NIKOLA JOHN TRBOJEVICH (NICHOLAS J. TERBO) 1886-1973

Nikola John Trbojevich (Nicholas J. Terbo)  1886-1973

Mathematician, inventor and perhaps the best-known gear expert of the modern age of the automobile, Nikola Trbojevich passed on December 2, 1973 at the age of 87 in Los Angeles. Mr. Trbojevich, also known socially as Nicholas J. Terbo, was the holder of 68 U.S. patents and a similar or greater number of foreign patents. The cause of death was septicemia and cardiovascular collapse. Surviving Mr. Trbojevich were his wife Alice Sinclair Hood (1891-1977) and his son William H. Terbo.

Mr. Trbojevich was a nephew of the great electrical genius Nikola Tesla “The Father of Alternating Current.” He was the last survivor of a group of ten nephews and nieces borne by Tesla’s three sisters. Both the Tesla and Trbojevich families were of clerical backgrounds, priests in the Serbian Orthodox Church. Tesla and Mr. Trbojevich were the only members of the extended family to pursue technological careers and the only ones to come to America.

Mr. Trbojevich’s most notable work that brought him international recognition was the invention of the Hypoid gear. First published in 1923, it was a new type of spiral bevel gear employing previously unexploited mathematical techniques. The Hypoid gear is used on the great majority of all cars, trucks and military vehicles today. Together with his invention of the tools and machines necessary for its manufacture, the Hypoid gear became an integral part of the final drive mechanism of automobiles by 1931. Its effect was immediately apparent in that the overall height of rear-drive passenger automobiles was reduced by at least four inches.

Other inventions of Mr. Trbojevich are in the fields of steering gears, worm gears, universal joints, positive displacement liquid pumps, gauges, and gear cutting and grinding machines. Many of these inventions found important commercial and industrial use. His Gleason gear shaping machinery, invented and produced in the late 1920s is in use to this day. His reversible worm steering gear innovation was the first of its type to allow a car’s steering mechanism to return to center after completing a turn maneuver. His inventions for angular and linear differential gauge block systems are in common use as measurement masters in factories throughout the world. His final patent (1967), for a nuclear reactor, was held in application form for many years because of its defense sensitivity.

Nikola Trbojevich was born on May 21, 1886, in the town of Petrovoselo in the Austrian county of Lika in the Austro-Hungarian province of Croatia (later Yugoslavia, now the Republic of Croatia.) His father was the Very Reverend (Prota) Jovo Trbojevich, at the time building a new Serbian Orthodox church in Petrovoselo, later to assume the post held by his father Very Reverend Danilo Trbojevich as Prota for the entire county of Lika based at the Trbojevich ancestral home at Medak. His mother was Angelina Tesla, eldest sister (by six years) of Nikola Tesla and daughter of the Very Reverend Milutin Tesla of Smiljan and later at Gospic, the county seat of Lika.

Nikola was the third of five children with two older brothers and two younger sisters. As was expected, the eldest son, Pero (church name Petronius), became a Serbian Orthodox priest rising to the highest rank, Arhimandrit (Archbishop), without offspring and breaking the family clerical connection with Lika. The other siblings also became professionals with careers away from the provincial county of Lika. The second son, Uros, became a lawyer and senator, representing Vojvodine nearer to Belgrade, older sister, Mica, became a medical doctor and director of the Woman’s Hospital in Belgrade and younger sister, Marica, a teacher at the upper school level.

After completing his primary schooling in Lika, Mr. Trbojevich was sent to Budapest for eight years of Gymnasium (middle and high school) continuing to the Royal Technical University, graduating in 1911 with the degree of Diploma Engineer. By the time young Nikola had arrived in Budapest, Tesla was a world-known personality. Whether by design or natural ability there were strong parallels in the professional careers of Mr. Trbojevich and the uncle thirty years his senior.

