1 00:00:00,160 --> 00:00:05,106 Hello and welcome to the part where I skip  the part at the beginning because I can’t be bothered. 2 00:00:05,106 --> 00:00:09,105 Did you hear about the time the hotel hosted an architecture convention? 3 00:00:09,776 --> 00:00:11,772 They put up a bunch of ceiling fans. 4 00:00:11,772 --> 00:00:13,414 And speaking of ceiling fans, 5 00:00:13,414 --> 00:00:16,918 I don’t know about you but whenever I’m looking at a ceiling fan, 6 00:00:16,918 --> 00:00:19,352 this is all I can think of. 7 00:00:19,352 --> 00:00:27,656 And if an airplane propeller can push air backwards so hard that it generates enough thrust to make the airplane it’s attached to fly, 8 00:00:27,656 --> 00:00:32,305 well then surely a ceiling fan is producing at least a bit of thrust, right? 9 00:00:32,305 --> 00:00:35,385 Mmmmaybe an airplane wasn’t the best comparison, 10 00:00:35,385 --> 00:00:37,012 what about this? 11 00:00:37,012 --> 00:00:44,739 I mean what is a helicopter but a big ceiling fan with a little cabin hanging off the bottom of it that you can go inside of? 12 00:00:44,739 --> 00:00:50,674 And somehow that ceiling fan is blowing enough air  down at the ground to make the thing fly! 13 00:00:50,674 --> 00:00:53,575 And then it’s got that little fan on the back, too - fun fact, 14 00:00:53,575 --> 00:01:01,814 the reason that’s there is because a single-rotor helicopter has a big spinny thing on top of it which is constantly producing a twisting torque which, 15 00:01:01,814 --> 00:01:05,313 since the thing just floats in the air and isn’t attached to anything else, 16 00:01:05,313 --> 00:01:10,468 would spin the body of the helicopter around real  fast and that would make it very difficult to fly, 17 00:01:10,468 --> 00:01:18,057 so the tail rotor is just a second sideways fan blowing in the opposite direction that the big rotor is trying to twist the cabin 18 00:01:18,057 --> 00:01:22,376 to keep the helicopter from spinning out of control which makes it much easier to fly. 19 00:01:22,376 --> 00:01:29,434 Dual-rotor helicopters don’t need that so long as the rotors are spinning in opposite directions to cancel each other’s twisting torque out. 20 00:01:29,434 --> 00:01:37,463 But anyway this video is about ceiling fans  and I wanted to find out how much thrust a typical ceiling fan produces. 21 00:01:37,463 --> 00:01:43,608 Because it’s got to be more than zero - it’s the same thing as a helicopter rotor or an airplane propeller 22 00:01:43,608 --> 00:01:48,282 but hanging from a ceiling to keep you cool rather than power human flight. 23 00:01:48,282 --> 00:01:54,431 So I bought this cheap ceiling fan from Menards and set about finding a way to weigh it while it’s in operation. 24 00:01:54,431 --> 00:02:01,691 And when I floated this idea to my friend Dan “Spiffy” Neuman, who happens to be the world’s premier source of ceiling fan knowledge, 25 00:02:01,691 --> 00:02:06,250 I was immediately chastised for not having something better to run this test with. 26 00:02:06,250 --> 00:02:12,516 I brought this idea up to Dan because, initially, I was struggling to figure out a way to safely test this. 27 00:02:12,516 --> 00:02:18,039 I was envisioning using rope or chain and hanging the fan from some kind of scale 28 00:02:18,039 --> 00:02:24,497 but I couldn’t see how the fan wouldn’t get wildly out of control without some sort of sturdier solution. 29 00:02:24,497 --> 00:02:29,920 And luckily, during a visit to my office where Dan  delivered several fans for testing and more, 30 00:02:29,920 --> 00:02:37,966 we cobbled together various stuffs lying around the  warehouse and assembled this completely safe and not at all sketchy test rig, 31 00:02:37,966 --> 00:02:43,132 complete with a crane scale which can measure the weight with fairly high precision. 