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  • This is my go to site for Naval weapons.

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    • Originally posted by Battleship IOWA View Post
      It's a common myth that a big gun ship like the Iowa actually recoils from a board sides and slides sideways. What you are seeing in the photo is the water being pulled away from the ship from the force of the blast wave. The weight of the shells being fired would have to outweigh the ship itself for it to slide sideways.
      Perfectly correct - unless you want to use Naval terminology. The "blast wave" you described is technically called "over pressure", or in Land Lubber terms "muzzle blast". In the 1980's the Navy finally had a chance to measure how much over pressure is created depending upon propellent load and position of the gun's muzzle. Dr. Yagla, of Dahlgren, was in charge of the tests and had sensors placed all around the New Jersey. Yes, some damage was caused. I was aboard at the time and after firing a gun at a certain angle near some superstructure of critical use (such as the fueling-at-sea kingpost on the starboard side, I merely asked him to hold off firing for a few minutes so I could go outside and inspect for any damage. I have a couple of pieces of what used to be WW II era antenna base (not used anyway for 1980's modernization).

      We already had some pretty good guesses as to what would happen. For example; Life Rafts. By that time all ships were being equipped with encapsulated rafts that are packed into a fiberglass container looking like a cross between a football and a beer barrel. They way they worked is that if the crew had to abandon ship (or provide rafts for survivors of another disaster) all the crew would have to do is "drop" the containers in the water. They were packed heavily enough so they would sink a couple of feet and then the pressure sensor would pop open the container into two halves, the raft would then automatically inflate and float to the circus.

      But suspecting that the over pressure from the 16-inchers would be too much we installed the old fashioned soft packs of three rafts per stowage rack. But to make sure, on the Big J's first gunnery trial we strapped down some encapsulated rafts on top of the soft packs nearest the guns.

      Sure enough, they all popped open. The three high soft packs survived however as their pressure trigger is located on the back side of the rack. It looks like the desk bell you would ring for a hotel manager because it was also designed to be manually activated also by merely whacking it with the edge of your fist rather than waiting for the ship to capsize and allow water pressure to release it.
      Able to leap tall tales in a single groan.

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      • The Iowa I believe also had some problems with covers on the CIWS mounts popping open or tripping interlocks, or so I was told by the CIWS techs onboard.

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        • Originally posted by DonBelt View Post
          The Iowa I believe also had some problems with covers on the CIWS mounts popping open or tripping interlocks, or so I was told by the CIWS techs onboard.
          During those gunnery trials, the fiberglass RADOMES on the CIWS (R2D2 with an attitude) were our highest concern. Therefore over pressure sensors were also mounted on them. They did withstand a higher pressure than we expected, but it doesn't take an Einstein to assume that after scores of rounds had been fired that the domes would start weakening and show some cracks. Though that did not affect their capability, keeping them dry inside was the problem. However, plastic duct tape (no metal in the weave) gave a temporary rain proofing until new domes could be issued.

          Remember; If it moves and not supposed to move you get out the Duct Tape.
          If it doesn't move but supposed to move, you get out the WD-40.

          Just some difference than the older Navy axiom; If it moves, grease it. If it doesn't move, paint it.
          Able to leap tall tales in a single groan.

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          • It's not the weight that would propel the ship; it's the momentum. Momentum = mass * velocity.

            That's why guns kick even though the mass of the bullet is considerably lower than the mass of the gun.

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            • Originally posted by Sanjac View Post
              It's not the weight that would propel the ship; it's the momentum. Momentum = mass * velocity.

              That's why guns kick even though the mass of the bullet is considerably lower than the mass of the gun.
              The 16"/50 main batteries of an Iowa class Battleship have a recoil slide of a full FOUR FEET. That's for full service loads of SIX 110 lb bags of propellent. Many shoots use reduced service charges. A reduced service charge could be fewer than six 110 lb bags or a number of 55 lb bags of "reduced" charge propellent.

              But there is a problem with those smaller bags. They are loaded behind the projectile while the barrel is at "Battery" position (about 3 degrees above zero level). Sometimes those smaller bags get pushed a tad too far in. Then when the barrel is elevated, they slide back against the mushroom head of the breech block and often "tilt" or "sag" just enough so the primer cartridge in the breech (sort of a modified 11mm Remington or a .43 Spanish) does not line up with any part of the red quilted patch of black powder that sets off the main propellent.

