Linear-alternator stator that clamps round a 2 in tri-clamp tube: four coils outside the pressure wall — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/canned-linear-alternator-stator-2in/  (CC BY 4.0)
Basis: Coil window and pitch from the alternator design in tools/gen_ta_power.py; gap field from a magnetic-circuit estimate
Catalog version: 2026-10-20

Sizes: see table below
- The coils sit outside the honed spool: a split bobbin clamps on the Ø50.8 tube with four 14 mm bays at the magnet rows' 32 mm pitch; the coils are wound in place, alternate hands, and joined in series; a split return-path shell (Ø66 / Ø74) clamps over them with three M4 × 16 and nuts each side. The shell has to carry the magnets' flux back; what it is made of is the builder's choice within that.
- The spool wall (1.40 after honing) and a 0.5 bobbin wall sit in the magnetic gap: the wall must not carry magnetic flux, or it short-circuits the magnets. In the 25 Hz field the eddy-current loss in a 1.4 mm wall is a fraction of a watt.
- Estimate: gap field 0.29 T (Br 1.3 T magnets, magnetic-circuit estimate with a 0.8 leakage factor), 369 turns of 0.45 mm wire per coil, Bl ≈ 79 T·m, coil resistance ≈ 31 Ω, inductance ≈ 132 mH; damping available Bl²/R ≈ 203 N·s/m. Measure Bl (EMF ÷ velocity) on the built engine; the model's power scales with it.
- No electrical pass-through, no wire in the gas: the generator's pressure boundary is only tri-clamp joints.
- Fits: bobbin bore clamps the tube (the 1 mm split is the take-up); shell bore clamps the bobbin flanges; ear holes are M4 clearance.

part  value
bays  4 × 14 at 32
coil  Ø65.8 / Ø51.8
shell  Ø74 / Ø66 × 112
turns per coil  369
Bl  ≈ 79 T·m
coil resistance  ≈ 31 Ω (all four)

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Xem Studio: tools/gen_ta_power.py: the network model and every dimension on this page — code — CC BY 4.0 — https://xemstudio.com/
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 3 parts): https://xemstudio.com/files/hardware/canned-linear-alternator-stator-2in/index.json
API: https://xemstudio.com/api/geometry?object=canned-linear-alternator-stator-2in