WEBVTT Kind: captions Language: en 00:00:00.000 --> 00:00:05.930 For whatever reason, I’ve always been more than a little fascinated by things involving water. 00:00:05.930 --> 00:00:10.740 Particularly the devices we use to carry it around, distribute it, keep it away, 00:00:10.740 --> 00:00:12.810 or even just make it look pretty. 00:00:12.810 --> 00:00:17.540 Be it fountains, aqueducts, water towers, roofs, or even a plain ‘ol pipe, 00:00:17.540 --> 00:00:20.540 there’s a lot to whet your inquisitive appetite. 00:00:20.540 --> 00:00:22.280 Such as these things! 00:00:22.580 --> 00:00:24.720 Ah, the humble lawn sprinkler. 00:00:24.720 --> 00:00:27.360 The irrigating sound of summer. 00:00:27.360 --> 00:00:31.740 Impact sprinklers like these have been around for a very long time and I’ve always been 00:00:31.740 --> 00:00:33.540 a little curious about them. 00:00:33.540 --> 00:00:36.600 See, the way they move back and forth is… 00:00:36.600 --> 00:00:37.719 intriguing. 00:00:37.719 --> 00:00:40.859 An oscillating sprinkler like this guy makes total sense. 00:00:40.859 --> 00:00:44.730 It’s just got a little water wheel in there that acts like a motor, robbing some of the 00:00:44.730 --> 00:00:48.380 kinetic energy of the flowing water to power a little gear train 00:00:48.380 --> 00:00:51.520 which makes the holey stick thing go back and forth. 00:00:51.520 --> 00:00:55.240 These dudes, though, well I’m sure you’ve heard how in one direction they go all… 00:00:55.240 --> 00:00:57.360 [tick tick tick tick tick tick tick tick] 00:00:57.360 --> 00:00:58.760 but in the other direction it’s more of a 00:00:58.760 --> 00:01:00.220 [tstststststststststststststs] 00:01:01.080 --> 00:01:02.480 Why does it speed up? 00:01:02.480 --> 00:01:05.240 And how does that make it go in the other direction? 00:01:05.240 --> 00:01:08.980 Well, I wanted to answer these questions for myself and also you 00:01:08.980 --> 00:01:14.460 because it turns out these sprinklers are downright fascinating, and for a bunch of reasons. 00:01:14.460 --> 00:01:17.100 Naturally, I have one right here. 00:01:17.100 --> 00:01:22.219 These sprinklers do that thing where their principle of operation is incredibly simple, 00:01:22.220 --> 00:01:26.040 but the design which makes it possible is visually complex. 00:01:26.040 --> 00:01:28.480 Let’s start with where the water comes from. 00:01:28.480 --> 00:01:32.720 Hook a garden hose up to this bit and water will flow up into the sprinkler head 00:01:32.720 --> 00:01:38.100 (and, if you wanted to, out that way to another hose for another one down the line). 00:01:38.100 --> 00:01:43.340 Now obviously the head is designed to spin and it’s pretty easy to turn. 00:01:43.340 --> 00:01:46.090 But notice that it has a lot of vertical play. 00:01:46.090 --> 00:01:53.620 I can actually lift up on it quite a bit, and if I hold it in this position it becomes a bit harder to turn. 00:01:53.620 --> 00:01:57.780 When the sprinkler is being used, the water pressure forces the sprinkler head up against 00:01:57.780 --> 00:02:01.780 its stop, the effect of which is that it takes a fair bit of force to turn it. 00:02:01.780 --> 00:02:04.800 You’ll see why that’s important shortly. 00:02:04.800 --> 00:02:07.380 Next let’s look at where the water comes out - 00:02:07.380 --> 00:02:10.220 it’s here, from this little brass nozzle. 00:02:10.220 --> 00:02:13.260 But notice how there’s a thing in the way. 00:02:13.260 --> 00:02:14.360 This little armature 00:02:14.360 --> 00:02:18.500 ♫ sudden low-fi fast jazzy dance hall music ♫ (or something like that) 00:02:29.420 --> 00:02:31.040 Can you believe I didn't put a ton of jokes in this bit? 00:02:31.440 --> 00:02:35.120 This little armature serves to redirect the water’s path. 00:02:35.120 --> 00:02:39.100 It will first hit this angled piece which throws it slightly to the left. 00:02:39.100 --> 00:02:43.160 But immediately after that it will hit this sort of scoop shape, throwing it back to the right 00:02:43.170 --> 00:02:45.750 and roughly on its original path. 00:02:45.750 --> 00:02:50.350 The armature isn’t fixed, in fact it can move but a spring acts to return it to its 00:02:50.350 --> 00:02:51.880 resting position. 