Fluidyne (liquid-piston Stirling) manifold and tees for 1/2 in copper U-tubes — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/fluidyne-manifold/  (CC BY 4.0)
Basis: West's fluidyne (Harwell, 1970s): a U-tube of water is the displacer, a second water column the power piston, gas spaces above; natural period of the U-tube sets the frequency: T = 2π√(L/2g) with L the water column length
Catalog version: 2026-10-20

Sizes: see table below
- No solid moving parts: water in a U-tube rocks back and forth (the displacer), shuttling the gas above it between a heated and a cooled leg; a third column (the output) is pumped by the pressure swing. Frequency comes from the U-tube: T = 2π√(L/2g): a 400 mm water column oscillates at ~1.1 Hz. The hot leg is heated above the water line, the cold leg left bare or water-cooled.
- Tube: 1/2 in Type L copper (15.88 OD, 13.8 ID) for the U legs; glass (test tube or 16 mm borosilicate tube) for a see-through cold leg. Gas space above each leg 2–3 × the swept volume; tuning line (4 mm) between the gas spaces sets the phase (West's 'tuning column'). Output column: another 1/2 in leg with check valves for a pump.
- The printed manifold joins the two legs at the top with a gas passage and the tuning port; the tee adds the output column. Seal copper into the sockets with silicone; everything above the water stays under 60 °C so PETG is fine, the heated copper is below it.
- LES: the no-moving-parts demonstrator next to the thermoacoustic one: same spools, water instead of pistons.

part  size  note
U legs  1/2 in copper, 300–500 long  water column
manifold  2 sockets @ 60 mm, 4 mm tuning port  printed
output tee  1/2 in + 4 mm port  pump column
period  2π√(L/2g)  L = water column length

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Fluidyne engine — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Fluidyne
- C. D. West: Liquid Piston Stirling Engines (1983) — book, reports (OSTI) — reference / US Gov reports public domain [verify license at link] — https://www.osti.gov/search/semantic:fluidyne
- Long Earth Society: Engine builds — web, video — LES site — https://longearthsociety.com/engineering/

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