Nut-weighted flywheels: Ø100–200 with hex pockets for M8, M10, M12, 3/8 and 1/2 in nuts — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/nut-weighted-flywheels/  (CC BY 4.0)
Basis: Hex nut envelopes from ISO 4032 (M8 13 × 6.8, M10 16 × 8.4, M12 18 × 10.8) and ASME B18.2.2 finished hex (3/8 in 9/16 × 21/64, 1/2 in 3/4 × 7/16 in); pockets drawn at the nut's nominal across-corners (press fit; nut masses computed from the hex envelope in steel, weigh yours
Catalog version: 2026-10-20

Sizes: see table below
- A printed flywheel is too light to carry a Stirling through its cycle; Each wheel has a ring of hex pockets with one flat facing outward, so every nut sits the same way, flush with the face, and the rim holds it against centrifugal load.
- Pockets come in multiples of six, so you can fill all of them (maximum inertia, balanced), every other one (half the weight, still balanced), every third, or only one half (a counterweight: the half opposite the crank pin). Press the nuts in; a drop of CA or a strip of tape over the face holds them for good.
- Hub: Ø3 (Ø100 and Ø120 only: can engine, LTD and crank-head Ø3 shafts), Ø5 (625 crank stands, rhombic gears, the gamma and alpha crankshafts) or Ø8 (tri-clamp crank frame), with an M3 grub on the shaft's D-flat; no adapter needed.
- Sizing: a 2 in tri-clamp gamma on a tea light runs well on Ø150 with a full set of M10 nuts (18 nuts, ~190 g, about +7.6 kg·cm² at the rim); the can engine on Ø100 M8 half-filled; LTDs want the lightest wheel that keeps them turning (start half-filled and add). Print flat, 4 walls, 30 % infill; the nuts are the mass.
- LES: the flywheels on the engines.

od_mm  nut  pockets  pocket_radius_mm  rim_mm  nut_g_each  full_set_g  added_inertia_kg_cm2  bores
100  M8  12  40.5  8.3  5.6  67  1.1  3 / 5 / 8
120  M10  12  49.0  9.9  10.3  124  3.0  3 / 5 / 8
120  3/8 in  12  49.9  9.8  7.8  93  2.3  3 / 5 / 8
150  M10  18  64.0  9.9  10.3  186  7.6  5 / 8
150  M12  12  63.0  12.3  16.0  192  7.6  5 / 8
150  1/2 in  12  62.5  12.6  18.5  221  8.6  5 / 8
200  M12  18  88.0  12.3  16.0  288  22.3  5 / 8
200  1/2 in  18  87.5  12.6  18.5  332  25.4  5 / 8

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- ISO: ISO 4032 Hexagon regular nuts (style 1) — standard — ISO [verify license at link] — https://www.iso.org/standard/72624.html
- ASME: ASME B18.2.2 Nuts for general applications — standard — ASME [verify license at link] — https://www.asme.org/codes-standards/find-codes-standards/b18-2-2-nuts-for-general-applications-machine-screw-nuts-hex-square-hex-flange-coupling-nuts-(inch-series)
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 24 parts): https://xemstudio.com/files/hardware/nut-weighted-flywheels/index.json
API: https://xemstudio.com/api/geometry?object=nut-weighted-flywheels