If you could go back to WW-2 with the knowledge you have now in engine design...what would you improve? No jets...
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ThomasP
Senior Master Sergeant
Hey GrauGeist and Shortround6,
re your posts: "The "motorkannon" was always mounted beneath the engine, as the Daimler-Benz and Jumo engines were inverted "V" types."
and "The motor cannon was mounted behind the engine with only the Barrel positioned in a tube."
and "Perhaps I should have said "mounted beneath the centerline of the inverted "V" engine""
Thank you for reminding me.
and re: "Another point to consider is that the rotational velocity of the barrel cluster imparts a slightly spiral trajectory to the rounds leaving the muzzle,..."
I had not thought of that, though I was familiar with the barrel cant. Thank you for pointing it out.
I may be miscalculating the sideways/tangental velocity (I do not know the diameter the Vulcan bores travel on) but the tangental velocity would only be 52-53 ft/sec (at a ROF of 6000 rpm) with a the bore travel diameter of 12". If I am correct in my math, the sideways movement would only be about .016" per foot of blast tube. I think that would be manageable.
I know that blast sleeves are used on some Vulcan aircraft installations (the F-104 being one example) to prevent internal build-up of gases and to prevent/reduce blast damage to the aircraft skin/structure near the muzzle, while still allowing aerodynamic shape in the area. The gasses are sometimes vented to atmosphere through slots/grid holes a little ways in front of the muzzles. I think that the F-104 installation could be considered to have a blast tube also? The blast sleeves are of much larger diameter than a typical WWII MG or cannon blast tube, but I think the sleeve could be stepped down to blast tube diameter (at the single firing position) over a short distance. Yes/No/Maybe?
You made me think of another possible problem. Would precise positioning of the barrel on firing be a bigger problem than sideways/tangental velocity? I have no idea what the positioning errors are for the Vulcan.
re your posts: "The "motorkannon" was always mounted beneath the engine, as the Daimler-Benz and Jumo engines were inverted "V" types."
and "The motor cannon was mounted behind the engine with only the Barrel positioned in a tube."
and "Perhaps I should have said "mounted beneath the centerline of the inverted "V" engine""
Thank you for reminding me.
and re: "Another point to consider is that the rotational velocity of the barrel cluster imparts a slightly spiral trajectory to the rounds leaving the muzzle,..."
I had not thought of that, though I was familiar with the barrel cant. Thank you for pointing it out.
I may be miscalculating the sideways/tangental velocity (I do not know the diameter the Vulcan bores travel on) but the tangental velocity would only be 52-53 ft/sec (at a ROF of 6000 rpm) with a the bore travel diameter of 12". If I am correct in my math, the sideways movement would only be about .016" per foot of blast tube. I think that would be manageable.
I know that blast sleeves are used on some Vulcan aircraft installations (the F-104 being one example) to prevent internal build-up of gases and to prevent/reduce blast damage to the aircraft skin/structure near the muzzle, while still allowing aerodynamic shape in the area. The gasses are sometimes vented to atmosphere through slots/grid holes a little ways in front of the muzzles. I think that the F-104 installation could be considered to have a blast tube also? The blast sleeves are of much larger diameter than a typical WWII MG or cannon blast tube, but I think the sleeve could be stepped down to blast tube diameter (at the single firing position) over a short distance. Yes/No/Maybe?
You made me think of another possible problem. Would precise positioning of the barrel on firing be a bigger problem than sideways/tangental velocity? I have no idea what the positioning errors are for the Vulcan.
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The only one I'm familiar with is the M39, and the gun guys didn't like it compared to the M61.
As far as your produceability comment? Agree 100% building to print isn't easy and sometimes it's easier to start over from scratch.
Maybe it's a question of scale, but I seem to remember the M39 not being as compact a design in the F-5 as the M61 in the F-14. Please feel to correct me.
BTW, my question was directed more as given the M39, the M213, and the Aden, is there any potential left in the revolver cannon? I'd think the barrel wear would still be a problem.
swampyankee
Chief Master Sergeant
- 4,002
- Jun 25, 2013
The latest revolver cannon from the various non-US makers seem to be a bit better than the M39 or the Aden, with greater muzzle velocities and greater rates of fire. Many of them will get the first few rounds off before a Gatling. Interestingly, the Russians use both Gatling and revolver guns, so they don't seem to have an institutional bias to either.
