Fixing the Italian Military, 1933~1945

[Airborne2001]

I believe this a version ( model?) of the SM.86 and not the SM.88. The SM.86 was a development of the SM.85.

View attachment 848907
Small wing and two 460hp 9 cylinder radials.
There were two SM.86 aircraft, one with a pointer nose and a pair of 600 hp Walter Sagitta inverted V-12 engines
and a second one with 540 hp Isotta Fraschini Gamma inverted V-12 engines.
The 2nd one may have had twin tails and more revisions to the cockpit/canopy.
These were all small aircraft with a single fuselage.

The SM.88 was somewhat larger and used two booms and a center fuselage (a bit bigger than a P-38).
A stepping stone to the SM.91
View attachment 848908
Problem with all of them is the lack of suitable engine produced in Italy and the lack of German supplied engines.

Now that you mention it, that does appear to be a different aircraft.

The SM.86 had a lot of potential, but it needed a few changes. First, it needed Isotta-Fraschini Delta engines that would've given it more power and speed (while also not requiring too big of changes). Then, give it a rear gunner and it would've been a good dive bomber.

 

[TM06]

Now that you mention it, that does appear to be a different aircraft.

The SM.86 had a lot of potential, but it needed a few changes. First, it needed Isotta-Fraschini Delta engines that would've given it more power and speed (while also not requiring too big of changes). Then, give it a rear gunner and it would've been a good dive bomber.

Why the Delta when we have the theoretical developed Asso engine? The Delta at the time topped out at around 750 hp, when the developed Asso would reach ~1,000 hp with similar weight and dimensions.

 

[Airborne2001]

Why the Delta when we have the theoretical developed Asso engine? The Delta at the time topped out at around 750 hp, when the developed Asso would reach ~1,000 hp with similar weight and dimensions.

I actually was not aware of that engine having the same dimensions! If that's the case, then that would be a good design as well.

 

[Shortround6]

Why the Delta when we have the theoretical developed Asso engine? The Delta at the time topped out at around 750 hp, when the developed Asso would reach ~1,000 hp with similar weight and dimensions.

The dimensions may have been similar, the weights were not. The V-12 Asso was about 80kg heavier except........................the Delta was air cooled and did not require a radiator and coolant. Around 140-150kg for 1000hp engine?
And you don't use the propellers from 600hp engines on 1000hp engines. (or even 750hp engines although that change isn't as great)

Now the real problem is that the two original engines (the 600hp Walter and the 540 hp Isotta Fraschini Gamma engines) were both around 380kg each.
The Delta was in the 510kg area and the V-12 Asso was about 594 without the radiator and coolant.

It might have possible but it was going to take a lot of work.

 

[tomo pauk]

Why the Delta when we have the theoretical developed Asso engine? The Delta at the time topped out at around 750 hp, when the developed Asso would reach ~1,000 hp with similar weight and dimensions.

Development of the Delta was probably (certainly?) the direct consequence of the Italian Air Ministry urge to have the engine companies make a switch to the air-cooled engines. The 'air cooled switch' was an self-inflicted wound, forcing the companies making the liquid cooled engines to abandon a lot of the institutional knowledge about these engines, and start anew.
We can just imagine the time and money lost at RR have they been forced to abandon their liquid-cooled engines and start making air-cooled types, especially if these are radials. Or, forcing the P&W or Wright to switch from the radials to the liquid-cooled V12.

About the Asso - I-F made the L.121 spin-off (900 HP @ 4km) and L.122 (1000 HP @ 4 km) before 1940. The best Deltas were supposed to do 840 HP at altitude, and by mid-war; I'm not sure these actually powered an in-service aircraft.

 

[TM06]

The dimensions may have been similar, the weights were not. The V-12 Asso was about 80kg heavier except........................the Delta was air cooled and did not require a radiator and coolant. Around 140-150kg for 1000hp engine?
And you don't use the propellers from 600hp engines on 1000hp engines. (or even 750hp engines although that change isn't as great)

Now the real problem is that the two original engines (the 600hp Walter and the 540 hp Isotta Fraschini Gamma engines) were both around 380kg each.
The Delta was in the 510kg area and the V-12 Asso was about 594 without the radiator and coolant.

It might have possible but it was going to take a lot of work.

I'd agree with you if this was a single-engined aircraft, but the CR.25 has more than enough space and heft to handle that extra weight.
And having to rework the design to deal with the Asso L.121/L.122 is a hell of a lot better than having to deal with the absolute nightmare that is the Ba.88.

 

[Shortround6]

I'd agree with you if this was a single-engined aircraft, but the CR.25 has more than enough space and heft to handle that extra weight.
And having to rework the design to deal with the Asso L.121/L.122 is a hell of a lot better than having to deal with the absolute nightmare that is the Ba.88.