              Check out Paul Stillwell's book on the New Jersey during her Viet Nam deployment. There is a photo of a 55 lb bag with a hole burned through the sulk covering but a couple of inches away from the edge of the black powder patch. After that bag was thrown overboard, Admiral Snyder (then Captain of the Big J) ordered NEVER to us those small reduced charges again.

              Unfortunately many of today's experts overlook such historical documentation and we have had some incidents of Reduced Service Charge bags not going off. If that gun had already fired some rounds just before the "miss-fire" you have to wait up to an hour for any embers left in the chamber to set off a "hang" fire.

              Out all the chances I had to cross train while in the Army Reserves (tank crewman) or the Naval Shipyard (shipfitter, draftsman, Naval architect), I always stayed away for Ordnance. I've had hang fires before with old .22 rimfire ammo (and even my .45 target pistol using archaic ACP steel cased ammo made in the 1940's) to EVER want to remove a "suspected" miss-fire and it turns out to be a hang fire.
              Able to leap tall tales in a single groan.

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              • Originally posted by Sanjac View Post
                It's not the weight that would propel the ship; it's the momentum. Momentum = mass * velocity.

                That's why guns kick even though the mass of the bullet is considerably lower than the mass of the gun.
                I guess I was thinking Newton's second & third laws of motion.

                Second law: The vector sum of the external forces F on an object is equal to the mass m of that object multiplied by the acceleration vector a of the object: F = ma.
                Third law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
                Craig Johnson

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                • I should mention that although I have never worked on battleships or any kind of marine systems, I am (or was) an engineer. I did airplanes and rockets and spacecraft instead of things that float on water; much easier in some ways easier than ships while in others much more difficult.

                  Recoil systems are great, but it's important to understand that they don't really absorb the change in momentum imparted by the departing shell; they spread out its effect over time. All of the momentum of the departing shells will eventually (in seconds) be reacted by the hull against the water.

                  So while the observable effect of the shells on the ship's motion might be too small for casual human observation, it definitely is happening and must happen.

                  For what it's worth, this discussion made me curious enough to root around on the web to see if I could find an authoritative answer to how pronounced the motion of the ship might be. I haven't found one; but I did find several essays about it, some even with really impressive-looking equations. A couple of guys seem to agree that if the Iowa were to fire all nine of her 16-inch guns in the same direction at zero elevation, this would give the ship an initial velocity increment of 6 inches per second.

                  That would not be enough to cause the wake shown in the picture I originally referenced. (That's clearly not the effect of the pressure from the muzzle blast. The muzzle blast appears as an elliptically shaped disturbance in the water, which you can see in other pictures of the Iowa firing her guns.) I suspect that what we are seeing is really just some smooth water from ocean surface waves being damped by the presence of the ship.

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                  • If the ship where to move that much that quickly it would put everyone standing on board on the floor and everything not bolted down would fly too. Can you imagine the carnage.
                    If you have ever stood on a truck bed and have it start moving before you are ready you know how little movement it takes to put you you on your ass.
                    Craig Johnson

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                    • Its the effects of overlapping muzzle blast. When you say another picture that showed an elliptical disturbance, that was one gun firing. Here you have the effects of 2 tubes per mount firing. And their fire is staggered within each mount. Blow the picture up and you can see that on the forward turret. Tube 1 (right) has just fired and is about to recoil, tube 2 is stationary and tube 3 (Left) has fired and most likely returning to battery (counter recoil).

                      In the picture, you have at least 2 separate shock waves per turret initiated at different times, although very close to each other. (0.06 sec?)

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                      • Originally posted by Sanjac View Post
                        For what it's worth, this discussion made me curious enough to root around on the web to see if I could find an authoritative answer to how pronounced the motion of the ship might be. I haven't found one; but I did find several essays about it, some even with really impressive-looking equations. A couple of guys seem to agree that if the Iowa were to fire all nine of her 16-inch guns in the same direction at zero elevation, this would give the ship an initial velocity increment of 6 inches per second.
                        That sounds about right; I was guessing, just doing a rough calculation, that it couldn't be more than a few inches of movement and, as you said, that would be at zero degrees elevation. After all, we're talking about a few 2,000 lbs. shells moving a 45,000 ton ship; even if it were a full broadside, that would be 18,000 lbs. trying to move 90,000,000 lbs.! As you can see, the math just doesn't add up.
                        "There is never enough time to do or say all the things that we would wish. The thing is to try to do as much as you can in the time that you have. Remember Scrooge, time is short, and suddenly, you're not there any more." -Ghost of Christmas Present, Scrooge

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                        • Okay guys, let's put this thing to rest. As far back as the Korean War (when all four Iowas were in action) we now had some fairly decent helicopters and high speed cameras. Photo studies of one of the ships (the name was never given as far as I know) showed that the ship did not move a single inch.