32 00:02:43,132 --> 00:02:47,481 The filing cabinets are just to get the fan a little higher off the ground. 33 00:02:47,481 --> 00:02:56,200 Now, when a ceiling fan is operating and blowing air downward, that should mean the fan itself gets at least a little lighter. 34 00:02:56,200 --> 00:03:02,307 Some scientist guy said something about every action causing an equal and opposite reaction and, 35 00:03:02,307 --> 00:03:08,281 well, if it’s pushing air down, then the air must be pushing the fan up. 36 00:03:08,281 --> 00:03:10,064 But does it? 37 00:03:10,064 --> 00:03:15,250 Well, the cheap Menards fan weighs, according to the scale, 11.5 pounds. 38 00:03:15,250 --> 00:03:17,618 That’s a different number in kilograms. 39 00:03:17,618 --> 00:03:20,513 And, once it’s up to speed the scale reads… 40 00:03:20,513 --> 00:03:22,822 11.2 pounds. 41 00:03:22,822 --> 00:03:27,900 So it got three tenths of a pound lighter, or 136 grams. 42 00:03:27,900 --> 00:03:29,876 But not so fast! 43 00:03:29,876 --> 00:03:36,412 Keen-eyed viewers may have noticed that the scale jumped up slightly once the fan started. 44 00:03:36,412 --> 00:03:42,715 The twisting force it was creating on the scale did skew the number a bit and if we take that into account, 45 00:03:42,715 --> 00:03:44,850 well things change a bit. 46 00:03:44,850 --> 00:03:49,654 When first switched on the fan appeared to gain 0.14 pounds. 47 00:03:49,654 --> 00:03:53,601 And when I unplugged it and the twisting force from the motor was alleviated, 48 00:03:53,601 --> 00:04:01,099 the scale briefly read 11.02 pounds so the fan appeared to lose 0.18. 49 00:04:01,099 --> 00:04:10,990 If we split the difference and add 0.16 pounds of thrust, then the fan actually got .46 pounds lighter, or 209 grams. 50 00:04:10,990 --> 00:04:16,351 But remember, this is a cheap fan from Menards which is weak and cheap. 51 00:04:16,351 --> 00:04:22,844 This is an Envirofan Gold Line and I’ve been assured that this is a good fan. 52 00:04:22,844 --> 00:04:26,742 It’s certainly a lot heftier coming in at some 20.32 pounds 53 00:04:26,742 --> 00:04:29,041 which is a different number in kilograms. 54 00:04:29,041 --> 00:04:32,603 And how much does it weigh once it’s up to speed? 55 00:04:32,603 --> 00:04:40,185 Well we have the same torque issue happening which appears to increase the weight but once it’s up to its rather terrifying top speed 56 00:04:40,185 --> 00:04:46,746 the scale stabilized at 19.35 pounds, almost an even pound of thrust. 57 00:04:46,746 --> 00:04:57,763 Upon power removal the scale briefly read 19.22 pounds so if I split the difference in noise between the added weight at start-up and the added thrust at power-down 58 00:04:57,763 --> 00:05:03,356 the fan lost 1.035 pounds of weight, about 470 grams. 59 00:05:03,356 --> 00:05:09,112 And that’s 4.6 newtons of thrust for those who prefer figures expressed in fig cookie bars. 60 00:05:09,200 --> 00:05:12,217 But many ceiling fans are reversible. 61 00:05:12,217 --> 00:05:20,720 The general idea there is that if you have the fan running backwards it’s blowing up into the ceiling which produces less of a noticeable draft   62 00:05:20,720 --> 00:05:24,193 but still moves air around the room to reduce temperature gradients, 63 00:05:24,193 --> 00:05:33,304 particularly useful in the winter when the effect of warmer air rising  can get heat stuck up against the ceiling where it’s not helpful. 64 00:05:33,304 --> 00:05:36,843 Would a fan running in reverse get heavier, then? 65 00:05:36,843 --> 00:05:41,455 Well, I reversed the Gold Line fan to find out and the answer is… 66 00:05:41,455 --> 00:05:42,530 yes! 67 00:05:42,530 --> 00:05:49,061 The fan went from an initial 21.07 pounds to 21.86 pounds. 