Charles Inglis (engineer)

Charles Inglis was the second son of Dr. Alexander Inglis (a general practitioner in Worcester) and his first wife, Florence, the daughter of newspaper proprietor John Frederick Feeney. His elder brother was the historian John Alexander Inglis FRSE Their father, Alexander Inglis was born in Scotland to a respectable family – his grandfather, John Inglis, was an Admiral in the Royal Navy and had captained HMS Belliqueux at the Battle of Camperdown in 1797. His family moved to Cheltenham and Inglis was schooled at Cheltenham College from 1889 to 1894. In his final year, he was elected head boy and received a scholarship to study the Mathematics Tripos at King's College, Cambridge. Inglis was 22nd wrangler when he received his Bachelor of Arts degree in 1897; he remained for a fourth year, achieving first class honours in Mechanical Sciences. Inglis was a keen sportsman and enjoyed long-distance running, walking, mountaineering and sailing. At Cambridge, he nearly achieved a blue for long-distance running but was forced to withdraw from a significant race because of a pulled muscle. After graduation, Inglis began work as an apprentice for the civil engineering firm of John Wolfe-Barry & Partners. It was during this time that he began his lifelong study of vibration and its effects on materials, particularly bridges. == Early academic career ==

In 1901 Inglis was made a fellow of King's College after writing a thesis entitled The Balancing of Engines, the first general treatment of the subject – which was becoming increasingly important due to the growing speeds of locomotives. Inglis maintained his interest in engine balancing and filed a US patent on 16 April 1902 for an improved engine with the cylinders mounted end to end to balance out the forces acting between them. Professor Ewing left the university in 1903 to become the first Director of Naval Education at the Admiralty but Inglis remained; he was appointed a university demonstrator in mechanism by Professor Bertram Hopkinson, Ewing's successor, and worked with him to study the effects of vibration. From 1911 Inglis became involved in hydraulic engineering and served on the board of the Cambridge University and Town Waterworks Company, serving as deputy chairman from 1924 to 1928 and chairman from 1928 to 1952. Inglis conducted research into the problem of fracture in the metal plates of ships' hulls and noticed that the rivet holes along the path of a crack were often deformed into an elliptical shape. This phenomenon led him to investigate the magnification of stress caused at the edges of an elliptical defect; in 1913 he published a paper of his theories that has been described as his most important contribution to engineering and the first serious modern work on the fracturing of materials. Alan Arnold Griffith later drew on Inglis's paper for his work on the apparent discrepancy between calculated and actual strengths of materials. Inglis had married Eleanor Moffat, daughter of Lieutenant-Colonel Herbert Moffat of the South Wales Borderers, in 1901, having met on holiday in Switzerland. They lived at Maitland House, Cambridge, until 1904, when Inglis built a house he named Balls Grove at nearby Grantchester, where his two daughters were born and the family resided until 1925. They later moved to 10 Latham Road, which Inglis renamed Niddrys after the first known address of his ancestors in Edinburgh. == Military service ==

in Aldershot is Grade II listed|alt=A patent drawing showing a footbridge constructed of triangular trusses Inglis was involved with the Cambridge University Officer Training Corps (CUOTC), being commissioned a second lieutenant on 24 May 1909. He served with the CUOTC's engineering detachment and noticed that when the unit was deployed on field days with the rest of the force it often had little to do. The army expressed interest in Inglis's bridge design; it was approved for use by a panel of army officers that included the general who had first commented on the design, to whom Inglis said "I hope, Sir, you will find I have profited by your advice". The design was composed of a series of Warren truss bays made from tubular steel sections, to a maximum span of six bays (). Inglis received a US Patent for his bridge on 25 April 1916 and for the type of joints used in it on 26 June 1917. In 1916, Inglis was placed in charge of bridge design and supply at the War Office in which role he was a proponent for the increased use of girder bridges in military applications. It was Inglis that first proved to the army that the heavy components essential to girder bridges did not prevent their rapid assembly in field conditions. He was promoted to the brevet rank of major as part of the King's Birthday Honours on 3 June 1918 and later that year worked with Giffard Le Quesne Martel to develop some of the earliest bridgelaying tanks. Inglis retired from the army on 9 March 1919, having been rewarded for his military service with an appointment as an Officer of the Order of the British Empire. == Return to King's College ==

