ThomasP
Senior Master Sergeant
Bummer for the airframes. Did the engine arrangement work reasonably well?
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The Soviets managed best not only to retain all the major problems of the highly unreliable VK-107A - the VK-107R version was no better - but also to introduce new compressor and turbine problems. The reliability of the propulsion system was extremely poor. In general, the persistence with which this airplane was attempted to be improved is respectable, but even more perplexing. Probably, some experience was accumulated by Soviet engineers while developing this bastard, but it is certain that this experience could have been accumulated in much more reasonable activities. Thanks to the British government though - they were able to help the Soviets solve their engine problems for many years.
PS. By the way, this is a rather interesting "what if" topic - Britain doesn't sell engines to the Soviets, and the Soviets are forced to develop the legacy of the Third Reich. I wonder if the Jumo 012 could replace the Nene. But that's too far away from Italy, maybe in another thread....
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Shortround6
Major General
It may actually trace it's History back to 1924-25?
Basically they hung a supercharger off the back of an existing engine and piped the air to the existing carburetors.
the dark color obscures some of the details. Older engine without reduction gear and supercharger.
It already has 4 valves in each cylinder. However it does NOT have one piece cylinder blocks and has separate cylinders and sheet metal water jackets joined together by a one piece cylinder head and valve assembley. They need to fix the basic construction (beef it up) before they get involved with fancy superchargers.
Engine turns a bit slower than the HS 12Y and is a bit smaller.
Compared to the DB 601 it uses 4 mm smaller cylinders, and runs about 150-250rpm slower. It weighs about the same. They may need a new crankcase and cylinder block to get the higher rpm and stand up to slightly higher boost pressures. With 87 octane there is a limit to how high the boost pressure can go. A better (more efficient) supercharger with two speeds would be very helpful, trying for a 2nd stage may not give results worth the effort with 87 octane fuel.
A P &W two stage R-1830 running on 87 octane might have been a disaster.
They later got the air cooled Delta engine using the same stroke
Isotta Fraschini Delta - Wikipedia
These air cooled engines may have borrowed the engineering staff needed to upgrade the liquid cooled engines?
- Thread starter
- #64
Honestly I'd ditch the air-cooled inline engines as soon as possible, they largely seem like a complete dead end and waste of time. At the very least making sure that the unholy abomination that is the Zeta never makes it further than the ink from the pen it was drawn up with.They later got the air cooled Delta engine using the same stroke
To run at 2600rpm using smaller pistons.Isotta Fraschini Delta - Wikipedia
en.wikipedia.org
These air cooled engines may have borrowed the engineering staff needed to upgrade the liquid cooled engines?
So assuming they do improve it with all the changes mentioned above (maybe going to 92 octane or higher depending on how feasible that is), how high is the ceiling? Would this theoretical improved Asso be able to compete with the other Tier 3 (DB 601A, Jumo 211, 12Y-50/51, M-105P, Merlin II) or Tier 2 (DB 605A, Merlin 45/61, VK-105PF3, 12ZTer) engines?
And - crucially - would it be good enough to warrant sticking with it over license-produced Daimler engines?
Switch towards the air cooling was government mandated IIRC.
Keeping I-F in the liquid cooled engines' business would've meant much more of the useful engines for Italy in the 1940s.
The L.122 was supposed to be having 1000 HP, that is probably the limit (without the option for better S/C that can add perhaps another 10% to that)?
Having the equivalent of a M-105 or a DB 601 from 1939 on would've been a boon. That was probably the limit until/unless basically a whole new engine is made, IMO.
Shortround6
Major General
Well, when the customer says they want air cooled engines you build air cooled engines
I wouldn't hold my breath waiting for 92 octane. I might try to use water injection instead. It has problems but at least 3 nations got it to work.
There a few clues here (or possible paths)
It was a 1500hp take-off, 1,690 hp (1,260 kW) at 2,475 rpm at 14,764 ft (4,500 m) W-18. At least that was what planned.
It does show that they were working on a crankshaft and crankcase that would handle that short of power (actually success?)
It also shows a central intake supercharger that they were planning to flow enough air to handle nearly 1700hp at 4500 meters.
Figure out a 2 speed drive and put it on the V-12? cut it down a bit/use less gear ratio?
At least don't try to just modify the old V-12 supercharger.
