Air cooled inlines: any advantages vs. the 'classics'?

[tomo pauk]

... ie. vs. liquid cooled in-lines and air-cooled radials? Was a 'big' engine of such a construction a missed opportunity, say, a 30-35 L, V-12 one? The real world examples were dH Gipsy Twelve (for dH Albatros), Isotta-Fraschini Delta (almost made it to Re.2001 and Hs-129), Argus, Napier Ranger types etc.

 

[Shortround6]

No chance.

The Argus and Ranger were much too small and help illustrate the problems. In physical size they are not enough smaller than the liquied cooled engines. They are 12 and 12.7 liters. Air cooling became a big problem with large v-12s.
In order to make high power they needed large amounts of volume for cooling fins which meant more space between bores which meant a longer crankshaft and crankcase than for a liquid cooled engine of equal displacement. This added torsional vibration problems and helped negate the weight savings of getting rid of the radiator and coolant. The even more critical problem of cooling the cylinder head then crops up. The big American radials used push rods and rocker arms and left plenty of head area available for fins. most of the V-12s went for overhead cams and 3-4 valves per cylinder which seriously cuts into the area/volume available for fins on the head.
Radials use short stiff crankshafts and short stiff crankcases. Liquid cooled V-12s use not only the crank case but the cylinder block and heads as part of the "beam" strength of the engine. Going to separate cylinders seriously compromises the strength of the crankcase assembly without extra "beefing" up. Trying to make a finned cylinder block 6 cylinders long with the depth of fins and pitch needed was probably beyond the state of the art in foundry work. It still might be.

 

[Siegfried]

The solution in modern aero piston engines is to air cool the cylinders but liquid cool the cylinder heads.

 

[tomo pauk]

Thanks for the feedback.
Issota Fraschini Delta was a cca 27 L engine, 510 kg dry , able to make 770 HP for TO on 87 oct fuel, 750 at 13000 ft, being claimed as capable for 900 HP in a prototype form (with German C3/100 oct fuel?). Almost perfect engine for Whirlwind - we now can install the fuel tanks in lieu of radiators

 

[Shortround6]

Perfect for what?
Peregrine was good for 885hp at 15,000ft with 87 octane fuel. Sounds like a step backward.
Stick the 100 octane iin the Peregrine and have done with it.

 

[tomo pauk]

Well, I've said 'almost perfect'

 

[wuzak]

The de Havilland Gipsy Twelve/King weighed about 100lbs less than the Peregrine, for 2.9l less (18.3l vs 21.2) and 525hp vs 885hp.

The Kestrel weighed less for 700hp.

The Gipsy Twelve was 82.6" long by 31.5" wide x 37.4" high. The Peregrine 73.6" x 27.1" x 41".

The Dagger in later versions could make nearly 1000hp from its 16.8l, but weighed as much as a V-1710/Merlin single stage/single speed engine. The Dagger also had a lot of coling problems.

The Exe weighed almost as much as a two stage Merlin.

 

[davebender]

I agree.

Air cooled twin row radial engines are at a cooling disadvantage vs liquid cooled engines. An air cooled V8 or V12 has an even more difficult time keeping the rear cylinders from overheating.

 

[tomo pauk]

The de Havilland Gipsy Twelve/King weighed about 100lbs less than the Peregrine, for 2.9l less (18.3l vs 21.2) and 525hp vs 885hp.

The Kestrel weighed less for 700hp.

The Gipsy Twelve was 82.6" long by 31.5" wide x 37.4" high. The Peregrine 73.6" x 27.1" x 41".

The Dagger in later versions could make nearly 1000hp from its 16.8l, but weighed as much as a V-1710/Merlin single stage/single speed engine. The Dagger also had a lot of coling problems.

The Exe weighed almost as much as a two stage Merlin.

Are the weights of the coolers calculated there, for the in-lines?

I agree.

Air cooled twin row radial engines are at a cooling disadvantage vs liquid cooled engines. An air cooled V8 or V12 has an even more difficult time keeping the rear cylinders from overheating.

You can check out the DH Albatros, in order to see that was not always the case. There is a great article in the Flight archives about the installation.

 

[wuzak]

Are the weights of the coolers calculated there, for the in-lines?

No, but they also didn't make nearly as much power.

The Pennine may have been an exception. 2750hp from 2850lbs - matches the best R-2800 (same capacity) for power at the start of development, but with extra weight.

 

[pbfoot]

Is there a reason so few inlines were used post war , my guess is they were done as a viable power source for aircraft.

 

[wuzak]

Is there a reason so few inlines were used post war , my guess is they were done as a viable power source for aircraft.

In lines were replaced by jets in military aircraft, and civilian users preferred the air cooled radials because they were cheaper to run.

 

[wuzak]

Is there a reason so few inlines were used post war , my guess is they were done as a viable power source for aircraft.

In lines were replaced by jets in military aircraft, and civilian users preferred the air cooled radials because they were cheaper to run.

 

[pbfoot]

no I disagree most post war military gas powered aircraft were radials in fact almost all

 

[davebender]

The Argus 410 / 411 was the most successful engine of this type with about 28,000 built. Argus Moteren was destroyed at the end of WWII, ending any chance for continued development of this engine.

 

[wuzak]

no I disagree most post war military gas powered aircraft were radials in fact almost all

P-82? P-51? Spitfire/Seafire/Spiteful/Seafang? Hornet? Mosquito?

These were obviously post war versions of aircraft used during WW2, or developed during WW2. The same could be said for most, if not all, of post war air cooled radial engines.

Perhaps I should have stated that high performance liquid cooled engine powered aircraft were replaced by jets.

Also, you have to look at what the manufacturers of liquid cooled engines were up to. Rolls-Royce very much headed in the direction of jets, as did Allison - especially since they wouldn't develop engines without outside funding/orders. Napiers went off in their own particular direction. Daimler-Benz and Junkers were heading down the jet engine route (the former reluctantly) if the end of the war hadn't stopped their aero engine development.

 

[Shortround6]

Well, I've said 'almost perfect'

Isotta Fraschini tried to bring the Delta back post war ( many European countries were trying to sell ANYTHING in the late 40s to bring what money they could). SO I figure this is as good as it gets.

580 KG, 33.1 in wide, 33.3 in high, 77.0 in long. a TWO speed supercharger and 92 octane gas.

1000hp for take off at 2850rpm and 5.2lbs boost.
940hp max at 2850rpm at 7550ft.
850hp max at 2850 rpm at 19,680ft.
800hp normal at 2560rpm at 6560ft
720hp normal at 2560rpm at 18,040ft.

The Delta RC40 ID-IS is also listed in the same 1949 book. Single speed supercharger fuel unspecified. 562kg.

Take off 800hp at 2500rpm and 4.3in boost.
Max rating 770hp at 2500rpm at 13,100ft.

I don't think any service Delta ran at more than 2500rpm during the war.

 

[tomo pauk]

Thanks for the info. Too bad Italians did not started with 30-32 liters for the Delta, instead of 27.

Could someone shed some light about the DH Gipsy Twelve it's supercharger - Wiki states the take off power with 0 lbs boost (I presume +0 lbs boost?). Was the supercharger only in the function of making the air-fuel mixture a more uniform there?

 

[wuzak]

Lumsden has the Gipsy Twelve as takeoff power as 505hp @ 2600rpm, +3.5psi boost. Max power is given as 425hp @ 2450rpm, 7250ft, +0psi boost. That is the supercharger is providing enough boost to compensate for the altitude, and thus is essentially unsupercharged.

 

[wuzak]

The Twelve was single speed single stage supercharged.

Here is the Albatross installation, which looks exceptionally clean.

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