WEBVTT - TechStuff Classic: TechStuff is Under Siege 0:00:04.440 --> 0:00:12.720 Welcome to tech Stuff, a production from iHeartRadio. Hey there, 0:00:12.760 --> 0:00:16.720 and welcome to tech Stuff. I'm your host, Jonathan Strickland. 0:00:17.000 --> 0:00:20.720 I'm an executive producer with iHeartRadio and how the tech 0:00:20.760 --> 0:00:24.240 are you. It's time for a tech Stuff classic episode. 0:00:24.760 --> 0:00:28.480 And this episode is titled tech Stuff Is Under Siege. 0:00:29.120 --> 0:00:30.480 And I had to look it up just to make 0:00:30.520 --> 0:00:33.640 sure that it wasn't about that one Stephen Sagal movie. 0:00:33.800 --> 0:00:34.360 It is not. 0:00:34.920 --> 0:00:39.280 It is about siege engines, as in the giant types 0:00:39.680 --> 0:00:43.559 of military hardware used in the Middle Ages and thereabouts 0:00:43.840 --> 0:00:48.440 in order to lay siege to a fortified position, typically 0:00:48.479 --> 0:00:53.000 something like a castle or fortress. This episode originally published 0:00:53.040 --> 0:00:57.600 on April twelfth, twenty seventeen. Hope you enjoy today. 0:00:57.600 --> 0:01:01.560 I'm going to talk about siege in I thought it'd 0:01:01.600 --> 0:01:03.720 be kind of fun and sort of in the theme 0:01:04.000 --> 0:01:06.160 of looking back on history. 0:01:06.720 --> 0:01:09.800 Well, what is a siege engine? While it's a device meant. 0:01:09.640 --> 0:01:12.760 To allow an attacking army to gain entry to a 0:01:12.800 --> 0:01:17.560 fortified space, typically a fortified city or a castle, something 0:01:17.600 --> 0:01:21.839 along those lines, they're used to penetrate or destroy fortress 0:01:21.840 --> 0:01:25.000 walls or gates, and they tend to be enormous and 0:01:25.040 --> 0:01:29.720 they exert tremendous force in their operation. I'm going to 0:01:29.880 --> 0:01:33.319 focus on siege engines from ancient times to medieval history, 0:01:33.360 --> 0:01:36.600 but you should know that siege engines continued to evolve 0:01:36.720 --> 0:01:42.880 even after medieval era, even after the invention of gunpowder 0:01:42.959 --> 0:01:45.800 and the distribution of gunpowder. To be fair, gunpowder had 0:01:45.800 --> 0:01:49.680 been invented for a very long time before anyone over 0:01:49.680 --> 0:01:52.160 in medieval Europe figured out how to use it as 0:01:52.320 --> 0:01:58.160 a means for weaponry. And also, gunpowder ended up making 0:01:58.160 --> 0:02:00.960 a lot of the traditional city defenses ineffective. I'll talk 0:02:00.960 --> 0:02:04.600 about that more later on in this episode, but siege 0:02:04.640 --> 0:02:08.680 engines were used in both world Wars, actually, but I'm 0:02:08.720 --> 0:02:10.520 going to save that for a different episode. We're going 0:02:10.600 --> 0:02:13.080 to talk about the old stuff, this kind of stuff 0:02:13.120 --> 0:02:15.760 you might see in a movie about knights and royalty 0:02:15.840 --> 0:02:20.400 and stuff like that. So siege weapons were necessary to 0:02:20.520 --> 0:02:23.960 penetrate a fortified position, typically, like I said, a city 0:02:24.040 --> 0:02:26.360 or a castle. So why would you lay siege to 0:02:26.400 --> 0:02:30.040 such a place at all. Essentially, it's an effort to 0:02:30.080 --> 0:02:33.120 make the people inside surrender to the people outside. It 0:02:33.160 --> 0:02:36.359 seems pretty simple. Usually the people inside would include someone 0:02:36.400 --> 0:02:39.680 of importance who kind of had the authority to hand 0:02:39.800 --> 0:02:43.920 over the rule of law for that region to somebody else. 0:02:44.760 --> 0:02:47.840 And the word siege comes from a Latin word sidare, 0:02:48.160 --> 0:02:51.600 which means to sit, And that's pretty much what a 0:02:51.680 --> 0:02:55.120 sieging force does. It sits outside a fortified area and 0:02:55.200 --> 0:02:58.760 it waits. It also usually attempts to cut off supplies 0:02:58.800 --> 0:03:01.760 that are heading into the foried location, both food and 0:03:01.840 --> 0:03:04.560 water and other things, to push the people inside to 