# HTD hot cup: 10 in tri-clamp closed-end cup (welded floor)

> How do I make a 10 inch tri-clamp hot end with no gasket in the flame?

- Category: Stirling engines › Tri-clamp engine parts
- Kind: Hardware
- Basis: Fabrication spec: an L14AM7-type 10 in ferrule end on Ø254 × 3.40 tube, closed by a 12.7 plate welded flush with the tube OD; exact geometry
- Page: https://xemstudio.com/objects/htd-hot-cup-10in/ · JSON: https://xemstudio.com/api/geometry?object=htd-hot-cup-10in · Plain text: https://xemstudio.com/objects/htd-hot-cup-10in/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

- The hot face is one piece: the floor is welded to the tube, so the only joint is the clamp at the top, 48 mm of tube wall above the flame (main HTD). That wall is also the engine's biggest heat leak: about 335 W conducted from a 450 °C floor to a 77 °C cap at 16 W/m·K (a lower-conductivity wall leaks proportionally less).
- Floor: 12.7 thick. At the 6 bar gauge relief setting, treated as simply supported at the bore (conservative for a welded edge), it sees 70 MPa at the centre and bows 0.25 mm (Roark Table 11.2). The floor must be rated for that at its working temperature; I hold the hot face at or below 450 °C.
- The cup's own ferrule face takes the standard 10 in gasket and clamp.

## 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 |
|---|---|---|---|---|
| face | ISO 2852 10 in | gasket-10in + 10 in clamp | clamp | all |
| bore | Ø247.19 to the floor | displacer Ø240 (3.6 radial, no contact) | designed | all |
| floor weld | Ø254 × 12.7 flush with the tube OD | tube end (welded, sealed) | designed | all |

## Sizes

| part | length_mm | floor_mm | chamber_face_to_floor_mm |
|---|---|---|---|
| hot-cup-10in-60.4 | 60.4 | 12.7 | 47.7 |

## Where the files are

- Steel & O'Brien: [Sanitary products catalog 2024: 16AMP end caps 10 / 12 in (A 0.480, B 10.570 / 12.570 in); L14AM7 ferrules 1.500 in; clamp ratings 13MHHM, 13MHP, 13ASME](https://www.steelobrien.com/wp-content/uploads/2024/03/Sanitary-2024-FINAL.pdf) — PDF — publisher's catalogue; dimensions cited, nothing copied
- Holland Applied Technologies: [Sanitary tri-clamp fittings: EG14AM7 ferrules 8 / 10 / 12 in (1.500, bore 9.732 / 11.732 in, tube 10.000 / 12.000 in); EG16A caps (10.570 / 12.570 in)](https://hollandapt.com/wp-content/uploads/2022/12/Sanitary-Tri-Clamp-Fittings.pdf) — PDF — publisher's catalogue; dimensions cited, nothing copied
- McGraw-Hill: [Young & Budynas, Roark's Formulas for Stress and Strain, 7th ed.: Table 8.1 (fixed–guided beam), Table 11.2 (circular plates under uniform pressure)](https://www.accessengineeringlibrary.com/content/book/9780071742474) — book — formulas are facts (verify at link)
- 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/htd-hot-cup-10in/index.json

- hot-cup-10in-60.4: [STEP](https://xemstudio.com/files/hardware/htd-hot-cup-10in/hot-cup-10in-60.4.step) · [STL](https://xemstudio.com/files/hardware/htd-hot-cup-10in/hot-cup-10in-60.4.stl) — 10 in × 60.4 closed-end cup: ISO 2852 face, Ø254 × 3.40 tube, 12.7 floor welded flush (main HTD: chamber 51.0 face to floor with the cap)

## Questions

**Why a welded floor instead of a cap?**

A cap would put a gasket and a clamp in the flame. With the floor welded on, the only joint sits up at the cold cap.

## Fits with

- [Build list: HTD engine, 10 in tri-clamp (high-temperature-differential flat engine)](https://xemstudio.com/objects/list-htd-10in/)
- [HTD cold caps: 10 in tri-clamp caps with a 2 in ferrule at the centre](https://xemstudio.com/objects/htd-cold-caps-10in/)
- [Sanitary clamp ferrules, 10 and 12 in (L14AM7, tri-clamp style)](https://xemstudio.com/objects/sanitary-clamp-ferrules-10-12in/)