Gamma frame: base plates for tri-clamp engines, rocker beam and pivot post — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/gamma-base-plate-and-beam/  (CC BY 4.0)
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
Catalog version: 2026-10-20

Sizes: see table below
- 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.

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

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Beam engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Beam_engine
- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 7 parts): https://xemstudio.com/files/hardware/gamma-base-plate-and-beam/index.json
API: https://xemstudio.com/api/geometry?object=gamma-base-plate-and-beam