Piston rings are the reason internal combustion engines can exist. They’re slim rings of metal that hug the outer edge of the piston, responsible for sealing the combustion pressure inside the cylinder and keeping oil out of the combustion chamber. The science behind piston rings is far more impressive than you could ever imagine.
The New Mind YouTube channel put together a detailed history and explainer on the piston ring, giving us an in-depth look at how the concept was conceived and developed over decades of trial and error and experimentation.
The earliest evidence of piston rings could be found in locomotive steam engines in the 1800s. As technology evolved, the rings turned into cast iron pieces that provided better sealing properties. From there, engineers eventually discovered using three rings—two for sealing the combustion process, and one for keeping oil out—was the most efficient way to go about using the rings.
The video goes into great detail about the types of rings that exist, how they’re measured to ensure the best sealing and efficiency properties, and how they go about operating in such demanding environments for hundreds of thousands of miles. It’s all incredibly fascinating stuff.
The most interesting example New Mind uses are the piston rings in a Formula 1 car. Unlike road cars, which use three rings, F1 cars use just two rings per cylinder, one for sealing combustion and another for oil containment. The combustion ring is made from a tungsten-carbide coated steel, while the oil ring is made from titanium. The tolerances are so thin, they don’t function properly outside of their very thin operating temperature window. They also require lots of oil cooling to maintain that temperature.