Italian air force is indifferent on on the air-cooled engines?

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tomo pauk

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Apr 3, 2008
'Indifferent' as in they don't make a push towards these in the 1930s, instead just say to the aero engines' companies something like: We will buy the ever better engines, provided you can make them?
How much the Italians are better (worse?) if eg. Fiat and Isotta-Fraschini continue to develop the liquid-cooled engines instead of making the air cooled detour?

Not saying it is an insta-win for the Italians in the ww2, of course.
 
I have to remind myself of the various italian engines of this period, but if for instance Fiat manages to level it's very comendable racing engine experience and has even a 1000 HP decent V12 inline by 1939 at the start of WW2, that would imo make the G50 and MC200 at least equal to the Hurricane speed wise, a big improvement. And if they invest all the time and resources into designing larger V12 engines rather than their 18 cyl radials, maybe they'll get a 1200-1300 HP engine in 1940-41 and 1400-1500 HP one in 1942. And they really need to get two-speed superchargers, however basic, on their engines, if i'm not mistaken none of their major production WW2 engines had a 2S supercharger.

Similarly I-F can continue to upgrade it's V12 Asso, and invest time and resources into a larger V12 instead of the absolutely useless air-cooled inlines, then they can provide an option/suplement to the Fiat TTL inlines.

Presumably Piaggio and Alfa Romeo still focus on radials? Then we will have an even distribution of 2 companies working on inlines and two on radials, so there would be plenty of options.

I guess this will not eliminate many of the inherent weaknesses of the italian aircraft industry, but they will imo be in a better position than OTL.

Of course, as soon as possible, get the DB-601/605 licences, and even DB-603, and build as many as possible. I suspect the italian inines would still be a bit behind the german ones.
 
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I have to remind myself of the various italian engines of this period, but if for instance Fiat manages to level it's very comendable racing engine experience and has even a 1000 HP decent V12 inline by 1939 at the start of WW2, that would imo make the G50 and MC200 at least equal to the Hurricane speed wise, a big improvement. And if they invest all the time and resources into designing larger V12 engines rather than their 18 cyl radials, maybe they'll get a 1200-1300 HP engine in 1940-41 and 1400-1500 HP one in 1942. And they really need to get two-speed superchargers, however basic, on their engines, if i'm not mistaken none of their major production WW2 engines had a 2S supercharger.

1000 HP (at ~4000m?) V12s would've brought the alternative MC.200 and G.50 to the level of performance closer to the Spitfire and Bf 109E, let alone Hurricane IMO. After all, the MC.202 have had 1050 HP at 4.5 km (a tad better than what the Bf 109Es had??), and was faster than either 109E or Spitfire I.
Granted, the cockpit canopies need to be of the closed type :)

2S supercharger brings another ~150 HP down low for these engines; yes, by 1941, at least, they need to up their game.

Similarly I-F can continue to upgrade it's V12 Asso, and invest time and resources into a larger V12 instead of the absolutely useless air-cooled inlines, then they can provide an option/suplement to the Fiat TTL inlines.

Continuation of the Asso line were the L.121 (900 HP at 4 km) and L.122 (1000 HP at 4 km), unfortunately the L.121 was installed on a fighter that was obsolete before the 1st ink dried on the drawings, and thus died in a quick death.
I-F would've really need to introduce the en-bloc cylinders, the individual cylinders of the Asso line were behind the curve by 1937-38.
Air-cooled I-F engines were indeed, at the end of the day, more of a liability than an asset for the Italian war effort.

Presumably Piaggio and Alfa Romeo still focus on radials? Then we will have and even distribution of 2 companies working on inlines and two on radials, so there would be plenty of options.

I guess this will not eliminate many of the inherent weaknesses of the italian aircraft industry, but they will imo be in a better position than OTL.

Agreed.
The technology switch from liquid-cooled to air-cooled engines cost a pretty penny the Italian budget and Fiat's resources, and they were again making the switch by the time the license deal for the DB 605 was in execution phase. Similar with AR, they were not in the inline business, yet they were the ones supposed to make DB 601 copies. IF - again, same story, the air cooled types were never able to compete with what Germany and UK were making to power the 1st line combat A/C.
 
