A sectioned Rolls-Royce Merlin engine.
A sectioned Rolls-Royce Merlin engine

When I was writing my book about the Rolls-Royce Merlin I discovered some amazing facts. There has never been another engine more thoroughly, continuously, aggressively and successfully developed than the Merlin.

How much does a Merlin Engine Cost? A Merlin cost £2,000 in 1940 during the Battle of Britain. That’s the equivalent of about £110,000 today. Auctioneers Bonham’s sold one for £20,700 in 2009 and Sotheby’s sold one for £44,000 ($57,000) in 2019.

Did you know the Spitfire was crowd funded? Lord Beaverbrook, who owned the Daily Express, unified the British nation around his Spitfire Fund, using the power of the press. He raised £13 million, the purchase price of around 2,600 Spitfires.

He claimed that each aircraft cost only £5,000 but in fact the actual price was £12,604 in 1940, or around £700,00 now. This included the cost of a brand-new Merlin engine (£2,000, now £110,000) and propeller (£350, now £18,600).

One of the oddest donations came from 2,500 British prisoners of war held at Oflag VIB camp near Warburg, who contributed one month’s pay “to charity”, the money being deposited with the German authorities who unwittingly forwarded it to England via the Swedish Red Cross. This paid for one Spitfire which was named Unshackled Spirit!

The Supermarine Spitfire was crowd-funded!
The Supermarine Spitfire was crowd-funded.

How much is a Merlin Engine worth?

Some would say that the Rolls-Royce Merlin was beyond value as the Spitfires and the Hurricanes it powered won the Battle of Britain. As a result the Luftwaffe failed to destroy the RAF, Hitler’s invasion never materialised, and so Britain remained free to act as a base for the successful invasion of Europe and eventual destruction of the German Third Reich. Which in turn led to a free Europe. If any engine won the Second World War, it was the Merlin. How do you put a price on that?

What does a Merlin sound like?

Listen to Jay Leno’s! https://www.youtube.com/watch?v=GYcKdK7hmEo

If you had to put a monetary value on the Rolls-Royce Merlin it cost £2,000 in 1940 which translates to about £110,000 today.  If you had to buy a Merlin today, auctioneers Sotheby’s sold one for £44,000 ($57,000) in 2019.

The Rolls-Royce Merlin engine powered over 40 British aircraft, and even one German one! A Merlin was put into a captured Messerschmitt Bf 109, all RAF personnel concerned agreeing that the aircraft was now much improved by the change. You might expect this kind of verdict, just as when a captured Spitfire was fitted with a German DB605 engine the same conclusion was reached by the Germans!

Even the Germans couldn’t get a Merlin into their Fieseler Fi 156

Which aircraft had Merlin engines? The Supermarine Spitfire had one Merlin, and it was perhaps the most famous piston engined aircraft ever and certainly one of the most beautiful weapons of war. There was one Merlin in the Hawker Hurricane and the Mustang fighters. Two Merlins made the de Havilland Mosquito the fastest aircraft in the world.  And four Merlins turned the disastrous twin-engined Avro Manchester into the best heavy bomber of the war: the Avro Lancaster. Read more about the Merlin and the aircraft it powered in my new book: “Merlin: The Power Behind the Spitfire, Mosquito and Lancaster.”

Which aircraft had Merlin engines?

The Supermarine Spitfire had one Merlin, and it was perhaps the most famous piston engined aircraft ever and certainly one of the most beautiful weapons of war. There was one Merlin in the Hawker Hurricane and the Mustang fighters. Two Merlins made the de Havilland Mosquito the fastest aircraft in the world.  And four Merlins turned the disastrous twin-engined Avro Manchester into the best heavy bomber of the war: the Avro Lancaster. Read more about the Merlin and the aircraft it powered in my new book: “Merlin: The Power Behind the Spitfire, Mosquito and Lancaster.”

Who Made the Merlin Engine, and is it made now?

The Merlin engine has been named the engine that won World War Two. In the writing of my book about it I found out lots of interesting facts:

The Merlin aero engine was first made in 1936 by Rolls-Royce, then considered the best engineering company in the world. It was made in their Derby factory at first, and all the Battle of Britain Merlins were hand-built in that factory. Later Rolls-Royce also made the engine in a factory in Crewe and another in Glasgow. These were shadow factories to keep production going if the Germans bombed Derby. Later still Merlins were made in a Ford factory situated where the Trafford shopping centre is now, and also in Detroit, USA, where Packard made the Merlin under licence.

The last Merlin was built in 1950. The rough design was laid out by Henry Royce, who was nearing the end of his life due to bowel cancer (Charles Rolls had already been killed in an early aeroplane accident). Royce stipulated that the Merlin be a 20% enlarged version of his successful Kestrel engine: a V-12 of 27 litres. But it wasn’t to be that easy…

Who Designed / Invented the Merlin Engine?

Henry Royce made some rather nice cars too…

Henry Royce correctly forecast the coming World War 2, and he was prepared to bet his company’s money on it. He designed the Merlin. However, the PV12 (as it was called: “Private Venture 12”) did not have an easy gestation, Rolls-Royce made a number of mistakes with the design and the Merlin, as it soon became known, was not a success at first.

Royce decided to build an engine similar to the Kestrel but bigger, suitable for the next generation of fighters that would need more power. The Buzzard and the R (the racing engine that won the Schneider Trophy) had the power but they were too big and heavy for the new monoplanes that were coming from Hawker and Supermarine. It is interesting to note that the Griffon, a new 37-litre engine, was first run on 6th January 1933, nine months before the PV12 first ran. This first Griffon was essentially a de-rated R engine with a smaller supercharger, and a much-changed Griffon was produced in 1939. This would eventually replace the Merlin. For now, though, there was no aircraft application in sight for it, and all attention was concentrated on the smaller engine.

 So Royce’s designers got their pencils and rubbers out and drew an engine that was an almost exact scale-up of the Kestrel, but 20% bigger in capacity: 27 litres. Then to give the pilot of the aircraft a better view they turned it upside down! The reason for this is that a V-configured engine is narrower at the bottom than the top. Also the exhaust ports can exit below the fuselage, improving the cooling. A wooden mock-up of this upside-down engine was made, and this was the cause of one of the most bizarre stories of inadvertent industrial espionage of the Thirties. A group of German aeronautical engineers was touring the Rolls-Royce factory and glimpsed the upside-down mock-up on Arthur Rowledge’s office floor:

“The Germans evidently thought they had noticed something of supreme significance. There is every reason to believe that the design of the inverted Daimler-Benz engine used in the Messerschmitt 109 and the Junkers engine sprang from this visit to Derby. From their point of view, the inverted engine was desirable because it enabled them to fire the cannon through the airscrew shaft, but this had the serious result of forcing them to mount the supercharger on the side of the engine instead of at the end, a position which necessitated complex piping and which made it difficult to find a suitable place for carburettors. The Germans’ later preference for direct fuel injection was attributable to the difficulty of carburettor layout, and not to any objection to carburettors as such.”

The visiting engineers had clearly taken notice of Ovid’s dictum: Fas est ab hoste doceri: one should learn even from one’s enemies.  It seems hard to believe now that potential enemies were allowed to roam freely around the most secret new designs. This is another one of the Rolls-Royce stories that appeared in the company’s official history, so presumably the directors believed it.

However, a Daimler-Benz historian might point out that their V12 engine had already been turned upside-down well before this factory visit: in fact the 1913 Mercedes aero engine featured this configuration.  The pilot’s-view theory doesn’t hold water with the German twin-engined wing-mounted installations, which were also inverted.