Hurricane Mk IIC cannon:drum-magazine or belt-fed?

[Bill Walker]

Here is a link to the Flight magazine on-line cutaways. A great time waster!

http://www.flightglobal.com/staticpages/cutaways.html

[Johnny .45]

Originally Posted by Bill Walker

Here is a link to the Flight magazine on-line cutaways. A great time waster!

http://www.flightglobal.com/staticpages/cutaways.html

Ah, and that's what I do best! I can waste time like NOBODY'S business!
Thanks. I'll be sure to check it out in a moment, once I've written this. And got another cuppa coffee.

-"Pilot": Perhaps I'm just misunderstanding you; when you say "When airplane have drum you could note bulge on the top of the wing", I hope you are talking about a specific TYPE of bulge. Because even planes without drum-magazines had bulges to cover the electric-feed mechanisms that pulled the belt of ammunition into the breech...it looks kind of like a "miniature drum".
The drum-magazine Spitfires like the "B" wing Mk V had a unique type of large bulge to cover the top of the drum. When they went to the "Universal" wing, they also went to belt-feed. But they still have bulges over the feed mechanisms...originally the four-cannon planes had a single wide bulge covering the two cannons in each wing. If it was a 2-cannon type, it had a single, much narrower bulge. A bit later on, they began using two narrow bulges to cover the cannons on the 4-cannon types, because it created less drag than the single wide bulge did.
Maybe you knew all that already; I'm just trying to be helpful.
(And if I have to type the word "bulge" one more time...I won't be responsible for my actions! )

LOL...I like this one!
I'll have to show that to my mother...I'm sure she still remembers me running around pretending to be a plane when I was a little kid!

