IN MEMORIAM: DIETERICH J. SCHURING (1922–2006)

Abstract

The topic of rolling friction is addressed in most mechanical engineering texts and handbooks; however, much of the data provided therein is dated and not relevant to tires. In general, friction in bearings and wheels refers to the energy loss retarding the rolling motion of cylindrical objects traveling over a flat or curved surface. For the specific case of tires, we often refer to such energy dissipation using various units of measurement—viz., power loss, energy consumption, or more commonly, rolling resistance. The investigation of tire rolling resistance, and its impact on vehicle fuel consumption, came to the fore during the oil shocks of the 1970s. Prior to that time, tread wear and traction were the dominant performance characteristics receiving the lion’s share of attention by the world’s tire manufacturers.Dr. Dieterich Schuring (1922–2006) was the industry’s foremost expert on tire loss mechanisms during his service with Firestone (1976–1990). He served the Tire Society in many key roles, including the following: Vice President (1993–1994), Editorial Adviser (1975–1993), Plenary Lecturer (1988), and Conference Program Chair (1986). His thirty publications addressing tire rolling resistance and/or vehicle fuel economy during his tenure at Firestone have continued to influence our research thinking, development efforts, and public policy choices into the present century. Known as “Dieter” to his colleagues, he was born in Germany in 1922, entered military service, but spent the last years of WWII as a prisoner-of-war in Egypt. Repatriated to Europe in late 1947, he then undertook mechanical engineering studies at the Technical University of Hannover. After receiving his Ph.D. degree, he investigated off-road locomotion and vehicle/soil interactions with research organizations on both sides of the Atlantic (1952–1968). At the Space Division of General Motors, he was a member of the design team that developed wheels for the lunar rover used on the Apollo 15, 16, and 17 missions to the moon. Dieter came to the attention of the tire industry because of his research studies at Calspan (1968–1976) in Buffalo, NY, during the development of the first commercially viable, flat surface, force and moment machine known as TIRF.Schuring’s magnum opus in the field of tire mechanics was his comprehensive (127-page) review, The Rolling Loss of Pneumatic Tires, published in 1980. To prepare for this work, he plumbed the depths of classic studies by C. A. Coulomb, Osborne Reynolds, and David Tabor for added insights into the subject of rolling friction—not satisfied with the summary treatments found in existing engineering textbooks. He updated his review in 1990, critically analyzing the multitude of studies that had been published during the preceding decade. He introduced and promoted the concept of the “return factor” (fuel consumption change/rolling loss change), showing that the fuel usage of fully loaded trucks is more than twice as sensitive to rolling loss changes as that of passenger cars. He postulated and demonstrated that pneumatic tires of all sizes, from bicycle to earthmover, are constructed such that, on average, about the same amount of loss energy (heat) is generated per unit mass and unit distance traveled. He emphasized fundamental principles, stressing, e.g., that rolling loss is a scalar and not a vector quantity. His expertise guided the activities of the industry committee on which he served that developed and issued the first recommended practice (SAE J1269) for measuring tire rolling resistance.Schuring had an inquiring mind and meticulous work ethic that he used to address a broad range of mechanical engineering subjects. He authored a well-received, still extant, 300-page text, Scale Models in Engineering: Fundamentals and Applications (Pergamon, 1977). An earlier version of this book was originally published in the Japanese language. His first publications (1958–1960), in German, dealt with rheological studies of soft materials, which served him well while interacting with materials scientists and rubber compounders in the tire industry. Dieter investigated other tire properties in the same disciplined fashion as rolling resistance. Overall, he published more than eighty technical papers: twenty dealing with off-road tire performance and mobility, and fourteen addressing tire force and moment measurement and analysis. Other publications dealt with heat-transfer, tire running temperatures, and airflow inside the pressure chamber of a rolling tire. The results of some of Schuring’s most compelling studies, dealing with nonuniformities in tires, utilized his mathematical skills in statistical analysis. Unfortunately, this work remained largely unpublished because of perceived proprietary and trade secret content. For example, he reasoned and demonstrated early on that there was no “silver bullet” in extant production processes for manufacturing more uniform tires. Schuring spent the last third of his R&D career directly in the tire industry; one can only imagine what other significant contributions he might have made if he had spent his entire professional life with us.