- Thread starter
- #67
I suppose that's another thing to add to the list of poor and avoidable development decisions.Well, when the customer says they want air cooled engines you build air cooled engines
Sigh
From what I've read the I-F engines seem to run at pretty low rpm (1,700~2,000 rpm)? Given that the Delta was run at a much higher RPM with the same stroke and smaller pistons, would it be feasible to crank up the rpm on the improved Asso in an effort to produce more horsepower?There a few clues here (or possible paths)
It was a 1500hp take-off, 1,690 hp (1,260 kW) at 2,475 rpm at 14,764 ft (4,500 m) W-18. At least that was what planned.
It does show that they were working on a crankshaft and crankcase that would handle that short of power (actually success?)
It also shows a central intake supercharger that they were planning to flow enough air to handle nearly 1700hp at 4500 meters.
Figure out a 2 speed drive and put it on the V-12? cut it down a bit/use less gear ratio?
At least don't try to just modify the old V-12 supercharger.
This might be an amateurish question, but what would be the reasoning for avoiding inline engines with more cylinders (AS.8, Re.103, Asso L.180 shown in the image)?
I understand that they would be more complex, more expensive and likely put more strain on the crankshaft - but given that Italy wouldn't have access to the higher octane fuels or exotic elements required to make a Tier 1 V12 engine, a V16 or W18 might be a decent gambit to increase power, no?
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From looking at the long list of failed X, H, W, coupled German engines, and whatever pretzel layouts one can imagine, it seems that going beyond the well understood V-12 proved considerably difficult. And then of course gas turbines happened and killed high power aviation piston engines. Had turbines not been developed, I'm sure some of these lots-o-cylinders approaches would have been developed to mature and reliable engines.
- Thread starter
- #70
Making a ~40L V12 is one thing, my concern is that it wouldn't be producing enough power to compete with other engines in its weight class. Making something like 1,500 hp out of a ~950 kg engine is not that impressive when your contemporaries are starting at 1,750 hp and only reaching higher.
Shortround6
Major General
They increased the RPM over the years, but yes, they didn't run much over 2000rpm even in the later versions. It looks like I-F was heading that way.
The Problem with the W-18 shown was that it weighed around 990kg. Yes dropping one cylinder bank will save weight, but not 1/3rd.
It was also around 936mm wide so keeping the 3rd bank means that the widest point of the engine (not including exhaust) is about 100mm wider than a DB 603.
Granted for the engine in the picture you can flip the reduction gear over and get rid of the cannon mount to fire though the prop. Not sure what they were thinking on that one. Entire engine is located below the propeller? how big is that nose?
Without the state "only air cooled engines from now on" mandate, a new big modern V-12 sounds like the best choice for producing something that could be somewhat competitive as well as actually delivering it to see wide-spread service before Italy is knocked out of the war. Monobloc construction, pressurized cooling, etc. Maybe license fuel injection technology from Germany, but only do single-point injection to avoid the cost and complexity of direct injection? MW50 system to compensate for lack of fuel octane?
Unfortunately I don't think the lots-of-cylinders at high rpm approach is a get out of jail free card either. Look at the Napier Sabre, about the only engine using that approach to see somewhat wide service; in terms of power to weight it's about equivalent to the traditional big slow V-12 such as Griffon. And that was made with the latest and greatest material science voodoo.
That will depend on the altitude that power is achieved. If it can make 1500 HP at 5 km/~16000 ft, it is great. For comparison, at 2700 rpm, the BMW 801C was not doing any better at 5 km, even when spun to 2700 rpm. It still weighted more and was a more draggier option.
Shortround6
Major General
The Packard boat engine may provide a few clues.
These specs are for the early aircraft engine
The boat engines did get superchargers and flywheels/clutches and water cooled exhaust manifolds so weight skyrocketed. Weight with clutch and reversing gear was 2590lbs.
The Is a Packard manual available here.
That shows the power output for several different models of the engine running on different grades of fuel.
Basically with 87 octane and using 40in of manifold pressure the engine was good for 1200hp at 2500rpm for emergency. This spelled out as 15 minutes in one 10 hour period.
With 91 octane and using 42.5in the engine could run at 1280hp.
With 100 octane and using 44in they could run 1350hp. Both are emergency ratings.
Later series engines got a different supercharger gear ratio and that boosted the power up to 1500hp using 48 in. with 100 octane.
