There remained the design of the intercooler between the blowers and the induction pipe necessary to cool the air/fuel charge before it entered the cylinders. Here the Chief Engineer took a major part, and it was most impressive to stand with him and others at a drawing board while he sketched in the principle of the construction and mounting of this new component. In fact, to go with Elliott into the Main Design Office was a great treat for us all. He was like the Specialist in a hospital, examining each drawing as he passed, criticising points and adding deft touches to solve any design problem. It was all highly educational to me to follow in the wake of such a great designer. The trouble was that he did so infrequently, but spent the major part of his time in his office trying to get abreast of yesterday’s problem.
I would add that he was the No 1 gentleman in Rolls-Royce, calm, serene and kind. The rest of us were roughnecks in comparison. I frequently travelled with him to visit the aircraft companies, and it was a pleasure to see him handle such tough and irate designers as Sydney Camm of Hawker Hurricane fame, and Roy Chadwick, the designer of the Lancaster bomber.
The first time I met Camm was with Elliott in the early days of 1940. Camm and his design office had been evacuated from the Hawker factory at Kingston to Claremont House, which Queen Victoria stayed at and loved. Camm occupied the drawing-room — I mean the drawing-room of a past age — which was still beautifully furnished and had a large, comforting fire going. Sydney greeted us in his usual way — which, I found later, was pure fun:
‘What the hell are you lot doing here, wasting my time, telling me how to put your rotten engines into my beautiful aeroplanes!’
I shivered in my shoes, for this was lèse majesté indeed, talking to the Chief Engineer of Rolls-Royce in such a manner. Elliott, smiling, replied, ‘What a splendid office to work in, Sydney. Such an elegant fireplace. So convenient for burning those mistakes in’.
Sydney grunted, and turned to me.
‘Who is this chap. I’ve not seen him before’.
Elliott introduced me. Sydney looked squarely at me and said,
‘I just want to get one thing clear with you, young Hooker. The only time I am wrong is when I am persuaded against my better judgement’.
Then he laughed, and we all sat down amicably to get on with the business of the day in the most constructive fashion.
To return to the intercooler, the internal matrix, through which the charge passed in one direction and the cooling water through in another, as it does in a motor-car radiator, posed a problem. There was no heat-exchanger matrix available in the country of high enough efficiency to do the job in the small space that was available. So we enlisted the help of the Engine Department of the Royal Aircraft Establishment.
Very soon, Farnborough’s Dr Remfrey appeared in my office at Derby with a small sample of a matrix made in copper sheet, which tests had shown would do the job. I examined it. The thing that worried me was its mechanical strength.
‘Oh, it’s strong enough to jump on’, said Remfrey.
Instinctively, I said ‘Show me’. Equally instinctively, Remfrey put the small sample block on the floor and jumped on it. It went as flat as a pancake, to the howls of nervous merriment from the assembled company. Remfrey was very crestfallen, and, since it was the only sample in existence, feared the wrath of his superiors. I said, ‘Never mind, tell them that clumsy idiot Hooker did it’.
In fact, the construction and efficiency of the matrix was excellent, and it was duly adopted for the intercooler. In a matter of months, a Merlin was made with the new design of the two-stage supercharger and intercooler. The test results fulfilled our highest hopes, and the engine worked beautifully on the test-bed first pop.
But the proof of the pudding was really in flying the engine. Although we could predict the power at 30,000 ft, we would only know the real answer in the air. In due course, two engines were installed in a Wellington and the first flight was made from Hucknall.
That day Hs sent for me. I went to his office and he asked ‘What do you say the full-throttle height of the two-stage Merlin is?’
Nervously, I replied, ‘I calculate it to be 30,000 ft, approximately’.
He passed me a piece of paper, and on it was written just 29,750. He said, ‘I have just had that figure from Dorey taken on the first flight of the Wellington’. He never indulged in compliments, but was obviously delighted.
At the next Monday meeting, he referred to the new Mk 60 engine, and then said something that had never occurred to us,
‘What would happen if we put this engine into a Spitfire?’
