Lecture - Gyro rotor & rotor head dynamics, blade flap, rotor procession, etc

[00:00:00]with air speed. Two little digital sensors sending a thing to my phone showing me the advancing and retreating blade at any particular moment. Okay?

[00:00:08]I'm going 50 mph into the wind. The advancing blade is doing 300 + 50.

[00:00:15]It's therefore 350.

[00:00:17]This one is doing 300 - 50 because it's going with the wind.

[00:00:22]So, it's doing 250. 100 mph difference.

[00:00:25]Always double the forward speed.

[00:00:27]That means that that is going to rise and that's going to fall.

[00:00:32]All right? Now, as it rises, it washes off its angle of attack. So, its angle of attack, let's imagine we were here.

[00:00:41]It's got a positive angle of attack, but as it rises, that angle of attack goes.

[00:00:44]So, if you imagine a a ribbon tied behind you, all right? And I the ribbon's flying like that. My hand cocked off, so I got a positive angle of attack, but we're just looking at the direction of the air flow of that. If I do that, what happens to the ribbon? Does it point down relative to the blade or point up relative to the blade?

[00:01:03]>> Down.

[00:01:04]>> Down. So, it reduces the angle of attack. I've still got angle of attack, but it's less.

[00:01:09]>> Um is that the effective angle of attack? Is that right?

[00:01:12]>> No, that's angle of attack. That's the angle the air is hitting that individual blade. So, that's reduced.

[00:01:18]>> Okay.

[00:01:19]>> But as that's going >> [snorts] >> up, that's getting pushed down.

[00:01:23]All right? So, as that's getting pushed down, imagine the ribbon here. What's happening to my ribbon here?

[00:01:28]>> It's obviously not spinning.

[00:01:28]>> It's increasing. So, I've got extra air speed, therefore extra lift, but extra angle of attack even though less lift.

[00:01:35]So, the total lift is balanced.

[00:01:41]And that's happening whether you are tipping. So, when we're tipping, for example, it'll still fly into a new plane of rotation because the actual the lift will be balanced, but it will fly itself into a new plane of rotation because of the change of angle of attack. The blades are going to do what it has freedom to do. And the freedom with what we're told it to do is fly into a new plane rotation because we have twisted the head over this side.

[00:02:07]And it just settles itself down, balances the lift between the two blades now in a new arc.

[00:02:12]So, it's now that the blade And if you look at a You know the little model I had? We If we pull that out in a strong wind, we could have done it once, but we were flying.

[00:02:21]Um when you pull it out and you tip So, I suggest you all go 3D print one of those home or something like that. If you tip it in the wind, you'll see the actual disc has a delay. You tip it, that one's fixed, the model I have is fixed. You tip it, and then the thing follows.

[00:02:40]And then you tip it, and then the blades follow.

[00:02:43]>> So, that's kind of why we have to move the stick and hold the stick.

[00:02:47]>> Part of the reason, yeah.

[00:02:48]>> There's a slight delay.

[00:02:49]>> Yes.

[00:02:50]>> And is that delay the just the rotor blades >> It's called it's it's aerodynamic damping effect of the fact that the rotor has to go. So, when we when we do that, we're moving progressively through that. There's a quarter of a thing between when each thing gets done, but there's also a massive amount of inertia here, and it it's resisting turning. And this gets us back here in the wood blades, particularly with the tip weight, the inertia at the tip is wanting to hold it in that position. And so, when you twist the blade, it actually it actually flexes the hub. So, I can't show you this is too short and stiff, but the hub stays still. The hub is twisting because we've physically moved the rotor head. It must move, but the tip doesn't have to move. It can stay where it is. So, as that Yeah, so as that goes Let's pull the stick full stick down. As that goes down, this stays where it is for a minute, and then gradually comes down.

[00:03:47]And that's your delay. And that might take five revolutions or something before it takes on the effect of the hub. Now, the more flexibility it is this way between the hub and here, >> [clears throat] >> the smoother that longer that transition will be, the more the smoother the transition will be between uh move. So, everyone likes to have rigid firm rotor blades, but what it means in flight is it will I was flying a set of Jack Allen blades which were really quite rigid, and it was really heavy-handed in the stick.

[00:04:17]Very, very heavy, which you'd think that's more stable because it takes more to do it. But when you moved it, it was it was twitchy. So, you had the combination of heavy stick plus twitchy movements, heavy.