This was at sea level. The engine was rated at 900 at 2000rpm max continuous and when they say continuous they mean it. The later engines had a higher 1 hour rating and that was one hour out of 25 hours. There are some other power robbing accessories, like the water pumps. There are Two, one for sea water.
They say the 1200hp engine was making 159 B.M.E.P. and at 1350hp it was 179 B.M.E.P.
Engine has a similar set up to an Allison, down draft carb located on an elbow feeding the center of the supercharger inlet.
Although manifolding looks like it could use work. Actual design of the supercharger inside may not be the best.
It was never going to run higher than sea level.
These specs are for the early aircraft engine
- Type: 12-cylinder V engine
- Bore: 6+3⁄8 in (162 mm)
- Stroke: 6+1⁄2 in (165 mm)
- Displacement: 2,540 cu in (41.6 L)
- Dry weight: 1,120 lb (510 kg)
The boat engines did get superchargers and flywheels/clutches and water cooled exhaust manifolds so weight skyrocketed. Weight with clutch and reversing gear was 2590lbs.
The Is a Packard manual available here.
Packard V12 Marine Engine
Description of the Packard 4M-2500 marine engine with drawings and photos. Discussion of special features and performance specifications.
uscrashboats.org
That shows the power output for several different models of the engine running on different grades of fuel.
Basically with 87 octane and using 40in of manifold pressure the engine was good for 1200hp at 2500rpm for emergency. This spelled out as 15 minutes in one 10 hour period.
With 91 octane and using 42.5in the engine could run at 1280hp.
With 100 octane and using 44in they could run 1350hp. Both are emergency ratings.
Later series engines got a different supercharger gear ratio and that boosted the power up to 1500hp using 48 in. with 100 octane.
This was at sea level. The engine was rated at 900 at 2000rpm max continuous and when they say continuous they mean it. The later engines had a higher 1 hour rating and that was one hour out of 25 hours. There are some other power robbing accessories, like the water pumps. There are Two, one for sea water.
They say the 1200hp engine was making 159 B.M.E.P. and at 1350hp it was 179 B.M.E.P.
Engine has a similar set up to an Allison, down draft carb located on an elbow feeding the center of the supercharger inlet.
Although manifolding looks like it could use work. Actual design of the supercharger inside may not be the best.
It was never going to run higher than sea level.
- Thread starter
- #75
Changing topics a bit to focus on armament.
The Breda-SAFAT 12.7 mm guns were quite mediocre for their class, being reliable but heavy and slow firing. It didn't have the same hitting power of weapons in the same class - apparently low propellant capacity in the cartridges had something to do with it? Performance of the HEF-T round was also abysmal.
The 7.7 mm Breda-SAFAT guns definitely need to be thrown out as soon as possible, perhaps they could be repurposed as an infantry light machine gun a la the M2 Stinger? It's a long shot, but anything is better than the Breda 30.
Italy did produce a licensed copy of the Hotchkiss 13.2 as the Breda Model 1931 which was used by the Navy, apparently the gun was well-liked due to excellent reliability and good performance. How difficult would it be to convert the Breda 13.2 for aircraft use with a belt-feed and higher rate of fire? They did start production in 1930 which was a whole 5 years before the Breda-SAFAT entered production - that gives them a good amount of time to modify the design.
The Breda-SAFAT 12.7 mm guns were quite mediocre for their class, being reliable but heavy and slow firing. It didn't have the same hitting power of weapons in the same class - apparently low propellant capacity in the cartridges had something to do with it? Performance of the HEF-T round was also abysmal.
The 7.7 mm Breda-SAFAT guns definitely need to be thrown out as soon as possible, perhaps they could be repurposed as an infantry light machine gun a la the M2 Stinger? It's a long shot, but anything is better than the Breda 30.
Italy did produce a licensed copy of the Hotchkiss 13.2 as the Breda Model 1931 which was used by the Navy, apparently the gun was well-liked due to excellent reliability and good performance. How difficult would it be to convert the Breda 13.2 for aircraft use with a belt-feed and higher rate of fire? They did start production in 1930 which was a whole 5 years before the Breda-SAFAT entered production - that gives them a good amount of time to modify the design.
IMO, the main shortcoming of the 12.7mm Breda MG was that only two were installed per a fighter until it was too late. Install 4 per a fighter and there is some good firepower to be had.
The MG FFM would've been a good companion to the Breda HMG, very light for the punch, and with the matching ballistics with the 12.7.
