# Long Earth Society

> Free-piston and thermoacoustic Stirling engines that turn heat into electricity, data-logged mead experiments, and software builds. Every project starts with a question and ends with the data, including the failures. Run by one builder, Travis Seamon (YouTube: LES Thermodynamics).

Pages are static HTML with JSON-LD. Engineering lab entries are written as a question and a measured answer. Product specs and technical drawings are sold, not published. Content may be quoted with a link back.

## Free tools

- [Halftank: how far can you drive on what's left?](https://longearthsociety.com/misc/halftank/live/): Browser tool: enter the miles left on your gauge (gas or EV) and see everywhere you can still reach as a circle that follows your GPS and shrinks as you drive. Location stays on the device. Short link: /halftank
- [Kalshi hourly crypto model vs. market scoreboard](https://longearthsociety.com/misc/kalshi/scoreboard/): Live forward test of a volatility model on Kalshi's hourly BTC/ETH/SOL/XRP/DOGE/HYPE markets, scored against Kalshi's own prices with Brier scores and calibration, published after each hour settles. Not investment advice.
- [Scoreboard data (CSV)](https://longearthsociety.com/api/scoreboard?days=3650&format=csv): Every settled call: model and price-blind probabilities, Kalshi bid/ask/last, official result.
- [Scoreboard summary (JSON)](https://longearthsociety.com/api/scoreboard?days=30): Aggregated hit rates, Brier scores and calibration.