                          BUT, recoil is NOT the effect of a 1900 lb Hi-Cap or a 2700 lb AP leaving the muzzle. It's the "rocket" blast of the propellant being expelled out of the muzzle.

                          THAT'S what operates a recoil operated firearm anywhere from a .380 pistol to a M1928 Thompson SMG to a .50 caliber "Mah-Deuce". So, forget how much the "bullet" weighs, calculate the overpressure (muzzle blast) coming out the end of that tube.

                          Umm, yeah. On tanks their main gun barrel is called a "Tube". Because basically that's all it really is. A steel tube with rifling in it --- except with the 8" smooth bore we tested on the USS Hull and the 120 mm smooth bore on our modern M1A1 tanks that use fin stabilized projectiles.

                          My M-1 Garands and my M-1 Carbine (which I wish I never sold) were GAS operated by tapping off some gas pressure through a hole in the barrel to push an operating rod back. But the M1919 Browning co-axially mounted MG on my tank and the M2 .50 on top of the turret were RECOIL operated. But the 76mm on my tank worked the same as the 5"/38's and the 16"/45's and /50's on the FAST Battleships. Recoil from the high pressure gases push the barrel housing back. On a 76mm it was only one foot (max). On the 16-inchers it was four foot (max). The return from recoil would open the breech on my 76 but on a BB it just allowed to breech to go back to battery so it could be manually opened for reload.

                          On tank guns you see a "can shaped" object just aft of the blast deflector (it is NOT a muzzle brake) or in the middle of the tube. It bleeds off high pressure gases from the barrel through angled holes drilled in the barrel itself. When the round clears and the propelling pressure drops, the pressurized gases in that "Bore evacuator" would shoot out the muzzle carrying noxious smoke and embers out so we didn't have to use the fan on top of the turret that much for "clean" air.

                          The 16 inchers, on the other hand, used a Medium Pressure Air Compressor (150 to 225 psi) down below the 3rd deck to push the smoke on out. If you ever watch a film (or video nowadays) of a 16-inch gun firing, you will see that right after the barrel returns from recoil a puff of grayish white smoke popping out. That then clears the tube well enough to open the breech and reload without the turret crew having to wear air resperators.

                          Oh, enough of this. I've had some bad days. I goofed up to download Windows 10 and it's horrible. I had a tech put me back on Windows 7 but I've lost my Adobe Flash Player and my scanning of negatives and I don't know what else. Since OPM has decided not to give me a COLA this year (since gas prices went down in September of last year -- anybody hear of a lamer excuse?) I'm trying to download new drivers but I'm not a computer Geek. HP keeps saying my credit card was not filled in right (I tried 3 of them) and I can't get a disk for my G4050 scanner to work off of Windows 7 (worked GREAT on XP -- my old PC).

                          So forgive me for sounding so up tight. I've got most of my strength back in my left leg after major back surgery but the left side of my lower back still feels like I couldn't outrun a Bull in a narrow Spanish street.
                          Able to leap tall tales in a single groan.

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                          • Recoil has everything to do with the projectile. (OK there as=re a lot more factors) Ask Mr Newton.

                            Or an easy way to prove it would be to take the projectile off a cartridge an fire it through your recoil operated gun. Nothing will happen. Same as firing a blank through a M101 Howitzer when used as a salute gun. No recoil.

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                            • Originally posted by Gun Grape View Post
                              Recoil has everything to do with the projectile. (OK there as=re a lot more factors) Ask Mr Newton.

                              Or an easy way to prove it would be to take the projectile off a cartridge an fire it through your recoil operated gun. Nothing will happen. Same as firing a blank through a M101 Howitzer when used as a salute gun. No recoil.
                              Sorry, but all the weight of the projectile does is allow the expanding gases of the propellent to build up pressure. I live out here near Hollywierd land and went to the MGM auction many years ago (bought a Dutch .43 Spanish Beaumont made in 1874 that had only 2 digits in the serial number).

                              The previous weekend was the pre-auction public inspection of all the items to be sold including M-1 Garands. They were all fairly well abused but their gas operated actions worked perfectly with blanks. Even recoil operated guns, such as Lugers, worked well.

                              Why with blanks? Simple. The prop department merely tapped a thread in the muzzle of each gun and screwed in a plug that had a small hole drilled through it. The plug allowed enough pressure to build up to work the action. The small hole allowed smoke and flame to spurt out to make the audience think live ammo was being used.

