# Crank discs Ø30 for a Ø3 crankshaft, 10 to 20 mm stroke

> What crank disc fits a 3 mm crankshaft?

- Category: Stirling engines › Drives & mechanisms
- Kind: Hardware
- Basis: Ø30 × 6 disc, Ø3 bore, Ø3 pin hole at stroke / 2, M3 grub
- Page: https://xemstudio.com/objects/crank-discs-3mm-bore/ · JSON: https://xemstudio.com/api/geometry?object=crank-discs-3mm-bore · Plain text: https://xemstudio.com/objects/crank-discs-3mm-bore/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

- A Ø30 × 6 disc with a Ø3 bore for the crank head's Ø3 crankshaft (623 towers) or the can engine's Ø3 shaft.
- A Ø3 pin hole at 5.0, 7.5 or 10.0 mm from the axis gives 10, 15 or 20 mm stroke.
- A radial Ø2.5 hole (M3 tap drill) at mid-thickness locks it to the shaft.

## 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 |
|---|---|---|---|---|
| crank-disc bore | Ø3 | Ø3 crankshaft (M3 grub) | slide | crank-disc-b3-* |
| crank-disc pin hole | Ø3 | Ø3 crank pin | press | crank-disc-b3-* |
| crank-disc grub hole | Ø2.5 | M3 tap drill | designed | crank-disc-b3-* |

## Sizes

| file | stroke | pin offset | disc | bore |
|---|---|---|---|---|
| crank-disc-b3-stroke10 | 10 | 5.0 | Ø30 × 6 | 3 |
| crank-disc-b3-stroke15 | 15 | 7.5 | Ø30 × 6 | 3 |
| crank-disc-b3-stroke20 | 20 | 10.0 | Ø30 × 6 | 3 |

## Where the files are

- Long Earth Society: [Tri-clamp Stirling 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/crank-discs-3mm-bore/index.json

- crank-disc-b3-stroke10: [STEP](https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke10.step) · [STL](https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke10.stl) — crank disc Ø30 for a Ø3 crankshaft (the crank head's 623 towers), pin at 5.0 mm (10 mm stroke), M3 grub
- crank-disc-b3-stroke15: [STEP](https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke15.step) · [STL](https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke15.stl) — crank disc Ø30 for a Ø3 crankshaft (the crank head's 623 towers), pin at 7.5 mm (15 mm stroke), M3 grub
- crank-disc-b3-stroke20: [STEP](https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke20.step) · [STL](https://xemstudio.com/files/hardware/stirling-linkage-fittings/crank-disc-b3-stroke20.stl) — crank disc Ø30 for a Ø3 crankshaft (the crank head's 623 towers), pin at 10.0 mm (20 mm stroke), M3 grub

## How it fits

### Goes in or on
- [Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat](https://xemstudio.com/objects/stirling-crankshafts/): Ø3 crankshaft in the bore
- [Tri-clamp displacer: Ø33.6, Ø46 and Ø70.9 for 1.5, 2 and 3 in spools](https://xemstudio.com/objects/tri-clamp-displacer/): on the crank head's Ø3 shaft between the 623 towers

### Connects to
- [Connecting rods 30 to 80 mm centres with 623 pockets](https://xemstudio.com/objects/connecting-rods-623/): 623 end on the Ø3 pin

### Alternatives
- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/): same discs for a Ø5 shaft

## Questions

**What crank disc fits a 3 mm shaft?**

Crank-disc-b3: Ø30 × 6, Ø3 bore, M3 grub, pin at 5, 7.5 or 10 mm.

**How is the stroke set?**

Stroke = 2 × pin offset: 10, 15 or 20 mm.

## Fits with

- [Crank discs for a Ø5 shaft, 10 to 30 mm stroke](https://xemstudio.com/objects/crank-discs-5mm-bore/)
- [Crankshafts Ø3, Ø5 and Ø8 with full-length D-flat](https://xemstudio.com/objects/stirling-crankshafts/)
- [Connecting rods 30 to 80 mm centres with 623 pockets](https://xemstudio.com/objects/connecting-rods-623/)
- [Crank and wrist pins Ø3 × 12, 16, 19, 20 and 23](https://xemstudio.com/objects/pins-3mm/)
- [Tri-clamp displacer: Ø33.6, Ø46 and Ø70.9 for 1.5, 2 and 3 in spools](https://xemstudio.com/objects/tri-clamp-displacer/)