## Engineering: Stirling and thermoacoustic engines

- [Engineering overview](https://longearthsociety.com/engineering/): How the Stirling cycle works (P-V diagram, the math), how thermoacoustic engines work, a heat-to-power estimator, and the lab index.
- [3-foot Stirling engine](https://longearthsociety.com/engineering/3-foot-stirling/): Q: Does the thermoacoustic design keep working when scaled up to a 3-foot resonator? A: Yes. The scaled-up engine runs. The channel's most-watched build, ~50k views.
- [Custom high-temperature thermoacoustic engine (final design)](https://longearthsociety.com/engineering/custom-high-temp-stirling/): Q: Can a thermoacoustic engine be built rugged enough to sit in a campfire or on a wood stove and still generate electricity? A: Yes. A single-piece 304 stainless engine with a water jacket ran on a blowtorch at 30–34 V open-circuit (45 V peak observed). Power under a real load is the open measurement.
- [Custom Stirling engine, SBC 2023 entry](https://longearthsociety.com/engineering/sbc2023-custom-stirling/): Q: How does the custom engine stack up in the 2023 Stirling engine building contest? A: Winner of the contest.
- [Designing a free-piston Stirling engine](https://longearthsociety.com/engineering/fpse-design/): Q: Can a free-piston Stirling engine be built with a planar spring for the displacer and a helium gas spring instead of a weight on the power piston? A: Design stage. The approach: planar spring for the displacer tuned to 5 Hz, a graphite-glass AIRPEL cylinder as the power piston with one port sealed as a gas spring, helium charge, and a direct-drive linear alternator. Target ~30 W. Trial pending.
- [Designing a displacer for a 3-foot free-piston Stirling engine](https://longearthsociety.com/engineering/displacer-design-3ft-fpse/): Q: What's the simplest displacer for a 6-inch free-piston engine that is light, rigid, and cheap to make? A: Two grooved end plates that clamp thin sheet-metal sides between them on a threaded rod. No welding. Quoted cost fell from ~$400 to $66 for the pair across iterations.
- [Stirling engine displacer build (8" × 6"), aluminum flashing](https://longearthsociety.com/engineering/displacer-build-8x6-flashing/): Q: Does the grooved-plate displacer actually assemble with off-the-shelf aluminum flashing? A: Yes. Flashing cut to length by wrapping it around the model seats in the grooves and clamps tight with the rod and a wing nut.
- [Water check valve, short demo](https://longearthsociety.com/engineering/water-check-valve-engine/): Q: If excess pressure is bled off through a water check valve, does the remaining 1 cubic inch of air oscillate faster? A: Yes. Venting the extra pressure through the water check valve lets the small air volume oscillate more quickly.
- [Stirling engine displacer build (full walkthrough)](https://longearthsociety.com/engineering/displacer-build-full/): Q: What does the real displacer cost and weigh once built from laser-cut plates, flashing, and foil tape? A: About $65 in materials, and heavy enough that the planar spring droops slightly under it, which suggests the spring rate is about right.
- [Running temperature and RPM measurements](https://longearthsociety.com/engineering/temp-rpm-measurements/): Q: What are the hot-end, cold-end and RPM figures for the engine at steady state? A: Hot end 215 °F, cold end 100 °F, 2,699 RPM.
- [Finned tri-clamp heat sink with PTFE thermal break](https://longearthsociety.com/engineering/finned-tri-clamp-heat-sink/): Q: Can a standard 2 in tri-clamp double as the engine's cold-end heat sink if fins are machined into it? A: In simulation, yes. Under identical conditions the finned clamp reached a peak heat flux of ~0.032 W/mm² versus ~0.012 W/mm² for the plain clamp, roughly 2× or better heat rejection in still air. Not yet built or measured.
- [Laser-cut linear flexure bearing](https://longearthsociety.com/engineering/laser-cut-flexure-bearing/): Q: Can a laser-cut linear flexure bearing guide a free-piston Stirling's moving parts without contact? A: Yes. The flexure works as a linear bearing.
- [Syringe air-injection test](https://longearthsociety.com/engineering/syringe-air-injection/): Q: How do amplitude and speed change as air is injected into a sealed Stirling engine? A: Measurable change. Injecting air with a syringe shifts amplitude and speed as internal pressure rises.
- [Generating electricity with any solenoid](https://longearthsociety.com/engineering/solenoid-generator/): Q: Can an ordinary solenoid be run in reverse as a generator? A: Yes. Moving a magnet through the solenoid's coil produces electricity; the actuator becomes an alternator.
- [Thermoacoustic engine spool (aluminum)](https://longearthsociety.com/engineering/aluminum-spool-eddy-currents/): Q: Does an aluminum spool work as the former for a moving-magnet linear alternator? A: No. Aluminum is conductive, so the moving magnet induces eddy currents in the spool that brake it; the magnet can't pass through. Use a non-conductive spool.
- [Piezoelectric diaphragm](https://longearthsociety.com/engineering/piezo-diaphragm/): Q: Can a home-made piezoelectric diaphragm act as the engine's diaphragm and generate electricity at the same time? A: No. It flexes and produces a signal when moved, but not meaningful electricity, and it doesn't work as a proper diaphragm. The flexible concept is interesting; it fails at both jobs.
- [Thermoacoustic turbine test](https://longearthsociety.com/engineering/thermoacoustic-turbine-test/): Q: Can a Wells turbine extract rotary work from the oscillating flow of a 2-inch thermoacoustic engine? A: Not in this test. A metal-printed stainless Wells turbine on a ceramic bearing spun freely by hand but did not turn under the engine's acoustic flow, at either end of the tube. The long shaft is the first suspect.
- [Water-tube valve: the self-regulating air charge](https://longearthsociety.com/engineering/no-moving-parts-thermoacoustic/): Q: Can a long, narrow tube with its end under water act as a one-way valve that holds a thermoacoustic engine at its ideal internal pressure without manual bleeding? A: Yes, and it ran harder than any other vent: the water column behaves as a resonant second piston, not just a valve. ~18 V on the prototype, high enough amplitude to tear diaphragms. Retired because it drinks the water on cool-down.
- [Collapsing one-way valve (balloon → duckbill)](https://longearthsociety.com/engineering/collapsing-one-way-valve/): Q: Can a collapsing one-way valve (balloon, then duckbill) manage the engine's excess pressure without drowning it? A: Yes. A balloon, then a large flexible breast-pump duckbill, then the water column, and finally a 6 in pipe rising out of the engine with a small duckbill at its end. The last one replaced everything and is the working solution.
- [Linear-to-rotational output converter](https://longearthsociety.com/engineering/linear-to-rotational-converter/): Q: Can the free-piston engine's linear stroke be turned into rotary output with a compact converter instead of a diaphragm alternator? A: None
- [S-type layout: does cold need to sit above hot?](https://longearthsociety.com/engineering/s-type-stirling/): Q: Does a thermoacoustic engine's cold end have to be directly above its hot end? A: No, not strictly. An offset S-type layout assembled from tri-clamp parts whistled, then self-started with a diaphragm. The cold end must be higher, not necessarily directly above.
- [Self-starting and restart behavior](https://longearthsociety.com/engineering/self-starting-stirling/): Q: Will the engine start on its own when heated, and restart after cooling? A: Yes with a lighter magnet. A 25 × 5 mm magnet was too heavy to self-start; a 20 × 2 mm magnet started unaided and restarted faster after cooling.

