If you could go back to WW-2 with the knowledge you have now in engine design...what would you improve? No jets...

[TheMadPenguin]

"No, the .50 Gatling was looked at in late '40s " So, it was overlooked until then (i.e. during WWII).

Mass: .50 Gatling GAU-19/A:138 lbs. (63kg) (6 barrel)
GAU-19/B:106 lbs. (48kg) (3 barrel)
Source: GD delivers GAU-19/B Archived

Where you get 144Kg, SR? That's the weight (approx) of the 20mm Vulcan. What's the weight of our M3 20mm cannon? About 100lb. So the 20mm Gatling weighs about 3 times the HS404 (with ROF significantly higher).

And we used rockets and hollow charges in WWII, OK? So we had all the tech we needed to make RPG-7 in 1940, OK?

Teach me right where I'm in error, but slap-downs based on twisted data don't help me learn.

As for the Penguin "dreaming on", that's what the OP posited.

 

[XBe02Drvr]

a major problem with high rate of fire guns in WW II was feeding them, conventional belts don't work well without some sort of delinking system,

The gatlings we worked on had no belts. The first thing discovered when they started trying to build high ROF guns post WWII was belts couldn't do the job. The ammo drums and feed paths on our Vulcans fed bare cartridges from a spiral drum through a "track", if you will, consisting of castings with sprockets in them that guided the rounds through every change of direction and into the gun. The ammunition was delivered planeside in belts which were delinked as the rounds were fed into the spiral drum by the ordnance people in the loading process. In the case of a jam, sprocket teeth would often puncture cartridge cases, spilling raw powder into the works.
Early guns ejected the empty brass overboard, but this was discovered to often have undesirable effects on the aircraft's tailfeathers, and pilots complained that the CG shift aft as ammunition was rapidly expended forward tended to draw their aim off target. Solution? Capture the expended brass and feed it back into the drum to minimize weight shift. This meant duplicating the feed path mechanism in reverse, adding weight, bulk, and cost.
We also manufactured a cute little number dubbed a "Micro" which was a miniaturized Minigun that fired 5.56 M16 ammo and was mounted in the noses of AT37 Dragonflies for RVN.
Cheers,
Wes

 

[Shortround6]

Teach me right where I'm in error, but slap-downs based on twisted data don't help me learn.

Try looking at the link given in post. we are both using twisted data,

" A ready to fire standard three-barrelled weapon, as used on a helicopter/vehicle pintle, comprises eight major components: the gun itself with standard barrels, which is 1.18 m long and weighs 34 kg; the electric motor, booster assembly, ammunition de-linker, 750-round ammunition box, flexible metal ammunition chute and combined handgrips and gun cradle. A single three-barrel GAU-19/A system ready to fire on a Black Hawk pintle mounting weighs 144 kg empty and 250 kg with 750 rounds. "

Where you get 144Kg, SR? That's the weight (approx) of the 20mm Vulcan. What's the weight of our M3 20mm cannon? About 100lb.

See above. Unfortunately, all too often weights are given for a bare gun, which in the case of some of Gatling guns is really deceptive because they had optional drive systems let alone the some of the "accessories". The GAU-19A had two different electric motors depending on the rate of fire desired, (and I really wonder about the proposed 8000rpm version).
Weights for the 20mm Vulcan are all over the place depending on the drive system

BTW that weight for the M3 20mm cannon may not include the weight of the external belt feeder. Most weights for Hispano cannon do not include it. Please note that I used about 80lbs for the weight of the .50cal M2 in the comparison to try to take into account accessories often used on wing guns. Like remote cockiing/charging mecanisms.

And we used rockets and hollow charges in WWII, OK? So we had all the tech we needed to make RPG-7 in 1940, OK?

No, it is not "OK" as both the technology of rockets and hollow charges advanced considerably during WWII, whar they could make in 1944-45 was considerably different than what they could make in 1940.

Showing up through our magic door in 1937 and say" build a rocket with a hollow charge warhead" without the details on how it was done would get them very far.
A 1940 hollow charge was lucky it penetrate more than 1 to 1.5 times it's own diameter. By 1945 a hollow charge could penetrate around 4 times it's own diameter, by the 1950s and the RPG7 it could penetrate up to 7 times it's own diameter.
Shape of the interior of the hollow charge was critical to this advancement as was the type (material) of the hollow charge liner and the type/composition of the explosive. You need the right burn rate matched to the right cone shape to get the best penetration. Copper works best as the cone liner. You also need the correct stand off distance (length of hollow nose cone) matched to the impact speed of the projectile to give optimum results. Detonate to clsoe to the armor surface and you do not get the best penetration.

