LTD (low-temperature differential, coffee-cup) Stirling kit: plates, chamber ring, displacer, top plate with syringe cylinder — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/ltd-coffee-cup-engine-kit/  (CC BY 4.0)
Basis: Senft / Kolin LTD gamma proportions: displacer diameter ≫ stroke (D/stroke ≈ 15–25), displacer swept volume 10–20× the power piston swept volume, thin chamber (height ≈ 1.5 × displacer thickness)
Catalog version: 2026-10-20

Sizes: see table below
- An LTD runs on a cup of coffee or a warm hand: a wide thin chamber between two conductive plates (aluminium, 1–3 mm), a foam displacer filling it with a 2 mm gap, a tiny power piston (syringe) and a crank with the displacer 90° ahead. Everything is about low friction and large area: Ø100 chamber, 16 mm tall, Ø96 × 8 foam displacer, 6 mm displacer stroke, 10 mL syringe at 4–6 mm stroke.
- Plates: the printed bottom plate is a drilling template; the real plate must be metal (aluminium 2 mm) for heat to get in. The top plate can be printed (it is the cold side: PETG, with the syringe socket and rod guide) or metal with the printed boss glued on. Chamber ring: printed, 10 mm wall, sealed to the plates with silicone or a 1.5 mm O-ring in the Ø100 groove (a static seal between ring and plates; nothing moving touches it, the piston and rod run on clearance fits).
- Numbers: 10 mL syringe (Ø14.5) at 5 mm stroke = 0.83 mL; displacer Ø96 × 6 mm stroke = 43 mL → ratio 52 (high, fine for ΔT 20 K). Flywheel Ø100 CD or the crank kit. Runs at 1–3 Hz on 15–20 °C ΔT.
- LES: the warm-hand demonstrator that opens the thermodynamics video.

part  Ø100 kit  Ø150 kit
chamber bore × height  100 × 16  150 × 16
displacer  Ø96 × 8 foam, 6 stroke  Ø146 × 8, 6 stroke
plates  Ø120 × 2 Al  Ø170 × 2 Al
power piston  10 mL syringe, 5 stroke  20 mL syringe, 5 stroke
displacer : piston volume  ~50  ~60
ΔT to run  15–20 K  10–15 K

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Stirling engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Stirling_engine
- James R. Senft: An Introduction to Low Temperature Differential Stirling Engines — book — Moriya Press [verify license at link] — https://www.stirlingengine.com/
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 9 parts): https://xemstudio.com/files/hardware/ltd-coffee-cup-engine-kit/index.json
API: https://xemstudio.com/api/geometry?object=ltd-coffee-cup-engine-kit