Youtuber builds bike with self-developed sterling motor
Youtuber Tom Stanton wants to use technology from the beginning of the 19th century to power a bicycle. But there are still many hurdles to overcome.
Energy is supplied to the Sterling motor on the bicycle by heating it with a burner.
(Image: Screenshot/Tom Stanton)
The technology used by aerospace engineer and Youtuber Tom Stanton to power a bicycle is more than 200 years old. The Sterling engine was first patented in 1816. Stanton's thermally driven motor is said to produce around 100 to 150 watts in its final form. That is about 0.2 hp. The goal: the bicycle should accelerate to around 15 mph (about 24 km/h) on a flat road.
The principle of the heat engine invented by Robert Stirling, which he developed as an alternative drive to steam engines in 1816, is comparatively simple. A gas is heated in a cylinder. The cylinder is closed by a movable piston. The gas expands and is transferred to a second cylinder, also closed by a movable piston, where it is cooled and compressed. The gas moves between the two chambers, whereby the temperature and pressure change. The two pistons are connected via a linkage to a flywheel, which then performs a circular movement that can be used as a drive. To improve efficiency, there is often a regenerator on the way from the hot to the cold cylinder. It also emits the absorbed heat as soon as the gas flows from the cold to the hot cylinder.
Stanton's Stirling engine is largely made of aluminum. The heating chamber, on the other hand, is made of steel and can be heated until it glows. The engineer uses a water cooling system to cool it down. Stanton had calculated in advance that the initially planned cooling by a CPU fan would not be sufficient.
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Minimizing friction losses
The biggest problem with Stirling engines is their efficiency. Even the smallest friction losses can greatly reduce performance. This is why Stanton focuses on low-friction running of all mechanically moving components. To this end, the engineer initially used PTFE rings for the piston seals as well as tensioners from the 3D printer and linear bearings. However, the PTFE rings produced too much blowout. Rubber rings, which he then experimented with, had too much resistance. Stanton therefore developed a flexible piston ring made of TPU, which he printed. This made it possible to achieve a high level of sealing with low friction and better maintain the pressure in the piston.
The pistons transmit their movements via rods to two toothed belt pulleys, which together transmit their power via toothed belts to a drive wheel and from there to the rear wheel of the bicycle. The motor itself is mounted between the top tube and the seat tube. Stanton had to subsequently adjust the length of the piston rods in order to make the entire drive system work. This worked after additional modification of the drive wheel. However, the Stirling engine only runs very slowly and is not yet sufficient to propel the bike together with the rider.
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Stanton is now in the process of making further improvements to the heat engine. He also wants to attach the burner for heating and the water supply for cooling directly to the motor. Stanton intends to report on the modifications on his YouTube channel as soon as they have been completed.
(olb)
