Alpha V-twin frame for two 10 mL syringes: frame, crank disc and con-rods sized so it actually runs — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/alpha-v-twin-frame/  (CC BY 4.0)
Basis: Computed in the generator: crank throw 8, rod 60, 10 mL syringe piston (pin 8.6 above the skirt, 19 long), barrel 15.9 OD / 14.5 ID; checked over a full turn: skirt never closer than the barrel mouth, rod never within 0.5 mm of the barrel wall
Catalog version: 2026-10-20

Sizes: see table below
- Phase: in a 90° V both con-rods ride ONE crank pin, and the 90° between the cylinders is the 90° alpha phase. (A two-pin disc with pins 90° apart is for parallel cylinders; under a 90° V it would give 0° or 180° and the engine would not run.)
- Geometry: crank axis at the origin; both barrel axes pass through it at ±45°. Barrel sockets start at R45 so the piston (bottom of skirt 43.4 mm from the axis at bottom dead centre) never leaves the barrel, and with a 60 mm rod the rod swings at most ±7.7°, keeping 0.8 mm from the barrel wall.
- Along the shaft (Y): 625 · boss · 625, 2 mm spacer, crank disc (6), 1 mm spacer, rod 1 (cylinder at +45°), 1 mm spacer, rod 2 (cylinder at −45°), Ø3 × 20 pin pressed 6 mm into the disc, 3 mm collar on its end. Flywheel (nut-weighted Ø100, b5) on the other end of the Ø5 × 80 shaft behind the boss.
- Barrels slide in from the crank side, tip outward, finger flange against the socket's inner face; M3 pinch screw. Pistons: syringe-piston-10ml (no plunger). Transfer: a short tube with a mesh plug between the tips (transfer tee).
- Foot: 2 × M5 at 50 mm into a 2020 rail; mount it at the rail's end so the flywheel hangs clear. Print the frame on its back (the plate on the bed).
- LES: the two-syringe alpha, complete.

parameter  value  note
crank throw  8.0  stroke 16 → 2.6 mL per cylinder
con-rod  60.0  Ø3 plain ends, H8/f7
V angle  90  = phase
socket inner face  45.0  radius from crank axis
min skirt radius  43.4  ≥ barrel mouth
rod-to-wall margin  0.83  > 0
shaft  Ø5 × 80  2 × 625
rod planes (Y)  9.5 / 15.5  1 mm spacers

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

Free files (CC BY 4.0, Xem Studio; STEP + STL, 3 parts): https://xemstudio.com/files/hardware/alpha-v-twin-frame/index.json
API: https://xemstudio.com/api/geometry?object=alpha-v-twin-frame