By the end of the war one British engine was powering the Spitfire, the Hurricane, the Lancaster, the Mosquito and the…

By the end of the war one British engine was powering the Spitfire, the Hurricane, the Lancaster, the Mosquito and the American Mustang. Rolls Royce could not build anywhere near enough of them, so the British government asked a car company for help. The car company studied the drawings and came back with a problem. Rolls-Royce's tolerances were too loose. This is the story of the Merlin..🧵1/4

🧵 2/4 The Merlin was a 27 litre V12, designed by Rolls-Royce in the 1930s, and it was the engine Britain built its air force around. It went into the Spitfire prototype in 1936 and was still going into front line aircraft nine years later. The problem was quantity. Rolls-Royce was a company that built superb things in small numbers, and it was now being asked to supply engines for a war. New Rolls-Royce factories went up at Crewe and at Hillington near Glasgow. It still was not enough. So the government brought in Ford of Britain to run another new Merlin factory at Trafford Park in Manchester. Ford knew how to make things in volume. That was the entire point of Ford. Ford's engineers spent months going through Rolls-Royce's drawings and methods. Then their chief engineer went to see Rolls-Royce.

🧵 3/4 The man he spoke to was Stanley Hooker, who wrote the conversation down years later in his memoirs. Ford's chief engineer said, plainly, that they could not make the Merlin to these drawings. Hooker, by his own admission, replied loftily. He assumed the tolerances were too tight, and that a car company simply could not hold the accuracy Rolls-Royce worked to. The answer came back the other way round. On the contrary, said Ford's engineer. 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, so everything is made far closer than you use. That is the only way we can achieve mass production. That is the difference between the two industries in one exchange. Rolls-Royce's methods still leaned on skilled fitting during manufacture. Ford's system demanded that a part coming off one line fit an engine coming off another, with no adjustment at all. Ford went on to build around 30,000 Merlins at Trafford Park.

🧵 4/4 Britain needed more still, so in September 1940 Rolls-Royce signed a licence with the Packard Motor Car Company of Detroit, on an order worth 130 million dollars. Packard hit the same problem Ford had. Before mass production could begin, they had to convert and extensively redraw Rolls-Royce's manufacturing drawings for American standards and methods. Jesse Vincent put more than 200 engineers and draughtsmen on the job. The first Packard Merlin ran on 2 August 1941. Packard alone went on to build roughly 55,000 Merlins. And that turned out to matter more than anyone expected. The P-51 Mustang was very good at low level with its original American engine and badly limited high up, where the bombers were. Rolls-Royce tried a Merlin in one in 1942, and the aircraft became something else entirely. The escort fighter that could take American bombers to Berlin and bring them home again. The Merlins that powered the great American P-51 escort force were not built in Derby. They were Packard built versions, made in Detroit. A British engine, mass produced by people who made cars, in an aircraft designed in California, flown by American pilots over Germany. This was the story of the Merlin. I post a story like this every single day. Most people never see them. Follow so you don't miss the next one.