00:02:51.880 --> 00:02:55.780 When the water comes flying at the armature as the restriction in flow created by the 00:02:55.780 --> 00:03:02.500 nozzle causes its velocity to increase dramatically, the armature gets flung with a fair bit of force to the left. 00:03:02.500 --> 00:03:07.540 That force gets absorbed all nice and soft like by the spring, but of course the spring 00:03:07.540 --> 00:03:12.120 returns the favor and eventually flings the armature right back where it started. 00:03:12.120 --> 00:03:15.720 And by the time it gets there, it’s moving pretty fast. 00:03:15.720 --> 00:03:20.900 The energy the armature picked up as it was thrown to the left by the water never went away, 00:03:20.900 --> 00:03:24.990 instead it was just dampened and absorbed by the spring. 00:03:24.990 --> 00:03:29.090 The spring then works to push the armature back to its resting position, and once it 00:03:29.090 --> 00:03:34.740 gets there the stored energy gets released all at once in a momentous occasion. 00:03:34.740 --> 00:03:40.140 The sudden impact as it slams against the head imparts a fair bit of torque. 00:03:40.140 --> 00:03:44.040 Bringing a moving object to a sudden stop isn’t exactly easy. 00:03:44.040 --> 00:03:47.940 That’s our friend Force equal Mass times Acceleration. 00:03:47.940 --> 00:03:52.210 When the armature is initially flung to the left by the jet of water, the total force 00:03:52.210 --> 00:03:55.910 (and thus, torque) generated isn’t that substantial. 00:03:55.910 --> 00:04:00.741 It gets moving, or is accelerated, fairly slowly, and the opposing force of the spring 00:04:00.741 --> 00:04:07.300 (another source of acceleration) is also pretty weak and so happens over a fairly long period of time. 00:04:07.300 --> 00:04:13.720 But once it returns to its starting position, it’s moving at a relatively high speed and hits a solid barrier. 00:04:13.720 --> 00:04:18.900 The near instantaneous acceleration that results from this impact, multiplied by the mass of 00:04:18.900 --> 00:04:22.980 the armature itself, imparts a substantial amount of rotational force 00:04:22.980 --> 00:04:25.340 (or torque) on the sprinkler head. 00:04:25.340 --> 00:04:28.800 That knocks it slightly to the right, or clockwise. 00:04:28.800 --> 00:04:33.960 And this is where the resistance brought about by the lifting force of the water comes into play. 00:04:33.960 --> 00:04:40.400 With the sprinkler head forced against its stop, now we have to overcome friction to get it to move. 00:04:40.400 --> 00:04:45.220 While there is a counterclockwise force imparted as the armature is flung to the left 00:04:45.220 --> 00:04:47.760 (and as the spring resists that movement), 00:04:47.760 --> 00:04:53.780 the small acceleration component diminishes that force to the point that it can’t overcome static friction. 00:04:53.780 --> 00:04:58.580 The upshot of this is that the sprinkler head can only rotate when there is a substantial 00:04:58.580 --> 00:05:04.260 peak force caused by an impact, which means it will only move clockwise. 00:05:04.260 --> 00:05:06.920 But of course, it can also move the other way. 00:05:06.920 --> 00:05:08.600 Just as your Auntie Clockwise! 00:05:08.600 --> 00:05:09.320 [awkward silence] 00:05:09.320 --> 00:05:14.200 That was a dumb joke, but in case you didn’t know these don’t have to change directions; 00:05:14.200 --> 00:05:17.280 you can make them just go in circles like most online arguments. 00:05:17.280 --> 00:05:22.580 If this little thing is flipped up, well then it will just go ‘round and ‘round and 00:05:22.580 --> 00:05:24.200 ‘round and 'round. 