# Two-pin crank disc, pins 90° apart, 6 / 8 / 10 mm throw

> What crank disc gives 90° phase for an alpha Stirling with parallel cylinders?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Alpha phase 90°: two pins a quarter-turn apart for parallel or in-line cylinders
- Page: https://xemstudio.com/objects/two-pin-crank-disc-90/ · JSON: https://xemstudio.com/api/geometry?object=two-pin-crank-disc-90 · Plain text: https://xemstudio.com/objects/two-pin-crank-disc-90/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

**Exact dimensions.** Every file is drawn at true size with no printing tolerance. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your printer's or process's clearance before making the part.

## Notes

- Ø30 × 6 disc with a Ø5 bore (fit: slide), a Ø2.5 radial hole (M3 tap size) for a grub screw, and two Ø3 pin holes (fit: press) 90° apart at the same throw.
- Throws 6, 8 and 10 mm give strokes of 12, 16 and 20 mm; on a 10 mL syringe (Ø14.5) that is 1.65 mL per 10 mm of stroke.
- For parallel or in-line cylinders only. Cylinders in a 90° V share one pin instead (alpha V-twin crank disc).

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| disc bore | Ø5 | Ø5 shaft (M3 grub) | slide | crank-disc-* |
| disc pin holes | Ø3 | Ø3 crank pins | press | crank-disc-* |
| disc grub hole | Ø2.5 | M3 tap drill | designed | crank-disc-* |

## Sizes

| file | throw | stroke | disc | bore | pins |
|---|---|---|---|---|---|
| crank-disc-2pin-90deg-e6 | 6 | 12 | Ø30 × 6 | 5 | 2 × Ø3 at 90° |
| crank-disc-2pin-90deg-e8 | 8 | 16 | Ø30 × 6 | 5 | 2 × Ø3 at 90° |
| crank-disc-2pin-90deg-e10 | 10 | 20 | Ø30 × 6 | 5 | 2 × Ø3 at 90° |

## Where the files are

- 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 (3 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/two-pin-crank-disc-90/index.json

- crank-disc-2pin-90deg-e6: [STEP](https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e6.step) · [STL](https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e6.stl) — crank disc with two Ø3 pin holes 90° apart at 6 mm (stroke 12): for PARALLEL alpha cylinders (not a 90° V, which uses one pin)
- crank-disc-2pin-90deg-e8: [STEP](https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e8.step) · [STL](https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e8.stl) — crank disc with two Ø3 pin holes 90° apart at 8 mm (stroke 16): for PARALLEL alpha cylinders (not a 90° V, which uses one pin)
- crank-disc-2pin-90deg-e10: [STEP](https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e10.step) · [STL](https://xemstudio.com/files/hardware/alpha-twin-crank-90/crank-disc-2pin-90deg-e10.stl) — crank disc with two Ø3 pin holes 90° apart at 10 mm (stroke 20): for PARALLEL alpha cylinders (not a 90° V, which uses one pin)

## How it fits

### Connects to
- [Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat](https://xemstudio.com/objects/stirling-crankshafts/): Ø5 shaft in the bore
- [Con-rods with Ø3 pin ends, 45 and 60 mm, 8 × 5](https://xemstudio.com/objects/pin-end-con-rods/): one con-rod per pin

### Alternatives
- [Alpha V-twin crank disc Ø26, one pin, 16 mm stroke](https://xemstudio.com/objects/alpha-v-twin-crank-disc/): one-pin disc for a 90° V
- [Ross yoke a = h = 20 for two parallel syringes](https://xemstudio.com/objects/ross-yoke/): parallel cylinders on a Ross yoke

### Also needed
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/): Ø3 crank pins

## Questions

**What phase angle does an alpha Stirling use?**

90°: with parallel cylinders put the two pins a quarter-turn apart, as on this disc.

**Can I use the two-pin disc on a V-twin?**

Not on a 90° V: it would give 0° or 180°. A 90° V uses one pin for both rods.

## Fits with

- [Alpha V-twin crank disc Ø26, one pin, 16 mm stroke](https://xemstudio.com/objects/alpha-v-twin-crank-disc/)
- [Transfer tee for 4 × 6 mm tube](https://xemstudio.com/objects/transfer-tee-4mm/)
- [Ross yoke a = h = 20 for two parallel syringes](https://xemstudio.com/objects/ross-yoke/)
- [Con-rods with Ø3 pin ends, 45 and 60 mm, 8 × 5](https://xemstudio.com/objects/pin-end-con-rods/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)