0:03:04.600 --> 0:03:08.760 the point of desperation so that they surrender. But sometimes 0:03:08.800 --> 0:03:12.200 a long wait just isn't convenient. You got places to go, 0:03:12.320 --> 0:03:15.920 people to meet, lands to conquer, so you can't really 0:03:16.000 --> 0:03:19.760 wait around for people to eat that last apple or 0:03:19.840 --> 0:03:23.639 to draw the last water from the well. You got 0:03:23.639 --> 0:03:25.639 to find a way to speed things up a little bit. 0:03:25.639 --> 0:03:27.880 You got to convince them that they need to give up, 0:03:28.600 --> 0:03:33.000 and maybe force them to give up, and that requires 0:03:33.040 --> 0:03:39.400 getting access to the place that's fortified. Thus seize engines. Now, 0:03:39.480 --> 0:03:44.000 archaeologists have uncovered evidence of fortified city walls from ancient 0:03:44.080 --> 0:03:46.840 cities all around the world, and in a way, you 0:03:46.840 --> 0:03:50.360 could say that human history is marked by innovations in 0:03:50.440 --> 0:03:53.960 ways to keep people safe and other innovations designed to 0:03:54.120 --> 0:03:58.240 overcome those protections. It gets a pretty grim when you 0:03:58.280 --> 0:04:01.840 start thinking about specifics and you get down to brass tacks, 0:04:01.880 --> 0:04:05.440 as it were. But if ancient people had fortified walls, 0:04:05.760 --> 0:04:11.200 what did the ancient attackers use to breach those walls. Well, 0:04:11.880 --> 0:04:13.840 there are a couple of different tactics that don't involve 0:04:13.880 --> 0:04:16.200 seize engines at all. For example, you might try and 0:04:16.320 --> 0:04:20.680 use fire to weaken walls. You might tunnel under walls, 0:04:20.760 --> 0:04:24.799 either to collapse the wall so that they just fall down, 0:04:25.120 --> 0:04:28.200 or you end up just bypassing the wall entirely in 0:04:28.200 --> 0:04:30.640 tunnel into the place that you're trying to get access to. 0:04:31.720 --> 0:04:34.279 Or you might just use ladders to try and access 0:04:34.279 --> 0:04:36.960 the top of the wall and scale it. Obviously, that 0:04:37.000 --> 0:04:39.040 could be dangerous if there are soldiers up at the 0:04:39.080 --> 0:04:41.160 top of the wall to push the ladders down. So 0:04:41.400 --> 0:04:44.279 you've got to hope that you can zerg rush it 0:04:45.400 --> 0:04:47.920 use a whole bunch of people all at once. If 0:04:47.960 --> 0:04:49.400 you don't know what a zerg rush is, you need 0:04:49.400 --> 0:04:51.520 to go listen to the Tech Memes episode that published 0:04:51.520 --> 0:04:56.240 not too long ago. So the ancients would start to 0:04:56.240 --> 0:04:59.279 construct massive tools to break through barriers. These are the 0:04:59.320 --> 0:05:03.920 siege engines. They're bigger than things like just a tunnel 0:05:04.040 --> 0:05:08.960 or a ladder. And arguably the oldest version of the 0:05:09.040 --> 0:05:13.000 siege engine is the battering ram. So I'm sure you're 0:05:13.000 --> 0:05:16.479 all familiar with the concept, but just in case. A 0:05:16.520 --> 0:05:20.240 battering ram is a large mass that can be swung 0:05:20.440 --> 0:05:23.920 so that it has its impact against a surface and 0:05:24.000 --> 0:05:28.359 that causes that surface to become damaged. In other words, 0:05:28.400 --> 0:05:31.839 it's like an enormous hammer breaking through a wall or 0:05:31.839 --> 0:05:35.599 a door. And an example could be just an enormous log, 0:05:36.560 --> 0:05:40.120 and the earliest battering rams were held by people, but 0:05:40.200 --> 0:05:44.039 that was problematic. People can only hold weight up to 0:05:44.080 --> 0:05:46.240 a certain limit and then it's just too heavy to move. 0:05:47.000 --> 0:05:50.400 It slows them down and they remain unprotected and can 0:05:50.440 --> 0:05:53.400 be picked off by archers or people with slings or 0:05:53.440 --> 0:05:58.279 other projectiles. So you want to improve upon this idea. 0:05:58.920 --> 0:06:01.599 So another example would be a log that is hung 0:06:01.760 --> 0:06:05.720 from a wooden frame by various ropes, and the ropes 0:06:05.760 --> 0:06:08.480 allow the log to swing horizontally so that the end 0:06:08.720 --> 0:06:11.160 can crash into that vertical surface like a. 0:06:11.040 --> 0:06:11.960 Wall or a gate. 0:06:13.680 --> 0:06:16.240 This would allow you to have a much heavier battering 0:06:16.320 --> 0:06:18.520 ram than something you would have to carry by hand, 0:06:18.600 --> 0:06:21.839 because you could put it on this rope system and 0:06:22.320 --> 0:06:24.600 just swing it and as opposed to having to lift it. 0:06:25.760 --> 0:06:26.960 According to ancient. 