Build · 2025-08-10
Stirling engine displacer build (full walkthrough)
What does the real displacer cost and weigh once built from laser-cut plates, flashing, and foil tape?
About $65 in materials, and heavy enough that the planar spring droops slightly under it, which suggests the spring rate is about right.
- Kind
- Build
- Status
- Built
- Date
- 2025-08-10
- End plates
- Laser-cut Al, 2 mm + 1 mm
- Plate cost
- $38 for two sets
- Walls
- Aluminum flashing (~$20)
- Seal
- Foil HVAC tape, ~600 °F ($7)
- Total
- ≈ $65
Video
What it is
The full build with production parts: laser-cut aluminum end plates, aluminum flashing walls, and high-temperature foil tape to seal the seams without eating into side clearance. Also a look at power-piston options.
Results
- →Overseas CNC and metal printing both quoted around $300 for two discs after tariffs; a US laser-cutting shop (the same one that cuts the planar springs) did four plates for $38.
- →Copper flashing was too thick and stiff; aluminum worked.
- →Fits the vessel with clearance intact; spring visibly sags under the weight.
Lab notes
Sealing
Leaky displacer walls let air pass through instead of being shuttled hot-to-cold. Thin foil tape seals the seams while adding almost nothing to the diameter, which matters with ~1 mm clearance.
Power piston candidates
An Airpot graphite-in-glass piston (used, ~$20–40; ~$200 new) works but isn't reproducible at that price. A smaller Airpot sample (~$50) on an ABS-printed 1.5 in tri-clamp mount with a silicone thermal break is cheaper but its swept volume is far smaller than the displacer's, so several would be needed. Likely final: a magnet piston with a wound cylinder and a gas spring above.
Notes transcribed from the build video.
Related
Questions about this one? Ask in the Discord. It's the fastest way to reach me.