A portent of the possibilities is for instance the gorgeous MC204 with an Asso engine, as well as the G50V (which can be imagined as having either an Asso engine or a Fiat V12). There's absolutely nothing imo stopping the italians flying these in 1937.

Not quite sure what engine the BR-20 bomber would initially have in this TTL, an option is the Piaggio P-IX if it's ready in time, unless, just like the A74 and A80, Fiat works on a smaller V12 for fighters and larger V12 for bombers.

They would also imo be better off focusing on G50 and MC200 families, no CR42 biplanes at all. I would still keep the Re-2000 family as purely radial engined (so no Re-2001 or Re-2005, all the inlines going to G50 or MC200 families), as a sort of italian fighter-bomber, evolving more or less like the Seversky family. My Re-2005 would have a Piaggio PXII or Alfa Romeo-135 18 cylinder radials, a sort of italian mini P-47.
 
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The production (non-racing) Fiat V-12s were not supercharged. Nothing against the Italians here, in the early 30s many/most V-12s were not supercharged. Many/most large radials used very modest amounts of boost, getting good/equal mixture distribution to the cylinders was as important as actual boost/power increase.

A problem for the Italians is that Fiat wound up building their most successful/widely used radial engine so the change to history would be large.

Fiat was using the standard V-12 engine construction of the 1920s. Unlike Curtiss, Hispano and RR (with the Kestrel) they were using separate cylinders. Each cylinder was a separate unit (cylinder bore/liner with a sheet metal water jacket) cylinder head was part of the cylinder and each cylinder assembley was bolted to the the crankcase. Six such assemblies made up each cylinder bank. The valve gear was in separate housing bolted to the top of the cylinders. Most or all of the longitudinal strength was handled by the crankcase, maybe a little help from the cam housings?
The Soviets were the only people who converted such an engine to a mono block (or at least the banks of cylinders into two blocks) or perhaps it is better to say they are the only ones who really tried?
Most engine makers just started fresh when they went to the mono-block construction. How much of this was money I don't know. Allison had close to zero money tied up in old tooling. The Germans had very little money tied up as their production of aero engines in the 1920s was very limited and was tied to their WW I stuff. In the early 30s the Germans could see RR changing to the mono-blocks and the influence of Curtiss.

Fiat had several choices, throw a supercharger on the old engine/s and beef them up a bit or start over.

The A.24 engine used 140mm X 175mm cylinders for 32.3 liters but was limited to 2000rpm continuous.
Most of the Fiat engines used small bores, or a bit smaller than more modern engines, This allows for the bore spacing needed for the separate cylinders.
The A.24 might have been able to run a bit faster with better bearings and a supercharger could have allowed better altitude performance even if not a large increase in peak power.

The A.30 seems to have been a better bet.
135mm X 140mm cylinders for 24 liters. rated at 600hp at 2,000rpm normal (sea level) but 800hp at 2900rpm for take-off?
Was also using 8 to 1 compression ratio there was room to stick on a supercharger and lower the compression ratio for a gain power without blowing up the engine. Increase in RPM at the "normal" rating?
After that we are stretching things. You have the AS. 5 engine used in racing that was developed into the AS.6 24 cylinder engine but we have to be careful between the short life racing engines and the racing fuel.
 
A portent of the possibilities are for instance the gorgeous MC204 with an Asso engine, as well as the G50V (which can be imagined as having either an Asso engine or a Fiat V12). There's absolutely nothing imo stopping the italians flying these in 1937.
+1 on that.

Not quite sure what engine the BR-20 bomber would initially have in this TTL, an option is the Piaggio P-IX if it's ready in time, unless, just like the A74 and A80, Fiat works on a smaller V12 for fighters and larger V12 for bombers.