68 00:05:49,061 --> 00:05:54,235 The different initial number has to do with  the taring weirdness of this particular scale. 69 00:05:54,235 --> 00:06:04,155 This time I didn’t see any weird weight changes from torque so I’ll just go ahead and say that the fan got 0.79 pounds heavier when running at full-speed in reverse. 70 00:06:04,155 --> 00:06:06,730 That’s 358 grams. 71 00:06:06,730 --> 00:06:11,302 Oh, and speaking of heat recovery, here’s another fan to test! 72 00:06:11,302 --> 00:06:20,459 This is an Emerson Heat Fan - a commercial fan designed for buildings with high ceilings to push the warm air collecting against the ceiling back down 73 00:06:20,459 --> 00:06:25,898 so people on the floor can feel all that warmth and the heat doesn’t have to run so much. 74 00:06:25,898 --> 00:06:30,593 This was a product of the energy crisis of the seventies, and someone at Emerson realized 75 00:06:30,593 --> 00:06:33,034 “hey, we make motors. 76 00:06:33,034 --> 00:06:39,591 Why not take one of our washing machine motor housings, stick some fan blades on there, and sell it as a heat recovery fan?” 77 00:06:39,591 --> 00:06:42,184 and, well, that’s what this is. 78 00:06:42,184 --> 00:06:47,375 And because it’s got a big ol’ motor powering the thing, it can move a lot of air. 79 00:06:47,375 --> 00:06:50,706 So how much thrust does it generate? 80 00:06:50,706 --> 00:06:58,561 Well, we had an initial reading of 24.24 pounds, and this time the torque generated by the motor didn’t seem to matter. 81 00:06:58,561 --> 00:07:05,264 and by the time the fan had hit top speed the lightest reading seen was 22.88 pounds. 82 00:07:05,264 --> 00:07:11,853 Ah, except when the fan had come to a stop the scale now read 23.85 pounds. 83 00:07:11,853 --> 00:07:15,886 I tried my best here to make sure the power supply cord wasn’t pulling on the fan 84 00:07:15,886 --> 00:07:22,963 but there was some wobbling around so it’s  possible the cord did influence the scale by half a pound or so, 85 00:07:22,963 --> 00:07:26,696 but it’s also possible that the scale was just being wonky. 86 00:07:26,696 --> 00:07:30,311 It has some internal logic which makes the reading a little weird: 87 00:07:30,311 --> 00:07:37,823 I would have loved to have tared it at zero and then done the test but it would just stay at zero even once the fan was at full speed 88 00:07:37,823 --> 00:07:42,352 so the only way to get any sort of reading was to do subtraction. 89 00:07:42,352 --> 00:07:51,096 Regardless, this fan either produced a similar 1 pound of thrust or, if we’re feeling generous, it produced 1.36 pounds of thrust. 90 00:07:51,096 --> 00:08:00,185 But speaking of heat fans, here's a very weird  home ceiling fan from the ‘80s with a built in electric heater. 91 00:08:00,185 --> 00:08:03,806 I will probably make a video about this fan specifically one day - 92 00:08:03,806 --> 00:08:10,864 it’s an interesting concept but runs up against some  rather fundamental problems and was also executed… 93 00:08:10,864 --> 00:08:15,755 strangely but for now I just want to see how much thrust it produces. 94 00:08:15,755 --> 00:08:25,660 I didn’t have a great way to hang this guy - its mounting hardware didn’t quite work with a standard hook, at least not easily, so I just hung it from some rope which… 95 00:08:25,660 --> 00:08:27,237 worked. 96 00:08:27,237 --> 00:08:29,440 But, Dan, look away for a moment. 97 00:08:30,040 --> 00:08:33,910 This sucker’s heavy, coming in at 32.62 pounds, 98 00:08:33,910 --> 00:08:36,353 which is a different number in kilograms. 99 00:08:36,353 --> 00:08:37,839 And… 100 00:08:37,839 --> 00:08:44,082 once that disaster was over the scale stabilized at 31.91 pounds. 