# Axial-flux rotor plates: Ø90 with 12 magnets (Ø8 bore), Ø70 with 8 magnets (Ø5 bore)

> How do I build a small axial flux generator rotor with neodymium magnets?

- Category: Stirling engines › Generators & instruments
- Kind: Hardware
- Basis: Coreless axial-flux layout: 12 poles on Ø90 or 8 poles on Ø70, pockets for Ø10 × 3 disc magnets, hub sized to the Ø8 / Ø5 shaft
- Page: https://xemstudio.com/objects/axial-flux-rotor/ · JSON: https://xemstudio.com/api/geometry?object=axial-flux-rotor · Plain text: https://xemstudio.com/objects/axial-flux-rotor/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

- The Ø90 rotor is a 5 mm plate with 12 pockets Ø10 × 3 deep on a Ø72 circle, a Ø32 × 8 hub underneath and a Ø8 bore through (13 mm overall).
- The Ø70 rotor has 8 pockets Ø10 × 3 on a Ø52 circle, a Ø26 × 8 hub and a Ø5 bore.
- A Ø2.5 radial hole (M3 tap drill) enters the hub 4 mm below the plate for a grub screw.
- Magnets alternate N-S around the ring; a second rotor facing it (N opposite S across the stator) doubles the flux.
- Frequency = rpm × poles / 120: 600 rpm on the 12-pole rotor is 60 Hz.

## 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 |
|---|---|---|---|---|
| rotor bore | Ø8 / Ø5 | shaft (M3 grub) | slide | rotor-* |
| magnet pockets | Ø10 × 3 | Ø10 × 3 disc magnet | press | rotor-* |
| grub hole | Ø2.5 | M3 tap drill | designed | rotor-* |

## Sizes

| rotor | plate_mm | magnets | magnet_circle_mm | hub_mm | bore_mm |
|---|---|---|---|---|---|
| rotor-90-12x-10x3-b8 | Ø90 × 5 | 12 × Ø10×3 | 72 | Ø32 × 8 | 8 |
| rotor-70-8x-10x3-b5 | Ø70 × 5 | 8 × Ø10×3 | 52 | Ø26 × 8 | 5 |

## Where the files are

- Wikipedia: [Axial flux motor](https://en.wikipedia.org/wiki/Axial_flux_motor) — web — CC BY-SA 4.0 (text)
- Wikipedia: [Alternator](https://en.wikipedia.org/wiki/Alternator) — web — CC BY-SA 4.0 (text)
- Hugh Piggott: [A Wind Turbine Recipe Book (axial-flux alternator design)](http://scoraigwind.co.uk/) — web, PDF — Author's site (verify at link)
- Long Earth Society: [Engine and rig builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (2 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/axial-flux-rotor/index.json

- rotor-90-12x-10x3-b8: [STEP](https://xemstudio.com/files/hardware/axial-flux-generator-kit/rotor-90-12x-10x3-b8.step) · [STL](https://xemstudio.com/files/hardware/axial-flux-generator-kit/rotor-90-12x-10x3-b8.stl) — rotor plate Ø90 × 5: 12 pockets for Ø10 × 3 magnets (alternating poles) on a 66 mm circle, Ø8 bore hub with set screw; two face each other across the stator
- rotor-70-8x-10x3-b5: [STEP](https://xemstudio.com/files/hardware/axial-flux-generator-kit/rotor-70-8x-10x3-b5.step) · [STL](https://xemstudio.com/files/hardware/axial-flux-generator-kit/rotor-70-8x-10x3-b5.stl) — rotor plate Ø70 × 5: 8 pockets for Ø10 × 3 magnets on a 46 mm circle, Ø5 bore hub with set screw

## How it fits

### Parts that fit it
- [Hall sensor mount for TO-92S (A3144 / SS49E)](https://xemstudio.com/objects/hall-sensor-mount/): faces a rotor magnet: 12 pulses per revolution

### Goes in or on
- [Metric shafts Ø3 to Ø10 with D-flats and clip grooves](https://xemstudio.com/objects/metric-shafts/): Ø8 / Ø5 bore on the shaft, M3 grub

### Connects to
- [Neodymium disc magnets, common sizes](https://xemstudio.com/objects/neodymium-disc-magnets/): Ø10 × 3 magnets in the Ø10 × 3 pockets (press)
- [608 ball bearing](https://xemstudio.com/objects/608-bearing/): the Ø8 flywheel shaft runs in 608s

### Also needed
- [Axial-flux stator plates: Ø90 9-coil and Ø70 6-coil](https://xemstudio.com/objects/axial-flux-stator/): coils on the same Ø72 / Ø52 circle

## Questions

**How many magnets for a small axial flux generator?**

12 magnets with 9 coils (3-phase) on a Ø90 rotor, or 8 magnets with 6 coils on Ø70; poles alternate N-S.

**What magnets fit the rotor?**

Ø10 × 3 disc magnets; the pockets are drawn Ø10 × 3 exact (press, see Mating features).

**What frequency does it make?**

Rpm × poles / 120: 60 Hz at 600 rpm on the 12-pole rotor.

## Fits with

- [Axial-flux stator plates: Ø90 9-coil and Ø70 6-coil](https://xemstudio.com/objects/axial-flux-stator/)
- [Coil bobbin Ø10 core × 8 mm, Ø13 flanges](https://xemstudio.com/objects/coil-bobbin/)
- [Hall sensor mount for TO-92S (A3144 / SS49E)](https://xemstudio.com/objects/hall-sensor-mount/)
- [Neodymium disc magnets, common sizes](https://xemstudio.com/objects/neodymium-disc-magnets/)
- [608 ball bearing](https://xemstudio.com/objects/608-bearing/)
- [Metric shafts Ø3 to Ø10 with D-flats and clip grooves](https://xemstudio.com/objects/metric-shafts/)