0:06:26.760 --> 0:06:31.719 Historians, the earliest example of this technology was the brainchild 0:06:31.800 --> 0:06:36.520 of a certain Pefrasminos of Tire, And I apologize for 0:06:37.160 --> 0:06:41.520 absolutely butchering the pronunciation of that name, because I'm certain 0:06:41.560 --> 0:06:45.320 I did. Anyway, This particular engineer would have lived sometime 0:06:45.360 --> 0:06:49.040 between five hundred and three hundred and fifty BCE, and 0:06:49.440 --> 0:06:53.000 his main invention was suspending a cross beam from a 0:06:53.040 --> 0:06:55.599 transverse beam for the purposes of swinging it as a 0:06:55.600 --> 0:06:58.000 battering ram. In other words, that design I was talking 0:06:58.040 --> 0:07:02.960 about hanging a wooden beam in a frame so that 0:07:03.000 --> 0:07:07.400 you can bash down a wall or a door. Now, 0:07:07.440 --> 0:07:11.160 typically you would also find that the frames holding these 0:07:11.200 --> 0:07:15.200 battering rams would be shielded by a roof, and often 0:07:15.240 --> 0:07:19.960 that roof would be covered with dampened animal skins. That 0:07:19.960 --> 0:07:22.760 would help cut down on the potential for fire. If 0:07:22.960 --> 0:07:27.760 your defending city was using flaming arrows or burning oil 0:07:27.880 --> 0:07:31.840 or something along those lines, it would reduce the possibility 0:07:31.880 --> 0:07:35.480 that your brand new, shiny battering ram would just become kindling. 0:07:36.640 --> 0:07:41.280 And you would also protect yourself from other just basic 0:07:41.320 --> 0:07:44.800 projectiles and allow the operators of the battering ram to 0:07:44.840 --> 0:07:47.640 continue hammering against the wall or the door. 0:07:50.240 --> 0:07:52.400 Obviously, this was risky. 0:07:52.600 --> 0:07:55.800 You had to get access to the actual wall, and 0:07:56.120 --> 0:08:00.320 according to Vitruvius, who was an author and engineered the 0:08:00.360 --> 0:08:05.440 first century, the first person to create a fireproofed roofed 0:08:05.520 --> 0:08:11.800 battering ram was Keros the Carthaginian, sometimes called Geros with 0:08:11.880 --> 0:08:15.520 a G the Carthaginian. Modern historians believe this person was 0:08:15.560 --> 0:08:20.920 alive sometime around the fifth century BCE, and this was 0:08:20.960 --> 0:08:25.280 after the Iron Age that had happened several hundred years earlier. 0:08:26.320 --> 0:08:30.360 So it was very common for the attacking party to 0:08:31.080 --> 0:08:36.040 cap a battering ram with a large iron or otherwise 0:08:36.200 --> 0:08:40.359 metal cap, often shaped in the form of a battering 0:08:40.600 --> 0:08:45.560 ram like a literal ram, like a goat's head with horns. 0:08:46.840 --> 0:08:50.320 The iron would give the battering ram even more weight 0:08:50.440 --> 0:08:53.800 and resilience, and it would make it more effective. The 0:08:53.840 --> 0:08:57.840 animals would, you know, forms made it look more interesting, 0:08:57.920 --> 0:09:02.160 but they also could help with bashing through the material, 0:09:02.280 --> 0:09:06.920 depending upon the shapes you were using. And yeah, it 0:09:06.960 --> 0:09:11.000 was a pretty effective means of knocking down your basic 0:09:11.080 --> 0:09:15.160 city walls. You also would see other improvements like pulley 0:09:15.240 --> 0:09:18.559 systems that would allow the battering ram to remain horizontal 0:09:18.559 --> 0:09:21.920 as it swung instead of tilting upward. So imagine a 0:09:21.960 --> 0:09:24.360 swing set swing. You know, when you're swinging on a swing, 0:09:24.400 --> 0:09:27.080 your feet tilt up in the air instead of staying 0:09:27.160 --> 0:09:31.600 horizontal unless you're actively moving your legs down, and the 0:09:31.640 --> 0:09:35.480 pulley system would counteract that tendency so that way you 0:09:35.520 --> 0:09:40.680 wouldn't be hitting the wall or door on an upward swing. 0:09:40.800 --> 0:09:44.400 It would be translated into a horizontal motion, so that 0:09:44.400 --> 0:09:48.840 that momentum that you're transferring would be in the proper direction. 0:09:48.920 --> 0:09:51.520 And that's what we're talking about. The working principle behind 0:09:51.559 --> 0:09:57.200 the battering ram is the transfer of momentum. Momentum quick 0:09:57.559 --> 0:10:00.440 recap for people who don't remember their physics. It's the 0:10:00.520 --> 0:10:03.600 quantity of motion and a moving body. And the way 0:10:03.640 --> 0:10:08.920 you arrive at the quantity of momentum is by multiplying 0:10:09.320 --> 0:10:14.360 the mass of a moving body by its velocity, So 0:10:14.360 --> 0:10:17.280 that means momentum of a small object that's moving very 0:10:17.400 --> 0:10:20.200 very very fast can be the same as a large 0:10:20.240 --> 0:10:23.760 object moving much more slowly if the numbers work out 0:10:23.800 --> 0:10:26.280 the right way. But if something is really big and 0:10:26.320 --> 0:10:28.959 really fast. It has a whole lot of momentum to it, 0:10:29.800 --> 0:10:32.640 and I've got some funny stories about momentum. I had 0:10:32.640 --> 0:10:35.640 to explain this to a friend of mine at the 0:10:35.679 --> 0:10:42.360 Renaissance Festival. There was a moment in a dance, a 0:10:42.440 --> 0:10:45.400 dance in which it is possible to steal the partner 0:10:45.600 --> 0:10:48.960 of another person, in which I was trying to steal 0:10:49.040 --> 0:10:52.440 the queen from the king. The king being played by 0:10:52.520 --> 0:10:55.280 a guy who looked an awful lot like Henry the Eighth, 0:10:55.880 --> 0:11:01.400 including Henry the Eighth's impressive mass. Fellow collided with me. 0:11:01.480 --> 0:11:03.640 He gave me a little hip check, and he wasn't 0:11:03.679 --> 0:11:07.360 moving fast, but he did outweigh me by a significant amount, 0:11:07.640 --> 0:11:10.920 and so I went flying, And thus the transfer of 0:11:11.040 --> 0:11:16.240 momentum was demonstrated in a very real and ultimately painful way. 0:11:17.360 --> 0:11:20.080 I have since forgiven him. It actually was pretty funny, 0:11:20.160 --> 0:11:22.360 but I did sprain both my wrist and my ankle 0:11:22.440 --> 0:11:26.720 in that incident. So with battering rams, your desired outcome 0:11:26.800 --> 0:11:29.280 is to have a very large mass, and you want 0:11:29.280 --> 0:11:31.960 it to move really quickly so that you can result 0:11:32.040 --> 0:11:34.960 in this large amount of momentum that you transfer to 0:11:35.000 --> 0:11:38.120 a stationary object like the wall or the gate and 0:11:38.320 --> 0:11:39.320 thus cause. 0:11:39.200 --> 0:11:39.880 Damage to it. 0:11:40.760 --> 0:11:44.480 So once battering rams started getting better, obviously cities needed 0:11:44.480 --> 0:11:48.360 to respond and they began to reinforce their walls, making 0:11:48.400 --> 0:11:52.000 them thicker at the base and trying to create new 0:11:52.040 --> 0:11:57.280 strategies to repel battering ram assaults. My favorite battering ram 0:11:57.679 --> 0:12:02.560 is actually a fictional one, like Grand Grand was the 0:12:02.600 --> 0:12:05.280 battering ram in Lord of the Rings. It was from 0:12:05.360 --> 0:12:08.880 Sauron's army. They used it in the siege on Minas Tirith, 0:12:09.480 --> 0:12:11.640 and it was one hundred feet long and had a 0:12:11.679 --> 0:12:14.520 metal cap that was shaped like a wolf, and in 0:12:14.559 --> 0:12:17.000 most of the depictions I've seen, the wolf has also 0:12:17.640 --> 0:12:21.320 got some sort of fire or lava coming out of 0:12:21.360 --> 0:12:24.239 its mouth, making it pretty intimidating. 0:12:25.440 --> 0:12:26.839 Awesome image. Really. 0:12:28.000 --> 0:12:31.120 Another ancient siege engine similar to this in the sense 0:12:31.160 --> 0:12:34.160 that you had to get super close to your target, 0:12:34.520 --> 0:12:38.360 was the siege tower. This is a pretty simple concept. 0:12:38.520 --> 0:12:42.760 It's usually it's like a tower that's on wheels, and 0:12:42.920 --> 0:12:46.320 you push this tower up against the city wall that 0:12:46.400 --> 0:12:50.760 you want to you want to get past, and you 0:12:51.280 --> 0:12:53.600 have a gang plank at the top of the tower 0:12:53.920 --> 0:12:57.559 that you lower so that it rests on the city wall, 0:12:58.080 --> 0:13:02.040 and then your force just goes through the siege tower, 0:13:02.880 --> 0:13:05.679 across the gang plank and into the city and you 0:13:05.760 --> 0:13:12.240 bipe past the wall. Entirely very basic idea. Obviously, things 0:13:12.320 --> 0:13:14.960 could go wrong. The tower if it were set on fire, 0:13:15.120 --> 0:13:17.760 could end up causing you to lose quite a few 0:13:17.880 --> 0:13:18.840 of your men. 0:13:20.200 --> 0:13:21.040 And also there. 0:13:20.880 --> 0:13:24.439 Are lots of different ways to create obstacles to make 0:13:24.480 --> 0:13:26.960 it more difficult to get the tower up against a 0:13:26.960 --> 0:13:27.679 city wall. 0:13:28.480 --> 0:13:29.840 One of those would be. 0:13:29.880 --> 0:13:35.160 Moats, So your basic moat around a castle was really 0:13:35.240 --> 0:13:39.080 a defense against siege engines. Like this, it meant that 0:13:39.120 --> 0:13:42.120 it was much harder to get something like a siege 0:13:42.160 --> 0:13:44.480 tower up against the castle walls because you had to 0:13:44.520 --> 0:13:47.320 get across the moat first, and the moat might either 0:13:47.400 --> 0:13:49.480 be dry or it could be filled with water. Not 0:13:49.520 --> 0:13:52.880 all moats were water. In fact, most of them weren't. 0:13:52.960 --> 0:13:55.040 Most of them were essentially just a very big ditch 0:13:55.200 --> 0:14:00.160 around the fortified area, so you would have to find 0:14:00.200 --> 0:14:01.880 a way to bridge that gap if you were an 0:14:01.880 --> 0:14:05.080 attacker to allow your siege engine to roll over the moat, 0:14:05.080 --> 0:14:08.040 So you had to build like essentially a temporary bridge 0:14:08.440 --> 0:14:11.000 to allow the siege engine to roll over it and 0:14:11.080 --> 0:14:14.520 get access to the city wall, and another defense was 0:14:14.559 --> 0:14:17.360 to redesign city walls. In the first place, Engineers began 0:14:17.400 --> 0:14:19.320 to make walls that were very thick at the base 0:14:19.360 --> 0:14:22.520 and would slope from the top down to the base, 0:14:22.960 --> 0:14:26.160 and that slope meant that the top of the wall 0:14:26.280 --> 0:14:29.080 would be further away from a tower than the base 0:14:29.160 --> 0:14:34.400 of the wall because it sloped away from the outside. 0:14:34.880 --> 0:14:37.520 So that meant that your gang plank had to be 0:14:37.640 --> 0:14:40.600 longer in order to reach from the siege tower to 0:14:40.800 --> 0:14:44.120 the top of the city wall. And gang planks were 0:14:44.520 --> 0:14:48.040 really the weak points of the siege towers. Assuming that 0:14:48.160 --> 0:14:51.280 you've major siege tower as fireproof as you can manage, 0:14:51.280 --> 0:14:55.040 which again mostly involved putting the hides of animals on 0:14:55.120 --> 0:14:58.520 the outside of the tower and wetting them down, drenching 0:14:58.560 --> 0:15:02.200 them in water as much as you possibly can. Then, 0:15:02.640 --> 0:15:04.920 once you set down the gang plank and you have 0:15:04.960 --> 0:15:08.760 attackers going across, their most vulnerable when they are on 0:15:08.800 --> 0:15:13.320 that gang plank. They're standing over the height of the wall. 0:15:13.600 --> 0:15:16.800 There's probably a moat below them. The gang plank's probably 0:15:16.840 --> 0:15:23.120 not incredibly sturdy or stable. So the further away the 0:15:23.120 --> 0:15:25.360 top of the siege tower is from the top of 0:15:25.400 --> 0:15:28.200 the wall, the harder it is for the attackers to 0:15:28.240 --> 0:15:31.280 get over. So that was just a basic defense mechanism, 0:15:31.400 --> 0:15:34.840 was to build these sloping walls for cities to help 0:15:34.960 --> 0:15:39.640 protect against siege engines. Now, both siege towers and battering 0:15:39.720 --> 0:15:43.280 rams were made obsolete by the invention of cannons later on. 0:15:43.360 --> 0:15:45.600 I'll talk about cannons toward the end of this episode. 