Inline engines: Modern air cooled vs WWII water cooled

[gjs238]

The big engines of WWII ate dust for months between overhauls. Ask ANYONE who flew from, say, Malta or in North Africa. I have and they ran just fine for longer than anticipated.

Some Hurricanes were "tropicalised" with Vokes air filters to deal with certain environments.

From Wikipedia:
Hurricane Mk IIB Trop.
For use in North Africa the Hawker Hurricane Mk IIB (and other variants) were tropicalised. They were fitted with Vokes and Rolls Royce engine dust filters and the pilots were issued with a desert survival kit, including a bottle of water behind the cockpit.[102]

I can't think of even ONE modern engine that could do it except maybe a diesel ... and they were NOT the engines of choice in WWII. The ONLY reason we are flirting with diesels in aviation today is the cost of fuel. If it weren't that, nobody would bother with them at all except in trucks hauling freight and large boats and ships. They are good for good torque at low RPM at one speed for a long time ... hardly an aviation need.

There was some brief use of diesels in aircraft in the early 1900's.
Even radial diesels.
https://en.wikipedia.org/wiki/Category:Aircraft_diesel_engines

Several aircraft used diesels, a famous one is the Junkers Ju 86
https://en.wikipedia.org/wiki/Junkers_Ju_86

 

[pbehn]

If the modern guys scaled up, they might do better and might not ... they have forgotten a LOT of tribal knowledge about large piston engines because they aren't made and have't been made for 50+ years. Go look at an Allison V-1710 or a Merlin 1650 V-12. 4 valves per cylinder and made very close to 1 HP per cubic inch or 61.02 Hp per liter and better.

Yes there are modern engines out there that make that power level, but do they do it like an aviation engine? Like maybe 100% power for takeoff and climb (say 15 - 20 minutes) and then 60 - 75% power for another 5 - 8 hours, and do it every other day or so for 400+ hours, and do it efficiently at 25,000 feet? Maybe four at a time as in a 4-engine bomber? And continue to run with bullet holes in the crankcase? With maintenance out in the open on an airfield that was recently a farmer's field, complete with rain, dust, bugs, birds, and everything else?

I could throw a handful of sand into the intake of ANY Formula 1 car and it would expire in less than 10 minutes. The big engines of WWII ate dust for months between overhauls. Ask ANYONE who flew from, say, Malta or in North Africa. I have and they ran just fine for longer than anticipated.

Greg Ive been thinking about this a little. In racing the engine just has to last to the end of the race the maximum power is therefor pretty much that. For an Aero engine it must last for the cycles you say and hold together. The maximum power is therefore not the maximum possible but the maximum certified to be used. Reading about engines there is frequently a remark somewhere that so and so engine produced 4,000 or 5,000HP on a test bed. They never say how long it held together and no one pretends it would be safe to run it in an AC at that power.

 

[Shortround6]

In racing the engine just has to last to the end of the race the maximum power is therefor pretty much that. For an Aero engine it must last for the cycles you say and hold together. The maximum power is therefore not the maximum possible but the maximum certified to be used.

In car racing or motorcycle racing if the engine blows up you can walk back to the pits (danger is from other drivers/vehicles). In Hydroplane racing you can float around waiting for the tow boat. Blow up the engine in an airplane and ?????????

 

[GregP]

Let's put this into perspective.

Nobody has made a 1500 - 2500 HP aero piston engine in about 70 years. The last ones that were liquied cooled displaced 1649 and 1710 cubic inches and made 1,850 - 2,200 HP reliably for 400+ hours between overhauls. The bearing technology has been lost and NOBODY is making steel mains with silver pressed into the steel and lead pressed into the silver. These are the bearings that lasted 400+ hours at high power levels ... no longer made and haven't been made for 70+ years.

Call me a doubter but I don't think anybody can make an engine that is as good a Merlin or an Allison today without suffering an entire rash of failures due to all the tribal knowledge about large piston engines that has been lost except for a few qualified overhaulers.

Just my opinion. Yours may vary and that's OK.

Yes they had a few aerial diesels, such as the Blohm und Voss BV.139's engines. None were of the high-performance variety and they STILL don't have a great diesel for general aviation aircraft today. So I very seriously doubt the claim about it being easy to make an aerial diesel. If it's so easy, where ARE they? We've been asking for them for abouit 20 years now and they are a VERY conspicuous no-show. The ones flying don;t even have a TBO! They have a TBR ... time between repalcement!

 

[gjs238]

Let's put this into perspective.

Nobody has made a 150 - 2500 HP aero piston engine in about 70 years. The last ones that were liquied cooled displaced 1649 and 1710 cubic inches and made 1,850 - 2,200 HP reliably for 400+ hours between overhauls.

1710?

 

[GrauGeist]

Here's some typical engines used in a variety of warplanes, certainly not the largest engines of the war, but does give an idea of how big those engines were on average:

Rolls-Royce Merlin 61: 1,647 CID (27L)
Allison V-1710-F30R: 1,710 CID (28.02L)
Daimler-Benz DB601A: 2,070.5 CID (33.93L)
Junkers Jumo 213E: 2,135.2 CID (35L)
Klimov VK-107A: 2,140 CID (35.08L)
Mikulin AM-35A: 2,847 CID (46.66L)

 

[gjs238]

I was thinking of the DB 603A at 44.52 L (2,716.9 in3)

 

[GregP]

The German and Soviet engines were not designed with the same fuel in mind as the Merlin and Allison were. Less energetic fuel means more cubic inches for the same power. Nothing WRONG with displacement, but better fuel renders smaller engine displacement with equivalent or better power.

I'm sure that had the Soviets had access to 150 octane fuel, their engines would have gained power or lost dispalcement or both. Nothing wrong with the existing engines since they often ran on fuel that was heavily contaminated and was strained through chamois or even bedsheets anf field jackets! I have a few Russian friends that have related stories about winter flying in the Soviet Union that would certainly make you glad you weren't there ... or wish you weren't if you WERE there.

The German engines were superb and really didn;t need much help. Nothing wrong with a DB or a Jumo except maybe the general lack of electric starters in the field.

 

[GrauGeist]

Like I said, those were average sizes and look at how they performed in the aircraft they were installed in.

There were much larger engines that were in use (this does not include prototypes or dead end projects):

Rolls-Royce Vulture V: 2,592 CID (42.47L)
Junkers Jumo 222A: 2,830 CID (46.5L)
Mikulin AM-42: 2,847 CID (46.66L)
Allison V-3420-A18R: 3,420 CID (56L)

 

[GregP]

I'm SURE you KNOW that the Allison 3420 was just two 1710's ona common crankcase. They were V-1710-based.

They only made 538 Vultures and they were unsuccessful. I never considered them and they were abaondoned early in the war.

The AM-42 started out in life as the AM-34, designed in Italy, and morphed into the AM-35, then the AM-38 and, finally, the AM-42. It had some Soviet input in that time, naturally, but was a larger-displacement engine than the MNerlin or the Allison ... alrgely due to les sophisticated fuel used in development and operation. It had the very unique characteristic of having a longer stroke on one side than the other due to articulated connecting rods on one side!

My entire point is nobody has made large HP or large-displacement piston aero engines in a LONG time. So there has been a very large loss of knowledge about how to do it. What is your point? No argument, just curious as to what direction your comments are leading. I agree with them, but they don't address my contention and I was just wondering.

 

[GrauGeist]

I'm SURE you KNOW that the Allison 3420 was just two 1710's ona common crankcase. They were V-1710-based.

They only made 538 Vultures and they were unsuccessful. I never considered them and they were abaondoned early in the war.

The AM-42 started out in life as the AM-34, designed in Italy, and morphed into the AM-35, then the AM-38 and, finally, the AM-42. It had some Soviet input in that time, naturally, but was a larger-displacement engine than the MNerlin or the Allison ... alrgely due to les sophisticated fuel used in development and operation. It had the very unique characteristic of having a longer stroke on one side than the other due to articulated connecting rods on one side!

My entire point is nobody has made large HP or large-displacement piston aero engines in a LONG time. So there has been a very large loss of knowledge about how to do it. What is your point? No argument, just curious as to what direction your comments are leading. I agree with them, but they don't address my contention and I was just wondering.

But those engines I listed were used in types, even if they weren't long-term production airframes.

The point is, gjs238 wanted to see bigass engines and so a list was put forth that delivered. Like I mentioned in the previous thread, the bigass engine list was not prototypes or dead-ends, but ones that actually saw service. There were much larger ones that were being fooled around with, but failed to materialize for one reason or another.

If we want to talk serious ass-kicking horsepower and cubic inches, we could talk Dragster engines. Pound for pound, these are technically the most powerful powerplants on earth...

* Even with nearly 3000 CFM of air being rammed in by the supercharger on overdrive, the fuel mixture is compressed into nearly-solid form before ignition. Cylinders run on the verge of hydraulic lock.

* Under full throttle, a dragster engine consumes 1 1/2 gallons of nitro per second, the same rate of fuel consumption as a fully loaded 747 but with 4 times the energy volume.

* Dual magnetos apply 44 amps to each spark plug. This is the output of an arc welder in each cylinder.

* At stoichiometric (exact) 1.7:1 air/fuel mixture (for nitro), the flame front of nitromethane measures 7050 degrees F.

* Nitromethane burns yellow. The spectacular white flame seen above the stacks at night is raw burning hydrogen, dissociated from atmospheric water vapor by the searing exhaust gases.

* Spark plug electrodes are totally consumed during a pass. After 1/2 way, the engine is dieseling from compression-plus the glow of exhaust valves at 1400 degrees F. The engine can only be shut down by cutting off its fuel flow.

* If spark momentarily fails early in the run, unburned nitro builds up in those cylinders and then explodes with a force that can blow cylinder heads off the block in pieces or blow the block in half.

* Dragsters twist the crank (torsionally) so far (20 degrees in the big end of the track) that sometimes cam lobes are ground offset from front to rear to re-phase the valve timing somewhere closer to synchronization with the pistons.

* Nitromethane-powered engines of NHRA Top Fuel dragsters and Funny Cars produce approximately 7,000 horsepower, about 37 times that of the average street car.

Now how about that technology in a warbird?

 

[GregP]

AA Fueler Dragster engines run about 10 - 12 seconds max. About halfway down the dragstrip the spark plugs are burned away and it is dieseling. They wouldn't last as long as a takeoff run for Piper Cherokee 180. I have never considered them to be anything but dragster engines and won't. But I DO love to watch them run. The WinterNationals will be soon at Pomona Raceway and I'll BE there. In addition to the dragsters, they will have a cacklefest, too. Don Garlits, Don Prudhome, and a lot of others will be there with cars from the past that start and run. Maybe they'll be allowed to do some slow runs ... if they stay under 200 mph or so.

If someone asked for a list of engines, then go for it.

I still say NOBODY could build a large-displacement, 1500 - 2500 HP, liquid-cooled piston aero engine today without a LOT of development. They have just lost the formula and would need to rediscover it. What is needed is GREAT power at LOW rpm ... depending on propeller diameter. Can't design one without the other unless you are resigned to a PSRU, and most WWII engines WERE geared except for some smaller radials that had both geared and direct drive units produced. They were NOT the power champs.

An engine is nothing more than a big air pump and direct drive engines will always pump less air than a geared unit of the same displacement.

 

[GrauGeist]

I had a GM 702.9 CID V-12 in my '68 Chevelle that was a real ass-kicker...

The 702 engine was about 1958 vintage and ran like a beast...plus it was a real head turner at the show and shines back in the 80's

Big cubes had their place in the sun at one time...

 

[tyrodtom]

I had a GM 702.9 CID V-12 in my '68 Chevelle that was a real ass-kicker...

The 702 engine was about 1958 vintage and ran like a beast...plus it was a real head turner at the show and shines back in the 80's

Big cubes had their place in the sun at one time...

I can remember some of the bigger coal trucks around here having those in the late 50's early 60's.
They looked like 2 V-6's welded together because of the 2 rocker arm covers on each side, but it was actually one big cylinder block.

They were the king of the haulers until the diesels started taking over.

 

[swampyankee]

Can modern air cooled inline engines compete with the water cooled engines of WWII?

Perhaps there are no modern engines of those ratings being produced, if that is the case, then could modern air cooled technology produce engines competitive with water cooled engines of WWII?

Cooling air-cooled inlines was difficult. Sometimes it was done successfully, but it required more care than cooling air-cooled radials, with no drag advantage (the drag advantage of liquid-cooled vs air-cooled engines is largely illusory, although it was, and is, easier to design a aircraft engine installation when there's an intermediate liquid heat transfer loop than when their isn't. Negative cooling drag is possible with both, but rarely achieved with either.)

Air-cooled engines clearly could be produced to compete with liquid-cooled engines in WW2, although only one really large air-cooled V-12 saw any kind of service, the Isotta Fraschini Delta. The big air-cooled engines were all radials. This wasn't accidental: radials are lighter than in-lines of the same capacity.

 

[GrauGeist]

They looked like 2 V-6's welded together because of the 2 rocker arm covers on each side, but it was actually one big cylinder block.

Yep!

Highly unusual for a street rod but sure drew a crowd wherever we parked. And torque, lots of torque!

Here's an info-graphic from back in the day, for those that might be interested...

And now, we return to the regularly scheduled aircraft engine talk!

 

[gjs238]

Awesome, all set for installation in aircraft.
Even has a propellor attached.

 

[GrauGeist]

Actually, there is a good number of automotive engines that have found their way into aircraft over the years.

Some examples would be the Chevrolet H-6 aircooled engine (best known for it's use in the Corvair automobile), Volkswagon's Type I H-4 aircooled engine amongst others...

 

[Shortround6]

I have read (but don't know it it's true) that one reason that nobody is using silver bearings on modern engines is that some of the anti-scuff additives in many modern motor oils attack and corrode the silver in the bearings leaving them in rather poor condition after a while. Modern oils work well with modern bearings, Not so good using modern oil with old bearings or old specification oil with new bearings. The modern bearings depending, in part, on the additives in the oil.

 

[pbehn]

An engine could be constructed air or water cooled, 2 or 4 stroke but who would make it it would in F1 terms require a team working for 5 years to produce it that is about 300 milion dollars for the first flight, just to prove a principle. If any one wants a high performance prop SE aircraft use a turbine.. Problem is with the sound and lack of WW2 connection.