The smaller V12 might've been the A.30, but with a supercharger added, so in effect the A.33 as a starting point. Gives the equivalent of the RR Kestrel - not too bad, but barely better than the radial A.74? If the engine can be run at 2900-3000 rpm while supercharged (will require reduction of the compression ratio), and it is outfitted with a decent S/C so it makes perhaps 800-850 HP at 4 km, that is a good value for 1939-40 compared with the A.74 since it will also have lower drag and better exhaust thrust possibilities.

But again, they already have the Asso IX with similar power and power to weight ratio, so perhaps it is better to go with a 35+-L V12, predominantly for the fighters? Bombers can have the radials in most of the cases :)

They would also imo be better off focusing on G50 and MC200 families, no CR42 biplanes at all. I would still keep the Re-2000 family as purely radial engined (so no Re-2001 or Re-2005, all the inlines going to G50 or MC200 families), as a sort of italian fighter-bomber, evolving more or less like the Seversky family. My Re-2005 would have a Piaggio PXII or Alfa Romeo-135 18 cylinder radials, a sort of italian mini P-47.

Agreed on what to install on respective fighter families.
Of the Italian 18 cyl engines, seems to me that Piaggio's types were the best - Fiat's A.80 seems like too much of complication to gte to 1100 HP, and Alfa's 135 never powered an in-service A/C due to excessive vibrations.
 
Of the Italian 18 cyl engines, seems to me that Piaggio's types were the best - Fiat's A.80 seems like too much of complication to gte to 1100 HP, and Alfa's 135 never powered an in-service A/C due to excessive vibrations.
The Italian 18 cyl engines all seemed to be from the same class room. They seemed to be too light. This seems to have restricted the rpm limits (?)

Engine.................................................Displacement.............................Weight............................RPM
R-2800-5.......................................2804 cu.in./ 45.9 L...............................2270lb..........................2600rpm
Alfa 135.........................................2940 cu.in./ 48.2 L...............................2094lb..........................2400rpm
Fiat A80.........................................2789 cu.in./ 45.7 L...............................1625lb..........................2200rpm
Fiat A82.........................................2873 cu.in./ 47.1 L...............................1910lb..........................2400rpm
Piaggio P.XII................................3232 cu.in./ 53.0 L...............................1874lb..........................2100rpm
Piaggio P.XXII.............................3691 cu.in./ 60.5 L...............................2094lb..........................2200rpm

Compare the R-2800 to the Piaggio XII, the Piaggio is 15% greater displacement but the R-2800 runs almost 24% faster.
If you can't use boost (high octane fuel) you have to use displacement and RPM. The Italians could not use high rpm.




Issotta-Fraschini ASSO XI
640px-Isotta_Fraschini_Asso_I_121_R.C._40.jpg

I have no idea how they got the mixture from the carbs to the end cylinders. The W-18s were worse. Middle bank of cylinders were fed by carbs on the outside banks and the passages went through the valve compartments.
Between the bearings and the intake passages there was room for improvement.
 
The Italian 18 cyl engines all seemed to be from the same class room. They seemed to be too light. This seems to have restricted the rpm limits (?)

Engine.................................................Displacement.............................Weight............................RPM
R-2800-5.......................................2804 cu.in./ 45.9 L...............................2270lb..........................2600rpm
Alfa 135.........................................2940 cu.in./ 48.2 L...............................2094lb..........................2400rpm
Fiat A80.........................................2789 cu.in./ 45.7 L...............................1625lb..........................2200rpm
Fiat A82.........................................2873 cu.in./ 47.1 L...............................1910lb..........................2400rpm
Piaggio P.XII................................3232 cu.in./ 53.0 L...............................1874lb..........................2100rpm
Piaggio P.XXII.............................3691 cu.in./ 60.5 L...............................2094lb..........................2200rpm

Compare the R-2800 to the Piaggio XII, the Piaggio is 15% greater displacement but the R-2800 runs almost 24% faster.
I'm not sure that R-2800 was an option for Italian air force, this being the what-if sub-forum never the less.
P.XII and P.XV were certainly the options, with caveat of the P.XV being a bit too late.