The CR.25 probably could have been modified to take the Asso L.121/L.122, but then the CR.25 was equipped with 840hp 570kg Fiat A74 14 cylinder radials.
Not the 380kg kg engines that the SM.86 was using.
CR.25 was about 33% heavier than the SM.86 empty so there was a lot more room/stretch to add/modify things.

 

[Airborne2001]

Development of the Delta was probably (certainly?) the direct consequence of the Italian Air Ministry urge to have the engine companies make a switch to the air-cooled engines. The 'air cooled switch' was an self-inflicted wound, forcing the companies making the liquid cooled engines to abandon a lot of the institutional knowledge about these engines, and start anew.
We can just imagine the time and money lost at RR have they been forced to abandon their liquid-cooled engines and start making air-cooled types, especially if these are radials. Or, forcing the P&W or Wright to switch from the radials to the liquid-cooled V12.

About the Asso - I-F made the L.121 spin-off (900 HP @ 4km) and L.122 (1000 HP @ 4 km) before 1940. The best Deltas were supposed to do 840 HP at altitude, and by mid-war; I'm not sure these actually powered an in-service aircraft.

I didn't know about this forced switch, interesting. I feel like the switch from further developing Asso to working on the Xeta was a mistake, especially given the lack of knowledge of liquid cooling when I-F was making an inherently difficult to work engine design. The Asso was doing pretty good already. I think they could've stayed with that. Another option would be to get Reggianes Re 1 engines in service since they were generally equivalent to other inline engines in power.

 

[TM06]

The CR.25 probably could have been modified to take the Asso L.121/L.122, but then the CR.25 was equipped with 840hp 570kg Fiat A74 14 cylinder radials.
Not the 380kg kg engines that the SM.86 was using.
CR.25 was about 33% heavier than the SM.86 empty so there was a lot more room/stretch to add/modify things.

I'll be 100% honest, I completely forgot we were talking about the SM.86. My bad!
But regardless, the SM.86 might not even be needed with a properly developed CR.25 - from what I understand the scramble for twin-engined aircraft was due to the Breda 88's failure. If the CR.25 was properly developed, it could almost certainly fill the dive bomber / strike aircraft niche the SM.85 and SM.86 were designed for.

 

[TM06]

I didn't know about this forced switch, interesting. I feel like the switch from further developing Asso to working on the Xeta was a mistake, especially given the lack of knowledge of liquid cooling when I-F was making an inherently difficult to work engine design. The Asso was doing pretty good already. I think they could've stayed with that. Another option would be to get Reggianes Re 1 engines in service since they were generally equivalent to other inline engines in power.

It was discussed earlier in the topic, but Reggiane's engines are generally off the table. Reggiane as a company was hanging by threads for a majority of the 30's and would likely be unable to produce a satisfactory amount of engines. Now given that they often worked with Piaggio gives us an interesting opportunity. Theoretically Piaggio could have mass-produced the Re 101 instead of some of their horrid radial engines and then we'd be getting somewhere. But the Re 103 and beyond were way too late to make a tangible difference.

Generally it would probably be best if Reggiane stuck to building aircraft, especially since the Re.2000 would have the inline engine (theoretical Asso) it was supposed to have from the get-go.

 

[z42]

It was discussed earlier in the topic, but Reggiane's engines are generally off the table. Reggiane as a company was hanging by threads for a majority of the 30's and would likely be unable to produce a satisfactory amount of engines. Now given that they often worked with Piaggio gives us an interesting opportunity. Theoretically Piaggio could have mass-produced the Re 101 instead of some of their horrid radial engines and then we'd be getting somewhere. But the Re 103 and beyond were way too late to make a tangible difference.

Generally it would probably be best if Reggiane stuck to building aircraft, especially since the Re.2000 would have the inline engine (theoretical Asso) it was supposed to have from the get-go.

Yes, as I mentioned back in post #6 of this thread, the Italian aviation industry spread it efforts too wide. Fixing the Italian Military, 1933~1945 , and the industry was very sub-optimally organized for political reasons.

 

[tomo pauk]

Theoretically Piaggio could have mass-produced the Re 101 instead of some of their horrid radial engines and then we'd be getting somewhere.

I'd say that out of the three Italian companies making the radials of military importance - Fiat, Alfa Romeo, Piaggio - the later made probably the best radials Fiat's main engine (A.74) was of low power, the 1-row Fiat and A.R. engines were badly behind the curve, and the 18 cylinders of both Fiat and A.R. were a show and tell of not how to make 18 cylinder engines.

 

[Shortround6]

18 cylinder engines by a lot of people ran into a number of problems. It seemed simple, just stick two 9 cylinder engines together...............What.............could............go.................WrOnG!!!

