一戰/二戰/冷戰/現代軍事 解析坦克履帶結構

Greetings all OK, I promise you a video on tracks, those parallel pieces of metal held together by concrete or wooden ties. I... armored track, never mind. Now, this was originally prompted by a question of how do you get additional grip from a track in the last Q&A, but I figured I might as well make a more comprehensive video on tanks in general. The basic premise of a track is you want to reduce ground pressure. The less your ground pressure, the less you sink in the soft ground and thus the more terrain you can cover. You can reduce ground pressure on a wheeled vehicle by letting some air out of the tires, but you can never get to as low a ground pressure as a track will provide because wheels will always have gaps between the contact patches. Track is continuous contact from the first to the last road wheel, and indeed even a little bit beyond, depending on how far it sinks into the surface. And that's why if you look at, let's say, a British World War I tank, you'll see a gradual increase in the curvature, which allows more track to be in contact with the ground the more the vehicle sinks into the mud. So in addition to contact length, pressure directly correlates with track width. Wider track results in less ground pressure. On the other hand, it also adds overall to the weight of the vehicle and to the amount of effort needed to simply haul the track around the suspension. So there is actually a balance to be struck. It's not that there was some epiphany in the 1930s that said, Oh, T-34, wider track, better off-road. Everybody knew it. But yes, sometimes it had to cut a balance somewhere. Now, it was not unheard of to split the difference and provide both a narrow and a wide track to suit local environment at the time. So Ost Ketten for the Germans in World War II, or let's say Panzer IV, would be an example. You had wide track in the eastern front where there was lots of mud, and narrower track on the western front where you had less mud and more metal roads. Or for the Americans, duct builds, which were officially known as extended end connectors. Tracks are generally held together by track pins, and that's normally your first distinguisher, single pin or double pin track. Single pin track generally works much like the hinge on your door. So you got two adjacent blocks which are designed to intermesh with each other, and then you drive a pin between them, holding them together. The two blocks then pivot around the pin. For a double pin track, there are two pins on each track block. They are placed next to each other, and then additional components, end connectors and sometimes center guides, are used to keep the track together. Double pin track is generally for heavier duty requirements like modern western MBTs. The distance from a point on one track block to the identical point on the next track block is called pitch. In their simplest format, these tracks are called dead tracks. There's nothing involved but metal on metal. Live tracks, however, have rubber bushings in the blocks to provide a little bit of spring. So in their natural position, it induces the track to curl upwards when laid on the ground. It simply helps the track get around the wheels more easily. Live and dead track is nothing to do with supported or unsupported suspension, by the way. It's quite possible to have live track which is unsupported, witness the M113, for example, or dead track which is supported, such as on Chieftain. And both supported and unsupported do need to be tensioned routinely in order to have a good chance of staying on as the vehicle maneuvers. The next question is that of the use of rubber. They can be on the inside of the track, the outside, or both. Rubber on the inside, preferably against the rubber of road wheels, strongly reduces the vibration and noise and increases the service life of components. Rubber on the outside, however, i.e. where it touches the ground, tends to often be a factor of civil infrastructure concerns. If you're expecting to be operated in an environment with metal roads such as Western Europe, rubber track pads are preferred. They provide additional grip on the surface which is so hard that it doesn't deform enough to allow metal track pads to dig in and bite. On the other hand, if you don't care about that sort of thing, all metal tracks are generally far more aggressive, and they give better traction. Another advantage is that they are less prone to damage. So note, for example, how Merkava uses all metal track treads. The terrain in the area is very rocky, and it would tear regular rubber track pads to shreds fairly quickly. Now, going back to rubber, it is still possible to have a tread pattern on rubber track blocks, witnessed by late Shermans through to early M1 Abrams. They can be permanently vulcanized onto the track links, or they can be separate pads which are bolted on. Generally speaking, the metal in a track has a longer life than the rubber on the track, so in theory, you can be more efficient by changing pads a couple of times before replacing the track. Although there was one World War II type that was just double thickness rubber on one side. In practice, though, our crowd basically found it too much to bother with, and we just exchanged the track anyway and let somebody else deal with the pads. But that's the theory. Anyway, those pad shapes, these days they tend to often be hexagonal, for example, will normally provide you with adequate grip anyway, so it doesn't matter if they're molded into a chevron or if they're just flat. Which brings us to the original question of additional grip. On a modern tank, if you need more grip due to snow or the like, there are grouser pads available. What you do is you knock out the rubber pads every tenth link or so, and you replace them with metal grip pads. And these are most obviously seen carried on German vehicles, those X shapes carried in rows. Each X replaces a rubber track pad. In effect, they perform as snow chains. Now, you can simply remove the track pad and not replace it with anything at all, but you don't get quite as much grip as you would from the X. In World War II, the traction grousers were basically long metal bars which would be attached across the extant track, and these would often be seen on the backs of M10s or on the sides of Stuarts, for example. Now, if you have neither available, it is not unheard of to reverse the occasional center guide so that the teeth on the center guide stick outwards, but you do want to be careful doing that if you're likely bedriving unmetalled roads. An interesting side note is the existence of snow chains for tracks. Now, I haven't yet in this video addressed rubber band track, which can be a single piece, such as found on half tracks or segmented on M56 SPATs, for example. Their advantage is that they are very light. The big disadvantages are less durability and the inability to repair battle damage as easily as a linked track vehicle. So you run over a mine in your Stuart, it blows up, you replace a couple of track and you're good to go. You run over a mine with a track of a half track and you've got to replace the entire track. However, being rubber and of limited tread depth, they too need additional aid sometimes, and the official answer is track chains. They're just like the chains which go on the front wheels or snow chains on your car, except they're much longer. Well, I think that about covers it. Basic information, but still important. Hope you find it interesting and informative. I'll talk to you on the next one.