Nemo_Tenetur Posted December 11, 2007 Posted December 11, 2007 A friend told me that bigger shells (I guess 10 inch and more?) must be launched with several different lift charges ignited in sequence. Does anybody know more details about it? Different mesh sizes of the lift powder, delayed by how many milliseconds, method of delay ... ? Any information is welcome.
asilentbob Posted December 11, 2007 Posted December 11, 2007 Not for lifting out of the mortar. “One oz. of 2FA per pound of shell weight up to 10lbs. (1/16th) and half an ounce for every pound over 10lbs (1/32).” This is more applicable to spherical shells though. For cylindrical a rule of thumb is 1/5 to 1/6 the shells weight in 2Fa lift based on fit in the mortar. Loose use 1/5, tight use 1/6... I'm not 100% on how well this scales up though, so ill let someone else answer on if this applies with bigger cylindrical shells. He was probably getting confused with large multi-break canister shells that are stacked with a little separation charge between the canisters sometimes. This can reduce the possibility of shells damaging each other when they go off, though i seem to recall seeing something about a busty 3"+ commercial multi-break that didn't separate the charges like this and still functions fine nearly all the time.
Mumbles Posted December 11, 2007 Posted December 11, 2007 My details on this is that he doesn't know what he's talking about. ASB, the rule of thumb you posted is indeed for canister shells, not ball shells. Per weight ball shells need more lift due to an inefficient seal. The rule of thumb really only works for big shells. You can't expect to be lifting 200g 3" shells with 15g of commercial 2FA. Home made finer product will be different. Big shells do sometimes employ special lift techniques. There is one method where a black powder salute is placed below the shell with a sabot in between that makes an excellent seal and very efficiently uses the power. This only works with big heavy shells, as it needs adequate compression. Big shells will often use a stand off as to not crush the powder below. This can be as simple as a baggy of rice hulls or something similar between the BP and the shell. Also used are metal rings that the shell sits on with the BP around the ring like a donut. The metal ring is attached to the mortar, not the shell BTW. Cardboard rings attached to the shell will do the same. I've even heard of people using car tires for this purpose in 24" shells.
JCrewPyros Posted March 27, 2008 Posted March 27, 2008 Ok but alittle off topic... 24" Shells? Wow... That would be an amazing site to see... Are there many shell makers out there that actually make 24" inch shells? Sorry for posting... Just got me curious... I am trying to stay off the boards till I actually get some hands on time... Sorry!
TheSidewinder Posted March 27, 2008 Posted March 27, 2008 Don't worry about that, JPC. Post your questions. We're here to help. We only slap idiots who obviously haven't done even basic reseach before coming here and asking stupid quesions, half of them being about flash. M
Arthur Posted March 27, 2008 Posted March 27, 2008 There were some tries at armament guns that had several charges ignited in the barrel as the shell passed them- like milliseconds apart. Nothing in real use like that though. The lift for big shells is designed just as part of the whole product. The large amount of lift needed (compared to a 2") may mean a different choice of granule size and size distribution. In a short mortar all the lift has to fire while a small shell travels say 12 inches, in a larger shell the mortar will be 30 to 50 inches long so the rising accellerating shell is in the barrel for longer. Using a coarser grain of powder for lift means the lift takes slightly longer AND importantly the barrel isnt subjected to the extreme pressures of a fast lift powder.
mormanman Posted March 27, 2008 Posted March 27, 2008 Ok but alittle off topic... 24" Shells? Wow... That would be an amazing site to see... Are there many shell makers out there that actually make 24" inch shells? Sorry for posting... Just got me curious... I am trying to stay off the boards till I actually get some hands on time... Sorry! Yeah they do, I once asked a question similar to this and I think crazyboy said that Japan makes one 48 inches. I saw it on youtube. I was full of crossettes and I think shell of crossettes and and salutes. It was bad ass. That would be awesome to see right there.I think there is quite a few of companies that make the 24 incher.
pudidotdk Posted March 27, 2008 Posted March 27, 2008 Yeah they do, I once asked a question similar to this and I think crazyboy said that Japan makes one 48 inches.They don't just make one... they make them for sale to fireworks displays! Can you imagine ending your private fireworks show with a "little" surprise like that The center burst inside those huge shells are small granules, in size of our normal coarse corned BP. And as we go further towards the stars the burst increases in size to huge chunks of black powder "grains."A pyro friend of mine has a friend who has the descriptions to make one of those 48" shells... nice!
TheSidewinder Posted March 28, 2008 Posted March 28, 2008 It's rumored there will be a 24" at the next PGI. Gillette does have the space to satisfy setbacks, from what I understand As far as I know, it's just a rumor. It's an intriguing one, nevertheless. M
Frozentech Posted March 28, 2008 Posted March 28, 2008 I've seen a 24", in a magazine. It's been saved for a few years now, I am told the owner plans to fire it at a show on the 50th anniversary of Alaska statehood on January 3, 2009. I hope I can work that show ! I probably won't though, and will have to work one of the smaller "outlying" shows. The big shell will get fired in Anchorage or down at the state capitol in Juneau Either way, it's gonna be a state-wide party that night
TheSidewinder Posted March 28, 2008 Posted March 28, 2008 God, if they fire it in Juneau, they may as well shoot it off Mt. Everest. About the same percentage of Alaska residents will see it. I've been to Anchorage and the Kenai area. It's odd, how you can't drive to your own Capitol from about 99% of the State.
Mumbles Posted March 28, 2008 Posted March 28, 2008 Oh no, they only make 2 48" shells a year for some special festival that I am aware of. I only know of 1 factory that makes them, or even has the gun to shoot it from. You might be thinking of 36" which is somewhat commercially available, though at a huge price. 24" shells are still pretty rare to see. As Frozen has said generally only being used for very special events. I believe the Olympics in Sydney, Aus had a couple. The burst in these "big 'uns" is generally BP on cork. I believe + 1/2" cork is used normally. I've seen some very interesting videos. They are loaded in special ways. A port hole is cut out of the top and the stars/comets/shells are loaded in then. The burst is separated from the stars or shells with a bed sheet. To settle everything they very literally pound on them with a giant wooden sledge hammer. As far as lifting them goes, nothing different. They still use 2FA or 1FA. The size isn't that big of a difference. I was talking to a guy who has made a few 36" shells. He joked around that GOEX made pre-measured liftbags for him. IE the 25lb bags. Big shells like this do use a stand off. The weight would crush the grains very easily. The shell sits off the base of the gun a few inches on a stand(usually steel) or a car tire in the case of a 24" shell. There are some 36" shell pics here http://www.pyro.com/photos01.htm
jacob Posted March 28, 2008 Posted March 28, 2008 Where on earth would you find a tube big enough to shoot stuff like that out of?I'm sure plastic or fiberglass is out of the question. And how much do those things weigh?
Mumbles Posted March 28, 2008 Posted March 28, 2008 16" shells weigh about 7024" about 150lb36" around 350-400lbs48" comes in around 7-800lbs It depends a lot on what they're filled with. And yes, generally all steel. I think you may be able to get HDPE 16" and 24" though.
mormanman Posted March 28, 2008 Posted March 28, 2008 Concrete suer pipe. LOL. That was huge though. I would lose my temper loading that.
JCrewPyros Posted March 28, 2008 Posted March 28, 2008 <-- that is all I could do for a few minutes... Wow I am speechless... That 36 incher is amazing... 48 Inchers? people trying to hit the International Space Station with those things? Albeit you probably could see the shell effect from space! Thanks for all the information... I know it was alittle off track... But nice to see random massive things lol... Take care all...
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