The first broken leg was on 29 December 1929, and the second on Good Friday, 1930. Thus it was that for ten months to October 1930 I did no studying or academic work of any kind. I had written to Mrs Busk telling her of the happenings and offering to forgo the money, but, generously, she would not hear of it, and so I continued to get the £50 per term.
I gave no thought to what should happen next, until one day at Faversham a letter arrived from Professor Bairstow saying that he had recommended me as a candidate for the Armourers and Braziers Research Fellowship in Aeronautics. I was bidden to appear at the Guild of Armourers and Braziers in London. Having delayed as long as I could, I appeared on crutches and that won the day! I now had £250 per annum to continue my studies and research in the Aeronautics Department of Imperial College. Fate had intervened again, and I was committed to at least two further years of academic life.
I do not wish to give the impression that this Fellowship was handed to me on a plate. Professor Bairstow had an all-consuming obsession, and that was to solve the equations of motion of a viscous fluid. All fluids have the property of viscosity, though in the case of air it is less obvious than with oil or treacle. It is this property which gives an aircraft its drag, and wings their lift. Without the property of viscosity, neither birds nor aeroplanes could fly, and winds would blow around the world undiminished for ever. In the real world in which we live air’s viscosity gradually dissipates, like friction, all air motion into heat. Unfortunately the equations, which are well established, are very intractable. Bairstow decided to try to solve them by numerical methods, and employed two ladies to operate with numbers, just as present-day computers do, although the ladies were a few million times slower.
For my part, I had taken a modified and much simpler form of the equations, called Oseen’s Equations, after their creator, and had managed to solve these for the case of low-speed flow past a circular cylinder. Bairstow was interested, and it was for this reason he recommended me for the Armourers and Braziers Fellowship.
But when I returned to Imperial in October 1930 I became much more interested in the flow of air at very high speeds, where another of its properties, compressibility, becomes very important. At speeds up to about 300 mph air can be regarded as incompressible, like water. In other words, the pressure differences caused by the air velocities are small compared with the pressure of the atmosphere, and so the air behaves as if its density remained constant.
For example, at 200 mph the maximum pressure that air can exert is only 5 per cent of the atmospheric pressure, which has a negligible effect on the air density and the flow. But at 400 mph the pressure increases to 21 per cent and at 600 mph to 51 per cent. These pressure increases have a significant effect upon the density of the air, and, hence, upon its flow pattern and the forces that the air exerts.
Since the speed of even the fastest fighters was only about 200 mph at that time, mathematical and experimental studies of airflow around wings and other aircraft parts had ignored the compressibility effects on the flow. But in 1930 Professor G. I. Taylor (later Sir Geoffrey Taylor of Trinity College, Cambridge) began to send his theoretical work on the flow of air as a compressible gas to the Aeronautical Research Committee, who duly published it in their Reports & Memoranda.
Of the many great applied mathematicians in the field of aerodynamics or fluid motion whom I have had the good fortune to know, G. I. Taylor ranks at the very top — before Prandtl of Göttingen, von Kármán of Aachen or Southwell of Oxford. The breadth of G. I.’s theoretical work was vast, and it always had a practical slant. He was adept at devising experiments to verify his theories, many of them of fascinating simplicity.
At this time, in the early 1930s, there were few people in the world studying the effects of compressibility on the flow of air. There was Büsemann in Germany, who went to the USA after World War II, Ackeret in Zurich, who evolved the first simple theory of the effect on the lift and drag of a wing, and there was G. I. Taylor in England. Years earlier Lord Rayleigh, Rankine and Stokes — all British — had shown how significant this property of the compressibility of air could become, especially when the velocity exceeded the speed of sound.
Taylor’s papers interested me greatly, and I began to dabble myself. I evolved what I thought to be a brilliant mathematical solution to the flow around a circular cylinder at speeds approaching the velocity of sound, and sent it to the Aeronautical Research Committee, of which G. I. was a member. Alas, the theory contained a subtle flaw, and Taylor slaughtered it in devastating fashion. I was stunned, almost to the point of physical sickness. How could a man of his eminence be so savage to a young man of my insignificance?
