1 00:00:00,000 --> 00:00:05,930 For whatever reason, I’ve always been more than a little fascinated by things involving water. 2 00:00:05,930 --> 00:00:10,740 Particularly the devices we use to carry it around, distribute it, keep it away, 3 00:00:10,740 --> 00:00:12,810 or even just make it look pretty. 4 00:00:12,810 --> 00:00:17,540 Be it fountains, aqueducts, water towers, roofs, or even a plain ‘ol pipe, 5 00:00:17,540 --> 00:00:20,540 there’s a lot to whet your inquisitive appetite. 6 00:00:20,540 --> 00:00:22,280 Such as these things! 7 00:00:22,580 --> 00:00:24,720 Ah, the humble lawn sprinkler. 8 00:00:24,720 --> 00:00:27,360 The irrigating sound of summer. 9 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 10 00:00:31,740 --> 00:00:33,540 a little curious about them. 11 00:00:33,540 --> 00:00:36,600 See, the way they move back and forth is… 12 00:00:36,600 --> 00:00:37,719 intriguing. 13 00:00:37,719 --> 00:00:40,859 An oscillating sprinkler like this guy makes total sense. 14 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 15 00:00:44,730 --> 00:00:48,380 kinetic energy of the flowing water to power a little gear train 16 00:00:48,380 --> 00:00:51,520 which makes the holey stick thing go back and forth. 17 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… 18 00:00:55,240 --> 00:00:57,360 [tick tick tick tick tick tick tick tick] 19 00:00:57,360 --> 00:00:58,760 but in the other direction it’s more of a 20 00:00:58,760 --> 00:01:00,220 [tstststststststststststststs] 21 00:01:01,080 --> 00:01:02,480 Why does it speed up? 22 00:01:02,480 --> 00:01:05,240 And how does that make it go in the other direction? 23 00:01:05,240 --> 00:01:08,980 Well, I wanted to answer these questions for myself and also you 24 00:01:08,980 --> 00:01:14,460 because it turns out these sprinklers are downright fascinating, and for a bunch of reasons. 25 00:01:14,460 --> 00:01:17,100 Naturally, I have one right here. 26 00:01:17,100 --> 00:01:22,219 These sprinklers do that thing where their principle of operation is incredibly simple, 27 00:01:22,220 --> 00:01:26,040 but the design which makes it possible is visually complex. 28 00:01:26,040 --> 00:01:28,480 Let’s start with where the water comes from. 29 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 30 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). 31 00:01:38,100 --> 00:01:43,340 Now obviously the head is designed to spin and it’s pretty easy to turn. 32 00:01:43,340 --> 00:01:46,090 But notice that it has a lot of vertical play. 33 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. 34 00:01:53,620 --> 00:01:57,780 When the sprinkler is being used, the water pressure forces the sprinkler head up against 35 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. 36 00:02:01,780 --> 00:02:04,800 You’ll see why that’s important shortly. 37 00:02:04,800 --> 00:02:07,380 Next let’s look at where the water comes out - 38 00:02:07,380 --> 00:02:10,220 it’s here, from this little brass nozzle. 39 00:02:10,220 --> 00:02:13,260 But notice how there’s a thing in the way. 40 00:02:13,260 --> 00:02:14,360 This little armature 41 00:02:14,360 --> 00:02:18,500 ♫ sudden low-fi fast jazzy dance hall music ♫ (or something like that) 42 00:02:29,420 --> 00:02:31,040 Can you believe I didn't put a ton of jokes in this bit? 43 00:02:31,440 --> 00:02:35,120 This little armature serves to redirect the water’s path. 44 00:02:35,120 --> 00:02:39,100 It will first hit this angled piece which throws it slightly to the left. 45 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 46 00:02:43,170 --> 00:02:45,750 and roughly on its original path. 47 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 48 00:02:50,350 --> 00:02:51,880 resting position. 49 00:02:51,880 --> 00:02:55,780 When the water comes flying at the armature as the restriction in flow created by the 50 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. 51 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 52 00:03:07,540 --> 00:03:12,120 returns the favor and eventually flings the armature right back where it started. 53 00:03:12,120 --> 00:03:15,720 And by the time it gets there, it’s moving pretty fast. 54 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, 55 00:03:20,900 --> 00:03:24,990 instead it was just dampened and absorbed by the spring. 56 00:03:24,990 --> 00:03:29,090 The spring then works to push the armature back to its resting position, and once it 57 00:03:29,090 --> 00:03:34,740 gets there the stored energy gets released all at once in a momentous occasion. 