## Write-ups and other builds

- [Misc overview](https://longearthsociety.com/misc/): Long-form field notes and background projects.
- [Racing the clock: an AI-built Kalshi trading bot](https://longearthsociety.com/misc/kalshi/): Q: Can a fair-value model beat Kalshi's hourly crypto markets in the minutes before settlement? A: On paper, yes: 93.9% win rate at the strictest filter. Live, it broke even. Spread, fees and thin books took the edge.
- [The hedge desk: fifteen backtests and one strange idea](https://longearthsociety.com/misc/hedge/): Q: Does anything in the stock market survive an honest train/test split, and can prediction markets hedge option bets? A: One modest edge survived: buying dips back to the 20-day average, about +1% a trade. The options-plus-Kalshi hedge is running on paper; its first four results all landed in the dead zone.
- [The watchlist: standing orders for a liquidation auction](https://longearthsociety.com/misc/nellis/): Q: Can a bot watch Nellis Auction for exactly what I resell, and email only what's worth a bid? A: Yes. 50 standing watches, a resale model that calls FLIP / MAYBE / PASS, and three deduplicated digests a day. Running since July.
- [Halftank: how far can you drive on what's left?](https://longearthsociety.com/misc/halftank/): Q: How far can I drive on the range I have left, and where exactly does that get me? A: A free browser tool that draws your remaining range as a circle around you, following your GPS and shrinking every mile. It grew out of a road-network reach map for scooters.
- [The report button that can't exist](https://longearthsociety.com/misc/report-button/): Q: Can a one-tap dashboard button report speed traps and wrecks into Google Maps, Apple Maps or Waze? A: No. All three take driver reports, but none accept them from another app. Voice is the only hands-free way in, and the steering-wheel voice button already does the job.
- [Hydrogen RC car conversion](https://longearthsociety.com/misc/hydrogen-rc-car/): Q: Can a battery RC car be converted to run on hydrogen generated on board from aluminum and gallium? A: Yes, it runs. Aluminum (soda-can tabs) alloyed with gallium forms reactive aluminum that splits water into hydrogen and aluminum hydroxide; the reaction is exothermic.
- [Corona motor concept](https://longearthsociety.com/misc/corona-motor-concept/): Q: Can a LaserSaber-style corona (electrostatic) motor be reproduced and made useful? A: Proof of concept runs. A CD rotor spun from a ~30 kV negative-ion generator drawing ~1 mA from 12 V, after a starting push. Next: stack stages at a 15° offset for torque.

## Brewing

- [Epistemic Brewing](https://longearthsociety.com/brewing/): Low-ABV carbonated hydromel and high-ABV mead with gravity, temperature and pH logged per batch and downloadable as CSV. Current batches are illustrative samples until the first real batch is logged.

## Machine-readable

- [About](https://longearthsociety.com/about/): Who runs the site, how entries are written, how to get in touch.
- [Privacy](https://longearthsociety.com/privacy/): No ads, cookies or accounts; what is counted and which outside services load.
- [Full text](https://longearthsociety.com/llms-full.txt): Every lab entry and write-up as plain text, one section per page.
- [Sitemap](https://longearthsociety.com/sitemap.xml): Every page with last-modified dates.
- [RSS feed](https://longearthsociety.com/feed.xml): New builds, tests and write-ups.

## Optional

- [Shop (Etsy)](https://www.etsy.com/shop/LongEarthSociety): Engines, ceramic stacks, parts and technical drawings.
- [YouTube](https://www.youtube.com/@LES_Thermodynamics): Build and test videos for the engineering lab.
- [Discord](https://discord.gg/ssWbfuQAGH): Questions, experiment requests and discussion.