1 00:00:04,400 --> 00:00:07,800 Speaker 1: Welcome to tex Stuff, a production from my Heart Radio. 2 00:00:11,880 --> 00:00:14,440 Speaker 1: He there, and welcome to tech Stuff. I'm your host, 3 00:00:14,520 --> 00:00:18,360 Speaker 1: Jonathan Strickland, and I'm an executive producer right here at 4 00:00:18,360 --> 00:00:22,639 Speaker 1: the Heart Radio. And how the tech are you. I've 5 00:00:22,680 --> 00:00:26,040 Speaker 1: got an upcoming episode with a special guest that I'm 6 00:00:26,120 --> 00:00:29,520 Speaker 1: really excited about. And in that episode, I'm probably gonna 7 00:00:29,600 --> 00:00:33,199 Speaker 1: talk a little bit about a system that uses cams. 8 00:00:33,720 --> 00:00:36,840 Speaker 1: So I thought today's Tech Stuff Tidbits, I would actually 9 00:00:36,840 --> 00:00:39,879 Speaker 1: talk about cams, what they are, what they do. This 10 00:00:39,920 --> 00:00:43,360 Speaker 1: will be a true tidbits episode. It will not be 11 00:00:43,520 --> 00:00:46,880 Speaker 1: a fifty minute tidbits episode. So we're just gonna look 12 00:00:46,880 --> 00:00:48,680 Speaker 1: at cams and what they do. Now. And now, first 13 00:00:48,720 --> 00:00:53,000 Speaker 1: of all, I am talking about mechanical cams mechanical systems, 14 00:00:53,400 --> 00:00:56,560 Speaker 1: So when I say cams, I am not talking about cameras. 15 00:00:56,680 --> 00:00:59,400 Speaker 1: So this is not about webcams or anything like that. 16 00:00:59,400 --> 00:01:02,880 Speaker 1: That's a totally different thing. Instead, we're talking about components 17 00:01:02,960 --> 00:01:06,280 Speaker 1: used in some mechanical systems for the purposes of generating 18 00:01:06,319 --> 00:01:10,960 Speaker 1: a particular motion at a specific timing. So, to put 19 00:01:11,000 --> 00:01:15,720 Speaker 1: it simply, cams are components in a mechanical system that 20 00:01:15,800 --> 00:01:23,240 Speaker 1: convert ordinary rotational motion into something else typically into a 21 00:01:23,360 --> 00:01:27,480 Speaker 1: reciprocating motion, a linear reciprocating motion, so it and up 22 00:01:27,520 --> 00:01:30,640 Speaker 1: and down or in and out motion, if you want 23 00:01:30,680 --> 00:01:34,039 Speaker 1: to think of it that way. Now, to talk about 24 00:01:34,440 --> 00:01:39,280 Speaker 1: cams and how they work, let's let's really consider mechanical systems, 25 00:01:39,640 --> 00:01:42,200 Speaker 1: and I'm going to really look at, you know, electro 26 00:01:42,280 --> 00:01:46,280 Speaker 1: mechanical systems in particular. So first let's let's think about 27 00:01:46,319 --> 00:01:49,920 Speaker 1: motors and electro magnets. And I know I talk about 28 00:01:49,920 --> 00:01:53,400 Speaker 1: electro magnets a lot on this show, but as it 29 00:01:53,440 --> 00:01:55,320 Speaker 1: turns out, there at the heart of a lot of 30 00:01:55,360 --> 00:02:00,240 Speaker 1: different mechanical and electrical systems. So it comes with the territory, right. 31 00:02:00,600 --> 00:02:02,880 Speaker 1: I'm sure most of us know that if you wrap 32 00:02:02,960 --> 00:02:07,520 Speaker 1: a conductive wire around, say a core of iron, like 33 00:02:07,560 --> 00:02:10,680 Speaker 1: a little iron rod, or the very simple version an 34 00:02:10,680 --> 00:02:13,160 Speaker 1: iron nail. So you get some copper wire and you 35 00:02:13,720 --> 00:02:17,080 Speaker 1: wrap several coils around a copper nail, and then you 36 00:02:17,120 --> 00:02:21,480 Speaker 1: connect that wire to something that generates a current, like 37 00:02:21,639 --> 00:02:25,120 Speaker 1: a battery. Then you get yourself an electro magnet. The 38 00:02:25,200 --> 00:02:28,560 Speaker 1: electro magnet will have its own magnetic field, with its 39 00:02:28,560 --> 00:02:32,079 Speaker 1: own magnetic north and magnetic south pole, and it will 40 00:02:32,160 --> 00:02:36,480 Speaker 1: behave just like a permanent