Linear alternator bobbin: Ø37 bore, two 10 mm bays — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/linear-alternator-bobbin/  (CC BY 4.0)
Basis: Bore = mover Ø35 + 2 × 1.0 gap; flanges at the back-iron sleeve bore Ø52.5; length = sleeve length 30
Catalog version: 2026-10-20

Sizes: see table below
- The coil former of the alternator stator: Ø37 bore (1.0 mm air gap to the Ø35 mover), Ø38.6 core, 30 long, so the coil pair is centred in the 30 mm sleeve.
- Flanges are Ø52.5, the back-iron sleeve's bore (fit: slide): 4 mm end flanges and a 2 mm divider make two 10 mm winding bays.
- Lead-out slots in both end flanges and a crossover notch in the divider; the second bay is wound the opposite way and joined to the first in series.

parameter  value
bore  37
core OD  38.6
flange OD  52.5
length  30
bays  2 × 10
divider  2
end flanges  4

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-bobbin/index.json
API: https://xemstudio.com/api/geometry?object=linear-alternator-bobbin