                              Today, we have blank adapters that fit on the muzzles of M-1 Garands and M-14s. They look like a miniature grenade launcher but serve the same purpose of a threaded plug that would otherwise ruin about an inch of the rifling. After all, our saluting teams in the American Legion and VFW actually OWN their own rifles and would club anybody with a walnut butt stock who would attempt to ream out the muzzle of their personal rifle. Their is no bullet that comes out and the blank adapter never moves.

                              Also I think on your Land Forces board somebody posted a photo of a BIG blank adapter fitted to an M-2 .50 caliber Machine Gun. But that was a real gun. In Audie Murphy's movie, "To Hell and Back" - a recreation of his own combat experience, it shows him firing an M-2 from the top of an M-4 Sherman tank (much to Audie's disgust as he said it was supposed to be an M-18 Hellcat -- but there were no restored M-18s around for the movie company to rent). If you look very closely (and very fast), you can spot the air hose and electrical wire that operated the COPY MODEL of the famous Mah-Deuce that works only on compressed air and electric sparks. That's if you have a copy of the original movie. DVD editions have photo shopped that hose and wire out.

                              So, since the gas restrictor plugs never leave the barrel (hopefully for the extras being "shot" at) it's the gas PRESSURE that builds up the force to "jet" out the end of a barrel to cause recoil. Try it sometime with your souvenir bazooka or RPG round. Take the warhead off, press the forward end against your shoulder with the exhaust end pointing about 45 degrees downward and fire it.

                              Oh, and make sure you have the phone number of NASA so you can say, "Houston. We have a problem here."
                              Able to leap tall tales in a single groan.

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                              • Originally posted by RustyBattleship View Post
                                Sorry, but all the weight of the projectile does is allow the expanding gases of the propellent to build up pressure. I live out here near Hollywierd land and went to the MGM auction many years ago (bought a Dutch .43 Spanish Beaumont made in 1874 that had only 2 digits in the serial number).

                                The previous weekend was the pre-auction public inspection of all the items to be sold including M-1 Garands. They were all fairly well abused but their gas operated actions worked perfectly with blanks. Even recoil operated guns, such as Lugers, worked well.

                                Why with blanks? Simple. The prop department merely tapped a thread in the muzzle of each gun and screwed in a plug that had a small hole drilled through it. The plug allowed enough pressure to build up to work the action. The small hole allowed smoke and flame to spurt out to make the audience think live ammo was being used.

                                Today, we have blank adapters that fit on the muzzles of M-1 Garands and M-14s. They look like a miniature grenade launcher but serve the same purpose of a threaded plug that would otherwise ruin about an inch of the rifling. After all, our saluting teams in the American Legion and VFW actually OWN their own rifles and would club anybody with a walnut butt stock who would attempt to ream out the muzzle of their personal rifle. Their is no bullet that comes out and the blank adapter never moves.
                                You understand that in describing the blank firing adapter that it acts in the same way that the projectile does in creating recoil don't you? No pressure=No recoil.
                                The weight of the projectile plays a part in that a heavier projectile will need more pressure to get it moving/expel it from the barrel. More pressure=more recoil

                                Try shooting a blank through a rifle/pistol that isn't outfitted with a blank firing adapter. There will be no recoil. Consequently powder ignited through a unrestricted single diameter tube will not cause any force to be exerted to that tube. No pressure will accumulate. No recoil.

                                The projectile is like the BFA in that it allows pressure to be built up in the chamber, However once the pressure reaches a certain level the projectile is discharged.

                                So, since the gas restrictor plugs never leave the barrel (hopefully for the extras being "shot" at) it's the gas PRESSURE that builds up the force to "jet" out the end of a barrel to cause recoil. Try it sometime with your souvenir bazooka or RPG round. Take the warhead off, press the forward end against your shoulder with the exhaust end pointing about 45 degrees downward and fire it.

                                Oh, and make sure you have the phone number of NASA so you can say, "Houston. We have a problem here."
                                The reason that a RPG rocket exerts force is that the discharge tube is restricted (necked down) from the combustion chamber.We call that the nozzle. A rifle barrel does not have that. Unless you look at the WW2 german 2.8 cm sPzB 41 which had a "Squeeze barrel" that took the projectile 2.8MM projectile and turned it to a 2.0mm projectile at the muzzle.

                                Also note that the RPG produces thrust but not recoil.

                                Click image for larger version

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                                Last edited by Gun Grape; 03 Jan 16,, 22:05.

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