Aircraft armaments are neither a particular area of expertise nor a major interest of mine, but there seems to be little or no advantage to an M61 Vulcan over the latest DEFA 30 mm in the Rafale or the 27 mm Mauser in the Typhoon except in raw rate of fire, with disadvantages in installation weight, complexity, and volume and a comparatively small shell.
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The problem with the blast tube idea is that you've got design it so that it captures all the escaping gas and directs it out the blast tube. Remember, you're in the engine compartment in close proximity to fuel lines, ignition wires, and other such tender objects, and you can't have the firing barrel actually intrude into the blast tube the way a conventional motorkannone did. It's the revolver gas leakage issue all over again. On steroids.
Position error shouldn't be a problem. The rounds are fired by an electrical charge applied to the firing pin, and that happens when an electrical contact is made at a specific point in the rotation, not unlike a Capacitive Discharge auto ignition. The gun is turning at a relatively leisurely 1,000 RPM (6,000 Rds/min ÷ 6 Rds/revolution = 1,000 RPM), so time lag is not a significant issue.
Cheers,
Wes
I've never seen either installation up close and personal with the panels open and innards visible, so I'm limited to the graphical depictions and photos I've seen. The cutaway drawings I've seen generally depict the F5 installation in its entirety, including ammo storage and feed mechanism. F14 drawings usually depict a portside forward quarter view which features the gun itself and de-emphasizes the drum and feed which are buried in the fuselage.
I'd be really surprised if you laid both guns out side by side on the tarmac with their feed mechanisms, and the M39 turned out to be bigger than the Vulcan.
Cheers,
Wes
If that's only advantage, perhaps it is not an advantage? Note that you've said: "the X configuration used in their Cub has the weight advantage of having only one crankshaft" - that I don't agree much. The Cub weighted almost 2500 lbs, a 60L engine for 1000 HP. RR Condor's weight was 55% of the Cub, power of the Condor being 2/3rd of the Cub - a ~20% better power to weight ratio for the Condor.
Packard's X-2775 seem to lack good data about power vs. reliability? We can recall that in it's max power listed it seem not to be as powerful as the RR 'R' engine.
I've seen both in the shop units complete with feed and magazine. I think the M39 magazine on the F-5 was around half the size of the one on the Tomcat. I also think the M39 revolver and "block" were wider and taller than round motor drive and feed mechanism for the M61. Weight wise, I don't think there's much to choose between the two. The M61 "looks" lighter, but I wouldn't be surprised if it was about the same weight.
Either way, I think I'd prefer the M61 just for the Wf.
About the only places a Squid would be likely to encounter an F5 would be at an ACM training base that supports aggressor aircraft: Miramar, Fallon, or Key West. Or maybe Lemoore? Isnt that the west coast Hornet RAG? Back in the day the Marines did their ACM at Cherry Point and Yuma. Is that still so? They didn't have specialized aggressor aircraft, just A4s, but those must be history by now. I've been out of the loop for 45+ years now.
Cheers,
Wes
On the engine front, seems like the twin crank engine (the Sabre) was actually in combat. The multi bank inlines with one crank were not. So, in fantasy land, making a multi bank single crank would be a good leap forward. On the other hand, the twin crank multi bank might make a good long range aircraft if shutting half the engine down would boost range.
Nonetheless, expansion chambers on 2 strokes still compel. The expansion chamber itself is reasonably low tech and one might even remember the rules of thumb post time travel. The difficulty of spark ignition 2 strokes is that either one accepts the loss of fuel out the exhaust, or one uses direct injection that occurs as or after the exhaust port or valve is closing. This technology has been available at the consumer level for several years, using crankcase compression no less. However it is very dependent on significant computing power. If one were to depend on mechanical fuel injection, spark ignition 2 strokes would require a lot more fantasy to be available in WW2.
