The Perfect Tip – Ceramic Seals In Rotary Engines

Published on Apr 7, 2017 | Last updated May 25, 2022

It’s over 85 years since German Engineer Felix Wankel first patented his design for a rotary engine. Development began in the 1950’s and by 1957 a working prototype had been built.

NSU Motorenwerke AG, a well-established German manufacturer of automobiles, motorcycles and pedal cycles and more commonly known simply as NSU, subsequently licensed the design of the Wankel engine to many companies around the world and whilst the basic design concept of the engine has remained steadfastly the same, many improvements have been made over the years.

The Wankel engine has the unique advantages of compact size, high performance, relative simplicity, low weight and reliability over the most commonly used internal combustion engine employing reciprocating pistons. Nowadays the engine is used in a wide variety of applications including cars, motorcycles, racing cars, aircraft, go-karts, jet skis, snowmobiles, chain saws, and auxiliary power units.

Whilst the design of the engine has enjoyed unprecedented success, one common problem has been the seals between the rotor and housing most commonly known as ‘tip’ or ‘apex’ seals. These have a tendency to wear against the rotor housing and over a period of time can distort causing a loss in compression and decrease in performance. In extreme cases, this distortion can stop the engine working altogether.

The Perfect Tip

One solution to this problem has been to install ceramic tip seals manufactured from a special type of silicon nitride. The seals – designed and manufactured by Precision Ceramics – provide an added degree of hardness and toughness over conventional steel seals which extends the operating life of the engine and reduces maintenance costs and downtime.

Unlike conventional steel seals, ceramic tip seals are dimensionally stable through all temperature ranges. They are manufactured to such high tolerances that the wear-in time is virtually negligible. Additionally, the seals have an almost perfect surface finish which promotes a better and longer lasting seal between the rotor and the housing.

In a rotary engine running at a low RPM, there is very little centrifugal force acting on the tip seal, the only force pushing the seal against the rotor housing coming from the seal spring. As the RPM increases, a combination of the spring force and the force of gases under the seal results in a much higher force between the seal and the rotor housing. As ceramic seals are much lighter than their steel counterparts, they are much less affected by these additional forces which results in less tip chatter and greatly improved performance.

Precision Ceramics have wide experience in tip seals and are enable to engineer bespoke seals for almost any rotary engine application.

Interested in finding out more and if any of our materials are the right fit for your application? Please don’t hesitate to get in touch.

Related topics:

Silicon Nitride CeramaSil-N Material Brand

Silicon Nitride


Silicon Nitride has the most versatile combination of mechanical, thermal, and electrical properties of any advanced ceramic material.



One of the most valuable characteristics of advanced ceramics in high-performance applications is their extreme hardness. Hard ceramic materials are used for a wide range of applications in diverse fields and applications such as cutting tools for milling and grinding.

Most Recent Posts

Precision Ceramics – Over a Decade of Trade Shows

Precision Ceramics – Over a Decade of Trade Shows

Precision Ceramics has attended a number of trade shows over the past 2 decades in various locations. Since 2012, it had been common for Precision Ceramics to attend two major exhibitions every year, generally one in Europe and the other in the USA. More recently, the...

Hypersonic Speed & Ultra-High Temperature Ceramics

Hypersonic Speed & Ultra-High Temperature Ceramics

The history of speed shows the greatest ingenuity, in developing from a single horsepower to some of the mightiest machines traveling at the greatest velocities.Speed has always required cutting edge technology to continue breaking the constraints, to allow us to move...

High Strength “Ceramic Steel” Zirconia

High Strength “Ceramic Steel” Zirconia

Unlike traditional ceramics that tend to be hard and brittle, Zirconia (ZrO2) has high strength, wear resistance and a flexibility far beyond those of most other technical ceramics. Zirconia (ZrO2) also has excellent corrosion and chemical resistance without the...