00:05:24.200 --> 00:05:27.700 But flip it down and when it hits these little things 00:05:27.700 --> 00:05:33.580 (which are adjustable so you can control its range of movement) it will change directions at each end. 00:05:34.080 --> 00:05:35.080 How? 00:05:35.080 --> 00:05:36.980 Well, look at what it does. 00:05:36.980 --> 00:05:42.600 The action of moving the little directiony changey bit causes this small metal piece to move. 00:05:42.600 --> 00:05:46.540 And when it’s in this position, it limits the movement of the armature 00:05:46.540 --> 00:05:49.020 by catching it with this little tab. 00:05:49.020 --> 00:05:53.740 Now you might think this wouldn’t do a whole lot, but it makes one significant change 00:05:53.740 --> 00:05:55.720 to the action of the armature. 00:05:55.720 --> 00:05:59.280 It changes when the impact occurs. 00:05:59.280 --> 00:06:04.280 Now, as before, the armature picks up speed from the jet of water throwing it to the left. 00:06:04.290 --> 00:06:08.260 But rather than have a nice and subtle spring slow it down and reverse its course, 00:06:08.260 --> 00:06:11.760 it slams right into the metal piece right away. 00:06:11.760 --> 00:06:18.220 That impact imparts pretty much the same amount of torque as before, but in the opposite direction. 00:06:18.220 --> 00:06:22.419 The energy the armature gains from the water pushing it to the left goes right into the 00:06:22.420 --> 00:06:26.260 sprinkler head, rather than into the spring as an intermediary. 00:06:26.260 --> 00:06:32.700 That high peak torque can overcome the static friction and nudge it to the left, or counter-clockwise. 00:06:32.700 --> 00:06:37.940 When it’s going in that direction, the impacts occur much more frequently because the spring is 00:06:37.940 --> 00:06:44.350 for the most part out of the picture, and the distance the armature can travel is quite small. 00:06:44.350 --> 00:06:49.460 Plus, thanks to that limited movement, the water jet now becomes not only a source of energy 00:06:49.460 --> 00:06:54.280 for pushing the armature to the left, but also a dampener when it returns. 00:06:54.280 --> 00:06:58.140 After making the impact, it will of course return to its resting position 00:06:58.140 --> 00:07:02.500 (partly because of the spring and partly just from bouncing off the tab thing), 00:07:02.500 --> 00:07:08.889 but it doesn’t have enough speed to overcome the jet of water and so a second impact doesn’t occur. 00:07:08.889 --> 00:07:12.760 Instead, the armature just gets pushed away again relatively gently, 00:07:12.760 --> 00:07:17.600 without enough acceleration to produce a torque which can overcome the static friction. 00:07:17.600 --> 00:07:22.840 Since the only impact occurs on its outward swing, the only movement generated is in the 00:07:22.840 --> 00:07:25.060 counterclockwise direction. 00:07:25.060 --> 00:07:27.360 And really, that’s it! 00:07:27.370 --> 00:07:31.900 As far as I can tell these got their name solely from the fact their driving force 00:07:31.900 --> 00:07:33.480 comes from an impact. 00:07:33.480 --> 00:07:36.620 And they’re not the only device to use this principle. 00:07:36.620 --> 00:07:39.140 Ever heard of an impact wrench? 00:07:39.140 --> 00:07:44.180 These things, rather than just spin a socket with a plain ol’ motor, instead spin a large 00:07:44.180 --> 00:07:46.500 metal thing inside them called a hammer. 00:07:47.080 --> 00:07:49.280 And not, like, this kind. 00:07:49.280 --> 00:07:51.860 It’s just called a hammer. 00:07:51.860 --> 00:07:57.440 That hammer, after it’s up to speed, periodically strikes an anvil which creates a large amount 00:07:57.440 --> 00:08:02.840 of torque as the energy from the spinning hammer is imparted into the stationary anvil. 00:08:02.840 --> 00:08:08.639 The socket is attached to that anvil, and so in effect gets struck in a twisted way repeatedly 00:08:08.639 --> 00:08:09.639 by the hammer. 00:08:09.639 --> 00:08:13.200 It’s the same principle as using a high amount of acceleration 00:08:13.200 --> 00:08:15.980 to create a large amount of instantaneous torque. 00:08:15.980 --> 00:08:17.840 Because… 00:08:17.840 --> 00:08:18.800 that’s what it is. 00:08:18.800 --> 00:08:23.229 The distinctive sound of an impact wrench, either air driven or as is the case here cordless 00:08:23.229 --> 00:08:26.740 is the result of the hammer repeatedly striking the anvil, 00:08:26.740 --> 00:08:31.220 and this process is what creates the repetitive bursts of very high torque. 