Tom Stanton, an aerospace engineer and popular YouTuber, has built a bicycle powered by a Stirling engine, a heat-powered machine first invented in 1816. In his latest 18-minute YouTube video, Stanton takes viewers through the entire process, from initial small-scale experiments to a full-sized, working prototype.
While the project is still in its early stages, it has captured the attention of tech lovers worldwide, showing how old technology can be reimagined using modern tools like 3D printing and CNC machining.
The Stirling engine is not new. It works by heating and cooling air to create movement, unlike internal combustion engines that burn fuel directly. Stanton wanted to see if this historic technology, often dismissed as impractical for transport, could generate enough power to move a bicycle. His goal was to create a Stirling-powered bike capable of producing around 100 to 150 watts, enough to travel at about 15 miles per hour.
At the start of his video, Stanton demonstrates a small glass syringe experiment where heated air expands and pushes the plunger outward. This miniature “air engine” successfully shows the principle behind Stirling engines. Encouraged by this result, he builds a tiny benchtop Stirling engine that spins under heat. But transforming this into a full-size engine that fits into a bike frame proved far more challenging.
To build the main engine block, Stanton machined aluminium parts himself. For the hot cap, which needed to survive extreme temperatures, he outsourced the work to get it made in steel. Early in his design, he considered using a CPU heatsink for cooling, but found it unsuitable because of its limited surface area. Instead, he developed a water-cooling system to keep the engine stable.
Friction quickly became a serious issue. Because Stirling engines produce low power, even tiny mechanical losses could prevent the bike from moving. To reduce friction, Stanton used low-friction PTFE rings backed by tensioners and installed linear bearings borrowed from 3D printer hardware. He also designed 3D-printed brackets to help mount the engine within the bicycle’s frame and created a custom rear support made from aluminium.
Connecting the engine to the bike wheels required innovative thinking. Stanton first cut crankshafts from solid aluminium but later replaced them with lightweight resin versions for testing. These crankshafts turned a timing belt, which synchronized the displacer and power pistons. He chose a belt instead of gears to avoid added complexity and noise.
Even with careful preparation, early tests failed. When Stanton first lit the small burner, the engine did not spin despite the hot cap glowing red. He stripped the engine, checked the silicone gaskets, and greased the displacer shaft’s O-ring. A compression test revealed air leaking past the PTFE rings.
He tried replacing them with a rubber O-ring, but it caused too much drag. Finally, he designed a flexible piston ring using TPU, a rubbery 3D-printing material, which sealed the system more effectively. Stanton noticed that with the new seal, the piston would rebound when turned by hand—a good sign that pressure had improved.
After solving the sealing issue, Stanton faced another problem: over-compression. The crank’s 30-millimeter throw was too long, pushing the piston beyond the air’s ability to expand efficiently. He shortened the crank to 25 millimeters and lengthened the displacer’s stroke to move more air between the hot and cold zones. These changes paid off. The engine finally caught and started spinning on its own, running almost silently on the small burner.
After the engine ran, Stanton made additional tweaks. He replaced the rear drive pulley with a flywheel. This allowed the engine to build momentum first. Then it connected to the bike’s drivetrain. Even after these improvements, bike stayed low-power concept.
The bike took time to warm up, produced limited torque, and lacked throttle control. Stanton said it’s not fast, not powerful, but it works. The video showed the bike moving under its own power for the first time.
Although the prototype cannot replace electric bikes or compete with modern transportation, Stanton sees more potential. Future improvements may include adding a regenerator to recycle heat. Pressurising the air increases power, and installing a radiator-based cooling loop is planned. A clutch system could also make the bike easier to ride.
Stirling engines have a fascinating design but have never become mainstream. They produce low power density and need long warm-up times. However, Stanton’s project shows how modern hobbyists use 3D printing and CNC machining. They also use online parts suppliers to experiment with ideas. These ideas once required entire engineering teams just a few decades ago.
