# Base plate for 1.5, 2 and 3 in tri-clamp spools

> What base plate holds a tri-clamp spool upright?

- Category: Hardware › Frames & stands
- Kind: Hardware
- Basis: Spool passage = ISO 2852 flange Ø + 2 (50.5 / 64 / 91); width flange + 90, depth max(70, flange + 30); M5 clearance Ø5.5 (ISO 273 medium)
- Page: https://xemstudio.com/objects/tri-clamp-spool-base-plate/ · JSON: https://xemstudio.com/api/geometry?object=tri-clamp-spool-base-plate · Plain text: https://xemstudio.com/objects/tri-clamp-spool-base-plate/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

- A 6 mm plate with 6 mm corner radii, sized to the tri-clamp flange: 140.5 × 80.5 (1.5 in), 154 × 94 (2 in), 181 × 121 (3 in).
- On centre a passage Ø52.5 / Ø66 / Ø93 (flange Ø + 2) that the spool or its cap goes through without contact.
- Either side, a 16 × 3.4 slot at flange radius + 18 for the crank stands' M3 screws; at the ends, 4 × Ø5.5 holes (50 mm apart across, 12 in from each end) for M5 into 2020 extrusion.

## 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 |
|---|---|---|---|---|
| base-plate spool passage | flange Ø + 2 | ferrule flange passes through | designed | base-plate-* |
| base-plate M5 holes | Ø5.5 | M5 screw clearance (ISO 273 medium) | designed | base-plate-* |
| crank-stand slots | 3.4 × 16, 2 per stand at y ±21 (42 apart), x ±(flange/2 + 16) | crank-stand-625 foot slots, M3 screws | designed | base-plate-* |

## Sizes

| file | plate | spool passage | stand slots at | M5 holes |
|---|---|---|---|---|
| base-plate-1.5in | 140.5 × 80.5 × 6 | 52.5 | ±43.25 | 4 × Ø5.5, 116.5 × 50 |
| base-plate-2in | 154 × 94 × 6 | 66 | ±50 | 4 × Ø5.5, 130 × 50 |
| base-plate-3in | 181 × 121 × 6 | 93 | ±63.5 | 4 × Ø5.5, 157 × 50 |

## Where the files are

- Wikipedia: [Beam engine](https://en.wikipedia.org/wiki/Beam_engine) — web — CC BY-SA 4.0 (text)
- 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 (3 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/tri-clamp-spool-base-plate/index.json

- base-plate-1.5in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-spool-base-plate/base-plate-1.5in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-spool-base-plate/base-plate-1.5in.stl) — base plate for a 1.5 in tri-clamp engine, 140.5 × 80.5 × 6: Ø52.5 spool passage (flange Ø + 2), two crank-stand-625 seats at x ±41.25, each 2 × M3 slots 3.4 × 16 (along y) on y ±21 (the stand's 42 mm foot pitch), 4 × M5 clearance (Ø5.5) at x ±58.25, y ±25 to 2020 extrusion
- base-plate-2in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-spool-base-plate/base-plate-2in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-spool-base-plate/base-plate-2in.stl) — base plate for a 2 in tri-clamp engine, 154 × 94 × 6: Ø66 spool passage (flange Ø + 2), two crank-stand-625 seats at x ±48, each 2 × M3 slots 3.4 × 16 (along y) on y ±21 (the stand's 42 mm foot pitch), 4 × M5 clearance (Ø5.5) at x ±65, y ±25 to 2020 extrusion
- base-plate-3in: [STEP](https://xemstudio.com/files/hardware/tri-clamp-spool-base-plate/base-plate-3in.step) · [STL](https://xemstudio.com/files/hardware/tri-clamp-spool-base-plate/base-plate-3in.stl) — base plate for a 3 in tri-clamp engine, 181 × 121 × 6: Ø93 spool passage (flange Ø + 2), two crank-stand-625 seats at x ±61.5, each 2 × M3 slots 3.4 × 16 (along y) on y ±21 (the stand's 42 mm foot pitch), 4 × M5 clearance (Ø5.5) at x ±78.5, y ±25 to 2020 extrusion

## How it fits

### Parts that fit it
- [Crosshead guide, Ø8 bore × 30](https://xemstudio.com/objects/crosshead-guide-8mm/): flanged to the frame in line with the liner
- [Beam pivot post, 60 mm](https://xemstudio.com/objects/beam-pivot-post/): 2 × M3 to the base
- [Shaft stands with a 625 bearing pocket, 40 and 60 mm axis height](https://xemstudio.com/objects/crank-stands-625/): M3 through the foot slots into the plate slots

### Goes in or on
- [2020 aluminum extrusion, 6 mm slot (20-series)](https://xemstudio.com/objects/2020-aluminum-extrusion/): 4 × M5 into 2020

### Connects to
- [Tri-clamp spool (two ferrules on a tube), 1.5 and 2 inch](https://xemstudio.com/objects/tri-clamp-spool/): spool through the passage
- [Rod clevises for a Ø2 or Ø3 rod or a Ø5 tube, 5 mm gap](https://xemstudio.com/objects/rod-clevises/): 625 crank stands in the slots
- [Flanged cylinder liners Ø16, 20, 25 and 30](https://xemstudio.com/objects/power-cylinder-liner/): liner flange on the plate

### Also needed
- [Slide-in T-nuts for 20, 30, 40, 45 mm and 1 in, 1.5 in T-slot extrusion](https://xemstudio.com/objects/slide-in-t-nuts/): T-nuts

## Questions

**How do I mount a tri-clamp Stirling engine?**

On the base plate: spool through the Ø66 passage (2 in), crank stands in the slots, 4 × M5 down into 2020 or a board.

**What size is the 2 in base plate?**

154 × 94 × 6 with a Ø66 passage.

## Fits with

- [Rod clevises for a Ø2 or Ø3 rod or a Ø5 tube, 5 mm gap](https://xemstudio.com/objects/rod-clevises/)
- [Flanged cylinder liners Ø16, 20, 25 and 30](https://xemstudio.com/objects/power-cylinder-liner/)
- [Tri-clamp spool (two ferrules on a tube), 1.5 and 2 inch](https://xemstudio.com/objects/tri-clamp-spool/)
- [2020 aluminum extrusion, 6 mm slot (20-series)](https://xemstudio.com/objects/2020-aluminum-extrusion/)
- [Rocker beam 60 / 80 / 100 mm on a 623 pivot](https://xemstudio.com/objects/rocker-beam/)