom plate have the same holes as the top plate?**

Yes: 6 × Ø3.4 on the same Ø112 / Ø162 circle as the top plate; the chamber ring between them has the same holes tapped M3.

## Fits with

- [LTD Stirling chamber ring, Ø100 and Ø150 × 20](https://xemstudio.com/objects/ltd-chamber-ring/)
- [LTD Stirling top plate with syringe socket, Ø120 and Ø170](https://xemstudio.com/objects/ltd-top-plate/)
- [LTD Stirling displacer Ø96 × 8 and Ø146 × 8](https://xemstudio.com/objects/ltd-displacer/)
- [Build list: LTD coffee-cup engine](https://xemstudio.com/objects/list-ltd-coffee-cup/)