But I did not then know G. I. Shortly afterwards I received a note asking me to meet him in the rooms of the Royal Aeronautical Society, which were then in Arlington Street, off Piccadilly.
With great trepidation, I turned up at the appointed time, to meet for the first time this great man. I was charmed immediately. He said that my theory was a brave effort, and that he was sorry that he had had to be so critical. He then went on to give me a personal tutorial on the subject, and encouraged me to pursue this type of study. He said, ‘Send your work to me first, and I will do all I can to help.’ And thus began a friendship which was to affect profoundly the whole course of my future.
I did not appreciate at the time — and very few other people did either — that the understanding of the aerodynamic flow of compressible air was to lead on to supersonic flight once an engine of sufficient power was available. Nor did I know that a young Royal Air Force officer called Frank Whittle was at the University of Cambridge designing the first jet engine which would ultimately give this power. Whittle had a superb grasp of the relationship between supersonic airflow and the thermodynamics of the gas turbine. He was one of the first men to weld together and formulate the science of Gas Dynamics, which is now a normal course for engineers at the beginning of their studies.
Fate decreed that I was to follow a course of study, first at Imperial College and afterwards at Oxford University, which by chance specifically trained me for the tasks which, years later, were to be allocated to me by Rolls-Royce. Now, on reflection, I would not wish to change a day of it. I sometimes think that perhaps I could have worked harder, but ‘unconscious of their fate, the little children play.’
Back at Imperial College, I continued to study G. I. Taylor’s work, and, to his evident satisfaction, even extended the scope of some of his publications.
It was well known, of course, that there was an exact similarity between the flow of a ‘perfect’ gas (one without viscosity) and the flow of an electric current through an electrolyte, such as a solution of copper sulphate. Taylor evolved a method of making the flow of the electric current simulate the flow of a compressible fluid. He took a shallow square tank which he filled to a depth of about one inch (25mm) with copper sulphate solution. Two opposite walls of the tank were made of copper strips, and a current was passed between them. Such an arrangement produced a uniform flow of electricity from one wall to the other, and if a non-conducting obstacle was placed in the centre of the tank, then the flow lines of the electric current would pass around it, exactly as air would if the obstacle was in a uniform stream of air. This was straightforward stuff, but Taylor made the base of the tank in paraffin wax, and used a circular cylinder embedded in the wax as the obstacle. By carving the wax away or adding more at the appropriate places, the depth of the electrolyte around the obstacle could be varied, and Taylor showed that this depth was exactly analogous to the density of compressible air as it flowed around the cylinder. Where the air velocity was high, the depth of the electrolyte had to be reduced; when the air velocity was low, the depth had to be increased. By this relatively simple experimental technique, Taylor was able to evaluate the effects of compressibility on the flow, and obtained the answer to a problem which was quite intractable by mathematical methods.
Although I was better with pen and paper than a
s an experimenter, I wrote to G. I. to ask him if I could use the tank at Imperial College. He replied that he had given it to Professor R. V. Southwell, who was head of the Engineering Science School at Oxford, but that he would write to Southwell and tell him of my interest. I had never met Southwell, but knew him from his reputation as an applied mathematician in the fields of Fluid Dynamics and the Elasticity of Materials.
A little later, I was delighted to get a letter from Southwell, inviting me to meet him for tea at London’s Athenaeum Club, a venue which I regarded with great ‘awe’. The upshot was that Southwell invited me to go to Oxford to work with the tank; moreover since he was a Fellow of Brasenose College (BNC), he undertook to persuade the Principal of that College to accept me as a member of it for post-graduate study.