All of this took several years to figure out (Germans went through four different 10cm howitzer shells to get the best results for them which was pathetic by post war standards)

Sort of the same with rockets, basic idea is easy, getting production rockets that don't have a fair number of fizzlers or the occasional blow up in the launch tube is a lot harder.
They got there, it just wasn't quick and easy.

 

[TheMadPenguin]

"No, it is not "OK" as both the technology of rockets and hollow charges advanced considerably during WWII, whar they could make in 1944-45 was considerably different than what they could make in 1940."

with, or without your help?

This is a fantasy thread as posited by the OP. What would YOU devise/invent/improve based on your knowledge if you walked through a door into 1938?
What was lacking in 1938 that could not be obtained/derived/invented such that the RPG-7 was not possible in 1940?

"Shape of the interior of the hollow charge was critical to this advancement "
and you know what the shape was that worked so well...

 

[Shortround6]

This was the state of the art in 1940.

The British No 68 rifle grenade. There were apparently 4 different MKs and the interior cavity did change in shape. There were also 3 to 4 different explosives used (or more?)
Millions were made, accounts of actual use are few?

With any sort of modern knowledge a better device is most certainly possible, but to jump to the RPG-7 is quite a leap. Design work started on the RPG-7 in 1958 and it is the RPG-7 because they had already gone through the RPG-1, RPG-2, RPG-3 and so on, The RPG-2 being the most common production model before the RPG-7.

If you are looking for maximum penetration the interior shape has to matched to the actual explosive used. Not whatever explosive is available this month. However quite useable weapons can be made using a relatively simple cone and any decent explosive.

rockets had a mixed reception in pre-war and early war thinking with the bean counters. Rocket launchers were cheap compared to cannon. Rockets themselves were also cheap (low grade steel tubes), however the low accuracy and sometimes poor target effect meant than many more rounds were needed to get the same target effect. Rockets also consumed prodigious amounts of propellent for the size of the warhead delivered meaning they weren't that cheap after all. It rather depends on if your industrial capacity has a bigger problem making high grade steel or making explosives.
British army had a real thing (almost fetish) for cheap ammo. Perhaps understandable given the shell scandals of the First World War, but it was pennywise and pound foolish in the 2nd World War.

 

[TheMadPenguin]

This is a fantasy thread as posited by the OP. What would YOU devise/invent/improve based on your knowledge if you walked through a door into 1938?

 

[ThomasP]

The subject of the OP was relating to ENGINES.

However, having said that, and since I am as susceptible to topic wander as the next person.

As to aircraft armament, I would try to bring back knowledge that would enable the manufacture of better and more compact Lead Computing Gun Sights (of whichever type). Aside from the obvious (greater hit %) it would make the use of gatling type weapons more practical.

One of the main problems with gatling guns (and other extremely high ROF weapons) is the lack of sufficient ammunition. For anti-bomber use, I am sure the Luftwaffe would have loved a 20mm Vulcan equivalent, if they could produce a platform capable of carrying it. As pointed out above the weight of the gun system and ammo is high, probably more than a single engine fighter could carry. It would have to be mounted on or near centerline, which would require synchronization (reducing the ROF enough to render the advantage moot), or fire through the hub. Maybe on twin-engined aircraft like the Me110 or FW187 (center fuselage) early-war, or something like the Do335 (hub?) late-war. I do not think anything smaller could carry the system effectively.

Then there is the short fire time. This would be a problem due to both weight and volume. There is no way that a 20mm Vulcan system (600 rounds for a maximum fire time of 10 seconds at the normal LOW ROF of 3000 rpm) could be fitted into anything smaller than a Do335 size airframe. An approximate .50 cal//13mm system would obviously fit in a smaller airframe, but the high ROF/low fire time would be the same (or worse if max possible ROF of 8000(?) rpm was used). Again it would have to be centrally located, unless you want to cary 1 in each wing (ammo drums in the fuselage), in which case the airframe would have to be large (ie no Bf109/Spitfire/P-40/P-51/etc).