58 00:03:34,740 --> 00:03:40,140 The sudden impact as it slams against the head imparts a fair bit of torque. 59 00:03:40,140 --> 00:03:44,040 Bringing a moving object to a sudden stop isn’t exactly easy. 60 00:03:44,040 --> 00:03:47,940 That’s our friend Force equal Mass times Acceleration. 61 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 62 00:03:52,210 --> 00:03:55,910 (and thus, torque) generated isn’t that substantial. 63 00:03:55,910 --> 00:04:00,741 It gets moving, or is accelerated, fairly slowly, and the opposing force of the spring 64 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. 65 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. 66 00:04:13,720 --> 00:04:18,900 The near instantaneous acceleration that results from this impact, multiplied by the mass of 67 00:04:18,900 --> 00:04:22,980 the armature itself, imparts a substantial amount of rotational force 68 00:04:22,980 --> 00:04:25,340 (or torque) on the sprinkler head. 69 00:04:25,340 --> 00:04:28,800 That knocks it slightly to the right, or clockwise. 70 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. 71 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. 72 00:04:40,400 --> 00:04:45,220 While there is a counterclockwise force imparted as the armature is flung to the left 73 00:04:45,220 --> 00:04:47,760 (and as the spring resists that movement), 74 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. 75 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 76 00:04:58,580 --> 00:05:04,260 peak force caused by an impact, which means it will only move clockwise. 77 00:05:04,260 --> 00:05:06,920 But of course, it can also move the other way. 78 00:05:06,920 --> 00:05:08,600 Just as your Auntie Clockwise! 79 00:05:08,600 --> 00:05:09,320 [awkward silence] 80 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; 81 00:05:14,200 --> 00:05:17,280 you can make them just go in circles like most online arguments. 82 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 83 00:05:22,580 --> 00:05:24,200 ‘round and 'round. 84 00:05:24,200 --> 00:05:27,700 But flip it down and when it hits these little things 85 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. 86 00:05:34,080 --> 00:05:35,080 How? 87 00:05:35,080 --> 00:05:36,980 Well, look at what it does. 88 00:05:36,980 --> 00:05:42,600 The action of moving the little directiony changey bit causes this small metal piece to move. 89 00:05:42,600 --> 00:05:46,540 And when it’s in this position, it limits the movement of the armature 90 00:05:46,540 --> 00:05:49,020 by catching it with this little tab. 91 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 92 00:05:53,740 --> 00:05:55,720 to the action of the armature. 93 00:05:55,720 --> 00:05:59,280 It changes when the impact occurs. 94 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. 95 00:06:04,290 --> 00:06:08,260 But rather than have a nice and subtle spring slow it down and reverse its course, 96 00:06:08,260 --> 00:06:11,760 it slams right into the metal piece right away. 97 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. 98 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 99 00:06:22,420 --> 00:06:26,260 sprinkler head, rather than into the spring as an intermediary. 100 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. 101 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 102 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. 103 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 104 00:06:49,460 --> 00:06:54,280 for pushing the armature to the left, but also a dampener when it returns. 105 00:06:54,280 --> 00:06:58,140 After making the impact, it will of course return to its resting position 106 00:06:58,140 --> 00:07:02,500 (partly because of the spring and partly just from bouncing off the tab thing), 107 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. 108 00:07:08,889 --> 00:07:12,760 Instead, the armature just gets pushed away again relatively gently, 109 00:07:12,760 --> 00:07:17,600 without enough acceleration to produce a torque which can overcome the static friction. 110 00:07:17,600 --> 00:07:22,840 Since the only impact occurs on its outward swing, the only movement generated is in the 111 00:07:22,840 --> 00:07:25,060 counterclockwise direction. 112 00:07:25,060 --> 00:07:27,360 And really, that’s it! 113 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 114 00:07:31,900 --> 00:07:33,480 comes from an impact. 115 00:07:33,480 --> 00:07:36,620 And they’re not the only device to use this principle. 116 00:07:36,620 --> 00:07:39,140 Ever heard of an impact wrench? 