magnet would, which means if 41 00:02:36,520 --> 00:02:39,680 Speaker 1: you bring the north end of your electro magnet near 42 00:02:39,720 --> 00:02:43,320 Speaker 1: the south end of a permanent magnet, the two magnets 43 00:02:43,320 --> 00:02:46,400 Speaker 1: will attract each other. If you bring the north end 44 00:02:46,400 --> 00:02:48,920 Speaker 1: of your electro magnet near the north end of a 45 00:02:48,960 --> 00:02:53,880 Speaker 1: permanent magnet, they will repel each other because opposite magnetic 46 00:02:54,200 --> 00:02:59,160 Speaker 1: charges attract, and like magnetic charges or poles, if you 47 00:02:59,200 --> 00:03:03,040 Speaker 1: prefer repel. Now, let's make things a bit more complicated. 48 00:03:03,880 --> 00:03:07,360 Speaker 1: Let's say that we connect our electromagnet not to a 49 00:03:07,440 --> 00:03:11,520 Speaker 1: battery which supplies direct current, meaning the current always flows 50 00:03:11,560 --> 00:03:15,600 Speaker 1: in the same direction, but to a source of alternating current. 51 00:03:15,680 --> 00:03:18,920 Speaker 1: So now the direction of current switches from one direction 52 00:03:18,960 --> 00:03:23,880 Speaker 1: to the other, often at very high frequencies, and each 53 00:03:23,919 --> 00:03:28,440 Speaker 1: time it switches, the magnetic field switches as well. So 54 00:03:28,480 --> 00:03:30,600 Speaker 1: when the current flows in one direction, the north poles 55 00:03:30,600 --> 00:03:32,680 Speaker 1: on one side of the electromagnet the south poles on 56 00:03:32,680 --> 00:03:37,600 Speaker 1: the other, current switches directions those poles flip. So what 57 00:03:37,680 --> 00:03:39,800 Speaker 1: was the north pole of the electromagnet is now the 58 00:03:39,840 --> 00:03:43,160 Speaker 1: south pole, and vice versa. Now, if you brought this 59 00:03:43,240 --> 00:03:47,200 Speaker 1: kind of electro magnet near a permanent magnets, poll doesn't 60 00:03:47,200 --> 00:03:51,160 Speaker 1: matter which of the poles we're talking about. Your electro 61 00:03:51,280 --> 00:03:56,280 Speaker 1: magnet would alternately attract and repel the permanent magnet because 62 00:03:56,880 --> 00:03:59,840 Speaker 1: the poll would be flipping on your electromagnet. So some 63 00:04:00,000 --> 00:04:01,960 Speaker 1: times it would be north to north and sometimes it 64 00:04:02,000 --> 00:04:05,200 Speaker 1: would be north to south. All right, Now, let's imagine 65 00:04:05,600 --> 00:04:08,000 Speaker 1: that we've got a permanent magnet. Let's say it's in 66 00:04:08,040 --> 00:04:11,280 Speaker 1: the shape of a U. Okay, and the north pole 67 00:04:11,400 --> 00:04:14,920 Speaker 1: is on the left tip of the U from our perspective, 68 00:04:15,360 --> 00:04:18,120 Speaker 1: and the south pole is on the right tip of 69 00:04:18,160 --> 00:04:21,080 Speaker 1: the U. This magnet does not move. It's in a 70 00:04:21,160 --> 00:04:24,680 Speaker 1: fixed position. We call it a statter. It is stationary, 71 00:04:24,800 --> 00:04:29,039 Speaker 1: so statters s T A T O R. In between 72 00:04:29,080 --> 00:04:32,360 Speaker 1: these poles. In the center between the two we mount 73 00:04:32,520 --> 00:04:36,120 Speaker 1: our electro magnet, which has no magnetic field. If we're 74 00:04:36,160 --> 00:04:39,000 Speaker 1: not running a current through those coils, right, and our 75 00:04:39,040 --> 00:04:42,480 Speaker 1: electro magnet is on an axle that can rotate, so 76 00:04:42,520 --> 00:04:46,919 Speaker 1: the electromagnet can spin freely between the two poles of 77 00:04:46,920 --> 00:04:51,240 Speaker 1: the permanent magnet. Now, if we run alternating current through 78 00:04:51,320 --> 00:04:55,200 Speaker 1: our electro magnet at the right frequency, we can cause 79 00:04:55,279 --> 00:04:59,920 Speaker 1: this electro magnet to rotate and keep rotating by flipping 80 00:05:00,040 --> 00:05:03,320 Speaker 1: the direction of the current and thus the electro magnets 81 00:05:03,400 --> 00:05:10,039 Speaker 1: magnetic field, and it will consistently push against the permanent 82 00:05:10,120 --> 00:05:14,560 Speaker 1: magnets magnetic field on either side, because that field is 83 00:05:14,600 --> 00:05:17,120 Speaker 1: not going to move right. The permanent magnets field is fixed. 