Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Wmaker on September 18, 2008, 12:50:01 PM
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I've played with the new IL-2 NS-37 gun loadout offline and what surprised me was the fairly low recoil compared to the Hurri IID's Class S cannons for example. As far as I know it should actually be vice versa. By recoil AH-wise I mean the force that causes a downward movement of the aircraft's nose on the pitch-axis caused by the firing of these guns. I really don't know how exactly this "force" is modelled in AH as it doesn't cause the plane to roll backwards when firing the guns on ground while the plane is stationary. I know there really isn't an easy way to objectively measure this effect other than to look on the outside sideview and observe the rotation around the plane's CoG while firing the guns but I think the difference in this recoil effect between the NS-37 and S Class cannons very noticeable.
Here are couple of quotes from Mr. Williams' excellent article on tankbusting guns of WWII:
"The choice of mechanism is interesting: the best performer in terms of rate of fire was the NS-37, but that used a short-recoil mechanism which imposed considerable stresses on the aircraft carrying it (the initial aircraft installation, mounted to the engine, resulted in a cracked engine block). A long-recoil design like the Vickers Class S had only half the rate of fire, but the recoil was moderated into a smooth push which was much easier to manage. This not only meant fewer installation problems, but also reduced the disturbance to the aircraft, making it easier to keep the sights on target during a firing pass."
"The Yak-9T, with one NS-37 mounted on the engine and a synchronised 12.7mm Berezin, was a good fighter well able to look after itself, but it wasn't perfect in the anti-tank role. The gun's heavy recoil pushed the nose out of alignment, so only two or three shots could be fired before the pilot had to correct the aim"
http://www.quarry.nildram.co.uk/tankbusters.htm (http://www.quarry.nildram.co.uk/tankbusters.htm)
So it it seems that it should actually be the other way around. 40mm S Class gun should have less recoil than the NS-37. Especially the effect in the Yak-9T seems to be fairly mild indeed in AH.
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Just a wild guess, but perhaps difference in mass between Hurricane/Yak airframe, and IL-2?
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When your throttle is chopped you engage wheel locks to keep you from rolling. This is why on a CV you have to throttle up juuuuust enough to disengage wheel locks without enough power to pull you forward.
Try it on a CV deck. Taxi forward with full flaps and then reduce throttle so you can just barely see the deck move beneath your wheels (you're essentially moving same speed as CV) then fire the guns, see how far backwards they blow you.
I did this with a P-47N with full ammo and 8 guns on a runway once. I can't remember how I did it. I had to throttle up, and then held "fire all" and checked E6B. I was going backwards about 10mph or so!
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When your throttle is chopped you engage wheel locks to keep you from rolling. This is why on a CV you have to throttle up juuuuust enough to disengage wheel locks without enough power to pull you forward.
Try it on a CV deck. Taxi forward with full flaps and then reduce throttle so you can just barely see the deck move beneath your wheels (you're essentially moving same speed as CV) then fire the guns, see how far backwards they blow you.
I did this with a P-47N with full ammo and 8 guns on a runway once. I can't remember how I did it. I had to throttle up, and then held "fire all" and checked E6B. I was going backwards about 10mph or so!
:huh :huh
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Was I unclear? He was talking about being unable to test the recoil of the guns on the runway.
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Was I unclear? He was talking about being unable to test the recoil of the guns on the runway.
A little... should had prefaced with "Gun Recoil Test Procedure". I see what your getting at now.
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Sorry about the confusion, was typing in a hurry
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Just tried it, first with the P47D11.. got to 7mph... then with the Hurricane IID, S guns only, got to 6mph, and with the Il2 w/ NS37s I got to 4 mph.
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Guys, the IL-2 is a friggin tank compared to the Hurricane or the Yak. The much heavier mass will make a huge difference in how the recoil is handled.
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Just tried it, first with the P47D11.. got to 7mph... then with the Hurricane IID, S guns only, got to 6mph, and with the Il2 w/ NS37s I got to 4 mph.
Think of them as thruster jets, though. The P-47 has 8 of them, they are weaker but much faster (steady burn) and fire for a lot longer. That'll mean a lot more. For any given number of rounds, naturally, the bigger guns have more recoil. It just dissipates in between reload cycles :cool:
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When your throttle is chopped you engage wheel locks to keep you from rolling.
Quite frankly, I had no idea that this was the case. I'll do some testing myself.
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The Hurricane dips because the cannons are on the wings, below the center of mass, while the P-39 has them in the nose cone. Putting it on the center of mass of the aircraft makes it so it slows the plane down evenly, effectively eliminating the obvious effects of recoil that the hurri sees.
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The Hurricane dips because the cannons are on the wings, below the center of mass, while the P-39 has them in the nose cone. Putting it on the center of mass of the aircraft makes it so it slows the plane down evenly, effectively eliminating the obvious effects of recoil that the hurri sees.
This is about the NS37 cannons on the Il2, not the 37mm on the P39.
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In IL2 the cannons are nearer to wing than in both HurriD or Ju87G so with smaller distance from gun to thrust vector the effect should be smaller, and of course there is the a/c weight...
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Charge, I agree that the points you mentioned have a recoil reducing effect. Still I think the difference is quite big. There are many sources discussing about IL-2 and Yak-9T which mention that the recoil of the NS37 was such that only couple of aimed shot could be made at a time because of the recoil. That is almost the case for the Hurri2D but not for the IL-2 with the NS37.
Btw, I played a bit more offline and got the IL-2 going 40mph backwards on the runway concrete and it was still firmly accelerating. :D By calculating friction force caused by the runway (assuming the friction is linear) and using cannons to accelerate to a certain speed the acceleration and the force needed for it could be measured. Idealizing the recoil force as constant force and counting the rounds it takes to accelerate into that certain speed horisontal force component of a single shot could be isolated even though the RoFs are different. To measure the exact angle at which the planes are sitting on the ground might a bit tricky though. That would be needed to get the total force per shot.
...but I think I'm a bit too lazy to test this. HTC knows the numbers they are using and I'm hoping they are aware of this thread and check their numbers. If there is a discrepancy on the recoils between these weapons I hope they adjust the game accordingly.
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"The Mark IID proved devastatingly effective, though its increased weight and the drag of the underwing cannon did impose a performance penalty, and pilots had to fly slightly nose-down when firing the cannon, since the recoil tended to make the fighter pitch up."
http://www.faqs.org/docs/air/avhurr.html
Interesting. Underwing cannon causes HurriD to pitch up.
The sentence itself does not make sense. I'd think that you need to fly so that your sight points at the target in order to hit it so "flying nose down" does not mean anything except that you need to fly a bit nose down to hit ground targets. :P
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It makes sense to me that if the nose is going to experience a 'rise' during firing of the guns that I would hold nose low and strafe through my target.
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I have an account from a Hurri IID pilot which says the opposite: the recoil made the nose pitch down, so they eased the stick back the instant before firing to compensate.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk)