The other factor was the incredibly low price of avgas in those days. I suspect that if ICE were still used today for airliners, that they would all be liquid cooled because of the lower specific consumption.
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The only liquid cooled airliners were a Few Canadian and British plane using Merlins. At the time the British (including the Commonwealth) had one heck of a trade deficit problem and foreign (meaning US) engines simple could not be afforded. That left the Merlin, Griffon, Sabre, Hercules and Centaurus engines. The Sabre and Griffon found no takers at all in the commercial field and Rolls, by expending a fair amount of effort and trading a bit on the Merlin reputation did make the above mentioned sales. Commercial Hercules ( even licence built in France) and Centaurus engines filled the British commercial aircraft until the jet and turbo prop.
The Americans, for a variety of reasons, dominated the post war commercial aircraft market and so did American engines, which after the Allison stopped production, meant air cooled radials.
One less system to fool with and maintain and with acceptably low operating costs ( and airline owners are a hard headed tight fisted bunch) the air cooled radial did the job.
It was "copied". Some Martin Mariner patrol bombers used fan cooled R-2600s. The P-47J used a fan cooled R-2800 ( dropped for the P-47M&N) I am not Sure if the Russians had a few fan cooled installations of the Ash-82. At least one Bristol Hercules commercial installation post war used fan cooling. I am not sure about the Hawker tempest II or Fury.
That is off the top of my head, there may certainly well be others without getting into buried or pusher installations.
Yes, by saying 'for the same horsepower' you are restricting yourself artificially in the same way a motorcyle manufacturor is by saying 'we must not go beyond 750cc'. In practice the designer of the figher aircraft is going to use the engine that gives the best balance of performance, fuel consumption etc, irrespective of whether it is defficient in one particular area like drag. The fact that radial engine fighters were matching the performance of the best inline engines right up to the end of the war indicates that their disadvantage in terms of drag was not enough to place the radial engine at a disadvantage compared to the inline V in practise .
I guess in theory it would be possible to build a mile-long V-100000 with no more frontal area than a V-12, whereas a radial of increasing capacity would have to get wider and wider. In practice all that was laid aside by the jet engine, and even if for some hypothetical reason the jet could not be made to work other alternatives eventually came along for driving airscrews.
The other factor was the incredibly low price of avgas in those days. I suspect that if ICE were still used today for airliners, that they would all be liquid cooled because of the lower specific consumption.
There are practical limits to anything.
Adding length to a V engine will lead to diminishing returns because of crankshaft flexibility, and other associated issues. Adding cylinders to air-cooled radials can increase the diameter (more cylinders per row) and/or length (more rows). After a cerain number of rows it will be getting very difficult to cool the rear cylinders.
Note that liquid cooled engines can be radials too - R-2160 Tornado, Lycoming, XR-7755, BMW 803, for example. Granted, these never went beyond prototype stage.
You will notice that the air cooled engine powered fighters late in the war which matched liquid cooled ones were generally more powerful.
I'm just wondering,it maybe the US Navy had a good reason I'm unaware of. You wouldn't want your matelots drinking the stuff
Steve
On why the db-604 got the axe the designer of it said the RLM said it cost a little more to make then the JU-222.So it and the BMW 802 got killed.
Not necessarily true. Me-109s had a radiator in each wing. They could be individually isolated in case of battle damage. As long as one wing remains undamaged you can limp home.
Annular radiators are another way to mitigate damage to liquid cooling systems. Hitting an annular radiator means hitting the prop and/or engine. Even without a radiator leak such damage is likely to seize the engine.
(Of the early war planes you may compare Bf109E and A6M3, both with about the same power and same speed. ) The 109 had about 17% more power and 20mph more speed than the zero, so hard to draw conclusions from that.
From automotive experience why does the bloody thermostat always fail in the closed position? (Ok the car companies need to sell parts)
From my experience Thermostats fail more often in the open position. We often get people coming into the garage at the start of the cold weather saying my heating isnt working, a classic sign of an open thermo. I always ask if they noticed the temp gauge wasnt going up to normal running temp and most people dont even know where the temp needle should be on the dial. Waste of time fitting temp gauges to cars which is probably why some new cars just have a warning light. Even then lots of people keep on driving with the dash flashing like a Xmas tree. Then when the ECU decides its time to shut down the engine and the car gets towed to the garage the owner starts ranting about modern cars having too many electronics despite the fact if it was an older car they would have kept on driving till the engine seized.
Great diagram Krieghung. Illustrates both the vulnerability of a liquid cooled engine and the way in which it allows the designer to pruduce a sleek, low drag profile
Corect me if I'm wrong, but the LaGG 3 had susbtantially less power than the La 7.
And there were some liquid cooled installations that weren't well designed.
When using leading edge radiators the Tempest I was some 20mph faster than the Tempest II with less power. And a Tempest V with an annular radiator was also about 20mph faster than the Tempest II. One Fury prototype was also fitted with the Sabre with annular radiator, an was about 25mph faster than the Centaurus version. In both those examples the Sabre had a bit more power (about the same difference between Tempest II and standard Tempest V).
a sleek, low drag profile
Ratio of speed is roughly the ratio of the cubic root of the power, so you can make estimates.
Do you have power and speed curves for Tempest I and this Fury prototype ?
LA610 was eventually fitted with a Napier Sabre VII, which was capable of developing 3,400-4,000 hp (2,535-2,983 kW). As a result it became the fastest piston-engined Hawker aircraft, reaching a speed of around 485 mph (780 km/h)
Elimination of the "chin" radiator did much to improve performance and the Tempest Mark I was the fastest aircraft Hawker had built to that time, attaining a speed of 466 mph (750 km/h).