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carguy_
06-08-2004, 08:09 AM
Please don`t flame me.I`m a physics bonehead.The question relates to single MG/cannon fitted planes.

Now I know that the bigger convergence on MG151/20(Me109) is set,the bigger lob effect it creates.This makes aiming from little distances ineffective,so for ex. Mr.Gemini sets his cannon to 100m.
But is the m velocity lower than in say conv 170m?
I dunno but if convergence has an influence on m velocity then shouldn`t the shell be deadlier becuz it strucks aeroframe with more power?

Yeah,really basic question but rather important for shooting down planes.

http://carguy.w.interia.pl/tracki/sig23d.jpg

carguy_
06-08-2004, 08:09 AM
Please don`t flame me.I`m a physics bonehead.The question relates to single MG/cannon fitted planes.

Now I know that the bigger convergence on MG151/20(Me109) is set,the bigger lob effect it creates.This makes aiming from little distances ineffective,so for ex. Mr.Gemini sets his cannon to 100m.
But is the m velocity lower than in say conv 170m?
I dunno but if convergence has an influence on m velocity then shouldn`t the shell be deadlier becuz it strucks aeroframe with more power?

Yeah,really basic question but rather important for shooting down planes.

http://carguy.w.interia.pl/tracki/sig23d.jpg

cueceleches
06-08-2004, 08:37 AM
I don´t think convergence has any effect on muzzle velocity. Convergence is set by adjusting cannons inclination along both X and Y axes. i mean, more inclination towards the longitudinal axe of the plane, more convergence, less distance until bullets from cannons of opposite wings cross each other.
Muzzle velocity will always remain the same, AFAIK.

Sorry, I forgot: of course, if your convergence distance is set to a short one, let´s say 100 m, it´s obvious that if you hit a target, bullets will have more power and speed than if they hit at 300m. but that is not muzzle velocity, which only represents the speed at which a bullet comes out from the cannon muzzle.

Cippacometa
06-08-2004, 09:07 AM
Convergence has nothing to do with muzzle velocity.
MV is the speed of the bullet when it comes out of the gun barrel, and it depends on the type and quantity of explosive charge utilized, the charachteristic of the gun and of the barrel, etc.

Convergence is the degree at which a group of weapons are oriented on the horizontal plan.
If you set, for example, to 250 m the convergence of two wing mounted cannons, it means that the bullets coming out from the two guns will not go just straight, but will converge and meet 250 m in front of the aircraft.

In FB, "MG convergence" is linked to the weapon #1, while "cannon convergence" is linked to weapon #2.
Obviously, in a Bf.109 (MGs=#1 and cannon=#2) setting the cannon convergence will have no effect, since it is a single weapon and cannot converge with anything! http://ubbxforums.ubi.com/infopop/emoticons/icon_biggrin.gif
On the other hand, if you set let's say to 200 m the 2 MGs convergence, it means that if you hit with MGs a target at around 200 m distance, it will thake the hits of both MGs concentrated in a very little spot, thus resulting in more damage.

To see the effect of convergence, pick a 6 wing mounted MGs aircraft, let's say a P-40. Then set MGs convergence as little as possible (I believe it's 100 m) and fire: you'll see the tracers crossing just in front of you! Now, set at max distance (1000 m?) and fire: you'll see the tracers spread wide.

Ok? http://ubbxforums.ubi.com/infopop/emoticons/icon_wink.gif

BitwiseOp
06-08-2004, 09:10 AM
Convergence takes into account only where the shell(s) need to be at a given distance... this doesn't require knowledge of muzzle velocity except that of course a low velocity shell may have to be 'lobbed' more to get it into the right spot because it has low KE.

A low muzzle velocity weapon will of course require more lead in deflection shooting though because it takes the shells longer to reach the intersection with the target vector.

El Turo
06-08-2004, 09:18 AM
Of note:


The ballistic trajectory of the round from the 109's 20mm hub-cannon is such that if you select a 100m convergence OR a 400m convergence, it is the EXACT SAME trajectory.

This is because the 100m point is reached as the round is travelling "up" through the center of the gunsight, while the 400m convergence point is reached as the round falls "down" through the gunsight. (The round is being fired from "below" the gunsight.. in the hub)

Just something to keep in mind for future reference.