0:15:45.760 --> 0:15:48.400 Cannons actually made those high city walls obsolete in the 0:15:48.400 --> 0:15:51.560 first place. Higher walls were more vulnerable to cannon fire, 0:15:51.800 --> 0:15:54.560 and so the design of city fortifications had to completely 0:15:54.640 --> 0:16:00.120 change once those became a major element in warfare. At 0:16:00.160 --> 0:16:02.680 that point, those siege engines began to fade into history. 0:16:02.720 --> 0:16:05.560 You didn't really see them anymore. But I'll get more 0:16:05.560 --> 0:16:08.200 into cannons a little bit later in the episode. And 0:16:08.240 --> 0:16:11.520 I'm sure you've already noted that the major disadvantage to 0:16:11.560 --> 0:16:14.040 both battering rams and siege towers is that you have 0:16:14.120 --> 0:16:16.080 to get close to your target for them to work. 0:16:16.360 --> 0:16:19.040 If the defending city has set up other defenses like 0:16:19.160 --> 0:16:22.880 those trenches or pits or spikes, and they have stuff 0:16:22.960 --> 0:16:27.400 like hot oil or flaming weapons, getting close isn't terribly attractive. 0:16:27.440 --> 0:16:30.640 You would much prefer to batter the city from a distance, 0:16:30.680 --> 0:16:34.360 and so attackers began to design new engines, things that 0:16:34.400 --> 0:16:36.200 could allow attacks for much further away. 0:16:36.640 --> 0:16:37.560 So next I'll. 0:16:37.360 --> 0:16:40.800 Talk about some of the massive projectile weapons that were used, 0:16:41.600 --> 0:16:45.880 and they relied purely on mechanical physics to hurl objects 0:16:45.880 --> 0:16:46.320 at walls. 0:16:46.320 --> 0:16:47.080 They're pretty cool. 0:16:47.680 --> 0:16:50.360 Before I do that, let's take a quick break to 0:16:50.480 --> 0:17:01.960 thank our sponsor. So the first project al seize engine 0:17:02.000 --> 0:17:04.800 I really want to talk about is the ballista. And 0:17:05.040 --> 0:17:07.360 if you were to take a casual glance at a blista, 0:17:07.400 --> 0:17:10.920 you might think it's an enormous crossbow, and it does 0:17:11.240 --> 0:17:14.920 resemble a crossbow. But they crossbow and the ballista work 0:17:15.000 --> 0:17:20.439 on two different principles, two different types of tension. The 0:17:20.480 --> 0:17:24.639 operation of the ballista depends upon two torsion springs, whereas 0:17:24.640 --> 0:17:30.280 the crossbow depends upon the natural tension of the bow itself. 0:17:31.640 --> 0:17:35.640 So let's talk about torsion springs. Torsion springs work by twisting. 0:17:35.720 --> 0:17:40.040 They store mechanical energy when you twist the torsion spring, 0:17:40.480 --> 0:17:44.119 and when you release the spring, it unleashes that mechanical 0:17:44.240 --> 0:17:48.080 energy through untwisting, So it's winding and unwinding when you 0:17:48.119 --> 0:17:50.800 wind it up. You've got the mechanical energy, and when 0:17:50.840 --> 0:17:54.080 you let it go, it unwinds itself and releases that 0:17:54.119 --> 0:17:55.680 mechanical energy. 0:17:55.760 --> 0:17:56.240 To make a. 0:17:56.200 --> 0:17:59.440 Ballista, you need a pair of torsion springs that you 0:17:59.520 --> 0:18:02.480 can twist tightly so that when you release them, they 0:18:02.600 --> 0:18:04.760 unleash that mechanical force in such a way as to 0:18:04.800 --> 0:18:08.240 throw a projectile, typically a large dart with an iron 0:18:08.320 --> 0:18:15.240 tip at a target. Now, in ancient times, a torsion 0:18:15.240 --> 0:18:19.360 spring might look like a loop of some stretchy elastic material. 