The Secret Horsepower Race - WW2 Aero Engines in detail

[Eric Mc]

Were any MkIIIs ever built?

[wolfracesonic]

Mark V GTD said:

My recollection is that the Ju86P threat to mainland UK was ended following a successful interception by a modified Spitfire IX of the High Altitude flight. This was an RAF unit formed to combat this type of incursion, the aircraft were modified but not pressurised. Although the 86 was not shot down the interception at 42,000 feet by P/O Prince Emmanuelle Gallitzine effectively ended these operations by the Luftwaffe.

(this is from memory by the way the full story is in Alfred Price's 'Spitfire at War III' (I think)

A video here about the encounter Mark Felton, WWII’s highest intercept

[aeropilot]

Eric Mc said:

Were any MkIIIs ever built?

None IIRC.

[samoht]

2xChevrons said:

What doesn't seem to get as much covering was the Bf109's (well, really the DB601 engine's) supercharger drive. At the time the Merlin in the Spitfire and Hurricane used a simple single-speed, single-stage supercharger with automatic boost limit but no other form of control.

The DB601 drove its single-stage supercharger through a hydraulic coupling which allowed infinite gradation of drive ratios between the minimum and maximum available.

... (lots more great info & explanation) ...

Interestingly, Geoffrey Wilde joined Rolls-Royce in 1939 and proposed a continuously variable hydraulic coupling drive for the Merlin supercharger (having previously worked at the British arm of Daimler). However, while Hooker was very supportive, after a discussion with suppliers they decided that it would be too much of a change too late in the day, so had to persist with the two fixed speeds. Wilde's proposal used a torque converter akin to an automatic gearbox, whereas the DB production solution was like a viscous LSD with alternating plates in a fluid bath, but with drive put through it and then the slip controlled by changing the oil level - a through-flow of oil also removing the heat generated from the slip. (Info from the aforementioned book, which also has a couple of neat diagrams of the two mechanisms).

[Eric Mc]

Did any of this get incorporated into the Griffon?

[aeropilot]

Eric Mc said:

Did any of this get incorporated into the Griffon?

Nope.

Griffon did have much larger capacity though, at 37 litres, compared to the Merlin's 27 litres and thus closer to the Daimler-Benz's at 35 litres.

For all the great engineering higher tech of the DB's though (and the Bf109) they had a much lower TBH figure than the Rolls/Packard or Allison V12's, and even more oddly, they still relied on human powered hand-cranking to load up the inertial starter to start the bloody things, which seems totally at odds to all the other high tech advances.

[Eric Mc]

I suppose using a crank and flywheel set up meant you didn't need so much ground equipment - just lots of brawn.

Rolls Royce did have lots of more advanced piston engines in development, but most of them got sidelined because of the need to concentrate on the Merlin and Griffon(I'm thinking of the Peregrine and the Vulture in particular).

[aeropilot]

Eric Mc said:

Rolls Royce did have lots of more advanced piston engines in development, but most of them got sidelined because of the need to concentrate on the Merlin and Griffon(I'm thinking of the Peregrine and the Vulture in particular).

Peregrine wasn't more advanced than the Merlin?

Peregrine was smaller in size, and was really just the most developed final version of the Kestrel V12.

The least said about the Vulture the better.

[Eric Mc]

I don't know much about the Peregrine apart from the fact that it was fitted to the Whirlwind but was never really reliable.

The Vulture was definitely complicated (if not advanced) but was even more unreliable than the Pergrine.

If Rolls Royce had had the time and resources, I'm sure they could have sorted all the problems with these engines out but they were more or less told to give up on them by the Air Ministry so they could concentrate on the Merlin and Griffon.

They were also developing an engine called the Eagle but they built very few of them. The prototype Westland Wyvern had an Eagle but production Wyverns were fitted with the Python turboprop.
The prototype (and its Eagle) is part of the Fleet Air Arm collection but when I was there a couple of weeks ago it wasn't on display.

[aeropilot]

Eric Mc said:

I don't know much about the Peregrine apart from the fact that it was fitted to the Whirlwind but was never really reliable.

If it hadn't of been for the war and the pressing need for Merlins, RR probably would have ironed out the issue's with the Peregrine, but, there was no room for further development really, as that was about as far as the old Kestrel design was going to go.
That's why, despite the fact that the Whirlwind was an excellent aircraft, the already fast pace of developments, meant that there really wasn't much point in trying to solve the problems of the engine, and the aircraft was designed around the engine, so that was that really.