It was blindingly obvious that the Spitfire was the true home for the engine, and it had been left to Hs to suggest it. We all sat back aghast and silent.
Dorey said, ‘I don’t know, but we will damned soon find out. I will start work on putting one into the Spit immediately’.
This was a considerable task, because the engine was 9 inches longer than the standard Merlin, and thus the whole of the nose of the aircraft, with the engine mounting and controls, had to be redesigned. A new four-blade propeller was needed to convert the power into thrust. An extra radiator had to be provided under the wing to dissipate the heat in the water that cooled the charge (and this helped to balance the extra weight at the front). But the job was done in double-quick time, and in 1941 the first Spitfire with the Merlin 61 engine flew at Hucknall and soared to over 40,000 ft (over 12 km).
This was the prototype of the famous Spitfire IX. The new engine increased its fighting altitude by 10,000 ft, and added 70 mph to its top speed. The Spitfire IX was in the hands of the RAF just in time to counter the formidable Focke-Wulf 190, which owed its performance to an aircooled BMW engine, much heavier and larger than the Merlin. The swept volume of the German engine was 2,560 cu in (41.8 litres); our new two-stage Merlin beat it with 1,647 cu in (27.0 litres). Years later Air Marshal Sir Harry Broadhurst, who had been one of our great fighter pilots at this time, told me of his first operational flight in a Mk IX, and of the look of astonishment on a German pilot’s face as he climbed up past him with much greater performance.
The new engine went into mass-production. Many thousands were made for Spitfires, P-51 Mustangs, Mosquitos and special Pathfinder Lancasters. Conceived for the Wellington bomber with a pressurized cabin — which never went into service — it became the principal fighter engine in the RAF. It had a major application in the outstanding North American P-51 Mustang fighter, which was the only aircraft that really challenged the supreme performance of the Spitfire.
After the War began, and after a major false start with the US Ford Motor Co, the Government placed a large contract for the manufacture of the Merlin engine with the Packard Motor Co, in Detroit. Full manufacturing details and drawings were sent to them from Derby. Ellor and Barrington were seconded to Packard to assist them in interpreting the English drawings, and to act as liaison engineers with the rest of us at Derby. They bore such a crushing load that Barrington died in the USA and Ellor soon after his return.
The departure of Ellor and Barrington in 1940 left a hole in the staff at Derby. Rubbra was appointed Chief Designer in Barrington’s place, and Lovesey was promoted to Chief Experimental Engineer to replace Ellor. To my great satisfaction, I was invited by Lovesey to become his chief assistant, and moved into his office. Now my engineering education really began. His remit to me was: ‘You look after the performance of the engine, and I will deal with the mechanical side’.
And so I had the opportunity of sitting in at many sessions with his staff. I learned the diagnostic way he examined the mechanical problems, and propounded the tests and solutions to overcome them. At the appropriate time, he would say to me,
‘Come along, today we will go and see Rubbra and clean this job up’.
Then would follow a session with the main engine designers. At these I learned of the constant interplay between design and development as Lovesey, in his very skilful way, would illuminate the problems, and t
he equally skilful designers would sketch the modifications to the drawings in such a way as to cause the minimum disruption to production — and yet maintain the high standards set out in the Manuals of Design Standards which had accumulated since the days of Henry Royce. So I learned about designing from them, although I could never hope to become an accepted designer, because it takes 20 years of dedicated application to become that.
The word ‘engineer’ covers a variety of expertises and people of very varying backgrounds. In my experience, the crème de la crème of these are the designers and, if it be true that the status of engineers is too low in Britain, then the charge applies first and foremost to designers.
They are enthusiasts who seek after something more than wealth and power. They lead a tiring and exacting life, standing long hours at their boards drawing in two dimensions engine parts that they visualise in their minds in three dimensions. Not only must they create the drawings which can be explicitly interpreted into instructions, which can be made by the many manufacturing processes available in the shops, but they must liaise with the designers on each side to ensure that their parts will match exactly with those of their colleagues, and that the whole can be manufactured and assembled as an engine with convenient access for inspection of the vulnerable parts.