-Graham- As far as I know a Hispano weighs about 90-something pounds...that's like a bit over 40 kilograms. I don't know if that includes the weight of the electric motor/drum magazine though. And I'm sure that 90 rounds of 20x110mm ammo weighs a considerable amount too.
What you say about guns being removed is entirely true, and most major combatants would do this from time to time...except the Italians. Their planes had barely enough firepower as it was, for most of the war. I think of it as the "Zero Approach"...when you have to choose between firepower/armor and performance, some pilots (usually the better, more aggressive ones) would choose lighter armament in the interests of better performance.
I guess they figured a shitload of firepower is no good if you can't bring the guns to bear on the enemy, and although armor is nice, it's better to be too quick to hit at all! The Zero was probably the most obvious example of this, as it was designed that way rather than modified, but it's the same idea. (Although one shouldn't forget that PART of the reason they never gave the A6M adequate protection was that there just wasn't an engine that could handle the extra weight).
I've been thinking about looking into the topic of the Zero and it's armament...perhaps I should make it a new thread? Anyway, the Japanese pilots at the beginning of the war weren't at all worried about the lack of armor or self-sealing tanks. They didn't even want the 20mm cannon at first, they thought it was too heavy. And in fact, some pilots DID remove the cannons, figuring that two 7.7mm RCMG's were plenty. Apparently a good pilot in a agile, vulnerable plane with very light armament is dangerous enough! Let's say, the Spitfire probably COULD have fought the whole war with nothing but it's eight .303's...it just would have been a lot harder!
"Yawn." I'm digressing. I have a bad habit of that, and it always takes me way to long to finish a post! Anyway, yes many German Fw 190 pilots would remove the outer pair of MG 151/20's to save weight. At least the remaining two cannons and two MG's were easily sufficient, especially since the wing-root cannons are more like fuselage-mounted guns than wing guns.
I suppose there's no real reason to re-iterate the whole "fuselage vs wing-mounted armament" debate, but like you said, it's been going on a long time! Fuselage-mounting may seem ideal in many respects, but it has it's drawbacks as well. I think that first, and perhaps most importantly, a single engine fighter must either: a.)synchronize the guns to fire through the prop, which decreases the rate of fire and reliability of the weapon, or b.)set it up to fire through the hub, i.e. Bf 109, P-39, Dewoitine D.520, MS.406, etc.
Of course, this has it's own score of problems...the plane AND the engine must be specifically designed for it, and the Germans had several difficulties in making in work, first with the Bf 109E, then when they tried to fit the larger MK 103 cannon in the later 109 variants, and also trying to fit an MK 103 (and 108, I think) into the Jumo engine of the Fw 190 Dora...I don't think they ever actually succeeded in giving the Dora thru-hub armament, but DON'T quote me on that! They DID finally manage to cram a hub-firing MK 103 into the Dornier 335, but I think that was the only one.
Back to fuselage guns: Space is also at a premium in a single-engine fighters fuselage. It's hard enough to fit an engine, accessories, oil/coolant tanks, engine bearers, fuel tanks, etc into such a space without adding bulky guns and ammo-tanks as well.
Plus, any switching of armament calls for a lot more relocating and fiddling-with of equipment...as the Germans again found out when they went from the MG 17 to MG 131. Eventually, the only way they could do it at all was by making the fuselage a bit bigger to cover the spent-case chutes...and that was AFTER a lot of careful thinking. Going from .303's to 20mm's in the Spitfire was a lot easier (although not exactly a piece of cake!).
Guns vary in reliability, but all automatic weapons are liable to extreme heating when fired in any length...a barrel can get so hot that it actually "droops" and is ruined, and bores will erode quickly once the maximum practical rate-of-fire is exceeded. Most importantly, unless it is an "open-bolt" design, hot machine guns are liable to "cook off" a round if the camber get too hot...meaning that the barrel is so hot, the round fires even though the trigger wasn't pulled. And once a round is fired, the next is loaded, and cooks off, and so on. So the already-too-hot gun will fire until it runs out of ammo, and will certainly be ruined.
Also, since a synchronizer only controls the trigger, there is no guarantee that there won't be a prop blade in front of it when the bullet leaves the muzzle...especially if the gun just automatically empties it's magazine. You'd probably shoot your whole prop right off! An infantryman with a machine gun that "runs away" can just grab the belt and stop the feed, but I don't think you can do that in a fighter.
So, obviously placing a gun between the hot cylinder-banks of an engine, or behind a hot air-cooled radial will mean you can fire it that much less before it's in danger. Designers had to figure out clever ways of venting air over the guns and to the ammunition, to keep it cool. (Of course, with wing-mounted guns, the problem is the opposite...they need HOT air to keep them from freezing up!)
The vibrations of the engine can effect reliability, and accuracy too, so you need vibration-absorbing mounts that will ALSO keep the gun aligned on target.
The benefits of course are that you get a tighter pattern, and can fire from any range...wing guns need to "converge" at a certain distance, and trying to hit a target at less or more than this distance is difficult. Probably the most notorious for this is the eight-gun Spitfires, who's guns were spread out along almost the entire length of the wing. Not only is convergence a problem, but an airplanes wings flex a considerable amount during maneuvers (you don't have to twitch very much to miss a target at 250yds with a rifle!). The further out on the wing, the more the gun will flex.
And then there's the whole issue with some guns freezing and not firing, so the designers have to pipe hot air to keep them warm, and the red squares around the muzzles of RAF fighters is actually tape, to keep condensation and cold air out of the gun bay until it fires. Maybe that's common knowledge to most people, but I only learned that myself a year or two ago.
And of course, like you said, having the weight out in the wings means the plane is less "snappy" in a roll. That's one major reason that the P-38 couldn't keep up with single-engine fighters...it rolled fast enough once it got going, but it took longer to "get moving" when the yoke was turned. (Of course, I'm speaking of the weight of the engines, not of guns...the P-38's centerline-mounted guns were just about ideal, but only because it wasn't competing with and engine for space)
So you could more or less say that no-one will ever agree to a "best" one...it's all a matter of perspective. In pure performance, fuselage guns were the best, providing a tighter pattern, reducing flex, no convergence, etc. But this superior performance was balanced against the difficulty of installation, and they tended to be less reliable and rate-of-fire was reduced. More or less, you could get the same effectiveness with only 2/3 or 1/2 of the number of guns needed to get the same effect from wing-mounted guns.
Simply put, one could say that for fighter-vs-fighter combat, fuselage guns gave an edge, less so for shooting down bombers, etc. But for a plane mostly used for strafing and ground attack, the convergence, etc was less of a problem. Mostly the targets were stationary, and an attack run would generally be made without much violent maneuvering.
Sigh...I said I wasn't going to go over all that! Why do I do these things to myself? I wonder what the maximum length of a post can be, anyway?
BTW...you really said "Haynes manual" for a Hurricane? LOL, the only "Haynes manuals" I've ever seen around here are the ones for home-mechanics who want to work on their own cars! Is this by any chance the same "Haynes"? Or is that just a coincidence?

Okay everyone...sorry for making it so long. I'll try to keep it shorter in the future...its just too much to absorb at once!

Cheers,
Johnny .45