What’s the Deal with Rotary Engines?
One major rotary design issue has stumped engineers for decades. What will it take to fix it?
Rotary engines, what’s the big deal? People still are building these artifacts of technology almost a century since their inception. The original design was made by a German engineer by the name of Felix Wankel back in the late 1920s. Since then, this unique engine configuration has seen its ups and downs. In recent years, the love and hate relationship with the engine continues to creep its way into the mainstream. Although Mazda may have been the manufacturer to bring the rotary to its current level of development, many brands have dipped their toes into the triangle-shaped powerplant. This includes OEM’s like Ford, Porsche, Mercedes-Benz, and Toyota.
However, Mazda was really the only brand to believe enough in the Wankel engine to produce it in mass quantities. Why did all those other manufacturers shy away? What about the design or engineering related to this engine wasn’t convincing enough to see it through long term? Well, this isn’t the easiest question to answer. Thus, we tune in to New Mind on YouTube so we can learn some more details about what makes these things tick.
This video starts off with the most important differentiation of the rotary: the design. The basis of this design comes from a geometric curve known as a Epitrochoid. This shapes what will become the rotor housing. The most natural shape to fit within this housing is a triangle. On each of this triangle’s three points is an “apex”, which when rotated along a shaft, increases and decreases the volume of each face on the rotor.
Sounds simple enough right? If that was the case, what aspect of this design has been the issue for engineers for decades? The apex seals. See, each of the three apexes requires a seal to retain compression in the housing. This seal comes into direct contact with the housing in order to create a seal. In order to reduce friction, oil is added to the combustion chamber to lubricate the seal. However, eventually wear ends up decaying the walls of housing due to the friction of the apex seal.
Designing an apex seal that could stay lubricated, not vibrate, and have low friction has been the single most difficult part of making rotary engines a viable solution. Mazda hasn’t released a Wankel engine since the RX-8, but continues to research technology to get this powerplant up to modern standards. If they can find a way to make seals last, have better fuel economy, and make fewer emissions, you might see a rotary in a new Mazda sooner than you’d think.
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