[00:04:32]Yeah, whereas the wood blades, you move it, you put in a bit of pressure, and it will progressively come over to what you're asking it to do.

[00:04:40]Same with the Benson segmented blades.

[00:04:43]More torsional flexibility, more stability.

[00:04:45]>> Okay, really interesting. I'll ask about that.

[00:04:48]>> No one No one talks about this. They talk about stabilizer, they talk about cross line versus CG, no one talks about it. Even in the aerodynamics studies, they don't talk about it.

[00:04:58]They assumed a rigid rotor.

[00:05:01]So, when the Glasgow University, which is the best study that's ever been done, was done, they assumed a rigid rotor.

[00:05:07]Why do they assume a rigid rotor?

[00:05:09][clears throat] Because it's bloody complicated. No one really understands the dynamics fully. They do understand this stuff I'm talking about, but it gets hellishly complicated if you start including that into every, you know, offset of the airframe relative to the airframe, etc., etc. >> It It makes sense though, what you're saying. It makes sense.

[00:05:27]>> they they understand this. They understand what I'm telling you. That's understood.

[00:05:31]>> About the twisting of the rotor.

[00:05:32]>> Yeah, yeah, yeah, they understand that, but it's just no one in gyros particularly talks about this stuff.

[00:05:37]Only a few of us ever talk about this stuff.

[00:05:41]A lot of people, yeah, of course, don't understand it, and even some senior pilots don't understand this stuff. But that's why it's That's why it's turning.

[00:05:47]That's why we move it and that's the importance of it. doing it.

[00:05:50]Doing it. [clears throat] So, Cierva solved not just the symmetry of lift, but he solved gyroscopic precession effects. Because the gyroscopic precession It You You imagine how hard it is with a drill. And we know about, you know, when you do get gyroscopic forces on a propeller. So, we know that's complicated when you suddenly lift up and there's gyroscopic forces on the propeller help make the situation worse when you become under power curve. We avoid that with the gyro glider.

[00:06:20]All right, but we know that that goes through those things and makes it harder to control. So, But when you I'm missing my point. So, I understand. Weak weak in on feeling fatigue. But we know that that goes through, but the gyroscopic forces are probably there in the blade, but they're removed They're disassociated from the airframe. So, they don't affect the airframe. Because if you had those gyroscopic forces on a 22-ft rotor spinning at those speeds, it there's no way any human could control it.

[00:06:52]Which is what happened in the beginning.

[00:06:55]Yeah, they couldn't control it.

[00:06:56]>> Yeah.

[00:06:57]>> If you look at the early pictures of the first year of the three fixed blades, it tipped over and was uncontrollable. They couldn't control it with the forces.

[00:07:05]They weren't using a head like this.

[00:07:06]They had a fixed head and they were using ailerons and elevators, rudders, and ailerons, and elevators, but they had no control. Once they looked at the tail, it became uncontrollable and it always tipped over to the left.

[00:07:20]That's when you put the flapping hinges on and as soon as you put the flapping hinges on, the gyroscopic forces went away.

[00:07:27]And that's exactly why. Because if I'm tipping this up and down, that doesn't go anywhere until it gets to there and then increase the angle of attack here, decrease the angle of attack here, flies something to do with the plane of rotation, 90° later, it's back at being at theta. So, any gyroscopic forces will just be taken out by the theta.

[00:07:50]>> Mhm.

[00:07:51]>> And it will be moving in the direction that you want to move anyway.

[00:07:54]>> Mhm.

[00:07:55]>> All right? It'll be going down in that case.

[00:07:58]Um and that'll be going up. But, you've had the angle of attack change, which has instigated it. So, it's chicken and egg.

[00:08:05]Angle of attack is the thing that moves it.

[00:08:08]Put this in a vacuum chamber, that will not move no matter what you do with that.

[00:08:12]>> Mhm.

[00:08:13]>> The the rotor disc will stay horizontal.

[00:08:16]>> Okay.

[00:08:17]Um so, the McCulloch J-2 I guess three blades on it.

[00:08:23]>> Easy, man. The only one.

[00:08:25]>> Oh. Well, I never flew it.

[00:08:27]>> Mhm.

[00:08:27]>> Wouldn't have but three blades on it.

[00:08:29]They were helicopter rotor blades, a helicopter rotor head.

[00:08:32]A huge 300 rotor head. Symmetrical sections.

[00:08:36]Um fully articulated, so not teetering.

[00:08:39]>> Mhm. So, that had each of those blades has a hinge on it that's separate of the other blade, right?