If you can't use boost (high octane fuel) you have to use displacement and RPM. The Italians could not use high rpm.

They, at least on the P.XII and P.XV, used displacement instead. Wishing for high-octane fuel does not help them, actual lighter weight might.

Issotta-Fraschini ASSO XI
I have no idea how they got the mixture from the carbs to the end cylinders. The W-18s were worse. Middle bank of cylinders were fed by carbs on the outside banks and the passages went through the valve compartments.
Between the bearings and the intake passages there was room for improvement.

At any rate, with a desire for 1200-1500 HP power, the brand new engine will be needed. Both by Fiat and I-F. Legacy engines might go to perhaps 1000 HP (and that is pushing it for the Fiat V12s).
 
I'm not sure that R-2800 was an option for Italian air force, this being the what-if sub-forum never the less.
Just using the R-2800 as bench mark to show my line of thinking. An R-2800 might have been good for 1700hp with 87 octane?
It is why I didn't list power, Just displacement and RPM.

What did the Italians have to do to make their 18 cylinder engines work and what would it cost? Weight?

Then figure out what you need to do to the V-12s (or get a license for another engine sooner?)

State of Italian industry also plays a part.
Can it handle more big castings?
Can it supply better bearings?

Go to the British/US style of on big carb before the supercharger?
 
Imo, the Fiat A33 is too small as a starting point. They need something bigger, at a minimum 30 litres (which gets us into Asso territory), or preferably even more, 33-35 litres like DB-600/Jumo-211, so i guess they can take the A33 and increase displacement while adding whatever design improvements they learned from racing engines. Still, due to lack of high grade materials and fuels they will never get the kind of power like Merlin or even the V-1710, but getting 1000 HP from it by WW2 and 1200-1300 HP in a 2S model would be a great result for them.

There is also the option of licensing for instance the HS-12Y (since OTL they got licences from France, UK and US for radials), and work to improve it like the soviets did. Getting the same levels of power as above (1000/1200 HP) would be a good result.

I-F could, instead of the inverted air-cooled (and utterly useless) Delta, work on an inverted Asso incorporating whatever more modern features they can. even a clean 1100 HP would be great. And instead of the 38 litre Zeta, an inverted V12 of the same capacity, actually workable and good for 1300-1400 HP, again a great result.

As to the radials, imo one of the reasons for their low rpm is again, materials. More rpm, more stress, better materials required which they didn't have. This also being one of the reasons they kept increasing displacement to get more power (which most of the time fatally unbalanced the engine). I made the case in the past how much better the japanese radials were compared to the italian ones (and we can't say Japan was overblessed with high quality materials), so it may also be a faulty italian design concept. They needed to nipponize their radials as much as possible. The japanese build thousands of reliable 1500 HP and 2S engines, and were getting close to 2000 HP (but unreliable due to war situation-lack of materials, fuels etc.), while the italians got almost nothing similar produced and in service.
 
Considering the size of the Italian aero engine R&D and production it might have made sense to concentrate on one kind of engine. But it seems they made the wrong choice, in that Italy was making ok-ish inlines when development was stopped, and was behind in radials?
 
Just using the R-2800 as bench mark to show my line of thinking. An R-2800 might have been good for 1700hp with 87 octane?
It is why I didn't list power, Just displacement and RPM.

What did the Italians have to do to make their 18 cylinder engines work and what would it cost? Weight?

Fiat has it easiest - they just don't embark on the 2-rows radials program, thus the 18 cyl engine never happens.
Piaggio - I'm not sure whether their engines had the central bearings (my guess is no), so this is one thing that need to happen before 1939. Yes, new engines will be heavier and a bit longer.
Alfa - don't do it, at all.

Then figure out what you need to do to the V-12s (or get a license for another engine sooner?)

State of Italian industry also plays a part.
Can it handle more big castings?
Can it supply better bearings?

Go to the British/US style of on big carb before the supercharger?

