Tweel inventors named co-recipients of Charles Goodyear Medal

PITTSBURGH—The ACS Rubber Division has settled on co-recipients of the Charles Goodyear Medal, the technical association's highest honor.

Steve Cron and Tim Rhyne, the duo who led the development of Michelin's Tweel non-pneumatic tire technology, will share the medal, the Rubber Division revealed Oct. 5 during its International Elastomer Conference in Pittsburgh. They will receive their medals at the association's 2022 Spring Technical Meeting.

The two collectively spent 70 years at Michelin, with Rhyne working there from 1978 to 2017, when he retired as a senior research fellow. Cron's career at the tire maker began in 1991, and he continues there as a senior principal product research engineer.

Rhyne and Cron in 1997 began informally working on various structural concepts for non-pneumatic tires. Their conversations led to working prototypes that proved the viability of the concepts, and in 2001 they successfully completed a drive from South Carolina to California and back on an early prototype of the non-pneumatic tires.

Michelin first unveiled the Tweel, as it was dubbed, at the 2005 North American International Auto Show. That was followed with applications in a wide range of non-automotive uses and Michelin's opening of a production facility in South Carolina in 2014 dedicated to manufacturing the Tweel.

The two were part of a working group at Michelin that was taking a look at the future of the tire industry, Cron said in a 2018 interview. One topic of discussion was why run-flat tires hadn't been successful up to that point. They determined that run-flats didn't work because they took the tire—a differential tension top-loaded structure when it's pneumatic—to being a bottom-loading direct from the ground to the rim.

Cron and Rhyne knew at this point that it was imperative to look at the problem differently, trying to develop a structure out in the tread band that could support the load being hung from it. They decided to take some of material used in Michelin's typical ZP run-flat tire and put it onto the summit of the design and see what could be done.

Years of work and development led to the Tweel now posting roughly $25 million in annual sales, with double-digit yearly growth. According to the nomination packet from the Rubber Division, Michelin is targeting 75,000 units of sale this year, spread over 75 SKUs. The technology also is utilized in the tire maker's Uptis tire, which is aimed at eliminating the need for a spare tire in passenger car applications.

"There were many challenging technical issues that were overcome in order to bring airless tire technology to a sufficiently high level of performance to compete in the marketplace," said one of the letters nominating them for the medal. "Drs. Rhyne and Cron have worked tirelessly and with unrivaled creativity to resolve the outstanding technical issues, and their work has clearly resulted in unprecedented success."

Rhyne received his bachelor's in mechanical engineering in 1973 and his doctorate in the same discipline in 1979, both from North Carolina State University. He has received four superior paper awards from the Tire Society and one superior paper honorable mentions. He served as an associate editor of the Tire Science and Technology Journal for a number of years. He received a number of patents in pneumatic tire design and tire uniformity, and many patents relating to non-pneumatic tires.

Cron received a bachelor's in mechanical engineering from the University of Missouri, and a master's in aeronautical engineering from the Air Force Institute of Technology. He started his career at Michelin working in tire dynamics and modal analysis. He then left the research role to work in product development, leading teams developing a wide range of passenger car tires for both the OE and replacement markets.

He received the Harold Herzlich Distinguished Technology Medal in 2019, and was an associate editor of Tire Science and Technology from 2017-21.