http://www.idkfa.com/v3 idkfa: syndicated http://www.idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5067 True, forces on the lid start to compare to the same force behind the bullet. The lid isn't the only thing in consideration. The BBs, the nails, the metal shards, the fine components of the bomb are much smaller area than the lid of the pressure cooker. 100 psig behind the BB, compared to 20,000psig behind the BB? The force behind the bomb components are much smaller compared to using a better delivery vehicle capable of higher pressures. This points to poor technical sophistication, and an amateur understanding. The maximum velocity of components from a bomb is dependent on the pressures generated during bomb's explosion/combustion. If it's topping out at 100psig, that's a mere fraction of what it's capable of. kitacek@idkfa.com (kitacek) Mercy General Wed, 17 Apr 2013 21:44:48 -0800 http://idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5067 http://www.idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5066 .45ACP diameter is 0.452", which yields a cross sectional area of 0.6418 in^2. Multiplying by 20E3 lb_f/in^2, you get 12837 lb_f. My pressure cooker at home is ~14" diameter, which yields a cross sectional area of ~154in^2. Multiplying by a (likely conservative) 100 lb_f/in^2 relief pressure, you get 15394 lb_f. There are, granted, probably some volume / force dispersion things going on, but the pent up forces themselves can be comparable. When you do blast radius surveys for industrial equipment, pressures in the neighborhood of 5psig cause serious concern. When considering damage potential, it's critical to include the area over which a force is applied. 8psig can be just as scary as 80,000 psig (well, if said force is blowing a building over onto you, that is. Or a manway / manhole cover). conrad@idkfa.com (conrad) Mercy General Wed, 17 Apr 2013 20:39:12 -0800 http://idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5066 http://www.idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5065 Terrible as it sounds, I'm glad to hear this didn't turn out as bad as it could have. Though, it's terrible to think on the crazies doing the same math you are, or, thinking they can do better. kaiden@idkfa.com (kaiden) Mercy General Wed, 17 Apr 2013 20:21:51 -0800 http://idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5065 http://www.idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5064 A pressure cooker is a poor choice for an explosive shell, compared to other options. The maximum velocity of components from a bomb is dependent on the pressures generated during bomb's explosion/combustion. High explosives are engineered to generate the highest possible pressures for a given weight of explosive. Gunpowder is capable of very high pressures, but a pressure cooker is a poor delivery vehicle. A common pressure cooker, in order to be a truly effective weapon, needs to have it's safety valves defeated, and the lid welded to the saucepan. Let's take a .45ACP cartridge. In order to send the bullet downrange, pressures of ~20,000 psig are generated by the gunpowder. Or a .300 Magnum. In order to send the bullet downrange, pressures of ~60,000 psig are generated. A pressure cooker's safety valves start releasing pressure at about 25 psig, and the lid's connections generally fail around 200 psig. This is orders of magnitudes less than what's capable in gunpowder. Which is why a pressure cooker is a poor choice. And one of the deformed lids was found on a roof? Only possible if the pressure cookers were set down with the lid up. If this person had set it up on the side, more than 3 people would have died. It would have sent most of the shrapnel, the lid, and most of the explosive force into the crowd. This goes to show that not much technical sophistication was involved in these bombs. Everything technical is pointing to garden-variety amateur. kitacek@idkfa.com (kitacek) Mercy General Wed, 17 Apr 2013 19:50:30 -0800 http://idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5064 http://www.idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5058 Ok, twitter and facebook won't work for this post, and no way in hell i'm posting in the comments section on news sites. The bombs that exploded in Boston yesterday were technically unsophisticated weapons. The white smoke following the fireball is characteristic of a rapid combustion event, such as black powder, not a chemical explosion, such as plastic explosives or gunpowder-laced nitroglycerin (TNT). ANFO, another rapid combustion based propellant, leaves black smoke after combustion due to the inclusion of diesel or heating oil as the oxidizer. So, if it's a black powder or similar explosion, and it used BBs or ball bearings, as news organizations are saying, that means it used materials that you could gather in a shopping trip to Walmart and Sportsman's Warehouse - black powder, BBs, a digital watch w/alarm, a primer from handloading (or even just a bullet, any caliber, any cartridge), and a container. that's technically unsophisticated. We know from two different wars in Asia that our opponent force there is very sophisticated, in the type of explosives, in the manner of delivery, in the activation device, and effectiveness of the placement. I'd be really surprised if we find out this attack comes from a foreign source. They'd either be really stupid or really smart. I can't decide. kitacek@idkfa.com (kitacek) Mercy General Tue, 16 Apr 2013 13:19:15 -0800 http://idkfa.com/v3/v_thread.php?thread_id=5058&msg_id=5058