84 00:05:17,800 --> 00:05:22,599 Speaker 1: It's a statu our rotor the electro magnet. It's poles 85 00:05:22,680 --> 00:05:27,960 Speaker 1: keep flipping so that it's consistently pushing against these magnetic fields, 86 00:05:28,040 --> 00:05:30,880 Speaker 1: causing the electro magnet to rotate. So if you just 87 00:05:30,960 --> 00:05:37,520 Speaker 1: time this perfectly, you can create this source of rotational force. Now, 88 00:05:37,520 --> 00:05:39,560 Speaker 1: if we want to use a direct current, we could. 89 00:05:40,120 --> 00:05:42,839 Speaker 1: You know, the problem with the direct current is unless 90 00:05:42,880 --> 00:05:46,800 Speaker 1: you have a way of flipping the poles of your 91 00:05:46,800 --> 00:05:50,919 Speaker 1: electro magnet, your electro magnet is just going to orient 92 00:05:51,000 --> 00:05:54,960 Speaker 1: itself so that the opposite poles are attracted to the 93 00:05:54,960 --> 00:06:00,720 Speaker 1: permanent magnet. Right, it'll move in a horizontal plane relative 94 00:06:00,800 --> 00:06:04,600 Speaker 1: to our our permanent magnet's polls, and it won't go 95 00:06:04,640 --> 00:06:07,000 Speaker 1: any further than that because it will be held in 96 00:06:07,040 --> 00:06:11,600 Speaker 1: place by magnetic force. But if we use a structure 97 00:06:11,640 --> 00:06:15,600 Speaker 1: called a commutator, which effectively flips the polarity of the 98 00:06:15,600 --> 00:06:20,239 Speaker 1: electro magnets magnetic field, by changing how the electromagnet connects 99 00:06:20,320 --> 00:06:26,080 Speaker 1: to the circuit that's providing the current as the electromagnet rotates, 100 00:06:26,560 --> 00:06:30,240 Speaker 1: then you have essentially the same effect as if you 101 00:06:30,279 --> 00:06:34,280 Speaker 1: had connected the electro magnet to an alternating current. There's 102 00:06:34,279 --> 00:06:36,800 Speaker 1: more to it than that, but we've already spent enough 103 00:06:36,839 --> 00:06:38,960 Speaker 1: time here, and I've done other episodes where I've talked 104 00:06:38,960 --> 00:06:43,599 Speaker 1: about commutators and how they work. Now, the point is 105 00:06:43,640 --> 00:06:48,479 Speaker 1: that these motors, these electric motors, generate rotational force. But 106 00:06:48,600 --> 00:06:51,680 Speaker 1: that's all they do, right. They can't they can't generate 107 00:06:52,000 --> 00:06:54,880 Speaker 1: a different kind of force there. The way that they 108 00:06:54,960 --> 00:07:00,280 Speaker 1: are designed mechanically means that they make things spin. They 109 00:07:00,279 --> 00:07:02,800 Speaker 1: don't make things go up and down or anything like that. 110 00:07:03,680 --> 00:07:06,520 Speaker 1: But rotational force can be useful for a lot of stuff. 111 00:07:06,560 --> 00:07:09,000 Speaker 1: Like you know, a relatively simple use would be to 112 00:07:09,160 --> 00:07:13,320 Speaker 1: drive an electric drill. The rotational force from the motor 113 00:07:13,400 --> 00:07:17,360 Speaker 1: provides the drilling action you need. It's providing the rotational 114 00:07:17,360 --> 00:07:21,239 Speaker 1: force to your drill. Bit. So there are legit uses, 115 00:07:21,360 --> 00:07:25,840 Speaker 1: simple uses for the electric motor, but a lot of 116 00:07:25,880 --> 00:07:31,720 Speaker 1: mechanical systems often require other types of motion, not just rotational. 117 00:07:32,000 --> 00:07:35,600 Speaker 1: So to accomplish that we have to get a little creative. 