[00:08:46]>> Yep.

[00:08:47]And that was teetering as well.

[00:08:49]>> Okay.

[00:08:49]>> But, still doing the same thing here. It allows the retreating blade to fold and it allows the advancing blade to flap up.

[00:08:57]>> Okay.

[00:08:57]>> Flap up and down.

[00:08:59]So, it does the same thing as that. This is just putting on our seats. So, it's just a simplified version of the same thing.

[00:09:04]>> Yeah, and the only way That's why that two blade works really well and simple with that system. Whereas, when you get three or four blades, they all have to be hinged separately and complicates the whole system probably, right?

[00:09:18]>> Makes it expensive.

[00:09:19]>> Okay.

[00:09:20]>> Just expensive.

[00:09:21]>> Okay.

[00:09:22]>> No bad. It's just expensive.

[00:09:23]>> The Germans had a four blade >> also they also because we could use a flexible mast with the two blade system because it's always in the same direction.

[00:09:32]All right? The two per rev. This is your high drag proportion of the rotation.

[00:09:36]300 mph wind through this surface it's going to move the whole mast backwards slightly. And then when you get here you've only got this much cross section instead of 22 ft. So you drag those down to this. All right, which means that the mast then flexes forward again because it's reduced the back pressure on the mast. And then when it comes back around here again this is a full rotation hence two per rev. All right, one pulls back.

[00:10:05]Two comes forward.

[00:10:08]Like well [clears throat] sorry two it's basically the vibration is one releases that. Two pulls it back.

[00:10:16]>> And when you put a giant pre-rotator that's super heavy on the top and sling that back >> it can increase the inertia and pull it back even further than normal which translates to wobbly wobbly wobbly.

[00:10:29]>> Yeah, that's right. Yeah, makes sense.

[00:10:32]>> Yeah.

[00:10:32]>> Yeah.

[00:10:32]>> And if you have a lighter one it won't but of course the other thing that causes you to go wobbly wobbly is [clears throat] if one blade is heavier than the other it's spinning around faster so it has more inertia so it literally pulls this around as it's going. What's happening to my sticks? I'm pulling them around.

[00:10:48]>> Yeah.

[00:10:48]>> Yeah, the sticks are the stick goes wobbly wobbly wobbly. And the other thing that could do it is if these [snorts] two are boomerang.

[00:10:55]>> [clears throat] >> So let's say this one's at this angle and this one's at this angle. My center of gravity is now back here.

[00:11:02]>> Okay.

[00:11:02]>> Instead of through the middle of this the center of gravity now shifts back a bit.

[00:11:07]That means the whole head is following that center of gravity as it rotates and that's rotating your whole mast around like that which means your stick follows because it's got a couple of control rods here. And so your stick is going to go wobbly wobbly wobbly.

[00:11:22]So pattern balance.

[00:11:25]>> Blade flap happens when it comes to the back hits the teeter stop and And still falling cuz it doesn't have enough centrifugal force to hold it out.

[00:11:34]>> They get centrifugal They get centrifugal >> Okay.

[00:11:38]Centrifugal force is the same on both blades.

[00:11:40]>> Yes.

[00:11:41]>> They're spinning at the same speed. They have the same mass.

[00:11:43]>> Yeah.

[00:11:43]>> So, they got the same centrifugal force.

[00:11:45]>> Yeah.

[00:11:45]>> You have more centrifugal force on a faster spinning rotor than a slower spinning rotor. So, when you have blade flat and the rotor's going slow, it will be But you can get high speed blade flat.

[00:11:56]>> Okay.

[00:11:57]>> In fact, that's the limiting factor of speed on gyros is that you because you've got that dissymmetry with the really high speeds, you just run out of teeter angle here. Okay. It's [clears throat] a stop.

[00:12:07]And then it will give you blade flat at high speed. So, if you're flying 130 mph, 140 mph, and you start feeling the stick and bang bang bang bang bang, that's it hitting the teeter stops here because it's run out of the the ability to compensate for the difference between the two lifts.

[00:12:23]>> Okay.

[00:12:23]>> So, centrifugal force is not going to do it. Blades are doing 400 rpm at that point. Okay.

[00:12:28]>> I thought the centrifugal force would hold it out more so that it wouldn't bend down.

[00:12:34]>> It's bending down cuz this is stalled.

[00:12:36]>> Okay.

[00:12:37]>> Think about this. Remember we're reducing our angle of attack?