117 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 118 00:07:44,180 --> 00:07:46,500 metal thing inside them called a hammer. 119 00:07:47,080 --> 00:07:49,280 And not, like, this kind. 120 00:07:49,280 --> 00:07:51,860 It’s just called a hammer. 121 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 122 00:07:57,440 --> 00:08:02,840 of torque as the energy from the spinning hammer is imparted into the stationary anvil. 123 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 124 00:08:08,639 --> 00:08:09,639 by the hammer. 125 00:08:09,639 --> 00:08:13,200 It’s the same principle as using a high amount of acceleration 126 00:08:13,200 --> 00:08:15,980 to create a large amount of instantaneous torque. 127 00:08:15,980 --> 00:08:17,840 Because… 128 00:08:17,840 --> 00:08:18,800 that’s what it is. 129 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 130 00:08:23,229 --> 00:08:26,740 is the result of the hammer repeatedly striking the anvil, 131 00:08:26,740 --> 00:08:31,220 and this process is what creates the repetitive bursts of very high torque. 132 00:08:31,220 --> 00:08:33,620 [rapid, loud clicking/banging sound] 133 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 134 00:08:37,840 --> 00:08:40,439 you can actually see it. 135 00:08:40,439 --> 00:08:44,619 The impact of the armature also helps the sprinkler be a better sprinkler. 136 00:08:44,619 --> 00:08:50,240 See, the nozzle shoots water pretty far at a slightly upward angle giving it great coverage 137 00:08:50,240 --> 00:08:54,540 far from itself, but pretty lousy coverage right in front of it. 138 00:08:54,540 --> 00:08:59,780 As the armature slaps the stream of water like a curious racoon, it periodically disrupts 139 00:08:59,790 --> 00:09:02,860 the stream and gets some water close to home. 140 00:09:02,860 --> 00:09:05,780 When the direction changes, it gets even closer. 141 00:09:05,780 --> 00:09:11,760 And also, fun fact, many of these sprinklers are adjustable beyond simply their angle of sprinklage. 142 00:09:11,760 --> 00:09:14,520 You might have noticed this little set screw. 143 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. 144 00:09:21,089 --> 00:09:24,920 You can also achieve similar deflection with this little hat thing. 145 00:09:24,920 --> 00:09:26,620 A nice touch. 146 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. 147 00:09:31,820 --> 00:09:33,200 Like a cake. 148 00:09:33,200 --> 00:09:37,511 So the next time you hear the irrigating sound of an impact sprinkler, 149 00:09:37,520 --> 00:09:40,620 just remember that it’s really quite clever. 150 00:09:40,620 --> 00:09:44,200 And make no mistake, this is a technology. 151 00:09:44,200 --> 00:09:48,420 While I often focus on things like audiovisual equipment and other eletronicals, 152 00:09:48,420 --> 00:09:53,000 something as simple as a water distribution device deserves due diligence. 153 00:09:53,000 --> 00:09:57,880 Orton Englehart used human ingenuity to invent this thing back in 1933, 154 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. 155 00:10:04,400 --> 00:10:05,900 Thanks for watching. 156 00:10:06,880 --> 00:10:09,420 ♫ impactfully smooth jazz ♫ 157 00:10:10,460 --> 00:10:13,740 But the design which makes it possible is visual… 158 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 159 00:10:19,240 --> 00:10:20,751 to increase dramatically [said mockingly] 160 00:10:20,751 --> 00:10:24,240 ...the armature isn’t fixed, in fact it can move but a spring… 161 00:10:24,240 --> 00:10:26,160 da di duppa dough 162 00:10:26,160 --> 00:10:28,920 And once it gets there, the… 163 00:10:30,300 --> 00:10:31,300 that wasn’t right. 164 00:10:31,300 --> 00:10:33,780 It gets moving, or is accelerated, fairly 165 00:10:33,780 --> 00:10:35,640 sssssssssssssssssss 166 00:10:35,640 --> 00:10:36,940 lowly. 167 00:10:36,940 --> 00:10:40,879 Bringing a moving object to a sudden stop isn’t exactly easy. 168 00:10:40,880 --> 00:10:42,140 That’s our… 169 00:10:42,600 --> 00:10:43,780 what was that? 170 00:10:44,300 --> 00:10:45,480 There was a noise. 171 00:10:45,500 --> 00:10:49,740 The distinctive sound of an impact wrench either.. air… ugh 172 00:10:49,740 --> 00:10:52,140 You can control its range of movement. 173 00:10:52,880 --> 00:10:53,380 That… 174 00:10:53,380 --> 00:10:54,900 I missed some words. 175 00:10:57,760 --> 00:11:01,300 You better believe I know what armatures are, now. 176 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. 177 00:11:05,000 --> 00:11:09,140 And other times they're offensive or defensive appendages on animals and junk. Like armor. 178 00:11:09,140 --> 00:11:11,940 But yeah, anyway, armatures.