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Callsign "Turo" in IL2:FB & WWIIOL
______________________
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was once
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[This message was edited by H_Butcher on Tue June 08 2004 at 08:57 AM.]

Cippacometa
06-08-2004, 09:22 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by H_Butcher:
This is because the 100m point is reached as the round is travelling "up" through the center of the gunsight, while the 400m convergence point is reached as the round falls "down" through the gunsight.<HR></BLOCKQUOTE>

http://ubbxforums.ubi.com/images/smiley/blink.gif ???

cueceleches
06-08-2004, 09:35 AM
Yes, he means that the bullet follows a "lofted" trajectory,cutting twice the horizontal plan of the plane at different distances.

Cippacometa
06-08-2004, 10:21 AM
Yes, but this has nothing to do with convergence! http://ubbxforums.ubi.com/images/smiley/blink.gif
Besides, just try changing the convergence parameters of a single weapon on IL-2, like the Bf.109 nose cannon.
100, 200, 400, 1000 metres: nothing happens!

Dash_C.
06-08-2004, 10:34 AM
So convergence settings in FB can affect the "loftedness" of shells?

If so, how did 109 crews do that in real life with a hub mounted cannon? The cannon must remain straight as it is in the driveshaft of the propeller. Did FB just make this up?

El Turo
06-08-2004, 10:51 AM
Dash,

The hub-cannon is most assuredly adjustable in trajectory/height (this is the only way TO change your "convergence" range).


Cipp,

This directly pertains to convergence because the setting at which you select "convergence" is the range where all your weapons will meet in the center of your gunsight.

It just so happens that you get a 2 for 1 deal with the 100/400m setting because they follow the same ballistic trajectory. Similarly, you will have other corresponding convergence settings that are the same ballistic trajectory... the lower you go under 100m, the longer out the round will fall back through the sight down range (because the higher your gun will be adjusted upwards in angle).

This is very likely the reason you don't see much difference between a 75m convergence or a 700m convergence... they're almost identical. (Don't have the exact matching-ranges for anything else but 100/400m off hand)


Callsign "Turo" in IL2:FB & WWIIOL
______________________
This place
was once
a place
of worship
I thought,
reloading my rifle.

~V.

horseback
06-08-2004, 11:04 AM
'Convergence' in the context of the game refers to the distance at which your guns' rounds will appear to intersect with the crosshairs of your gunsight. In RL, armorers would set the a/c up so that it was level, and align the sight & each of the the guns so that they were all centered at the same point at a distance specified by the assigned pilot or the Squadron gunnery officer.

In some units, particularly P-47 operators, the guns were "harmonized." That is, the inner gun on each wing would be set to converge with the sight's crosshairs at, say, 400 yds, the next pair would be set to converge at 300 yds, the next at 225 yds, and the final pair would be set at 150 yds, thus getting that 'shotgun' effect some people like to talk about.

Muzzle velocity issue has been cleared up already.

cheers

horseback

"Here's your new Mustangs, boys. You can learn to fly'em on the way to the target. Cheers!" -LTCOL Don Blakeslee, 4th FG CO, February 27th, 1944

El Turo
06-08-2004, 11:26 AM
Yes, quite.

Although.. "harmonization" of that nature was put into place largely because the bulk of folks have/had very little gunnery skill.

Nearly every ace I have spoken with or listened to has said they used settings as low as 50m across the board.. and most preferred point-harmonization or even pattern-harmonization rather than spread-harmonization for the increase in concentrated hitting power.

Callsign "Turo" in IL2:FB & WWIIOL
______________________
This place
was once
a place
of worship
I thought,
reloading my rifle.

~V.

carguy_
06-08-2004, 11:29 AM
Ok,thanks for answers.

Regarding the lob effect.I understand that shells -say conv 200m- will have different(higher) lob than at conv 150m,so if they would contact an aeroframe at a certain distance and moment those two shells would hit it from a different angle?AFAIK optimal angle is 90deg vs the frame.

Uum,taking this all into account imagine a plane being hit from dead six.No way it`s gonna be even around 60deg contact with the frame of a wing for example,same with the tail.Thus a shell will not impact will full or even half of the potential force(at 90deg angle vs aeroframe) which leads to lesser damage.