Inglis returned to Cambridge in 1918 and was appointed as the professor of Mechanism and Applied Mechanics (renamed Mechanical Sciences in 1934). On 25 March 1919, he was selected to head the Cambridge University Engineering Department as the successor of Hopkinson, who had died in an air crash the previous year. Inglis acquired the Scroope House on Trumpington Street for the department and constructed a laboratory on the site by 1923, followed in 1931 by a structure containing lecture theatres and a drawing office. He was also in contact with Russian railway engineer Yury Lomonosov and lectured to biochemist Albert Chibnall. Despite mentoring some of the best engineers of their generation Inglis was realistic about the actual intentions of many of his students at the time. He once told a new intake class: "Your fathers, gentlemen, have sent you to Cambridge to be educated, not to become engineers. They think, however, that reading engineering is a very good way of becoming educated. In 10 years' time, however, 90% of you will have become managers, whether of design, manufacturing, sales, research or even accounts departments in industry. The remaining 10% of you will have become successful lawyers, novelists, and things of that sort". Undeterred, Inglis sought to give his students the broadest possible engineering education, covering all fields to prevent them becoming "cramped by premature specialisation". He was also successful in arranging with the War Office for Royal Engineers officers to study the Engineering Tripos at the university. Inglis was appointed to a sub-committee of the British government's Department of Scientific and Industrial Research Bridge Stress Committee by Ewing, who was chairman, and became responsible for almost all of the mathematics of the investigation. Inglis's work on bridge vibration has been described as his most important post-war research. This work is related to the later method used by Myklestad and Prohl in the field of rotordynamics. Inglis was also a prolific writer, publishing 25 books and academic papers on a wide range of engineering topics. Inglis founded the Cambridge Engineers' Association to promote social activities at the University, and saw Sir Charles Parsons appointed as its first president in 1929. In the same year, he was awarded the honorary degree of Doctor of Laws by the University of Edinburgh. Inglis delivered the Trevithick Memorial Lecture for the ICE in 1933, and was elected British Waterworks Association president in 1935. He was a proposer for the Royal Society fellowship of Andrew Robertson, the mechanical engineer, in 1936. == Second World War and after ==

Inglis was due to retire from the university in 1940, but was persuaded to remain for another three years so that John Baker could be appointed in his stead. Testing of a prototype of the Mark III revealed a weakness in the top chord of the truss and the subsequent redesign complicated the production process. The Inglis design remained in service for some time owing to a lack of resources for production of the Bailey bridge and saw service in rear areas and with the 1st Canadian Infantry Division. Inglis was elected as ICE president for the 1941–42 session, having been vice-president in 1938, and gave an inaugural address on the education of engineers that was judged to be one of the best ever given. In his address, he stated that "the soul and spirit of education is that habit of mind which remains when a student has completely forgotten everything he has ever been taught", a quote which has since been used by several organisations to describe the importance of an engineering education. He delivered the Thomas Hawksley Lecture on "Gyroscopic Principles and Applications" for the Institution of Mechanical Engineers in 1943 and the fiftieth ICE James Forrest lecture on "Mechanical Vibrations, their Cause and Prevention" in 1944, being awarded the ICE's Charles Parsons medal the same year. He gave the Parsons Memorial Lecture to the North-East Coast Institution of Engineers and Shipbuilders in 1945 in which he presented his Basic Function Method, an alternative to the use of Fourier series for the analysis of vibrations in beams. Inglis continued to develop his theories on teaching engineering and wrote in the Proceedings of the Institution of Mechanical Engineers in 1947 on the teaching of engineering mathematics: "Mathematics [required by engineers] though it must be sound and incisive as far as goes, need not be of that artistic and exalted quality which calls for the mentality of the real mathematician. It can be termed mathematics of the tin-opening variety, and in contrast to real mathematicians, engineers are more interested in the contents of the tin than in the elegance of the tin-opener employed". He published the textbook Applied Mechanics for Engineers in 1951, following which he spent three months as a visiting professor at the University of the Witwatersrand in South Africa. == Notes ==