For bomber defensive installations (particular in the tail) the size/weight would not be to much of a problem (I think) but the low low fire time would be. I ran across a post-WWII US study on aircraft armament, and one of the problems mentioned relative to the B-17 and B-24 was that they would often run out of ammo for the guns, often before they reached the target. Can you imagine the increased chances of that with a 10 second time of fire instead of the normal 45-60 seconds. The major effect of bomber guns vs fighters was found to be the morale factor for the bomber crews and discouragement factor for the attacking fighter pilots. As to the adverse morale effect on the Luftwaffe fighter pilots, the Luftwaffe late-war reports and the post-war US study reported that the addition of the chin turret to the B-17 and nose turret to the B-24 only decreased head-on attacks by about 4% (the head-on percentage was still in the low 40% range, the tail attack in the mid-40% range, with other types accounting for the remainder).

A better Lead Computing Gun Sight would increase the hit chance for normal gun installations (whether in fighters or bombers) and would (maybe) allow the decreased time of fire for gatlings to be effective.

 

[jetcal1]

So where does the Mauser revolver cannon fall into the high ROF weapons in regards to "What would you improve?"

 

[XBe02Drvr]

So where does the Mauser revolver cannon fall into the high ROF weapons in regards to "What would you improve?"

Well, it might be possible to install one for through the hub firing in a largish V12 piston fighter, something that would never work for a multi barrel 20MM gatling due to bulk issues. The Vulcan is about as compact as they can reliably be, and I don't think anybody who's seen one up close and personal would think of trying to stuff it into the nose of a single engine piston fighter. Now a 20MM revolver cannon could be made more compact and might have a chance, but it would have barrel life issues. Compare a .36 cal pepperbox pistol to a Colt Navy: the difference is obvious. (Oops, maybe that's a bad example. Pepperboxes in .36 are pretty rare, as most were .32 or smaller: gambler's hideaway pistols.)
Cheers,
Wed

 

[Shortround6]

So where does the Mauser revolver cannon fall into the high ROF weapons in regards to "What would you improve?"

Another example of it's sounds simple in theory but in practice things are a bit different.
The Americans, British, French and Russians all looked at it in 1945, all started working on a version of it shortly thereafter with greater or lesser urgency depending on country and year, By 1948 things were getting more urgent and with the Korean war and the Russians exploding a nuclear weapon the urgency got pretty high. First production examples are fitted to aircraft in 1953?
Even throwing a set of blue prints on the table in 1937 isn't going to get you a gun in 1940-41 unless you also have the details of the metallurgy and manufacturing techniques.
I would remind people that the allies knew about the german "mine" shell in 1940, they never made one (for service use) during WW II, not because they didn't know what the Germans did but because they didn't have the expertise in deep drawing steel that Rhinemetel did. They could analyze the shells and figure out what was done but not how to actually do it.

 

[Reluctant Poster]

The subject of the OP was relating to ENGINES.

However, having said that, and since I am as susceptible to topic wander as the next person.

As to aircraft armament, I would try to bring back knowledge that would enable the manufacture of better and more compact Lead Computing Gun Sights (of whichever type). Aside from the obvious (greater hit %) it would make the use of gatling type weapons more practical.

One of the main problems with gatling guns (and other extremely high ROF weapons) is the lack of sufficient ammunition. For anti-bomber use, I am sure the Luftwaffe would have loved a 20mm Vulcan equivalent, if they could produce a platform capable of carrying it. As pointed out above the weight of the gun system and ammo is high, probably more than a single engine fighter could carry. It would have to be mounted on or near centerline, which would require synchronization (reducing the ROF enough to render the advantage moot), or fire through the hub. Maybe on twin-engined aircraft like the Me110 or FW187 (center fuselage) early-war, or something like the Do335 (hub?0 late-war. I do not think anything smaller could carry the system effectively.

Then there is the short fire time. This would be a problem due to both weight and volume. There is no way that a 20mm Vulcan system (600 rounds for a maximum fire time of 10 seconds at the normal LOW ROF of 3000 rpm) could be fitted into anything smaller than a Do335 size airframe. An approximate .50 cal//13mm system would obviously fit in a smaller airframe, but the high ROF/low fire time would be the same (or worse if max possible ROF of 8000(?) rpm was used). Again it would have to be centrally located, unless you want to cary 1 in each wing (ammo drums in the fuselage), in which case the airframe would have to be large (ie no Bf109/Spitfire/P-40/P-51/etc).