118 00:07:35,920 --> 00:07:38,920 Speaker 1: We have to think of ways to convert rotational force 119 00:07:39,040 --> 00:07:43,559 Speaker 1: generated by the electric motor into something else, and that's 120 00:07:43,680 --> 00:07:48,160 Speaker 1: kind of where cams can come in. So a cam 121 00:07:48,280 --> 00:07:51,600 Speaker 1: rotates on the axis of a shaft that could be 122 00:07:51,680 --> 00:07:55,920 Speaker 1: driven by something like an electric motor, So it's getting 123 00:07:56,000 --> 00:08:00,800 Speaker 1: rotational force from some part of the mechanical system. And 124 00:08:01,080 --> 00:08:06,040 Speaker 1: a cam on a shaft is frequently and a regularly 125 00:08:06,280 --> 00:08:09,640 Speaker 1: shaped object. It can be sort of like an eccentric 126 00:08:09,680 --> 00:08:15,040 Speaker 1: wheel is a very frequent example. So imagine you have 127 00:08:15,080 --> 00:08:17,560 Speaker 1: a wheel. Let's start with a perfect circle. Just imagine 128 00:08:17,560 --> 00:08:22,960 Speaker 1: a perfect circle on your mind. Now imagine deforming this 129 00:08:23,040 --> 00:08:28,000 Speaker 1: perfect circle a bit. Maybe parts along the circumference bulge out, 130 00:08:28,360 --> 00:08:30,720 Speaker 1: making it a little more oblong, or maybe they dip 131 00:08:30,920 --> 00:08:34,960 Speaker 1: inward a bit, so that you have still generally a 132 00:08:35,000 --> 00:08:38,319 Speaker 1: circular shape, but it's not perfect anymore. There are parts 133 00:08:38,559 --> 00:08:43,360 Speaker 1: of the circumference where it's a different shape. So by 134 00:08:43,400 --> 00:08:48,200 Speaker 1: positioning cams at specific points along a shaft where they 135 00:08:48,240 --> 00:08:51,920 Speaker 1: will make contact with other mechanical elements such as levers, 136 00:08:52,679 --> 00:08:56,040 Speaker 1: you can translate rotational motion into something else, like reciprocating 137 00:08:56,120 --> 00:09:00,599 Speaker 1: linear motion. So let me give you an example imagine 138 00:09:00,840 --> 00:09:05,320 Speaker 1: you have a horizontal shaft that can rotate in a 139 00:09:05,360 --> 00:09:09,199 Speaker 1: particular way. And this shaft, and in this example, we'll 140 00:09:09,240 --> 00:09:11,760 Speaker 1: say it connects to an electric motor. So the electric 141 00:09:11,800 --> 00:09:15,959 Speaker 1: motor is providing the rotational force turning the shaft, and 142 00:09:16,280 --> 00:09:19,760 Speaker 1: you know, let's say it's a clockwise direction from our perspective. 143 00:09:20,480 --> 00:09:23,280 Speaker 1: And then let's say that we have a cam positioned 144 00:09:23,880 --> 00:09:27,400 Speaker 1: midway down the length of this shaft. It is permanently 145 00:09:27,480 --> 00:09:31,959 Speaker 1: attached to the shaft. It will rotate along with the shaft. 146 00:09:32,240 --> 00:09:35,240 Speaker 1: It is as as far as we're concerned, part of 147 00:09:35,280 --> 00:09:38,959 Speaker 1: that shaft. This cam, let's say his egg shaped, so 148 00:09:39,360 --> 00:09:43,480 Speaker 1: one side of the cam bulges outward compared to the 149 00:09:43,520 --> 00:09:49,360 Speaker 1: rest of it. And positioned above this cam is a 150 00:09:49,400 --> 00:09:54,360 Speaker 1: type of lever that will call a cam follower. So 151 00:09:54,720 --> 00:09:58,560 Speaker 1: this follower is actually making contact with the surface of 152 00:09:58,600 --> 00:10:02,720 Speaker 1: the cam itself. So if you're thinking about let's say 153 00:10:02,840 --> 00:10:06,880 Speaker 1: a vinyl record or a wheel, it's making contact with 154 00:10:07,080 --> 00:10:10,959 Speaker 1: the the outer surface of this wheel, like the edge 155 00:10:11,080 --> 00:10:15,680 Speaker 1: of it. In other words, and the lever is attached 156 00:10:15,720 --> 00:10:18,480 Speaker 1: to something else in this mechanical system. So let's say 157 00:10:18,520 --> 00:10:21,680 Speaker 1: in our example, this lever which