After serving two years as an assistant to the Chief Engineer of the Royal Hungarian Post Office telephone department Mr. Trbojevich was offered a post as intern at the Western Electric Company in Chicago with postgraduate courses at Northwestern University. (His mother wrote very much as an older sister to her younger brother, Nikola Tesla, “Please be good and pay strict attention if you intend to do some good; help the boy in your firm. I know this would be the best school for him. He would be happy and at peace.”) He arrived in March 1914, but the position at Western Electric lasted a very short time as the war in Europe began. His Austrian citizenship interfered with the national security aspect of the American telephone system and forced Mr. Trbojevich to change direction toward the mathematics of gear design.

Mr. Trbojevich joined the Illinois Tool Works as an engineer from 1915 through 1920 where he developed his specialty of gear design and received his first U.S. Patent (issued in 1920). As the principal consumer of gears is the automobile industry, he moved to Detroit in 1921 and became an independent inventor and consultant. The four patents that define the radical design of the Hypoid gear (U.S. 1,647,157) and the method of forming and cutting it (U.S. 1,465,149-1,465,151) were issued in 1923 and 1927. The reaction was exceptional. Several years were devoted to inventing the dozens of design details for the Gleason machinery necessary to cut the geometrical shapes of the gears. Nearly a dozen patents were issued to Mr. Trbojevich to secure the Gleason equipment.

In 1921 Mr. Trbojevich married Alice Hood of Evanston Illinois, the daughter of William Hood a commodities dealer, investor and member of the Chicago Board of Trade. Miss Hood had already established a business career in Chicago at the time. When they settled in Detroit they anglicized the difficult Trbojevich name to Terbo for social and her professional reasons. Of course, Mr. Trbojevich’s name was already established in his profession and was never changed. He received his U.S. citizenship in Detroit on March 21, 1922. Their first son John (Jackie) was born in 1924 followed by William in 1930. Tragically, Jackie died in a fall in 1937. This was an unfortunate parallel to the Tesla family, who lost Nikola’s older brother, Dane, in a fall at a similar age.

During the 1930s Mr. Trbojevich concentrated on improvements in automotive steering mechanisms, constant velocity universal joints and various implements to aid in their manufacture, areas intimately associated with American car and truck companies. Many of his improvements appeared on vehicles of several of the major marques. He was issued about two-dozen patents during the decade for novel equipment and concepts.

Mr. Trbojevich’s success and wide reputation changed his relationship with Nikola Tesla from that of uncle and nephew exchanging information of family matters to that of colleagues. They wrote and visited regularly and commented and assisted on some of the complicated technical problems they each faced. (After Tesla’s death in 1943, Mr. Trbojevich cooperated with his cousin, S.N. Kosanovich, another nephew of Tesla and after the war Yugoslavia’s first ambassador to the United Nations, in directing Tesla’s thousands of pieces of memorabilia to be placed in a new museum in Belgrade.)

Although Mr. Trbojevich worked with a number of major firms at that time, he retained his independent status until World War II became imminent. His familiarity with automotive drive systems and the specialized machinery necessary to manufacture them made his talents appropriate for the conversion to military vehicles.

After the war, he faced many of the problems other inventors face: his own earlier patents were cited against his new patents in his areas of expertise. This made a decision to become a professor at the Lawrence Institute of Technology in Detroit a more practical path. In 1960 Nicholas and Alice Trbojevich (Terbo) retired to Los Angeles where their son William was involved in the missile and space industry.

For more information contact:

William H. Terbo
21 Maddaket, Southwyck Village
Scotch Plains, New Jersey 07076
(732) 396-8852

Postscript: The lack of progeny in the direct line following Nikola Tesla and his three sisters is remarkable. The ten nephews and nieces mentioned above produced only six of the next generation, five of which are descended through the Trbojevich line. Of these six only William Terbo, son of Nikola, and Jovan Trboyevic, son of Uros, survive to this date. I have often commented that while most family trees are shaped like a Christmas tree, Tesla’s family tree most resembles a telephone pole!