Turns out there are all kinds of vibration problem that don't exist on the 9 cylinder parent engines. Trying to balance 18 cylinder engines gets difficult. Something to do with the firing order vs the physical layout ? Remember that a 9 cylinder has 4 cylinders fire on crankshaft rotation and 5 on the other rotation. And 18 cylinder engines get a worse rocking couple than the 14 cylinder engines. Rocking couple is when the forward row of cylinders is trying to go up when back row is trying to go down ( and various variations on this) and the entire engine is trying to twist in the mounts at the same time as the two rows are offset from each other.

I don't know what some of the problems with Italian radials were. They were light for size which usually means not strong. I don't know if they were late getting 87 octane fuel and had not worked on stronger engines? They used lower RPMs than some other nations, Bearing or oil problems? It is like the Italians sort of stalled when the British boosted the Mercury from 585-645hp to the 800hp range. The Piaggio's seem to be a bit behind the parent Gnome-Rhone engines in 1938. Italian metallurgy?

I would also suggest comparing rated power (30 min or max continuous) at altitude instead of take-off power. Italians never seemed to get a two speed supercharger into production reach really hurt low altitude or take-off power. Imagine P&W R-2800 or R-1830 locked in high gear

Italian and indeed most of Europe was positively incestuous in regards to cylinder dimensions or radial engines (or inline air cooled).
A lot of European radials used 146mm X 165mm cylinders for 7 cylinder, 9 cylinder and 14 cylinder radials. A few ambitious companies tried 18 cylinder engines.

The Piaggio P.XI also points back to the single speed supercharger problem. In 1938 it is advertised as offering 1000hp at 4000meters at 650kg on 87 octane.
A P&W R-1830 running on 87 octane offered 1000hp at 11,500ft (3505 meters) for 654kg. Granted the P&W did have a two speed supercharger at that weight and could offer a bit more power lower down.
Maybe the Italians should have investigated water injection?

 

[TM06]

I'd say that out of the three Italian companies making the radials of military importance - Fiat, Alfa Romeo, Piaggio - the later made probably the best radials Fiat's main engine (A.74) was of low power, the 1-row Fiat and A.R. engines were badly behind the curve, and the 18 cylinders of both Fiat and A.R. were a show and tell of not how to make 18 cylinder engines.

Sure, of the three manufacturers Piaggio made the "best" radials. But on the other hand, that's a bar so low you could trip over it.
I believe someone somewhere mentioned the possibility of an Italian manufacturer license-producing a Japanese radial? Say, Alfa Romeo mass producing the Ha 5 or Kinsei families as they wouldn't be license-producing the DB 601 with the advent of the improved Asso? IMO that would be a better use of resources than any of the Italian radial projects.

 

[Shortround6]

Sure, of the three manufacturers Piaggio made the "best" radials. But on the other hand, that's a bar so low you could trip over it.
I believe someone somewhere mentioned the possibility of an Italian manufacturer license-producing a Japanese radial? Say, Alfa Romeo mass producing the Ha 5 or Kinsei families as they wouldn't be license-producing the DB 601 with the advent of the improved Asso? IMO that would be a better use of resources than any of the Italian radial projects.

The Italian industrial base was much smaller than the Japanese industrial base and some of the key questions are..........
1. When? Wanting the late Ha 5 (the Ha 109=1942) in 1939-40 wasn't going to happen.
2. Were the Japanese engines in 1938-39 any better than the Italian engines of 1938-39 or enough better?
3. Could the Italians build the Japanese engines in quantity given the Italian industrial base.
4. What is power loss of the Japanese engines running on Italian fuel? 91-92 octane is not the same as 87. Actual difference is a lot more than the octane scale would appear.

If 1938-39 is too early for you then when? Alfa acquired the DB 601 license in Nov 1939 and even with a bit faster deal making you are not going to get production Japanese engines showing up until some time in 1941, and if you keep retooling the factories for the updated Japanese engines how many engines do you get of each type and when?
The Japanese don't start shifting to the two speed versions of the engines until 1941 and 1942 and the Japanese made a lot more changes than sticking a two speed gearbox between the existing engine models and the existing supercharger.

 

[Airborne2001]

I'll be 100% honest, I completely forgot we were talking about the SM.86. My bad!
But regardless, the SM.86 might not even be needed with a properly developed CR.25 - from what I understand the scramble for twin-engined aircraft was due to the Breda 88's failure. If the CR.25 was properly developed, it could almost certainly fill the dive bomber / strike aircraft niche the SM.85 and SM.86 were designed for.

I looked it up, and Wikipedia claims that the CR.25 was considered for bigger wings and DB 601s in 1943. If this is real, then that idea being moved back to 1940/41 would be a good plan IMO.

 

[tomo pauk]

I believe someone somewhere mentioned the possibility of an Italian manufacturer license-producing a Japanese radial? Say, Alfa Romeo mass producing the Ha 5 or Kinsei families as they wouldn't be license-producing the DB 601 with the advent of the improved Asso? IMO that would be a better use of resources than any of the Italian radial projects.