For bomber defensive installations (particular in the tail) the size/weight would not be to much of a problem (I think) but the low low fire time would be. I ran across a post-WWII US study on aircraft armament, and one of the problems mentioned relative to the B-17 and B-24 was that they would often run out of ammo for the guns, often before they reached the target. Can you imagine the increased chances of that with a 10 second time of fire instead of the normal 45-60 seconds. The major effect of bomber guns vs fighters was found to be the moral factor for the bomber crews and discouragement factor for the attacking fighter pilots. As to the adverse moral effect on the Luftwaffe fighter pilots, the Luftwaffe late-war reports and the post-war US study reported that the addition of the chin turret to the B-17 and nose turret to the B-24 only decreased head-on attacks by about 4% (the head-on percentage was still in the low 40% range, the tail attack in the mid-40% range, with other types accounting for the remainder).

A better Lead Computing Gun Sight would increase the hit chance for normal gun installations (whether in fighters or bombers) and would (maybe) allow the decreased time of fire for gatlings to be effective.

The B-17 and B-24 had CoG problems, adding weight to the tail would have exacerbated this. The Reed B-17 attempted to correct this.
Boeing B-17E Flying Fortress The Dreamboat nose
The B-24 was worse. The Emerson turret was developed as a tail turret but the extra weight precluded this so they stuck with the inferior Consolidated turret in the rear and installed the Emerson in the nose. In addition Consolidated actually developed a MANUAL rear turret to save 200 lbs.
Aircraft Gunnery_Tail Turret
As an aside here is a training film on the Emerson Turret

 

[swampyankee]

A surprisingly large number pf aircraft had c/g problems in the design and prototype phases. This includes just about any propeller aircraft with swept wings and the Me262. Moving around accessories was another method.

 

[ThomasP]

Hey XBe02Drvr,

I agree that that the actual Vulcan, as it currently exists, would be impractical to fire through the hub of a WWII . Too heavy and long if nothing else. But for the Luftwaffe I thought (maybe?) a lighter/shorter barrel/lower velocity/minengeschoss version could be mounted above the engine. Since the gun only fires from one barrel position I figure that a blast glove/tube through the hub might be used. I used the Do335 as an example because it is a large airframe, with the ability to carry a 30mm MK103 firing through the hub. It only carried 70x 30mm rounds but maybe with the flexible-chute feed system the ammo drum for a 20mm gatling could be mounted farther to the rear, maybe between the engine and cockpit? Possibly not, but maybe?


Hey jetcal1,

As XBe02Drvr pointed out above, it would certainly be easier to install a revolver cannon in limited space, whether through the hub or in the wings. The weight increase is significantly less than for a gatling. The ROF of the successful revolver cannon designs seems to be about 2x that of a conventional weapon, so while the reduced time of fire effect would not be as drastic as for a gatling, it would still be a significant factor.


Hey Reluctant Poster (and others),

I agree that, as you point out above, the problems of CoG can be a factor, but for the sake of this thread I think we have to assume that the changes we are proposing have to be started early enough to be implemented in a practical manner, whether for engines or weapons. Otherwise we are defining the changes as impossible before we even start (regardless of the reason). In some cases this is a valid view as it may be impossible to develop the technology in a short enough time (eg printed circuits on silicon wafers). Others, like maybe integrating a gatling weapon into a 4-engine bomber platform is entirely possible, more or less like any other weapon system if trade-offs are accepted. The level of performance of a gatling using WWII manufacturing technology (with modern knowledge) would probably not be up to modern standard but might still be a worthwhile improvement (eg if the reduced time of fire can be made up for through increased chance of hit, and if the increased chance of hit results in significantly reduced bomber losses).

The CoG problem could be solved in several ways if the improvement was considered worth trade-offs elsewhere. The 'Dreamboat' design you mention above is a good example of this, even though it was not deemed to make up for the trade-off of a temporary reduction in production.

 

[GrauGeist]

But for the Luftwaffe I thought (maybe?) a lighter/shorter barrel/lower velocity/minengeschoss version could be mounted above the engine. Since the gun only fires from one barrel position I figure that a blast glove/tube through the hub might be used.