They are fed (often to the teeth) with information and advice from experts in specialized fields such as performance and gas dynamics, mechanical integrity and material properties, and they must work within the limits of stress imposed by the experts.
They are the ‘keepers of the Trade’, which embodies all the details of past experience so hardly learned. They are indeed an elite body, yet they are almost always quiet and modest, capable of defending their creation with lucid arguments. At the end of the day, they have the most satisfying and rewarding job of all. They can look at an engine and say, ‘I created those parts, and they are exactly as I saw them in my mind when I took my pencil and began to draw on a blank sheet of paper, and they work!’
For myself, I frequently look at an engine and think, ‘That is how I visualised it’, but, however much one might have influenced the design and laid down the general arrangement, the men who created it were the designers. This does not mean that designers necessarily make the best Chief Engineers, although in the case of Royce this was so. An analogy might be that Yehudi Menuhin, with his superb interpretations, would not necessarily make the best conductor of the orchestra, with its many lesser, but still important, ‘prima donnas’.
In my enthusiasm, I considered that Rolls-Royce designs were the ne plus ultra, until the Ford Motor Co in Britain was invited to manufacture the Merlin in the early days of the War. A number of Ford engineers arrived at Derby, and spent some months examining and familiarizing themselves with the drawings and manufacturing methods. One day their Chief Engineer appeared in Lovesey’s office, which I was then sharing, and said, ‘You know, we can’t make the Merlin to these drawings’.
I replied loftily, ‘I suppose that is because the drawing tolerances are too difficult for you, and you can’t achieve the accuracy’.
‘On the contrary’, he replied, ‘the tolerances are far too wide for us. We make motor cars far more accurately than this. Every part on our car engines has to be interchangeable with the same part on any other engine, and hence all parts have to be made with extreme accuracy, far closer than you use. That is the only way we can achieve mass production’.
Lovesey joined in, ‘Well, what do you propose now?’
The reply was that Ford would have to redraw all of the Merlin drawings to their own standards, and this they did. It took a year or so, but was an enormous success, because, once the great Ford factory at Manchester started production, Merlins came out like shelling peas at a rate of 400 per week. And very good engines they were too, yet never have I seen mention of this massive contribution which the British Ford company made to the buildup of our air forces.
The demand for Merlins seemed insatiable. Starting as the ‘hot rod’ engine for the Spitfire and Hurricane, it rapidly found homes in other aircraft types, one of the most famous, of course, being the Lancaster bomber.
Roy Chadwick, the great designer of the Avro company, had originally designed the aircraft as a twin-engined bomber called the Manchester which had two 1,800 hp Rolls-Royce Vulture engines. For various reasons, the Manchester was very unsuccessful with two Vulture engines. In late 1940, therefore, in double-quick time, Chadwick redesigned the wings and installed four Merlin engines, rated at that time at 1,250 hp each. The result was the Lancaster, the supreme RAF bomber of the war. Over 7,000 were made and Air Chief Marshal ‘Bertie’ Harris described it as ‘a shining sword in the hands of Bomber Command’.
Another Merlin aircraft was the versatile twin-engined Mosquito, designed by Bishop and Clarkson of de Havilland Aircraft. The airframe was made of wood, and thus the wood constructing industry was harnessed to the war effort. Although originally a bomber, the Mosquito had the performance of a fighter, and flew at high altitudes and speeds. It was thus almost invulnerable to anti-aircraft gunfire, and was very difficult to intercept. It was a most popular aircraft in the Royal Air Force.
A third, and perhaps the most outstanding, adaptation of the Merlin was to the North American Mustang fighter. This aircraft was originally fitted with an American Allison engine, but its performance at high altitude was so improved by the Merlin that this became its standard powerplant. Such was its efficiency that, despite having larger wings and three times the fuel capacity, it was faster than any Merlin-Spitfire at all altitudes. It was most successful in shooting down or ‘tipping over’ the V-1 flying bombs, when Hitler launched that devastating weapon against London and south-east England in the summer of 1944.