As noted by SR6 above, Japanese radials are too late for the Italian needs. They need the competitive engines in 1940-42.

Getting Alfa Romeo to make V12 liquid cooled engines was asking too much from that company. It would've been far better to have Fiat making DB 601, since they were a bigger company, and have had experience in making the V12s. Once Czech Avia facilities are under German control, barter the tooling for raw materials and food, so the Italian V12 program gets even faster on their feet. A part of captured HS facilities past 1940 should've also been transferred to Italy. Later make the switch to DB 605.
Both Czech and French workers will have easier time to relocate to Italy than to work under the German boot, and Germany was in surplus of tooling (they lacked raw materials and manpower to use the available tooling anyway)
As for Piaggio, on the quantitative side they can get a lot if the deal can be made with Germany about either Polish, Czech, or, best, G&R tooling to be shipped to them, even if not competely. Qualitatively, they need to get a good, hard look at the 2-row radial engines with all three bearings ASAP, as well as on what a good S/C looks like - here a peek on the G&R 14R might've helped.

I will always agree with the notion that I-F best keep making and developing the liquid cooled V12s.

 

[Shortround6]

I will always agree with the notion that I-F best keep making and developing the liquid cooled V12s

You may be right. But it was going to take lot to turn the I-F into a first rate engine.

1. Make sure the crankcase and crankshaft (and con rods) can stand up to the desired power and try for 2600rpm?
2. Replace the individual cylinders with either a 6 cylinder block or at least two three cylinder pieces.
Stronger, better cooling, fewer leaks.
3. Throw out that cylinder head and either redesign the intake system to use one big carb on the supercharger or go the the Hispano system of using 6 carbs. How does the intake charge get to the end cylinders? Poor breathing and poor mixture distribution means the adjacent cylinders do NOT have the octane mixture and the lean cylinder/s will start detonating first. One big carbs means you can put the intake the middle of the engine?
4. Fix the supercharger(swipe the one off the W-18?)
5. Design two speed drive for the supercharger.

 

[tomo pauk]

You may be right. But it was going to take lot to turn the I-F into a first rate engine.

I have no dreams about the Asso being a 1st rate engine. What it might've been is the 'Italian M-105', once the 2-speed S/C is installed on the L.122.
Still the far cry vs. what I-F were making after ~1938, and same vs. the Fiat A.74. Possibly the combination of bigger valve overlap allowed by the direct fuel injection + a more refined S/C might've added another 15% to the power?

My plan B for I-F to make 1st rate engine is pretty boring - make the DB engines under licence. The suggestions you've listed are all good, however the engine made after that list is basically a brand-new type.

 

[Shortround6]

My plan B for I-F to make 1st rate engine is pretty boring - make the DB engines under licence. The suggestions you've listed are all good, however the engine made after that list is basically a brand-new type.

True but that is problem when you take a 1920s engine and put a reduction gear on the front and supercharger on the back and keep all the old stuff inbetween.

I have no dreams about the Asso being a 1st rate engine.

OK 2nd rate engine

Still the far cry vs. what I-F were making after ~1938, and same vs. the Fiat A.74. Possibly the combination of bigger valve overlap allowed by the direct fuel injection + a more refined S/C might've added another 15% to the power?

You have a 32.65 liter engine turning at 2350rpm (at best?) and the DB 601 is 33.9 and turning 2400rpm and 2500rpm for take-off.
M-105 engine was 35.1 liters at 2700rpm. You have the smallest displacement and the least rpm. You need really good breathing and/or a lot boost. Except that your gas is not very good.
The 4 valve heads they used may have been hot stuff in 1924 but in the 1930s?
Mixture goes just about all the way through the heads and then turns and goes down passages on the inside of the V to reach the cylinders. Not sure if this cools the mixture or heats it?
But passage size may be restricted and sharp bends do not help. Good flow is not there.
Basic construction is right out of WW I. Cylinders are closed top steel tubes with the valve seats in the closed part of the Cylinder. Which means we are back to trying to cool the cylinder head area with the water jackets in the one piece aluminum head trying to not develop any air gaps between the steel cylinder head/top and aluminum water jackets. Much like a lot of air cooled engines in the 1920s.
So not the best cooling in the cylinder head/valve area unless things are done very well (low production?).

Using expensive German style fuel injection and refined superchargers is sort of like using a lot of small Band-aids on an arterial bleed.
Make sure the heat can get out of the combustion chamber before you stuff more heat into it. Take some of the kinks, bends and small passages ways out of the intake path before you put a fancier supercharger on the engine. With the Italian lack of machining capability having them try to build fuel injection units with around 500 small parts with tight tolerances may not work. Perhaps one or two big carbs is better than 4 small ones?