Linear alternator coil Ø50 × 10 (≈ 314 turns) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/linear-alternator-coil/  (CC BY 4.0)
Basis: Winding volume of one bobbin bay; turns and resistance computed in the generator for 0.30 mm wire
Catalog version: 2026-10-20

Sizes: see table below
- One coil of the alternator, as the solid of its winding: Ø50 outside, Ø38.6 inside (the bobbin core), 10 long.
- About 314 turns of 0.30 mm wire fill it. Two per alternator, the second wound the opposite way; both in series come to about 21.3 Ω.
- At 12 Hz and 12 mm stroke the pair gives about 22.7 V peak per tesla of gap flux.

parameter  value
outside  50
inside  38.6
length  10
turns  ≈ 314 of 0.30 mm
resistance, both in series  21.3 Ω
EMF per tesla  22.73 V peak at 12 Hz, 12 mm

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- NASA (NTRS, public domain): Linear alternator design for free-piston Stirling convertors (2005) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=20050182934
- NASA (NTRS, public domain): Sunpower/NASA 80 We free-piston Stirling convertor (2002) — PDF — US Government work, public domain — https://ntrs.nasa.gov/search?q=20020047256
- Wikipedia: Linear alternator — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Linear_alternator
- Wikipedia: Free-piston engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Free-piston_engine
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/linear-alternator-coil/index.json
API: https://xemstudio.com/api/geometry?object=linear-alternator-coil