At the outbreak of war, the Merlin had lately been substituted for a less-powerful engine in the Armstrong Whitworth Whitley bomber. This machine had two engines and was slow and ponderous by later Lancaster and Mosquito standards. Nonetheless, it was at the time the only bomber that could reach Italy with a useful bombload, and was used by the Bomber Group commanded by Alec (later Air Chief Marshal Sir Alec) Coryton for that purpose. En route, it had to climb over the Alps, and at that speed and altitude the Merlin had to be used at maximum power, and the cooling was found to be inadequate. A number of engine failures occurred, and Coryton, who was an enthusiastic amateur engineer, waxed very wrathful with Rolls-Royce, as he thought that insufficient attention was being paid to his aircraft and the safety of his crews. He wrote to Hs inviting any of us to go on one of the raids and to see for ourselves what the problems were. Hs read the letter to us at one of his Monday afternoon meetings, and then surveyed us all.
‘Are there any takers?’, he demanded. There was no scramble, but Coryton certainly got a better service from us.
Throughout the war, the power of the Merlin was continuously increased by Lovesey and Rubbra from 1,000 hp to 2,000 hp. I have described earlier how its power at 30,000 ft was doubled from 500 hp to 1,000 hp by the two-stage supercharger and intercooler. At the maximum engine speed of 3,000 rpm the power developed in the cylinders was divided between the frictional horsepower required to rotate the engine, the power to drive the supercharger and the useful power at the propeller in the rough proportions of 20 per cent, 10 per cent and 70 per cent.
The maximum recommended cruising rpm for the engine was 2,650. In the early days, pilots tended to use this speed for all their long flights, even if they could get the aircraft speed and altitude they required at lower revs. By so doing, they used the engine at part-opened throttle, and wasted fuel. The frictional horsepower lost could be more than halved by reducing the speed from 3,000 to 2,000 (losses are proportional to the square of the rpm), and the power to drive the supercharger was also halved. Thus, the proportions at 2,000 rpm became 10 per cent, 5 per cent and a healthy 85 per cent. In other words, get the throttle wide open and reduce the revs to a minimum by coarsening the variable-pitch propeller and maximum range would b
e obtained. This caused me to enumerate the simple maxim, ‘Use low revs and high boost’ in cruising operations. The RAF printed thousands of large posters saying ‘Reduce the revs and boost the boost, you’ll have enough petrol to get home to roost’.
There was another engine control lever in the cockpit which adjusted the fuel/air mixture. It was labelled at one end of its travel, ‘rich’, and at the other end, ‘weak’. The idea was that at take-off power surplus fuel (rich mixture) was fed to the engine to cool the charge and thus suppress detonation; at lower power the mixture strength could be reduced to the correct value, when it was called ‘weak’.
Hs hated this control, and said, ‘If you were going into battle, which would you select, rich or weak?’ And, of course, pilots did, in fact, leave the control in rich or forgot to pull it back to weak, and many ran out of fuel as a consequence. So the mixture lever was deleted and the control was connected to the throttle in such a manner that the correct mixture strength was obtained automatically.
The formidable foe in the Battle of Britain was the Messerschmitt Bf 109 fighter powered by the Daimler-Benz engine. This engine had fuel injection direct into the cylinders, in contrast to the Merlin where the fuel was fed from the carburettor into the air upstream of the supercharger, and then the compressed mixture passed to the cylinders. The SU carburettor had normal float chambers, and the German pilots soon found that, if they had a Spitfire or a Hurricane on their tail, all they had to do was to put their nose down and dive. If the Spitfire followed, the negative-g would throw the fuel in the float chambers to the top; the engine would be starved, and would cut out. By the time that the power had restored itself, by the fuel returning to the bottom of the float chambers, the 109 would be safely out of range. Our pilots soon found that they could mitigate this unfortunate situation by quickly rolling inverted as they went into the dive, thus retaining positive-g. But they were very critical, and rightly so.
Not Much of an Engineer Page 8