The primary issue with compression ignition 2 strokes is weight and driveline resonance, primarily in the crankshaft. A radial would do better and a low compression engine would help. How low can one go? Using boost to stabilize ignition, 12:1 compression ratio is probably achievable. What would that do to maximum altitude? Either way, 12:1 is about twice the compression ratio of WW2 spark ignited engines. Plus the quality of compression ignition power strokes would still be challenging on driveline resonance.
As for alternative guns, seems like the Gast gun offered the easiest significant improvement for non synchronized non motor cannon. Not as complicated, not as fast as the revolver or rotary guns
Nonetheless, expansion chambers on 2 strokes still compel. The expansion chamber itself is reasonably low tech and one might even remember the rules of thumb post time travel. The difficulty of spark ignition 2 strokes is that either one accepts the loss of fuel out the exhaust, or one uses direct injection that occurs as or after the exhaust port or valve is closing. This technology has been available at the consumer level for several years, using crankcase compression no less. However it is very dependent on significant computing power. If one were to depend on mechanical fuel injection, spark ignition 2 strokes would require a lot more fantasy to be available in WW2.
The primary issue with compression ignition 2 strokes is weight and driveline resonance, primarily in the crankshaft. A radial would do better and a low compression engine would help. How low can one go? Using boost to stabilize ignition, 12:1 compression ratio is probably achievable. What would that do to maximum altitude? Either way, 12:1 is about twice the compression ratio of WW2 spark ignited engines. Plus the quality of compression ignition power strokes would still be challenging on driveline resonance.
As for alternative guns, seems like the Gast gun offered the easiest significant improvement for non synchronized non motor cannon. Not as complicated, not as fast as the revolver or rotary guns
wuzak
Captain
Actually the Vulture was in service with the Manchester from late 1940, almost a year before the Sabre powered Typhoon, until 1942.
ThomasP
Senior Master Sergeant
I do not know if this is true, but I have read in a couple of quasi-official reports that the Vulture was pretty much up to snuff by the time the Manchester (still being used for training purposes) was removed from service in late(?) 1942.
wuzak
Captain
It had been cancelled for months, if not a year, when the Manchester was withdrawn from service.
Development had been suspended around the time of the BoB, due to the priority of improving the performance of the Merlin, and Rolls-Royce concentrating it efforts on that goal.
Issues, primarily with the connecting rod design, remained when the Vulture was cancelled, largely because the time and effort required to fix those problems would have affected Merlin and Griffon development.
One suggested solution was to go from the master and slave rod design to a pair of fork and blade rods on each crank pin. This would have required offsetting two banks with respect to the other two, which would have necessitated a redesign of the crankcase.
It has been confirmed to me by RRHT that the Vulture had been bench tested at 2,500hp in 1941, and Lumsden states that a figure of 3,000hp was achieved, though RRHT could not confirm that.
NAS Miramar along with VF-43 at NAS Oceana.
I remember when VF43 was established as an aggressor squadron. We heard a new VF squadron was coming to town, but were surprised when a formation of eight A4s hit midfield in a very impressive single point G separation break, landed nose to tail, taxied to the ramp in a single large diamond formation, and pulled off a Blue Angels style synchronized shut down and dismount. Notice had been served there was a new gang in town and VF101 was no longer the uncontested ace of the base.
ACM training underwent a major sea change, as aggressor aircraft were no longer flown by VF101instructors, but by professional "bad guys".
Cheers,
Wes
And, and they had a much better coffee mess than 400 division.
Dunno 'bout that. I was headed for the gate with DD214 in hand. P.F.C. at last!
As a TD you would have had to get into a different rate or transition to contractor within a few years as well.
I got out in '74. That happened in '88. In '90 I had a new hire FO in my right seat, a TD who got an early out rather than transition to IC and go to sea for a year. He said most TDs were converted to ICs, yanked from the airedale Navy and sent to sea as black shoes. He said they had to take on short notice the IC exam for the rate they held as TDs just to hold their paygrade, and depending on their scores, many were set back a paygrade or two. Not happy campers. A lot of folks went to work for GD, MacD, and CAE about then.
Probably a good thing from a taxpayer standpoint, as when I left in '74 Naval Air seemed to be functioning more on the expertise of tech reps than of sailors.
Cheers,
Wes