Secretly, I had always wanted to go to Oxford, but had thought that I would have difficulty in getting a college to accept me, and that I could not afford it. But now, with £250 per year from the Armourers and Braziers Fellowship, I had ample funds, and so jumped at this God-sent opportunity. In those days, one could buy a made-to-measure suit for £5, and a reasonable secondhand motor car for £20, so that £250 was equivalent to several thousand pounds today.
I realised that I was in danger of becoming a ‘professional student’, but jobs were very difficult to get, and pay was low. I was doing at least as well on my emolument as I would have done in a job, even if I could have got one! So, with all the other young men fresh from the great public schools, I went up to Oxford in October 1932, and became a commoner of Brasenose “in statu pupillari”.
I must confess that I had always been jealous and envious of public school boys. Coming from my humble origins, I expected to get the cold shoulder, and was prepared to be cold and distant myself. After all, was I not already 24 years old with a Bachelor’s Degree in mathematics, so why should I bother about these snobbish young puppies, who had been born with a silver spoon in their mouths?
But I had got it all wrong; and they soon showed me what a fool I had been. I was immediately accepted by all, and spent four of the happiest years of my life enjoying the great camaraderie that existed in BNC. There is no doubt that the public schools give to their product an indefinable something which is of inestimable value to Britain. Those jealous and bigoted people who seek to destroy them — in the name of anti-class privilege or for votecatching — are misguided, small-minded fools. We should have more public schools, and not fewer; thus could we increase the output of leaders for all walks of life, with their unparalleled record of excellence.
Alas, the young men I lived with in BNC for those unforgettable four years were ripe for slaughter in World War II. It is so terribly sad to read their many names on the Roll of Honour at the entrance to the College Chapel. Yet I always remember them as generous, happy, high-spirited young men, who promised to have the world at their feet.
The School of Engineering Science was situated at the junction of Parks Road and the Banbury Road. It was a small two-storeyed building, with a tiny library up an iron staircase in the attic. The staff was small. Under Professor Southwell were E. B. Moullin, a fellow of Magdalen, as the Reader in Electricity, and A. M. Binnie, a don of New College, specialising in Hydraulics. There was a small workshop in the basement, where a very skilful man made the apparatus necessary for the experimental work.
At this period, engineering was hardly the ‘in-thing’ at Oxford. The annual intake of students was about a dozen, several of whom were Rhodes Scholars from the Empire. For these reasons, Southwell concentrated on the mathematical and theoretical background to Engineering Design, and how wise he was. My later experience in Rolls-Royce showed me that no university course could possibly compare with the knowledge gained by rubbing shoulders with experienced, practising engineers actually doing the job in a factory. On the other hand, once one’s student days are over, and one is gaining practical experience by doing a job, it is extremely difficult again to pick up the mathematical and theoretical background so vital to anyone who aspires to lead in engineering.
Although I had no examinations to sit, I was in the end aiming to write a thesis for a doctorate in Philosophy, so I attended many of Southwell’s lectures, particularly those on the Strength of Materials. I supplemented these by attending A. E. H. Love’s course on Elasticity held in the Clarendon Laboratory.
Love was an old man with a white walrus moustache, who lectured straight from the enormous tome he had written — the classic work on the subject. It was a purely mathematical treatise of great erudition, and the old boy could reproduce page after page of it on the blackboard without a note or reference. I watched him with awe and admiration. Although I never specialised in this subject, the grounding I got from him and from Southwell has served me in great stead. Many times it prevented me from being “blinded by science”, when the real test of the strength of materials came in the gas turbine engine.
When I first arrived at the Engineering Laboratory, Southwell was away on sabbatical leave as a visiting professor at the Massachusetts Institute of Technology. So I was left to my own devices for a couple of terms. I had been allocated a small office overlooking The Parks, and in this seclusion I again turned to G. I. Taylor for inspiration.
It was well known that if air was compressed to, say 100 lb per square inch, and then released to the atmosphere through a nozzle which first contracted to a throat and thereafter expanded in a divergence, the velocity of the escaping air would exceed the velocity of sound. In the case just quoted the jet would reach approximately twice the speed of sound.