Erm,so if the conv is set to minimum lob,there`s less chance for the target to take heavy damage,because the shell will always hit the frame from the same angle,whereas other,"higher" convergences create bigger lob thus varieting the possibilities of angles at which shells will hit the frame(never 90deg,but maybe 60,45,50).Deduction is that if I set conv to higher than 100m,even 140m then I`ll have bigger chances of causing serious/effective damage.

What do you think guys?

http://carguy.w.interia.pl/tracki/sig23d.jpg

horseback
06-08-2004, 12:00 PM
Butch-

Harmonizing wing mounted guns to a range as short as 50m pretty much limits you to 'tailgating.' A pilot with gunnery skills and a wing mounted armament of heavy MGs might find a cone of fire 250 yds/m long useful for deflection and or chopping up his target a bit before he has him 'ranged in.'

Nose mounted armament convergence would seem to be a simple matter of the rounds converging higher or lower than the center of the crosshairs, according to range. For that, especially given the lighter weight of fire, the greater impact from short range would be desireable, so you might want to 'dial in' a closer setting for your guns, knowing that your cone of fire is almost of infinite length, and as long as your target is centered N/S on your sight, you can hit him.

Wing mounted armament, on the other hand, imposes a certain amount of dispersion as your target moves away from your convergence range, so creating as long a tube of convergences as practical seems to me a good way to maximize your marksmanship.

I'll agree that nose mounted guns are more accurate, but I would dispute the idea that using wing guns to their best advantage is an indication of a lack of skill. Air combat is not skeet shooting; you have to make the most of the tools you have to work with, not conform to what the other guy arbitrarily supposes to be 'sporting' (and just coincidentally to his advantage).

cheers

horseback

"Here's your new Mustangs, boys. You can learn to fly'em on the way to the target. Cheers!" -LTCOL Don Blakeslee, 4th FG CO, February 27th, 1944

El Turo
06-08-2004, 12:32 PM
Carguy,

The mistake you're making in visualizing this is that the round does not come DOWN at 150m or 200m... it is still going UPwards on it's ballistic trajectory.

So, when you are firing at a plane from dead six at 100m range, your rounds are going to be coming from below your gunsight to target. That is why you must aim slightly above them if you are closer than your convergence range to hit them... and conversely a bit under them if you are too far (while using the 100m setting).

At some point beyond 100m, the projectile peaks out and begins dropping, finally falling back through the center of your gunsight at about 400m distance. THIS is where the projectile will actually be travelling slightly downward. However, the angle of impact will hardly be as much as 40 or 60 degrees when fired from straight 6 o'clock.. these rounds are travelling as much as 800-1000m/s, afterall. The slower the muzzle velocity, the more arc the round will have down-range. This is why P39 pilots often referred to the 37mm cannon as a grapefruit tosser (or as a softball pitching machine in a recent panel discussion I attended).

Hope that helps?

==============



Horse,

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>I'll agree that nose mounted guns are more accurate, but I would dispute the idea that using wing guns to their best advantage is an indication of a lack of skill. Air combat is not skeet shooting; you have to make the most of the tools you have to work with, not conform to what the other guy arbitrarily supposes to be 'sporting' (and just coincidentally to his advantage).<HR></BLOCKQUOTE>

Ehh.. I'm not sure I understand what you're responding to or trying to say here really. Sorry.

But I would take exception to your statement about skeet shooting. I would actually argue that air combat IS about skeet shooting. He who can estimate range, deflection and put rounds on target is going to kill the other guy and that, my friend, is the ONLY thing that matters in air combat. You don't get flags painted on the side of your ride for fancy flying.

As for the point-convergence 50m setting.. it suprised me too. But, that's what a panel of Aces giving a seminar panel discussion said they used (between 50-100m). Some of the other non-ace pilots in attendance said that they used the standardized harmonization settings because they weren't as good of shots and just wanted to land hits on the chance of a random lucky shot instead of a concentration of fire that was more likely to kill but more likely to miss as well.

Keep in mind that these were P47 and P51 pilots that I'm referring to.. so they didn't HAVE centerline armament. I've heard of P38 pilots setting their convergence pretty far out for lack of worry about angle-in of wing mounted armament (gunpods not withstanding).

