Ricky Posted October 26, 2014 Share Posted October 26, 2014 Don't know how to word the title properly. Basically I'm getting into hosting military simulation/reenactment type events and some fields have allowed me to use pyro.So far we've just used some small artillery type things that shoot up in the air and go bang. Nothing fancy, but I'm hoping to increase the immersion and have pyro go off on the ground to re-present mortar. Few things I'm aiming for: 1. Very loud sound - we use replica grenades that go a little over 110db so around that range would be great2. Very big smoke cloud - since its trying to re-create a mortar it should make a nice big smoke cloud after.3. Be safe to be near - goal is to have an admin place these around a group of people (maybe 25ft+ away) and have it go off yet still be safe by avoiding shrapnel and burns. Some people have suggested getting a short but large metal tube and put a black powder charge in there and remote detonate it so the explosion gets forced upwards so its relatively safe to be near. Any ideas? I'd appreciate it! Here's a short clip of what we had used. Makeshift build, but its all metal and worked great.Unfortunately the pull string popper ignitor things didn't arrive in time so had to use a fuse. Link to comment Share on other sites More sharing options...
MrB Posted October 26, 2014 Share Posted October 26, 2014 Thick steel wook, explosive charge, and sand or moist sawdust. I'd avoid over wetting, or wetting the sand much at all.These types of effects are used to mimic shell impacts in movies, (Well, they don't use wooks, but a specially manufactured device, with approximately the same shape) are fairly directional, and given that the load isn't made up with content that has shrapnel potential, shouldn't hurt anything not standing directly in the line of fire. But 25 feet... I dunno about that one. I'd want something that stopped the direct path, to the people, a small mound of dirt, a couple of sandbags, something like that.B! Link to comment Share on other sites More sharing options...
Ricky Posted October 26, 2014 Author Share Posted October 26, 2014 Thanks! It doesn't have to be extremely realistic though. Safety is first over how it looks. Link to comment Share on other sites More sharing options...
nater Posted October 26, 2014 Share Posted October 26, 2014 Again, the same advice I gave in another thread. When you have "performers", make sure you know and follow NFPA 1126 for close proximate effects. This means having the proper licenses and permits from the AHJ where the event is held. Link to comment Share on other sites More sharing options...
MrB Posted October 26, 2014 Share Posted October 26, 2014 Thanks! It doesn't have to be extremely realistic though. Safety is first over how it looks. Actually, ground effects like these are VERY realistic. It's the real deal, and that means people that get caught in the fire actually gets hurt. You can limit the range, and damage caused by selecting lighter substrate, but make no mistake. A ground effect set up to mimic a projectile impact will cause just as bad secondary damages as the actual projectile impact would. Make sure you use debris free loads. There can be absolutely no rocks or gravel on this, or it will find someone to hit, and hurt. I swear, it's a freaking homing missile. Small grain sand turns in to a dust-cloud, potting earth looks like "dirt" impacts, and sawdust looks like... Well, something. Not really natural, but close enough to make people not notice. You can mix the lot, just make sure nothing that can burn is left dry, and don't compress it over the charge. The charge might need it's own confinement, use paper, preferably hemis so you don't need any hard plugs. We used flash for this, making the confinement needed quite low. With BP i imagine you need the equivalent of any shell used for a pyro display.B! Link to comment Share on other sites More sharing options...
Arthur Posted October 26, 2014 Share Posted October 26, 2014 With movie type SFX you need to do lots of tests before you get to put people near. Sometimes the effect is done in pieces, with air cannons moving soft light debris being a separate cue from the things that go bang, flash or smoke. Link to comment Share on other sites More sharing options...
Mumbles Posted October 26, 2014 Share Posted October 26, 2014 You might want to check out this thread: http://www.amateurpyro.com/forums/topic/8536-fake-explosions/ You've gotten good advice here. We love seeing projects like this, but only if they're done safely. Hopefully we can help you figure stuff out. Out of curiosity, are you more interested in simulated mortar hits from a flying debris side of things, or more the actual explosion side of things? The flashpot method you described will work for sound. BP will probably better simulate cannonfire or larger explosions, as it will be a lower toned boom. Flashpots with actual theatrical flash will be a higher pitch crack, but probably perceptibly louder. Arthur is right. Please run plenty of tests without people around first just to make sure you have this down. Link to comment Share on other sites More sharing options...