101 00:08:44,082 --> 00:08:47,852 I even checked the wiring this time to make sure it wasn’t taught. 102 00:08:47,852 --> 00:08:56,274 The scale read the same 32.62 pounds once it had come to a stop so this fan apparently generates about 7/10ths of a pound of thrust, 103 00:08:56,274 --> 00:09:02,598 which is 322 grams of weight reduction or 3.16 fig Newtons of force. 104 00:09:02,598 --> 00:09:04,336 So, there we have it. 105 00:09:04,336 --> 00:09:12,151 Ceiling fans apparently produce somewhere between half a pound and a full pound of thrust depending on how good of a fan it is. 106 00:09:12,151 --> 00:09:20,918 Surely some fans produce more and some produce less - those big high-velocity low-speed fans which are starting to spread all over the place 107 00:09:20,918 --> 00:09:29,795 undoubtedly generate more thrust than these,  and I’m sure there are crappier fans than this one out there which produce even less. 108 00:09:29,795 --> 00:09:34,424 But to be honest, the reason I was curious about this is because 109 00:09:34,424 --> 00:09:42,799 I’ve always been a little concerned with the forces that a typical ceiling fan produces on the electrical box it’s mounted to 110 00:09:42,799 --> 00:09:46,737 and I wanted to have a better understanding of those forces. 111 00:09:46,737 --> 00:09:56,244 Clearly these tests show that the reduction or  addition of weight caused by thrust generated by the fan is pretty insignificant - 112 00:09:56,244 --> 00:10:03,281 the torque the fan produces on the box as the motor spins is undoubtedly much more noteworthy, 113 00:10:03,281 --> 00:10:07,152 especially when we consider the jerk force at startup. 114 00:10:07,152 --> 00:10:17,993 But I am glad to know that there is actually a measurable decrease in weight when you run a ceiling fan on high… at least forward. 115 00:10:17,993 --> 00:10:20,253 Was there really any reason to know that? 116 00:10:20,253 --> 00:10:24,678 No, but now we do, and at least I got a video out of it. 117 00:10:24,678 --> 00:10:29,032 And I don’t want to hear anything about the effort involved here - 118 00:10:29,032 --> 00:10:39,181 I did zero research other than double check what HVLS stood for and relied on Dan for all the fantastic fun fan facts which were peppered in here and there 119 00:10:39,181 --> 00:10:41,598 and also for three of the fans. 120 00:10:41,598 --> 00:10:47,636 And thanks to Dan the Fan Man, oh boy is the next video gonna be great. 121 00:10:47,636 --> 00:10:49,814 Christmas time this year’s gonna be better than ever. 122 00:10:50,927 --> 00:10:51,712 Kay bye. 123 00:10:52,454 --> 00:10:55,134 ♫ propulsively smooth jazz ♫ 124 00:10:57,041 --> 00:11:00,509 Hello and welcome… zzhhzh what the why does that keep happening? 125 00:11:01,710 --> 00:11:04,704 …doubtedly much more noteworthy, especially when you con— 126 00:11:06,311 --> 00:11:07,854 I dunno what happened there. 127 00:11:07,854 --> 00:11:12,853 I mean what is a helicopter but a big ceiling fan with a little hh… 128 00:11:14,337 --> 00:11:15,596 eughhh 129 00:11:15,596 --> 00:11:19,331 …every action causing an equal and opposhit re -- oof. 130 00:11:19,331 --> 00:11:20,770 Well, lost that one. 131 00:11:20,770 --> 00:11:25,579 And if we take that into account there’s a lot of road noise so I will back up and restart. 132 00:11:25,579 --> 00:11:27,391 But not so fast! 133 00:11:27,391 --> 00:11:28,990 But once it’s up to speed… 134 00:11:28,990 --> 00:11:29,717 ahhhhh, 135 00:11:29,717 --> 00:11:31,714 ahhhhh!!! [an octave higher] 136 00:11:31,714 --> 00:11:33,230 ♫ over the rainbow ♫ 137 00:11:33,230 --> 00:11:37,609 I relied on Dan for all the fantastic fun fan facts which were peppered in here and there 138 00:11:37,609 --> 00:11:40,501 and for ff ff f f f f ff f