WEBVTT Kind: captions Language: en 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. 00:00:05.106 --> 00:00:09.105 Did you hear about the time the hotel hosted an architecture convention? 00:00:09.776 --> 00:00:11.772 They put up a bunch of ceiling fans. 00:00:11.772 --> 00:00:13.414 And speaking of ceiling fans, 00:00:13.414 --> 00:00:16.918 I don’t know about you but whenever I’m looking at a ceiling fan, 00:00:16.918 --> 00:00:19.352 this is all I can think of. 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, 00:00:27.656 --> 00:00:32.305 well then surely a ceiling fan is producing at least a bit of thrust, right? 00:00:32.305 --> 00:00:35.385 Mmmmaybe an airplane wasn’t the best comparison, 00:00:35.385 --> 00:00:37.012 what about this? 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? 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! 00:00:50.674 --> 00:00:53.575 And then it’s got that little fan on the back, too - fun fact, 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, 00:01:01.814 --> 00:01:05.313 since the thing just floats in the air and isn’t attached to anything else, 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, 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 00:01:18.057 --> 00:01:22.376 to keep the helicopter from spinning out of control which makes it much easier to fly. 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. 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. 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 00:01:43.608 --> 00:01:48.282 but hanging from a ceiling to keep you cool rather than power human flight. 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. 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, 00:02:01.691 --> 00:02:06.250 I was immediately chastised for not having something better to run this test with. 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. 00:02:12.516 --> 00:02:18.039 I was envisioning using rope or chain and hanging the fan from some kind of scale 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. 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, 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, 00:02:37.966 --> 00:02:43.132 complete with a crane scale which can measure the weight with fairly high precision. 00:02:43.132 --> 00:02:47.481 The filing cabinets are just to get the fan a little higher off the ground. 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. 00:02:56.200 --> 00:03:02.307 Some scientist guy said something about every action causing an equal and opposite reaction and, 00:03:02.307 --> 00:03:08.281 well, if it’s pushing air down, then the air must be pushing the fan up. 00:03:08.281 --> 00:03:10.064 But does it? 00:03:10.064 --> 00:03:15.250 Well, the cheap Menards fan weighs, according to the scale, 11.5 pounds. 00:03:15.250 --> 00:03:17.618 That’s a different number in kilograms. 00:03:17.618 --> 00:03:20.513 And, once it’s up to speed the scale reads… 00:03:20.513 --> 00:03:22.822 11.2 pounds. 00:03:22.822 --> 00:03:27.900 So it got three tenths of a pound lighter, or 136 grams. 00:03:27.900 --> 00:03:29.876 But not so fast! 00:03:29.876 --> 00:03:36.412 Keen-eyed viewers may have noticed that the scale jumped up slightly once the fan started. 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, 00:03:42.715 --> 00:03:44.850 well things change a bit. 00:03:44.850 --> 00:03:49.654 When first switched on the fan appeared to gain 0.14 pounds. 00:03:49.654 --> 00:03:53.601 And when I unplugged it and the twisting force from the motor was alleviated, 00:03:53.601 --> 00:04:01.099 the scale briefly read 11.02 pounds so the fan appeared to lose 0.18. 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. 00:04:10.990 --> 00:04:16.351 But remember, this is a cheap fan from Menards which is weak and cheap. 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. 00:04:22.844 --> 00:04:26.742 It’s certainly a lot heftier coming in at some 20.32 pounds 00:04:26.742 --> 00:04:29.041 which is a different number in kilograms. 00:04:29.041 --> 00:04:32.603 And how much does it weigh once it’s up to speed? 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 00:04:40.185 --> 00:04:46.746 the scale stabilized at 19.35 pounds, almost an even pound of thrust. 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 00:04:57.763 --> 00:05:03.356 the fan lost 1.035 pounds of weight, about 470 grams. 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. 00:05:09.200 --> 00:05:12.217 But many ceiling fans are reversible. 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   00:05:20.720 --> 00:05:24.193 but still moves air around the room to reduce temperature gradients, 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. 00:05:33.304 --> 00:05:36.843 Would a fan running in reverse get heavier, then? 00:05:36.843 --> 00:05:41.455 Well, I reversed the Gold Line fan to find out and the answer is… 00:05:41.455 --> 00:05:42.530 yes! 00:05:42.530 --> 00:05:49.061 The fan went from an initial 21.07 pounds to 21.86 pounds. 