MrB Posted October 26, 2014 Share Posted October 26, 2014 Arthur is right. Please run plenty of tests without people around first just to make sure you have this down. Insane amounts of tests should be done. Luckily, these tests are fun to do, so i doubt that will be a problem. Also, something worth noting. The shape of the "device" has a lot to do with the way it throws out stuff.Shallow wok shapes are good for creating large non-directional, or perhaps i should say omni-directional clouds of what ever they are charged with. They also look the same regardless of the direction people see them from. Round cone shapes tend to be at a steeper angle, and throws stuff more "up" and then there is always more exotic shapes where a side, two or even three is a straight edge, and the other / others are at a steep angle. These throw stuff in pretty predictable directions and can therefore be used closer to stuff that cant be allowed to take damage. I'd say these are more dangerous then the wok shape, since they tempt you to put them closer to people, and people really aren't made to be near explosions. Small or other-ways. The thread Mumbles links is a good read indeed. I seam to have missed that thread, had no idea it was there. This forum never stop amazing me.B! Link to comment Share on other sites More sharing options...
Arthur Posted October 27, 2014 Share Posted October 27, 2014 Go ferret through the UKPS forum and youtube channel. Malcolm Smith did the pyro for a remake of the Thunderbirds series and his lecture at the 2014AGM should be on the youtube channel and discussed on the forum. OK it was small scale model work run at 125fps but all the techniques you need are there just smaller. Bits of leather and rubber from a shoe repairer are probably the best for low impact, reusable debris. Big bags of potting compost provide debris that you can just leave there without clearing up too much Link to comment Share on other sites More sharing options...
Arthur Posted October 27, 2014 Share Posted October 27, 2014 Link to comment Share on other sites More sharing options...
AldoSPyro Posted November 11, 2014 Share Posted November 11, 2014 (edited) What they use for artillery shell impact effects in movies is usually (if not cgi), a black powder charge surrounded by cement powder i think :/ here's a video of one: Edited November 11, 2014 by AldoSPyro Link to comment Share on other sites More sharing options...
Arthur Posted November 11, 2014 Share Posted November 11, 2014 Cement is a poor material for dust clouds, 1/it's corrosive and 2/ it compacts at the explosion site to make small bits of shrapnel. A better material is potassium chloride which is available as a fertiliser but doesn't explode. It spreads as white dust and there is no need to remove it later as green plants love a dose of it. Link to comment Share on other sites More sharing options...
Ubehage Posted November 12, 2014 Share Posted November 12, 2014 Cement is a poor material for dust clouds, 1/it's corrosive and 2/ it compacts at the explosion site to make small bits of shrapnel. A better material is potassium chloride which is available as a fertiliser but doesn't explode. It spreads as white dust and there is no need to remove it later as green plants love a dose of it. Unfortunately, that is going extinct in Europe Last shipment for anyone, was september 1st. Link to comment Share on other sites More sharing options...
dagabu Posted November 13, 2014 Share Posted November 13, 2014 Really? I just emailed a cohort in England about a chloride cell and he can get bags and bags of it easily off the shelf... Link to comment Share on other sites More sharing options...
MrB Posted November 13, 2014 Share Posted November 13, 2014 Really? I just emailed a cohort in England about a chloride cell and he can get bags and bags of it easily off the shelf...Weird, since EU banned the stuff. Official pyro clubs have been granted the "same" ability to buy the stuff as commercial manufacturers have, but as a "person" it's pretty much impossible to be granted that right. Late 2016 it's going to be a "terrorist offense" even to own the stuff as a private person, without a special permit. Supposedly UK pyros will be provided some means of achieving such a permit, but for as far as i know, everyone else in the EU is pretty much screwed, not having a active pyro hobby scene. Meh, even as i type this, i feel my linguistic skills working against me. Let me know if anything is unclear.B! Link to comment Share on other sites More sharing options...
Arthur Posted November 13, 2014 Share Posted November 13, 2014 Chlorates and perchlorates are restricted from sale to individuals in the EU, the UK enactment of the precursors directive included the possibility of an individual getting a permit to purchase. Chlorides are still on sale if you have the money! Link to comment Share on other sites More sharing options...
MrB Posted November 13, 2014 Share Posted November 13, 2014 Crap, i simply wasn't paying attention enough. Yes, as Arthur is saying, the ban is (per)chlorates, not chloride.B! Link to comment Share on other sites More sharing options...
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