Hjalmar D. (Ham) Bruhn, emeritus professor of agricultural engineering at the University of Wisconsin-Madison, died July 1, 1997 at his summer cottage on Black Oak Lake near Land O”Lakes, Wis. He was 89 years old.
During his 44-year career at UW-Madison, Bruhn and his graduate students were noted for machinery-design work. A tree planter that Bruhn designed during World War II is still in use, and its design is incorporated into planters sold today. His other equipment designs include a portable rotary sprinkler irrigator, a self-propelled cherry harvester, harvesters for lake weeds, and snowmobile trail levelers. Bruhn”s lab designed chopped-hay storage systems, jetted wells for irrigation, and a system to determine the conditions that lead to hay-mow and silo fires.
Bruhn worked extensively on forage handling and processing equipment. His paper on forage mower-conditioners won the American Society of Agricultural Engineers (ASAE) outstanding paper award in 1956; today, the machines are used on virtually every forage-producing farm in the United States and Europe.
Bruhn used his knowledge of mechanical dewatering of forages to design and build a low-tech protein extraction system to combat malnutrition in Mexico. The system produces a protein-rich paste from local alfalfa crops, and the villagers eat the “alfalfa butter” with red bean paste on tortillas. Under the sponsorship of several charitable organizations, this project continues in Mexico and elsewhere.
Bruhn taught more than 4,000 short-course, undergraduate and graduate students during his career, and received the Polygon Outstanding Instructor Award from the ASAE in 1970. He served as advisor to Alpha Gamma Rho fraternity for more than 20 years, and also advised the student branch of the ASAE.
Bruhn published more than 150 research papers during his career. He was a member of the American Association of University Professors, the American Association for the Advancement of Science, and the New York Academy of Science; and a Fellow of the ASAE. He was awarded the McCormick-Case Gold Medal in 1992 in honor of his engineering achievements and his professional influences on his students.
Bruhn grew up on a dairy farm near Spring Green, Wis. He earned bachelor”s degrees in agricultural engineering and mechanical engineering from the UW-Madison, and a master”s degree in mechanical engineering from Massachusetts Institute of Technology. Bruhn began his career at UW-Madison in 1933 as a research assistant. He retired in 1978, but continued his design work at the department, as well as lecturing on the dangers of spontaneous combustion in stored forages, and working with the sponsors of the Mexican alfalfa-juice project.
Bruhn is survived by his wife, Janet Weber Bruhn; his daughter, Janet Bruhn Jeffcott; his brother-in-law, Walter F. Weber and his family; and many nieces and nephews.