At the National Physical Laboratory, Stanton had made such a jet of air, and in it had measured the lift and drag of wing sections. Because of the large power required to compress the air initially, the experiments had to be conducted on a small scale; Stanton’s jet was just 2 in (50mm) in diameter. Nonetheless, the measured results were the first that had ever been made. They provided the first tentative information necessary for the dream of supersonic flight, which 20 years later was to become a reality for fighter aircraft, and 40 years later a routine occurrence for old ladies in the Concorde.
When an aircraft accelerates through the speed of sound, it generates waves or pressure pulses in the air. At the speed of sound the pressure waves are small, like sound waves. As the speed increases, a bow wave is set up at the nose and at the leading edge of the wings like the wave at the prow of a ship. This has a large amplitude, and can no longer be regarded as a simple sound wave. This shock-wave is responsible for the supersonic ‘bang’ of the Concorde and other supersonic aircraft.
Professor Ackeret at Zurich had already evolved a theory of the lift and drag of a wing at supersonic speeds, on the basis that the waves generated were small, like sound waves. His theory, therefore, applied to speeds near the velocity of sound. Despite this, Taylor applied Ackeret’s theory to Stanton’s experiments, and compared the measured results with the theoretical calculations. The agreement was reasonably good, even though the experiments had been made at Mach 1.8 (1.8 times the velocity of sound). I decided to extend Taylor’s calculations, using real shock-waves, such as would be generated at Mach 1.8. The results, as expected, were even closer to Stanton’s experimental measurements. Both theory and experiment showed that, as the speed increased from below to above that of sound, the centre of lift of the wing moved rearwards from about one-quarter of the chord (distance across the wing) at subsonic speeds to one-half of the chord at supersonic speeds. Thus, an aircraft flying through the speed of sound would rather suddenly become nose-heavy, since the centre of lift would move rearwards from the centre of gravity. This effect was to confuse pilots when, in the early 1950s, they first ventured through the speed of sound in conventional fighters.
In 1932-33 this work was only an interesting hobby. I had no conception whatever that it would prove basic to my first job in Rolls-Royce, and that the knowledge I was acquiring would ultimately give me such a head-start in that great firm.
In another
part of the Laboratory, young Frederick Llewellyn Smith was experimenting with the only internal-combustion engine the Lab possessed. It was a single-cylinder petrol engine, and Llewellyn Smith was interested in the combustion process that went on during the power stroke. He had designed a highspeed valve which opened very briefly during the power stroke; out would puff a little of the combustion gases into a collector. The gases were then analysed chemically, and he could vary at will the point in the power stroke when he took his sample.
I asked him, ‘What are you going to do when you leave Oxford?’.
‘I am going to get a job with Rolls-Royce at Derby’, he replied.
‘Have you fixed it?’.
‘No’, he said, ‘but I am sure they will take me on’.
I admired his confidence, and was envious of his engineering degree and the practical work he was doing on piston engines. He, on the other hand, was very intrigued by my theoretical work, and regarded it with the same awe that I lavished on his engine.
We became good friends, but our ways parted in 1934 when he went off, sure enough, to join Rolls-Royce. Three years later he wrote to me to ask if I would like a job at Derby with Rolls-Royce, and it was through Llewellyn Smith, who eventually became a Director of Rolls-Royce and ran the Motor Car Division at Crewe, that I was first introduced to the company that was to change my whole life.
When I arrived at Oxford a post-graduate student from the Laboratory was just finishing, and offered me his rooms in the Woodstock Road. In those days every member of the University was required to live either in College or in registered and approved lodgings where the landlady could keep an eye on one — which most did, very unwilling to risk the danger of losing their licences. Having taken these rooms, which were exceedingly comfortable — and, thereby, having acquired a landlady who was a splendid cook — I found to my consternation that for the first two years a freshman had the option of rooms in College. Thus, of the entrants in my year, I was the only one not to live in College.
Not Much of an Engineer Page 2