0:18:19.520 --> 0:18:25.200 That material was often either hair from animals sometimes humans, 0:18:25.280 --> 0:18:28.760 all woven together to make really strong ropes, or sometimes 0:18:28.760 --> 0:18:32.440 it was ligaments and other tissue that was turned into 0:18:32.480 --> 0:18:36.080 this kind of elastic material and then looped around a 0:18:36.160 --> 0:18:39.680 frame like a skein that's inside a frame. So imagine 0:18:39.680 --> 0:18:42.679 a loop of material. In fact, just imagine a rubber band, 0:18:43.640 --> 0:18:47.439 and imagine that you've got two pegs that are a 0:18:47.440 --> 0:18:50.440 few inches apart from each other. They're further apart than 0:18:50.480 --> 0:18:53.159 the length of the rubber band, so you have to 0:18:53.200 --> 0:18:57.240 stretch the rubber band a little bit to loop either 0:18:57.400 --> 0:19:01.280 end over the two pegs. Put more rubber bands that 0:19:01.320 --> 0:19:04.160 are the same length over those two pegs, so you've 0:19:04.160 --> 0:19:07.600 got a few of them, maybe four or five. These 0:19:07.680 --> 0:19:12.879 rubber bands represent an unwound torsion spring. If you then 0:19:12.920 --> 0:19:18.600 inserted a throwing arm, what would be considered like the 0:19:18.640 --> 0:19:23.240 shaft of a throwing arm, into that gap the middle 0:19:23.400 --> 0:19:27.600 of all those rubber bands, and then use it to 0:19:27.760 --> 0:19:32.879 twist the rubber bands in a circle, either clockwise or counterclockwise, 0:19:33.440 --> 0:19:38.480 you would create the torsion. This twisted tension. You loop 0:19:38.520 --> 0:19:40.520 them over and over again. You can do this with 0:19:40.560 --> 0:19:44.040 a pencil, so again, just have a rubber band. You 0:19:44.080 --> 0:19:46.480 can even have maybe someone stand in front of you 0:19:46.600 --> 0:19:49.359 putting their two thumbs up, and you loop the rubber 0:19:49.400 --> 0:19:52.760 bands around their two thumbs so that they're stretching them together. 0:19:53.200 --> 0:19:55.880 You put a pencil in there. You twist the pencil 0:19:55.960 --> 0:19:59.360 around a few times so that it's twisting the rubber bands, 0:20:00.000 --> 0:20:02.440 and you'll start building up that tension. If you let 0:20:02.520 --> 0:20:05.760 go of the pencil, then it will unleash all that 0:20:05.800 --> 0:20:09.360 mechanical energy and it'll make the pencil flip around like crazy. 0:20:09.640 --> 0:20:12.960 Make sure you use an unsharpened pencil, and be very 0:20:13.000 --> 0:20:14.800 careful with this sort of stuff because it might fly 0:20:14.920 --> 0:20:16.720 up and hit you in the face. But this is 0:20:16.760 --> 0:20:21.199 the basic principle of the ballista. Now, with the ballista, 0:20:21.600 --> 0:20:25.480 you have two of these torsion springs, and that meant 0:20:25.520 --> 0:20:31.480 that they're actually vertically aligned, not horizontally aligned. In other words, 0:20:31.560 --> 0:20:34.880 you would have imagine you have one thumb higher than 0:20:34.920 --> 0:20:37.480 the other thumb directly in front of you, and you 0:20:37.520 --> 0:20:40.479 put the rubber bands on so that you were holding 0:20:40.480 --> 0:20:41.480 the loop that way. 0:20:41.760 --> 0:20:43.560 That's the way the ballista. 0:20:43.680 --> 0:20:46.840 Torsion springs are aligned. You have to have those that 0:20:46.960 --> 0:20:51.160 vertical alignment, and they're parallel to each other. And between 0:20:51.240 --> 0:20:54.800 the two torsion springs you have your stock or channel. 