Callsign "Turo" in IL2:FB & WWIIOL
______________________
This place
was once
a place
of worship
I thought,
reloading my rifle.

~V.

Martial1
06-08-2004, 12:46 PM
Just think of convergance like focusing the suns rays through a magnifying glass. Like sun light bullets will deliver more damage when focused on a single spot. Most damage caused the closer everything is. So convergance = 250m and firing from 250m behind you enemy = big damage. Firing from 500m away means your bullets will cross 250m behind your enemy and miss.

Regards

The Martial1

carguy_
06-08-2004, 01:01 PM
Ahh yes Butcher this helps alot.Finally understood.

http://carguy.w.interia.pl/tracki/sig23d.jpg

El Turo
06-08-2004, 01:11 PM
!S

BTW.. give that 100/400m convergence a try with the 20mm cannon.. I think you'll find that little bit of information rather helpful when closing on your prey from distance and then again as you make your final close-in pass.

Remember that a Spitfire fills the center-circle of the sight on the 109 wingtip-to-wingtip when they are at ~300m.. and will cross your sight from outer tickmark-to-tickmark at ~100m. With your 100m convergence, you will line them up on the center pipper when they are about 3/4 of the way filling your center circle or completely filling the whole sight (tickmark-to-tickmark).

(of course, this is assuming you're not using range-icons)

Otherwise you must adjust slightly above or below your target according to their actual range vs. your convergence/harmonization range setting.

Best,

~T.

Callsign "Turo" in IL2:FB & WWIIOL
______________________
This place
was once
a place
of worship
I thought,
reloading my rifle.

~V.

horseback
06-08-2004, 04:39 PM
Butch-

My reference to skeet shooting was because it's a game, a sport, but not life and death. I had (mistakenly) assumed that you were taking the point of view of many of the German aces who talked a great deal about the 'sport' of aerial combat, and spoke in the most condescending way about their American opponents who forced them to fight in a way not to their liking. There's always the implied idea that the Americans didn't have the marksmanship or flying skills needed to fight 'fair', despite the fact that aerial combat is more often like a knifing in an alley than a duel between 'knights of the air.'

They tend to emphasize the swarms of US fighters after the spring of '44, and ignore the hard fought air war over the Channel and France from early '43 until air superiority was largely acheived just before D-Day. It irks me to no end, and I went off on that theme a bit.

I agree with you about rounds on the target, but my recollection about the graduated convergences may have come from Pacific based units facing a more fragile and actively maneuvering opponent (although by US standards, everything else out there was pretty small & fragile).

I do recall some very successful Hellcat units using the kind of convergence I mentioned, and the Navy had a much higher standard for aerial gunnery than the Army Air Force pre-war (Naval Aviators were the only fighter pilots other than the Luftwaffe with formal training in deflection shooting). With the inner guns set for the greater ranges, your chances of hitting your target short of the convergence with them was still pretty great, so your fire would get heavier the closer to your target you got.

As I said, it was supposed to extend your cone of effective fire, instead of limiting you to a fifty yard long area of convergence, beyond or short of which your target is unlikely to take a disabling series of hits, even though he's right in front of you.

A really close-in convergence says more (to me) about your flying skills and ability to stay on top of a small plane trying to evade your fire without colliding with it.

cheers

horseback

"Here's your new Mustangs, boys. You can learn to fly'em on the way to the target. Cheers!" -LTCOL Don Blakeslee, 4th FG CO, February 27th, 1944

El Turo
06-08-2004, 05:22 PM
Ahh.. gotcha. I was really lost there for a minute!

http://ubbxforums.ubi.com/images/smiley/53.gif

Hehe..


The "standardized" pattern harmonization was put into place for just the reasons you state.. generally speaking, they were going up against lightly (relatively) armored fighter aircraft that didn't need many hits to bring down and had the group-tactics to wear down their opponents.

The bulk of pilots just weren't that great of shots, really.. most of us online are better shots than about 99% of the pilots that ever actually participated in WWII because of the sheer number of engagements we are able to jump into without any real reprocussion for screwing up.

That whole lack of "refly" button in your average WWII-era cockpit was rather unforgiving.

=]

Callsign "Turo" in IL2:FB & WWIIOL
______________________
This place
was once
a place
of worship
I thought,
reloading my rifle.

~V.