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Alpha V-twin: 90° two-pin crank discs, V block, transfer tee

How do I set the 90 degree phase on an alpha Stirling engine? · Hardware · 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

Long Earth Society build part. Alpha demonstrator and the twin-crank for the two-spool alpha. The engines

sizes
3 in table

Notes

  • 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.

Sizes

partsizenote
crank disc 2-pine 6 / 8 / 10pins 90° apart
V block2 × Ø16.05 @ 90°10 mL syringes
transfer tee4 mmregenerator between

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

WikipediaStirling enginewebCC BY-SA 4.0 (text)
Long Earth SocietyEngine buildsweb, videoLES site

Free files

★ Free files 5 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

crank-disc-2pin-90deg-e6single crank disc with two Ø3 pin holes 90° apart at 6 mm (stroke 12): both alpha con-rods on one discSTEP · STL
crank-disc-2pin-90deg-e8single crank disc with two Ø3 pin holes 90° apart at 8 mm (stroke 16): both alpha con-rods on one discSTEP · STL
crank-disc-2pin-90deg-e10single crank disc with two Ø3 pin holes 90° apart at 10 mm (stroke 20): both alpha con-rods on one discSTEP · STL
v-block-90-2x-syringe-10ml90° V block for two 10 mL syringe barrels over one crank (alpha V-twin)STEP · STL
transfer-tee-4mm4 mm transfer tee (hot cylinder → regenerator → cold cylinder)STEP · STL

Plain text: sheet.txt · JSON: /api/geometry?object=alpha-twin-crank-90

Alpha V-twin: 90° two-pin crank discs, V block, transfer tee, isometric render of a generated part
Render of crank-disc-2pin-90deg-e8 from the free STEP; not to scale.

Fits with

Ross yoke kit (alpha Stirling with parallel cylinders), isometric render of a generated part
Ross yoke kit (alpha Stirling with parallel cylinders)5 sizes★ 6 files
Crank discs, connecting rods and flywheels for model engines, isometric render of a generated part
Crank discs, connecting rods and flywheels for model engines3 sizes★ 15 files
Plastic syringes 1–60 mL as pistons and cylinders, isometric render of a generated part
Plastic syringes 1–60 mL as pistons and cylinders7 sizes★ 7 files
Regenerator and heat materials: stainless mesh counts, steel wool, scrubbers, mica, fiberglass, ceramic, firebrick, isometric render of a generated part
Regenerator and heat materials: stainless mesh counts, steel wool, scrubbers, mica, fiberglass, ceramic, firebrick9 sizes★ 5 files
Stirling engine configurations: which type needs which parts on this shelf14 lineslist

Questions

What phase angle does an alpha Stirling use?

90°: the cold piston lags the hot piston by a quarter turn. One disc with two pins 90° apart (and cylinders in a 90° V) gives it automatically.

Which alpha cylinder gets the heat?

The one whose piston leads: expansion space hot, compression space cold; gas flows through the regenerator between them.