Big carb is certainly a simpler affair than the handful of smaller ones on each V12; adds up quickly with air force needing thousands of engines. Industry will have a longer lead-in period, than it was the case for the needs of DB licenced engines. Licence the bearings from Allison?
Buying the licence for the DB 600 would've possibly been prudent. Or maybe the RR Buzzard?
 
There is also the option of licensing for instance the HS-12Y (since OTL they got licences from France, UK and US for radials), and work to improve it like the soviets did. Getting the same levels of power as above (1000/1200 HP) would be a good result.
The Italians should have stayed with their own engines instead of flushing money down the toilet with the Hispano. The Hispano's that made much over 1000hp required a huge amount of work. New cranks, new cylinder heads, new superchargers, etc. Just work on their own engines.
And instead of the 38 litre Zeta, an inverted V12 of the same capacity, actually workable and good for 1300-1400 HP, again a great result.
Won't work.
The Problem for air cooled engines in general was getting them from over heating. 24 small cylinders have better cooling that 12 large ones.
The US built high power radial aircraft engines by pushing the manufacturing technology into making more fin area. Close pitch, thinner fins, deeper fins and fins out of different material than the actual cylinder barrels.
A 12 cylinder engine using the displacement of the Zeta needs bigger cylinders than the Wright R-3350 and that didn't work so well ;)
 
The Italians should have stayed with their own engines instead of flushing money down the toilet with the Hispano. The Hispano's that made much over 1000hp required a huge amount of work. New cranks, new cylinder heads, new superchargers, etc. Just work on their own engines.

Won't work.
The Problem for air cooled engines in general was getting them from over heating. 24 small cylinders have better cooling that 12 large ones.
The US built high power radial aircraft engines by pushing the manufacturing technology into making more fin area. Close pitch, thinner fins, deeper fins and fins out of different material than the actual cylinder barrels.
A 12 cylinder engine using the displacement of the Zeta needs bigger cylinders than the Wright R-3350 and that didn't work so well ;)
Should have specified, i was refering to a LIQUID COOLED 38 litre V12 instead of Zeta. It's only 1 litre bigger than Griffon, and 2 litre bigger than HS-12Y, basically a bigger Asso. I-F air cooled inlines were a complete waste of time imo.
 
Piaggio - I'm not sure whether their engines had the central bearings (my guess is no), so this is one thing that need to happen before 1939. Yes, new engines will be heavier and a bit longer.
According to Aircraft engines of the World by Wilkinson all of the 18 cylinder engines had central bearings but since that is not a primary source ???
The Piaggio 14 cylinders engines had no center bearing.

and there is a problem with going to the large cylinders, the cylinder volume (amount of fuel burning per second) goes up faster than cylinder wall area (and head area) to get rid of the heat. This was a problem that just switching to higher octane fuel did not solve. Every time that Wright built a new higher power version of an existing engine they did it by changing the amount of finning on the cylinders in addition to what ever else they did to the mechanical parts.
P&W too, They got from 1850hp to 2000hp on the basic 2800 but they needed new cylinders to get to 2100hp (not counting WEP). They also needed new cylinders to get the R-1830 to 1350hp.
 
Should have specified, i was refering to a LIQUID COOLED 38 litre V12 instead of Zeta. It's only 1 litre bigger than Griffon, and 2 litre bigger than HS-12Y, basically a bigger Asso. I-F air cooled inlines were a complete waste of time imo.
We had a recent-ish discussion about air cooled inlines here: Air cooled inline engines - a missed opportunity?

The takeaway seems to be that an air cooled V12 could be a decent enough engine for a trainer or small transport, but for the power levels required for a WWII fighter air cooled inlines start to run into various limitations making them no longer competitive with liquid cooled inlines nor with air cooled radials.
 
Bristol tried it and it was (predictably) a catastrophe without a centre bearing.

You can do it, but only at low powers when the resulting crankshaft flex is not fatal. Its an extremely bad idea, in general
principle
I was not being precise - I hoped that you could confirm whether the Italian 18 cyl radials were with the cental bearings (or not).
 

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