can move up and 158 00:10:21,760 --> 00:10:25,400 Speaker 1: down is connected to a little mechanical gopher, and this 159 00:10:25,480 --> 00:10:28,800 Speaker 1: gopher will pop out of a hole that's in some 160 00:10:28,920 --> 00:10:32,600 Speaker 1: rundown and yet still vaguely charming theme park attraction at 161 00:10:32,600 --> 00:10:38,000 Speaker 1: your local amusement park. So as the shaft rotates, the 162 00:10:38,080 --> 00:10:41,319 Speaker 1: cam rotates too, because it's attached to the shaft, it's 163 00:10:41,400 --> 00:10:45,360 Speaker 1: part of the shaft, and the bulging bit of this 164 00:10:45,600 --> 00:10:50,760 Speaker 1: oblong cam's surface rises up to meet the lever, which 165 00:10:50,800 --> 00:10:54,320 Speaker 1: means it pushes against the lever, pushing it upward. So 166 00:10:54,360 --> 00:10:56,640 Speaker 1: the lever goes up, which in turn pushes our little 167 00:10:56,640 --> 00:11:00,439 Speaker 1: mechanical gopher up out of the hole. The cam continues 168 00:11:00,480 --> 00:11:04,040 Speaker 1: to rotate with the shaft, and so the bulging bit 169 00:11:04,520 --> 00:11:08,280 Speaker 1: of this part of the cam is now sloping away 170 00:11:08,320 --> 00:11:10,360 Speaker 1: from the lever, so the lever can actually start to 171 00:11:10,360 --> 00:11:13,720 Speaker 1: come back down again. It's sliding along the surface of 172 00:11:13,760 --> 00:11:17,320 Speaker 1: the cam as the cam rotates away, and you know, 173 00:11:17,400 --> 00:11:20,040 Speaker 1: gravity just pulls our little gopher back down the hole. 174 00:11:20,960 --> 00:11:23,400 Speaker 1: The full distance that the lever is able to travel 175 00:11:24,120 --> 00:11:27,199 Speaker 1: due to how it connects to this cam is called 176 00:11:27,240 --> 00:11:30,880 Speaker 1: the throw. That is the throw of our cam follower. 177 00:11:31,400 --> 00:11:34,480 Speaker 1: Now the cam followers don't have to rely purely on 178 00:11:34,520 --> 00:11:36,720 Speaker 1: gravity to move back down. In fact, that would be 179 00:11:36,760 --> 00:11:39,680 Speaker 1: a very bad design because over time the leaver could 180 00:11:39,679 --> 00:11:43,040 Speaker 1: start to stick in the up position. Our gopher might 181 00:11:43,080 --> 00:11:45,120 Speaker 1: not ever go back down into its hole. It just 182 00:11:45,200 --> 00:11:48,079 Speaker 1: stays up there, which is just another reminder of how 183 00:11:48,080 --> 00:11:49,959 Speaker 1: this park isn't the same as it was when you 184 00:11:50,000 --> 00:11:54,840 Speaker 1: were a kid. No, I made myself sad. We'll tell 185 00:11:54,880 --> 00:11:56,920 Speaker 1: you what. We're gonna take a quick break. When it 186 00:11:57,000 --> 00:12:10,160 Speaker 1: come back, we'll get happy again. Okay, let's get back 187 00:12:10,200 --> 00:12:13,600 Speaker 1: to our discussion about cams and and the example we 188 00:12:13,600 --> 00:12:15,640 Speaker 1: were thinking about with the little gopher that can pop 189 00:12:15,720 --> 00:12:18,720 Speaker 1: up and down based upon the rotation of this cam 190 00:12:18,760 --> 00:12:23,480 Speaker 1: pushing against a lever. Again, you probably wouldn't just rely 191 00:12:23,559 --> 00:12:26,520 Speaker 1: on gravity on these systems. You would probably have some 192 00:12:26,600 --> 00:12:30,720 Speaker 1: other form of device that would ensure that the lever 193 00:12:30,840 --> 00:12:36,000 Speaker 1: would return to uh it's full down position in this case, 194 00:12:36,040 --> 00:12:38,880 Speaker 1: so we would probably have something like maybe a spring 195 00:12:39,360 --> 00:12:43,160 Speaker 1: connected to this lever, so that when the cam is 196 00:12:43,200 --> 00:12:46,480 Speaker 1: pushing against the lever, pushing it up, you know, moving 197 00:12:46,520 --> 00:12:49,280 Speaker 1: the gopher up out of the whole. In the process, 198 00:12:49,600 --> 00:12:53,360 Speaker 