As for the 7.7 MG, indeed let the infantry/Army have it.
Italians indeed have a lot of time to pefect the 13.2mm for the airforce needs.
It might even be a good platform for a 20mm cartridge, perhaps the 'short Solothurn'?
Shortround6
Major General
Try about the Breda 30 but.........The Breda-SAFAT used the same ammo as the British, the 7,7 x 56R or .303. Being able to use your enemies ammo is an advantage. Having him be able to use your ammo not so much. Nothing the Italian army has (any guns of any sort) use the British ammo. Italians got themselves in enough trouble trying to switch from the 6.5mm to the 7.35mm cartridge. Army is also already using an 8mm cartridge in their AFV and tripod heavy machineguns.
It might work but perhaps scattering them around air fields for light AA defense means less of a complication to the logistics problem.
Well, yes, if you use a shorter cartridge by 18mm and also make it smaller in diameter you get les propellent capacity. But please note, it had about the same hitting power as the Japanese Army 12.7 machine gun and the German 13mm (MG131) did. If you actually make the gun/s smaller and lighter you get at lease some benefit/s.
Same gun and ammo was used by both the Japanese navy and Japanese army. So the French, Italians and Japanese all decided to look elsewhere for a 12.7-13.2mm gun (Japanese navy stuck the 13.2mm cartridge in a copied M2 Browning). This may tell us something.
Shortround6
Major General
The Breda guns fired on the slow side, better than WW I guns but they don't seem to have advanced much beyond late 20s or early 30s. The Americans and British got their small Brownings to fire at around 1200rpm which is around 33-50% faster than the Italians got their 7.7 Breda-SAFAT (disguised Browning) to do. This should have been an easy fix.
Same for the 12.7 Breda. Japanese Army got around 900rpm from their Browning copy using the same ammo. 27% faster(?). Americans got around 800rpm with the longer, heavier American ammo after 1940.
Switching gun types/mechanisms when they are not getting even near the best out of existing guns seems like a wrong path.
Tomo is right, they need more guns even if they get the existing ones up to speed. They needed double if not triple firepower, not 25-33% more. Double the guns and increase the rate of fire.
That is what happens when you use a bullet that is around 33-35grams. 1/4 to 1/3 the weight of a 20mm shell. Expecting big results from small shells is going to be very disappointing.
- Thread starter
- #79
I'd lean on the side of 'no' for that - primarily due to the fact that the Breda 20/65 or Scotti 20/77 both use that cartridge already, and it would likely be easier to lightly modify those designs than attempt to scale-up the Breda 13.2 to take 20 mm.
The Hotchkiss 13.2 gun was good for what it was, the reasons they were being moved away from by France and Italy didn't have to do with the performance.
France made the idiotic mistake of demanding a belt feed while refusing to actually give Hotchkiss the money for it (classifying the belt-fed developments in the process), then when Hotchkiss decided to export it, the French government only permitted the magazine-fed version to be exported.
Italy (like many other nations at the time) realized that heavy machine guns were inadequate for deck-mounted anti-air roles against torpedo bombers. Thus, they replaced them with the Breda 20/65 in the SHORAD role.
As for Japan, I have no idea what they were thinking with the Type 3. I believe they decided to abandon it because it was heavier than the Type 99 mark 1?
It might be a good idea to rechamber it for 8x59mmRB Breda then - it's the closest in dimensions to .303 British and was already in circulation.
I'm pushing for the Breda-SAFAT to be turned into an infantry LMG due to the fact that it would require the least amount of changes to become man-portable compared to other LMGs like the Breda M37/38 or Fiat-Revelli mod 35. It was already sufficiently light (similar in weight to the Bren Mk 1 and MG 42, great deal lighter than the M1919A6), fired quickly (800-900 rpm), fired from belts instead of magazines and was highly reliable.
It may take a bit to get there, but it beats being stuck with that cruel joke of a weapon that is the Breda 30.
These cannons used the 'long Solothurn' cartridge. Very fitting for a light AA piece, similar in power to the Hispano or the big Oerlikon S, but it made also the weapons for it to be heavier than if the weapons were designed around the 'short Solothurn'. Not a biggie if just one cannon is installed, or you have a big fighter with a powerful engine, but on a small fighter powered with the engine of the modest power, installing two of these might be a tricky business. Two heavy guns with a lot of heavy will might represent a brake to the RoC, and perhaps speed.