The "motorkannon" was always mounted beneath the engine, as the Daimler-Benz and Jumo engines were inverted "V" types.

 

[Shortround6]

The motor cannon was mounted behind the engine with only the Barrel positioned in a tube.

Revolver cannon will fit (work is another story) Gatling gun?????????
tube was 70mm in diameter. You better plane early for what kind of gun you want inside the V. Don't forget the DB and Jumo engines had their intake manifolds on the inside.
Hispano (and the Russian engines) had both the intake and exhaust on the outside leaving the V fairly clear. Even so, the ejection port has to outside (to the rear) of the V on an upright engine.

 

[XBe02Drvr]

Too heavy and long if nothing else. But for the Luftwaffe I thought (maybe?) a lighter/shorter barrel/lower velocity/minengeschoss version could be mounted above the engine.

They spent years trying to make the Vulcan lighter and more compact, only to blow up gun after gun on the test range. When one of those things comes unglued you don't want to be cooped up in an airframe with it. The test cells at the range got rebuilt over and over again. When the Vulcans were being tested the noise echoed up and down the valleys of central Vermont and could be heard for miles. My high school biology teacher would pause his lecture, turn toward the direction of the noise and say: "Jupiter, SHAME ON YOU! Excuse yourself when you do that in public!", then hold his nose and fan his other hand in front of his grimacing face.
When the extended burp sound ended in a "pop" or a "ting", it always aroused speculation, but since we didn't know at the time what those strange burping/buzzing sounds were, we were stabbing in the dark. Years later, I learned that "pop" was a Vulcan blowing up. I saw (from a safe distance!) a test failure. Impressive! A frag grenade would have done less damage to the test cell.
Another point to consider is that the rotational velocity of the barrel cluster imparts a slightly spiral trajectory to the rounds leaving the muzzle, and the barrels are canted slightly to attempt to counter this, but you'll notice that no known Vulcan installation has the projectiles traversing a tube after leaving the muzzle. Bad idea!

As XBe02Drvr pointed out above, it would certainly be easier to install a revolver cannon in limited space, whether through the hub or in the wings.

While closer to a viable solution, the high ROF revolver cannon has two potential pitfalls:
1) Barrel wear. Barrels will wear out quickly, and need to be quickly and easily changeable.
2) Cylinder to barrel gas seal. This is the bugaboo of all revolver type weapons. My Uberti 1861 New Model Army warms my fingers every time it goes off, despite the Crisco flashover protection I put over the chambers. Not the kind of issue I want in my engine compartment, thank you.
Cheers,
Wes

 

[swampyankee]

I would suspect revolver cannon would be more viable than Gatlings, mostly because of installation volume, but their need for external power could also be problematic. A much smaller step would have been developing the Oerlikon FFL for aircraft use ( ANOTHER MISSED OPPORTUNITY: THE OERLIKON FFL CANNON)
or, less conservatively, a 20 mm Gast-type gun.

Returning to engines: no H-engines. While Napier seemed very enamored of them, the X configuration used in their Cub has the weight advantage of having only one crankshaft. A liquid-cooled radial would also have the potential for being lighter, and has the potential for more cylinders.

 

[GrauGeist]

The motor cannon was mounted behind the engine with only the Barrel positioned in a tube.

Perhaps I should have said "mounted beneath the centerline of the inverted "V" engine"

 

[tomo pauk]

...
Returning to engines: no H-engines. While Napier seemed very enamored of them, the X configuration used in their Cub has the weight advantage of having only one crankshaft. A liquid-cooled radial would also have the potential for being lighter, and has the potential for more cylinders.

X configuration was no bed of roses, either. RR Vulture have more than it's share of troubes, the less we say about Jumo 222 the better (although the layout itself was not the only problematic area). Napier's problem with Sabre was that company was not making good sleeves, that was cured by using Bristol's sleeves (from Taurus - oh, the irony) and later by import of some specific machine tools from the USA. With Dagger, they tried to skip on displacement while pushing up the rpm (4400, max) - didn't worked all that well. We also don't know how good/bad the cooling of the air-cooled Napier engines was.
Fairey's H24 Prince was non-problematic.

 

[swampyankee]

Napier and Packard seemed to have relatively few problems with X-engines.

They still have one fewer crankshaft.