1: the lever is also compressing a spring, and as the 199 00:12:53,480 --> 00:12:56,240 Speaker 1: cam's edge slopes away from the lever, allowing it to 200 00:12:56,280 --> 00:12:59,840 Speaker 1: move back down again. The spring actually forces the lever 201 00:13:00,480 --> 00:13:03,520 Speaker 1: to move back down towards the cams surface, so that 202 00:13:03,679 --> 00:13:06,560 Speaker 1: you don't just have a gopher stuck out of its hole. 203 00:13:07,679 --> 00:13:11,880 Speaker 1: Internal combustion engine cars use cams. In fact, they have 204 00:13:11,960 --> 00:13:15,440 Speaker 1: a special shaft called the cam shaft that uses these 205 00:13:15,480 --> 00:13:19,320 Speaker 1: to govern the intake and exhaust valves in the combustion engine. 206 00:13:19,320 --> 00:13:22,800 Speaker 1: That's why I specifically say internal combustion engine cars. The 207 00:13:22,920 --> 00:13:27,880 Speaker 1: cams in this case are used to to govern, or 208 00:13:28,000 --> 00:13:31,920 Speaker 1: to control when an intake valve is open and when 209 00:13:31,960 --> 00:13:34,120 Speaker 1: it's closed, and when the exhaust valve is open and 210 00:13:34,160 --> 00:13:36,920 Speaker 1: when it's closed. You don't need those in an electric 211 00:13:37,000 --> 00:13:41,800 Speaker 1: vehicle because you don't have the combustion uh cylinders. So 212 00:13:41,880 --> 00:13:46,760 Speaker 1: let's talk about internal combustion engines and cams in those 213 00:13:47,000 --> 00:13:50,160 Speaker 1: really quickly to kind of understand how cams are used 214 00:13:50,160 --> 00:13:56,120 Speaker 1: in modern mechanical systems. So, an internal combustion engine burns 215 00:13:56,280 --> 00:14:01,679 Speaker 1: a mixture of fuel and air inside fix cylinders. The 216 00:14:01,800 --> 00:14:06,160 Speaker 1: energy generated from this combustion it's really an explosion, is 217 00:14:06,280 --> 00:14:10,640 Speaker 1: used to push a piston outward. The piston, in turn 218 00:14:10,720 --> 00:14:14,319 Speaker 1: provides power to the car's power train. Via a crankshaft 219 00:14:14,920 --> 00:14:17,880 Speaker 1: and then in turn provides power to the wheels. The 220 00:14:17,920 --> 00:14:21,320 Speaker 1: crankscheft also, by the way, provides rotational power for the 221 00:14:21,360 --> 00:14:24,360 Speaker 1: actual camshaft. That's part of this system too. Will get 222 00:14:24,400 --> 00:14:27,400 Speaker 1: to that. And all of this means that you can 223 00:14:27,520 --> 00:14:30,280 Speaker 1: have your car go without having to do the flintstones 224 00:14:30,360 --> 00:14:33,880 Speaker 1: thing and just use your feets. So the pistons connect 225 00:14:33,920 --> 00:14:37,000 Speaker 1: to a crank cheft via piston rods. It's that connection 226 00:14:37,040 --> 00:14:39,920 Speaker 1: that allows the reciprocating motion of the pistons, the in 227 00:14:40,080 --> 00:14:43,800 Speaker 1: and out motion of the pistons as they move relative 228 00:14:43,880 --> 00:14:48,640 Speaker 1: to the cylinders, into rotational motion for the shaft itself. 229 00:14:49,200 --> 00:14:51,840 Speaker 1: These are really tricky things to talk about without the 230 00:14:51,960 --> 00:14:54,960 Speaker 1: use of visual aids, but you know, just think that 231 00:14:55,000 --> 00:14:58,040 Speaker 1: the up and down motion of the piston is connected 232 00:14:58,200 --> 00:15:02,200 Speaker 1: via this rod to a shaft that can then rotate 233 00:15:02,800 --> 00:15:04,840 Speaker 1: due to the up and down motion of the piston. 234 00:15:05,640 --> 00:15:08,600 Speaker 1: All right, Now, let's talk about a four stroke engine 235 00:15:08,640 --> 00:15:12,720 Speaker 1: because that will illustrate how this is all working and 236 00:15:12,840 --> 00:15:16,040 Speaker 1: where the cams come involved. So when we say stroke, 237 00:15:16,560 --> 00:15:20,600 Speaker 1: what we mean is one full travel of a piston, 238 00:15:20,800 --> 00:15:26,240 Speaker 1: either inward into the cylinder or outward relative to the cylinder. 