Alpha V-twin: 90° two-pin crank discs, V block, transfer tee — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/alpha-twin-crank-90/  (CC BY 4.0)
Basis: Alpha configuration: two pistons in separate hot and cold cylinders, 90° apart in phase; here with one crank disc carrying both pins 90° apart (V-twin) or two discs clocked on one shaft
Catalog version: 2026-10-20

Sizes: see table below
- Alpha phase: the cold piston follows the hot piston by 90°. Simplest way: one crank disc with two pins 90° apart, cylinders in a 90° V over it (V-twin); both con-rods ride the same disc, each pin at the same throw e. Or two separate crank discs on one shaft, clocked 90° with set screws.
- V block: two 10 mL syringe barrels at 90° over the shaft; the hot barrel is glass if you have it (a plastic syringe survives a tea-light hot end at 80 °C only with the heat going into a copper tube, not the barrel). Transfer tee: 4 mm bores, hot → regenerator → cold.
- Strokes 12–20 mm (e 6–10) suit 10 mL syringes (Ø14.5: 1.65 mL per 10 mm). Alpha engines have the highest specific power of the three but need the piston seal on the hot side; the Ross yoke kit is the parallel-cylinder alternative.

part  size  note
crank disc 2-pin  e 6 / 8 / 10  pins 90° apart
V block  2 × Ø16.05 @ 90°  10 mL syringes
transfer tee  4 mm  regenerator between

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- 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, 5 parts): https://xemstudio.com/files/hardware/alpha-twin-crank-90/index.json
API: https://xemstudio.com/api/geometry?object=alpha-twin-crank-90