[Eric Mc]

I often think it could have been the "Mosquito" two years earlier - if they'd sorted the engines out.

[aeropilot]

Eric Mc said:

I often think it could have been the "Mosquito" two years earlier - if they'd sorted the engines out.

It would have never been that as only single seat, but had they been even 9-12 months ahead in its initial development, they would have been excellent bomber destroyers in the BofB.
Again, though issues with the early Hispano cannon's might have been an issue, and with them only being fed from 60 rd drum mags, 3 x 2 sec bursts and you were out of ammo.
At least in the Beaufighter, the W/O could re-load the under fuselage cannon from drum mags stored in racks inside the fuselage. And by the time the Mossie came along the cannon issue had been solved with much greater belt fed systems.

[Eric Mc]

The Mossie was only put into production because it used sections of the U.K. work force that were under utilised. It very nearly didn’t happen.
Westland did look at fitting Merlins to the Whirlwind but they were too big for the airframe and it would have caused all sorts of CoG issues.

[aeropilot]

Eric Mc said:

Westland did look at fitting Merlins to the Whirlwind but they were too big for the airframe and it would have caused all sorts of CoG issues.

Yes, as I already said, the aircraft was designed around the small Peregrine, and once RR said they didn't have the capacity to 'fix' the Peregrine because of the demands for the Merlin....that was it.

[Ayahuasca]

Simpo Two said:

Piginapoke said:

It's an interesting subject. My understanding is that the Spitfire Mk 1 and Messerschmitt 109 were close in enough in performance that the pilot and tactical situation were the defining factors, rather than another 10mph top speed. Is that right?

There are many factors, only one of which is speed (level, dive or climb?), and they all combine. Otherwise, the a/c that was 10mph faster would always win and the other one would always get shot down.

The dastardly German’s 20mm cannon was an advantage over the Spit’s .303 guns. Fuel injection vs carb was another.

[GliderRider]

aeropilot said:

There's a well known photograph taken on 18th August 1940 (known as the Hardest Day) from Portsmouth, of a long high level contrail in the sky, which was a Ju86P on a recce of the UK.

My father, who was in Chichester during the war, recalled seeing the Ju86 going over at high altitude. I guess it was the contrail that allowed him to see where it was.

[Yertis]

Eric Mc said:

I don't know much about the Peregrine apart from the fact that it was fitted to the Whirlwind but was never really reliable.

The Vulture was definitely complicated (if not advanced) but was even more unreliable than the Pergrine.

If Rolls Royce had had the time and resources, I'm sure they could have sorted all the problems with these engines out but they were more or less told to give up on them by the Air Ministry so they could concentrate on the Merlin and Griffon.

They were also developing an engine called the Eagle but they built very few of them. The prototype Westland Wyvern had an Eagle but production Wyverns were fitted with the Python turboprop.
The prototype (and its Eagle) is part of the Fleet Air Arm collection but when I was there a couple of weeks ago it wasn't on display.

That Wyvern, and its engine, is an absolute work of art. I stood and feasted my eyes upon it.

[Yertis]

aeropilot said:

At least in the Beaufighter, the W/O could re-load the under fuselage cannon from drum mags stored in racks inside the fuselage. And by the time the Mossie came along the cannon issue had been solved with much greater belt fed systems.

This Beaufighter ammo-drum hassle is well-described by Jimmy Rawnsley in his excellent autobiography 'Night Fighter'. (A great read by the way, I found the slow deliberation of the intercepts quite haunting, for want of a better word.)

[Penguinracer]

Vulture & Eagle - a step too fatrin terms of complexity IMHO.

Mucho love for the Griffon.

The Griffon 101 in the Spiteful Mk 16 was only there right at the end of the war.

To me the Griffon 101 & 130 were peak piston.

[Simpo Two]

Yertis said:

This Beaufighter ammo-drum hassle is well-described by Jimmy Rawnsley in his excellent autobiography 'Night Fighter'. (A great read by the way, I found the slow deliberation of the intercepts quite haunting, for want of a better word.)

You might like 'Pursuit Through Darkened Skies' by Michael Allen DFC. That documents the Intruder raids, ie where they flew over Germany during Allied raids, homing in on the radars of the defending German night fighters. Quite different from the home front.