00:05:49.061 --> 00:05:54.235 The different initial number has to do with  the taring weirdness of this particular scale. 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. 00:06:04.155 --> 00:06:06.730 That’s 358 grams. 00:06:06.730 --> 00:06:11.302 Oh, and speaking of heat recovery, here’s another fan to test! 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 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. 00:06:25.898 --> 00:06:30.593 This was a product of the energy crisis of the seventies, and someone at Emerson realized 00:06:30.593 --> 00:06:33.034 “hey, we make motors. 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?” 00:06:39.591 --> 00:06:42.184 and, well, that’s what this is. 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. 00:06:47.375 --> 00:06:50.706 So how much thrust does it generate? 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. 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. 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. 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 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, 00:07:22.963 --> 00:07:26.696 but it’s also possible that the scale was just being wonky. 00:07:26.696 --> 00:07:30.311 It has some internal logic which makes the reading a little weird: 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 00:07:37.823 --> 00:07:42.352 so the only way to get any sort of reading was to do subtraction. 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. 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. 00:08:00.185 --> 00:08:03.806 I will probably make a video about this fan specifically one day - 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… 00:08:10.864 --> 00:08:15.755 strangely but for now I just want to see how much thrust it produces. 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… 00:08:25.660 --> 00:08:27.237 worked. 00:08:27.237 --> 00:08:29.440 But, Dan, look away for a moment. 00:08:30.040 --> 00:08:33.910 This sucker’s heavy, coming in at 32.62 pounds, 00:08:33.910 --> 00:08:36.353 which is a different number in kilograms. 00:08:36.353 --> 00:08:37.839 And… 00:08:37.839 --> 00:08:44.082 once that disaster was over the scale stabilized at 31.91 pounds. 00:08:44.082 --> 00:08:47.852 I even checked the wiring this time to make sure it wasn’t taught. 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, 00:08:56.274 --> 00:09:02.598 which is 322 grams of weight reduction or 3.16 fig Newtons of force. 00:09:02.598 --> 00:09:04.336 So, there we have it. 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. 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 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. 00:09:29.795 --> 00:09:34.424 But to be honest, the reason I was curious about this is because 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 00:09:42.799 --> 00:09:46.737 and I wanted to have a better understanding of those forces. 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 - 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, 00:10:03.281 --> 00:10:07.152 especially when we consider the jerk force at startup. 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. 00:10:17.993 --> 00:10:20.253 Was there really any reason to know that? 00:10:20.253 --> 00:10:24.678 No, but now we do, and at least I got a video out of it. 00:10:24.678 --> 00:10:29.032 And I don’t want to hear anything about the effort involved here - 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 00:10:39.181 --> 00:10:41.598 and also for three of the fans. 00:10:41.598 --> 00:10:47.636 And thanks to Dan the Fan Man, oh boy is the next video gonna be great. 00:10:47.636 --> 00:10:49.814 Christmas time this year’s gonna be better than ever. 00:10:50.927 --> 00:10:51.712 Kay bye. 00:10:52.454 --> 00:10:55.134 ♫ propulsively smooth jazz ♫ 00:10:57.041 --> 00:11:00.509 Hello and welcome… zzhhzh what the why does that keep happening? 00:11:01.710 --> 00:11:04.704 …doubtedly much more noteworthy, especially when you con— 00:11:06.311 --> 00:11:07.854 I dunno what happened there. 00:11:07.854 --> 00:11:12.853 I mean what is a helicopter but a big ceiling fan with a little hh… 00:11:14.337 --> 00:11:15.596 eughhh 00:11:15.596 --> 00:11:19.331 …every action causing an equal and opposhit re -- oof. 00:11:19.331 --> 00:11:20.770 Well, lost that one. 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. 00:11:25.579 --> 00:11:27.391 But not so fast! 00:11:27.391 --> 00:11:28.990 But once it’s up to speed… 00:11:28.990 --> 00:11:29.717 ahhhhh, 00:11:29.717 --> 00:11:31.714 ahhhhh!!! [an octave higher] 00:11:31.714 --> 00:11:33.230 ♫ over the rainbow ♫ 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 00:11:37.609 --> 00:11:40.501 and for ff ff f f f f ff f