239 00:15:26,600 --> 00:15:30,720 Speaker 1: So in is one stroke, out is another stroke, and 240 00:15:31,560 --> 00:15:36,640 Speaker 1: internal combustion engines traditionally use four strokes, so those four 241 00:15:36,640 --> 00:15:41,080 Speaker 1: strokes are intake. This is where a cylinder pulls in air, 242 00:15:41,240 --> 00:15:45,000 Speaker 1: and it does this by opening the intake valve. As 243 00:15:45,040 --> 00:15:49,920 Speaker 1: the piston is traveling outward from the cylinder, This draws 244 00:15:50,000 --> 00:15:53,240 Speaker 1: air into the cylinder, kind of like if you were 245 00:15:53,240 --> 00:15:56,960 Speaker 1: pulling the plunger back on a syringe. At the end 246 00:15:57,000 --> 00:16:01,360 Speaker 1: of the stroke, the intake valve closes, which is absolutely critical. 247 00:16:01,400 --> 00:16:05,360 Speaker 1: It has to close, and that seals the cylinder. You 248 00:16:05,400 --> 00:16:07,640 Speaker 1: also get a mix of fuel that enters into the 249 00:16:07,680 --> 00:16:09,960 Speaker 1: cylinder at this point, so in older cars that would 250 00:16:10,000 --> 00:16:13,320 Speaker 1: come from a carburetor, in modern vehicles from the fuel 251 00:16:13,320 --> 00:16:17,680 Speaker 1: injection system. The next stroke, the piston is moving back 252 00:16:17,920 --> 00:16:22,080 Speaker 1: inward relative to the cylinder, and this stroke is called 253 00:16:22,160 --> 00:16:25,840 Speaker 1: compression because the piston, which is you know, snugly set 254 00:16:25,840 --> 00:16:29,200 Speaker 1: in the cylinder so nothing can escape along the sides 255 00:16:29,240 --> 00:16:32,280 Speaker 1: of the piston. As it moves back into the cylinder, 256 00:16:32,720 --> 00:16:36,520 Speaker 1: the piston compresses this mixture of air and fuel that 257 00:16:36,640 --> 00:16:40,520 Speaker 1: has entered into the cylinder. At the end of this stroke, 258 00:16:40,960 --> 00:16:43,960 Speaker 1: the piston is as far into the cylinder as it goes, 259 00:16:44,600 --> 00:16:48,320 Speaker 1: and both intake and exhaust valves have to be closed, right, 260 00:16:48,360 --> 00:16:51,720 Speaker 1: because if either valve were open, then that would mean 261 00:16:52,320 --> 00:16:55,880 Speaker 1: that you couldn't compress the mixture. The mixture would be 262 00:16:55,920 --> 00:16:58,400 Speaker 1: forced out of the cylinder because one of the valves 263 00:16:58,400 --> 00:17:01,400 Speaker 1: had opened, So these valves have to be shut. The 264 00:17:01,440 --> 00:17:06,200 Speaker 1: next stroke is combustion. This is when the spark plug sparks, 265 00:17:06,240 --> 00:17:09,200 Speaker 1: which ignites the mix of air and fuel. It causes 266 00:17:09,200 --> 00:17:13,280 Speaker 1: the explosion that forces the piston outward again, so the 267 00:17:13,320 --> 00:17:16,159 Speaker 1: piston moves down the length of the cylinder. It's this 268 00:17:16,240 --> 00:17:19,919 Speaker 1: force that provides the rotational force to the crank shaft 269 00:17:20,240 --> 00:17:24,720 Speaker 1: that ultimately makes the car go. As the crank shaft turns, 270 00:17:25,080 --> 00:17:28,479 Speaker 1: it pushes the piston rod as it rotates a one 271 00:17:28,520 --> 00:17:31,639 Speaker 1: full rotation around that therefore makes the piston go back 272 00:17:31,800 --> 00:17:35,280 Speaker 1: into the cylinder. For the fourth and final stroke of 273 00:17:35,280 --> 00:17:38,840 Speaker 1: this process, this is the exhaust stroke. So this is 274 00:17:38,880 --> 00:17:42,639 Speaker 1: when the exhaust valve opens and it allows the spent 275 00:17:42,960 --> 00:17:46,719 Speaker 1: air fuel mixture to escape the cylinder. At the end 276 00:17:46,760 --> 00:17:49,879 Speaker 1: of the stroke, the piston is as far into the 277 00:17:49,920 --> 00:17:52,720 Speaker 1: cylinder as it can be. The whole process is set 278 00:17:52,760 --> 00:17:56,840 Speaker 1: to repeat with the next intake stroke. And we do 279 00:17:56,880 --> 00:17:59,680 Speaker 1: it all again. So let's finally get to the cams, 280 00:18:00,119 --> 00:18:03,919 Speaker 1: because it's the cams that control the opening and closing 281 00:18:04,080 --> 00:18:07,840 Speaker 1: of those intake and exhaust valves. The cams are on 282 00:18:07,880 --> 00:18:11,640 Speaker 1: a cam shaft that ultimately receives its rotational power from 283 00:18:11,840 --> 00:18:17,040 Speaker 1: the crank shaft. As the cams rotate, their surface forces 284 00:18:17,080 --> 00:18:20,240 Speaker 1: their respective valves to open at just the right spot 285 00:18:20,440 --> 00:18:24,080 Speaker 1: during that rotation, and then the valves will close again 286 00:18:24,200 --> 00:18:27,840 Speaker 1: as the cams slopes away from the lever that is 287 00:18:27,880 --> 00:18:30,840 Speaker 1: attached to the valves. The cams are positioned in such 288 00:18:30,840 --> 00:18:33,080 Speaker 1: a way that they will always cause the valves to 289 00:18:33,119 --> 00:18:36,119 Speaker 1: open at just the right part in the stroke process 290 00:18:37,080 --> 00:18:39,400 Speaker 1: as the pistons are moving in and all of the cylinders, 291 00:18:39,440 --> 00:18:43,120 Speaker 1: and then they will remain closed for the other three 292 00:18:43,200 --> 00:18:48,040 Speaker 1: strokes of the four stroke process. Now, cams are used 293 00:18:48,040 --> 00:18:50,280 Speaker 1: in all sorts of mechanical systems, not just cars, And 294 00:18:50,320 --> 00:18:52,520 Speaker 1: the reason I even wanted to touch on these today 295 00:18:52,640 --> 00:18:54,840 Speaker 1: is because again, next week, I should have a new 296 00:18:54,840 --> 00:18:56,920 Speaker 1: episode up in which I'll talk about a theme park 297 00:18:57,359 --> 00:19:00,399 Speaker 1: that used cams in its attractions. Very some alert to 298 00:19:00,480 --> 00:19:04,080 Speaker 1: the gopher example I gave out, but far more complicated, 299 00:19:04,359 --> 00:19:07,120 Speaker 1: and I think it's good to occasionally reflect on mechanical 300 00:19:07,200 --> 00:19:11,000 Speaker 1: systems and get an understanding and appreciation for how humans 301 00:19:11,000 --> 00:19:14,720 Speaker 1: were able to create one and and and create devices 302 00:19:14,760 --> 00:19:18,679 Speaker 1: that could generate forces and also figure out ways to 303 00:19:18,720 --> 00:19:20,800 Speaker 1: harness that force to do work, even if it meant 304 00:19:20,840 --> 00:19:23,239 Speaker 1: having to convert one form of motion into another. It's 305 00:19:23,280 --> 00:19:26,480 Speaker 1: really clever stuff. And with cams, it's also old stuff. 306 00:19:26,480 --> 00:19:29,639 Speaker 1: There are illustrations of Chinese mechanical systems that used cams 307 00:19:29,640 --> 00:19:33,040 Speaker 1: to convert rotational motion like that provided by a water 308 00:19:33,080 --> 00:19:36,520 Speaker 1: wheel into reciprocating motion, so they've been around for a 309 00:19:36,560 --> 00:19:40,360 Speaker 1: really long time. Anyway, I hope you found that interesting 310 00:19:40,359 --> 00:19:43,760 Speaker 1: in this Tech Stuff Tidbits episode, and you know I'm 311 00:19:43,800 --> 00:19:46,760 Speaker 1: looking forward to that episode for next week. Keep an 312 00:19:46,760 --> 00:19:50,520 Speaker 1: ear out for it should be pretty fun and I'll 313 00:19:50,520 --> 00:20:00,200 Speaker 1: talk to you again really soon. Text Stuff is an 314 00:20:00,200 --> 00:20:03,879 Speaker 1: I Heart Radio production. For more podcasts from I Heart Radio, 315 00:20:04,200 --> 00:20:07,399 Speaker 1: visit the i Heart Radio app, Apple Podcasts, or wherever 316 00:20:07,480 --> 00:20:13,520 Speaker 1: you listen to your favorite shows. H