 In this video, I'm going to talk about other gear types that we might look at beyond the basic spur gear. So the spur gear is kind of the standard gear that we might first talk about. It's relatively cheap, 98 to 99% efficient, and usually just kind of a good all-around choice. However, it's not the only possible gear that we might look at. The first type of gear that I want to talk about is a helical gear. So a helical gear has a slightly different geometry. The gear teeth are angled relative to the axis of the shaft that it's measured on. And we define the angle as the helix angle. And so this helix angle is part of the gear tooth geometry for a helical gear. Helical gears in general are 95 to 98% efficient. Generally speaking, they are usually quieter than a spur gear because the teeth are meshing in a sliding action instead of kind of clacking together as a spur gear when the teeth come together. It's a little bit quieter. They do allow for non-parallel shaft mounting with some limitations. However, it does come at the cost of efficiency. You could reduce the efficiency possibly down to 50% by having non-parallel shafts. They're a little bit stronger generally speaking, so they have higher torque capacities. And in a comparison with spur gears, due to the helix angle, if you can imagine how forces are applied at that contact between two teeth, that helix angle introduces a thrust load or a load that's in the axial direction of the shaft. So that's something to kind of keep in mind when it comes to helical gears. Slight variation on helical gears would be a herringbone gear. So a herringbone gear is very much like a helical gear, but now has two sections, one with teeth in one direction and one with teeth in the other direction. You can basically think of it as two helical gears being smushed together and mounted together. Obviously going to be more expensive in that case, so a little bit more involved, more material, all sorts of things like that. However, we talked about the thrust load for helical gears. Again if you can imagine the force being applied at those tooth interactions, we have one set of teeth angling one direction and the other set angling the other direction. So this means that those two thrust loads are going to cancel each other out on the gear and not then be applied to the shaft and have to be dealt with at the bearings. So in this case you get the added benefit of cancelling out the thrust load with a lot of the features of the helical gear in terms of quietness and strength and things like that. Bevel gears are a little bit different shape rather than being shaped in a circular fashion. They're shaped more like cones or portions of cones. And typically if we had a mating pair, they might look something like this. And you can obviously see from this little poor drawing that the shafts can be mounted in varying configurations. So again allow for non-parallel shafts. They have this geometry which is kind of based on rolling two cones relative to each other. And there is a spiral version of bevel gears which is similar to the variation between a helical gear and a spur gear, a bevel gear and a spiral bevel gear would have that same sort of variation in that you change the angle of the teeth and you get some different features out of that. We have worm gears. See if I can draw something that approximates a worm gear. Imagine that's a gear. So a worm gear is a gear mounted to the shaft where you have basically a spiral around that shaft which represents the teeth of the gear. But in the case of the worm, it actually only has one tooth and then it's interacting with something like a spur gear on the other side. And this allows this mating pair to have very high gear ratios because in the theory, the application of the basic theory, the worm gear only has one tooth and that gives it a high ratio, high gear ratio, which means it can have a very high load capacity. So you can rotate that worm gear and get very high loads. It's kind of the mechanical advantage thing going on there. Not the greatest efficiency in comparison with other gears, depending on the design in the range of 40 to 85% efficiency. One sometimes benefit of a worm gear is generally they can't be back driven, meaning you can't rotate the spur gear and expect that you're going to drive the worm. You can only drive the worm and cause an output at the spur gear. And that can be useful as a safety feature in that your load can't fight or drive backwards against your driven element. So that can be a useful feature. Rack and pinion is kind of a similar idea to the worm gear configuration, but now we're talking about a gear mated to a rack, which basically has, or excuse me, the pinion, I guess, in the rack and pinion nomenclature, is mated to a rack and the rack in theory has an infinite number of teeth in that this could be, for all intents and purposes, infinitely long and therefore from a gear ratio perspective, you can imagine what that involves. This is kind of where that notion of rack and pinion steering comes from, in that you are rotating one element and translating another element. So you're converting rotational motion into linear translation. And that's obviously useful for a lot of applications. So these are just some of the gear types that I wanted to talk about as alternatives to spur gears. In additional videos, I'll go into some of the details of a couple of these, not all of them. I'm going to talk a little bit more in my next video about heel gears, and then we'll get into bevel gears. And I want to talk a little bit about planetary gear systems, which is kind of just a special arrangement of gears that does something useful for us. So we'll follow up with that in later videos. Thanks.