# Gamma frame: base plates for tri-clamp engines, rocker beam and pivot post

> What frame do I need to mount a tri-clamp Stirling engine with its crank?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Base plate sized to the ISO 2852 flange of each spool size with slotted crank-stand mounts and the 2020 hole pattern; classic beam-driven gamma uses a rocker beam on a 623 pivot to drive the displacer from the crank
- Page: https://xemstudio.com/objects/gamma-base-plate-and-beam/ · JSON: https://xemstudio.com/api/geometry?object=gamma-base-plate-and-beam · Plain text: https://xemstudio.com/objects/gamma-base-plate-and-beam/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

## Notes

- Base plate: the spool (or its cap) sits in the bore; crank stands bolt into the slots so the crank height and rod alignment can be set; four M5 holes drop it onto 2020 extrusion or any bench. Print in PETG 6 mm, or use it as a drilling template for aluminium.
- Rocker beam: pivot in the middle on a 623 bearing on the post; one end to the crank con-rod, the other to the displacer rod. It converts the crank's motion to the displacer stroke with a lever ratio (set by where the pins sit) and lets the crank sit beside the engine instead of above it: the classic 'beam engine' gamma. Ratio 1:1 at the end holes; drill nearer the pivot for a shorter displacer stroke.
- Everything mounts on Ø3 pins and M3 screws; stands and heads from the other entries.

## Sizes

| part | size | fits |
|---|---|---|
| base plate 1.5 in | 140 × 70 × 6 | 50.5 flange |
| base plate 2 in | 154 × 70 × 6 | 64 flange |
| base plate 3 in | 181 × 70 × 6 | 91 flange |
| rocker beam | 60 / 80 / 100 | 623 pivot, Ø3 ends |
| pivot post | 60 tall | M3 foot |

## 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 (7 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/index.json

- base-plate-1.5in: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-1.5in.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-1.5in.stl) — base plate for a 1.5 in tri-clamp engine: spool bore, slotted crank-stand mounts, 4 × M5 to 2020 extrusion, 6 thick
- base-plate-2in: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-2in.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-2in.stl) — base plate for a 2 in tri-clamp engine: spool bore, slotted crank-stand mounts, 4 × M5 to 2020 extrusion, 6 thick
- base-plate-3in: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-3in.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/base-plate-3in.stl) — base plate for a 3 in tri-clamp engine: spool bore, slotted crank-stand mounts, 4 × M5 to 2020 extrusion, 6 thick
- rocker-beam-60: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-60.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-60.stl) — rocker beam 60 mm, centre pivot on a 623, Ø3.2 ends (beam-driven displacer)
- rocker-beam-80: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-80.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-80.stl) — rocker beam 80 mm, centre pivot on a 623, Ø3.2 ends (beam-driven displacer)
- rocker-beam-100: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-100.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/rocker-beam-100.stl) — rocker beam 100 mm, centre pivot on a 623, Ø3.2 ends (beam-driven displacer)
- pivot-post-60: [STEP](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/pivot-post-60.step) · [STL](https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/pivot-post-60.stl) — beam pivot post 60 mm, Ø3 pin, 2 × M3 foot

## How it fits

### Parts that fit it
- [Power cylinder liners, piston blanks, crosshead and guide (the non-syringe power piston)](https://xemstudio.com/objects/power-cylinder-piston-crosshead/): liner on the base plate

### Goes in or on
- [Aluminium T-slot extrusion: 2020, 2040, 2060, 2080, V-slot, 3030, 3060, 4040, 4080, 1010, 1515](https://xemstudio.com/objects/t-slot-extrusions/): 4 × M5 to 2020

### Connects to
- [Stirling linkage fittings: rod clevises, shaft adapter, 625 crank stands, Ø3 crank discs, rhombic frame heads](https://xemstudio.com/objects/stirling-linkage-fittings/): 625 crank stands in the slots
- [Tri-clamp spool (two ferrules on a tube), 1.5 and 2 inch](https://xemstudio.com/objects/tri-clamp-spool/): spool bore

### Also needed
- [T-slot attachments: slide-in and drop-in T-nuts, corner brackets, gussets, end caps, slot covers, feet, hole plates](https://xemstudio.com/objects/t-slot-brackets-and-nuts/): T-nuts

## Questions

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

Base plate with the spool bore and slotted crank-stand mounts; bolt it to 2020 extrusion with M5 button heads or to a board.

**What is a beam-driven Stirling engine?**

The crank drives a rocker beam whose far end lifts the displacer: the crank can sit beside the cylinder and the beam's lever ratio sets the displacer stroke.

## Fits with

- [Aluminium T-slot extrusion: 2020, 2040, 2060, 2080, V-slot, 3030, 3060, 4040, 4080, 1010, 1515](https://xemstudio.com/objects/t-slot-extrusions/)
- [T-slot attachments: slide-in and drop-in T-nuts, corner brackets, gussets, end caps, slot covers, feet, hole plates](https://xemstudio.com/objects/t-slot-brackets-and-nuts/)
- [Can-engine printed kit: can caps, diaphragm clamps, displacer guides, crank stands, CD/platter hubs, syringe cradles](https://xemstudio.com/objects/can-engine-printed-kit/)
- [Crank discs, connecting rods and flywheels for model engines](https://xemstudio.com/objects/crank-conrod-flywheel-kit/)
- [Tri-clamp displacers and engine heads: 1.5, 2 and 3 in spools](https://xemstudio.com/objects/tri-clamp-displacers-and-heads/)