00:08:31.220 --> 00:08:33.620 [rapid, loud clicking/banging sound] 00:08:33.940 --> 00:08:37.840 In these sprinklers, though, it’s a lot more simpler and also just easier to see because 00:08:37.840 --> 00:08:40.439 you can actually see it. 00:08:40.439 --> 00:08:44.619 The impact of the armature also helps the sprinkler be a better sprinkler. 00:08:44.619 --> 00:08:50.240 See, the nozzle shoots water pretty far at a slightly upward angle giving it great coverage 00:08:50.240 --> 00:08:54.540 far from itself, but pretty lousy coverage right in front of it. 00:08:54.540 --> 00:08:59.780 As the armature slaps the stream of water like a curious racoon, it periodically disrupts 00:08:59.790 --> 00:09:02.860 the stream and gets some water close to home. 00:09:02.860 --> 00:09:05.780 When the direction changes, it gets even closer. 00:09:05.780 --> 00:09:11.760 And also, fun fact, many of these sprinklers are adjustable beyond simply their angle of sprinklage. 00:09:11.760 --> 00:09:14.520 You might have noticed this little set screw. 00:09:14.529 --> 00:09:21.089 Tighten that and this pin will enter the jet stream and break it up, reducing the effective range of the sprinkler. 00:09:21.089 --> 00:09:24.920 You can also achieve similar deflection with this little hat thing. 00:09:24.920 --> 00:09:26.620 A nice touch. 00:09:26.620 --> 00:09:31.820 These really are pretty versatile sprinklers, unless of course what you need to sprinkle isn’t round. 00:09:31.820 --> 00:09:33.200 Like a cake. 00:09:33.200 --> 00:09:37.511 So the next time you hear the irrigating sound of an impact sprinkler, 00:09:37.520 --> 00:09:40.620 just remember that it’s really quite clever. 00:09:40.620 --> 00:09:44.200 And make no mistake, this is a technology. 00:09:44.200 --> 00:09:48.420 While I often focus on things like audiovisual equipment and other eletronicals, 00:09:48.420 --> 00:09:53.000 something as simple as a water distribution device deserves due diligence. 00:09:53.000 --> 00:09:57.880 Orton Englehart used human ingenuity to invent this thing back in 1933, 00:09:57.880 --> 00:10:04.400 and while it may seem like a simple and down-to-earth device, it is still full of lessons we can learn from it. 00:10:04.400 --> 00:10:05.900 Thanks for watching. 00:10:06.880 --> 00:10:09.420 ♫ impactfully smooth jazz ♫ 00:10:10.460 --> 00:10:13.740 But the design which makes it possible is visual… 00:10:14.640 --> 00:10:19.240 When water comes flying at it as the restriction in flow created by the nozzle causes its velocity 00:10:19.240 --> 00:10:20.751 to increase dramatically [said mockingly] 00:10:20.751 --> 00:10:24.240 ...the armature isn’t fixed, in fact it can move but a spring… 00:10:24.240 --> 00:10:26.160 da di duppa dough 00:10:26.160 --> 00:10:28.920 And once it gets there, the… 00:10:30.300 --> 00:10:31.300 that wasn’t right. 00:10:31.300 --> 00:10:33.780 It gets moving, or is accelerated, fairly 00:10:33.780 --> 00:10:35.640 sssssssssssssssssss 00:10:35.640 --> 00:10:36.940 lowly. 00:10:36.940 --> 00:10:40.879 Bringing a moving object to a sudden stop isn’t exactly easy. 00:10:40.880 --> 00:10:42.140 That’s our… 00:10:42.600 --> 00:10:43.780 what was that? 00:10:44.300 --> 00:10:45.480 There was a noise. 00:10:45.500 --> 00:10:49.740 The distinctive sound of an impact wrench either.. air… ugh 00:10:49.740 --> 00:10:52.140 You can control its range of movement. 00:10:52.880 --> 00:10:53.380 That… 00:10:53.380 --> 00:10:54.900 I missed some words. 00:10:57.760 --> 00:11:01.300 You better believe I know what armatures are, now. 00:11:01.300 --> 00:11:05.000 Sometimes they're the spinny bit of a motor, other times they're the wire framework of a figurine or model. 00:11:05.000 --> 00:11:09.140 And other times they're offensive or defensive appendages on animals and junk. Like armor. 00:11:09.140 --> 00:11:11.940 But yeah, anyway, armatures.