0:20:55.080 --> 0:20:58.840 That's where the projectile moves through. So with a crossbow, 0:20:58.920 --> 0:21:02.800 this would be where the bolt would slide through as 0:21:02.840 --> 0:21:05.520 it's being launched from the crossbow. Same sort of thing 0:21:05.560 --> 0:21:08.280 with a ballista. It's got that stock with a channel 0:21:08.320 --> 0:21:11.240 in it. That's where the projectile moves through it, and 0:21:11.280 --> 0:21:15.520 it's between these two vertically aligned torsion springs. So you've 0:21:15.560 --> 0:21:20.360 got your enormous dart loaded into your blista, and you've 0:21:20.359 --> 0:21:24.560 got your two vertically aligned torsion springs. In each torsion spring, 0:21:24.720 --> 0:21:29.560 you have a throwing arm. Now the torsion spring on 0:21:29.800 --> 0:21:34.720 the left side is wound counterclockwise if you were looking 0:21:34.760 --> 0:21:38.360 at it from above. That means that when the tension releases, 0:21:38.400 --> 0:21:42.119 it's going to spin its throwing arm in a clockwise direction. 0:21:43.000 --> 0:21:46.920 The torsion spring on the right side is the opposite. 0:21:46.960 --> 0:21:50.000 It's wound clockwise, so that when you release the tension, 0:21:50.080 --> 0:21:54.360 it will spin the throwing arm counterclockwise. And on the 0:21:54.400 --> 0:21:57.840 opposite end of the throwing arm, you have a line 0:21:58.000 --> 0:22:00.800 attaching the two together, a rope if you will, or 0:22:00.800 --> 0:22:04.760 a string. This rope is looped around the end of 0:22:04.800 --> 0:22:08.480 your projectile. This is the thing that's going to transfer 0:22:08.560 --> 0:22:12.000 the force to the projectile and make it fly at 0:22:12.000 --> 0:22:16.600 your target. So just imagine you've got this crossbow looking 0:22:16.680 --> 0:22:19.080 thing in front of you. The two arms of the 0:22:19.119 --> 0:22:22.639 ballista in its rest position you haven't wound it yet, 0:22:23.040 --> 0:22:27.479 are extended outward to the side, so the left one 0:22:27.600 --> 0:22:30.800 is almost parallel with the front of the ballista, the 0:22:30.840 --> 0:22:33.600 right one is almost parallel with the ballista, and you 0:22:33.640 --> 0:22:36.520 have a device called a windless. The windless is what 0:22:36.600 --> 0:22:40.360 allows you to crank back those arms. It's creating tension 0:22:40.520 --> 0:22:43.919 in those torsion springs, so it starts to twist the 0:22:43.920 --> 0:22:47.320 torsion springs, and as a result, the two throwing arms 0:22:47.560 --> 0:22:53.320 start tilting back towards you. It's they bend backwards, although 0:22:53.359 --> 0:22:56.560 the torsion the throwing arms themselves are not bending, it's 0:22:56.680 --> 0:23:01.600 just the torsion springs are rotating as you're twisting them, so. 0:23:01.600 --> 0:23:02.520 They've bend backward. 0:23:02.560 --> 0:23:04.800 Now that means that you start getting slack in that 0:23:04.920 --> 0:23:10.040 rope that's between the two ends of the throwing arms. 0:23:10.600 --> 0:23:13.200 You can use that slack to put it behind your projectile. 0:23:13.720 --> 0:23:17.240 And when you release the tension on those torsion springs, 0:23:17.920 --> 0:23:22.480 they untwist. That pulls the throwing arms forward, and that 0:23:22.800 --> 0:23:27.800 pulls that rope forward as well, transferring the energy to 0:23:27.880 --> 0:23:32.600 your projectile and shooting it at your target. It's pretty 0:23:32.640 --> 0:23:35.360 cool to see this, I mean, it's interesting to see 0:23:35.640 --> 0:23:38.800 this as two torsion springs as opposed to a crossbow, 0:23:39.040 --> 0:23:43.280 which would just use the tension of the material itself, 0:23:43.320 --> 0:23:46.560 the wood, if you will, of the bow. It's all 0:23:46.600 --> 0:23:49.800 due to mechanical physics. You don't need any chemicals to 0:23:49.880 --> 0:23:53.359 do this kind of seige engine, and you could also 0:23:53.520 --> 0:23:56.080 just build this thing when you needed it. In fact, 0:23:56.119 --> 0:24:01.160 most seiege engines were constructed at site the siege was happening. 0:24:01.600 --> 0:24:04.320 Because they were so big and heavy that moving them 0:24:04.400 --> 0:24:07.679 from one place across country to another place was not 0:24:07.760 --> 0:24:11.159 really practical. So usually we just go to the closest forest, 0:24:11.359 --> 0:24:14.879 cut down some logs, and have some workers start to 0:24:14.960 --> 0:24:18.000 build seage engines right there on site, wheel them into 0:24:18.000 --> 0:24:20.119