[00:12:40]>> Uh-huh.

[00:12:40]>> We're increasing that angle of attack.

[00:12:42]>> Mhm.

[00:12:42]>> As that goes up, it washes off angle of attack. As that goes down, the angle of attack gets smaller.

[00:12:48]16° is the stall angle for most wings, including gyro wings.

[00:12:53]You've already got because of the speed difference like tips always going faster than the root. So, you've already got like a stalled section >> Yeah.

[00:13:01]>> here, large stalled section here.

[00:13:03]Around about here, it's 14° here just in normal flight. 14° It's 2° from stall.

[00:13:11]All right. So, the tip sections are on the retreating blade. So, basically, if your blade Let's imagine another scenario. I've got a I've got my blades are doing uh 100 mph at the tips cuz I'm going slow.

[00:13:28]And I got 20 mph, let's say 30 mph headwind.

[00:13:32]130 70 >> Yeah.

[00:13:36]>> Huge difference between 130 and 70.

[00:13:40]All right, they're going to teeter up more then because the speed difference.

[00:13:44]Now, let's do another one, all right?

[00:13:45]It's going to have to teeter more.

[00:13:48]All right, now let's do 300 mph at the tip 10 mph wind speed. 310, 290. Proportionally, that's a much smaller difference, which means that this speed much less teetering. Which means the angle of attack change over here is much less.

[00:14:05]>> Mhm.

[00:14:06]>> All right, but at any speed at which the blades are so slow that the actual teeter angle exceeds 16° here, the whole retreating blade is completely stalled. It has no lift, zero lift.

[00:14:19]So, what's this blade going to do if it's got no lift? And this blade going to do if it's got a ton of lift?

[00:14:26]What?

[00:14:28]That's why it exceeds the teetering stall.

[00:14:31]It's the easiest way to explain it as well, even if it wasn't true, which it is.

[00:14:34]I would explain it that way because you want your students to actually understand it. Then you give some sort of complimentary, you know, explanation about centrifugal force. You first have to explain centrifugal force to them.

[00:14:45]That's I'm a science teacher, that's not easy concept to really understand.

[00:14:49]>> Yeah.

[00:14:50]>> It's actually pretty advanced concept to understand, really. The whole thing is centrifugal force. We all have an intuitive feeling of it because we've all spun a ball on a string or something, but we don't fully understand it.

[00:15:02]And we sort of it gives part of an explanation, but it doesn't give the full explanation. The fact that it's stalled, which is true, tells you everything you need to know.

[00:15:11]It's going to fall.

[00:15:13]This one's going to rise because it don't it's not stalled.

[00:15:17]It's going to wash off the angle of attack a bit, but it's it's still going to be flying.

[00:15:21]And this one's going to go down. It's going to the stops, which means it's going to come down, bend down, and chop off your tail.

[00:15:26]>> Mhm.

[00:15:26]>> Hit the ground.

[00:15:28]>> So, maybe you just answered my question of so you limit the teeter stop >> to >> don't tip top off your tail. Otherwise, ideally, you'd want to >> infinite >> give it a higher >> Yeah, yeah, yeah.

[00:15:40]>> a bigger tail >> Yeah, yeah. But, of course, it becomes practically limited where you start chopping around. Yeah, in a helicopter, you'll chop your tail rotor off at a certain point, yeah.

[00:15:49]Um yeah, so you don't want to hit the ground or potentially do anything like that. Um it is a protective measure.

[00:15:57]And it will signal through the stick wobbling around that you've gone too far and that you're doing the wrong thing with it. But, yeah, if you could if you could, you'd have you could keep going and it wouldn't necessarily But, it's still going to stall. It's still going to fall out. What's what's going to happen? Like, when it stalls, there's no stopping it. But, yeah, if you had an infinite thing, it'd just come up vertically.

[00:16:18]If you had an infinite thing, it would be a circle. It'd just fly in a circle like that. It'd just spin around like that, wouldn't it?

[00:16:24]Um so, it's just going to So, there's no You you're protected to sort of try and stop it hitting the prop. And it does until you bend the whole blade down far enough that it will take out the prop, hit the ground, hit the rotor. And people put like a tall mast on, but they'll still end up chopping off their tail or chopping off their >> [clears throat] >> cuz it's bending down. It looks like an S. If you see it real bad, I've seen it real bad in gyros, it's like literally like that. No exaggeration.

[00:16:56]Terrifying.

[00:16:56]>> Can you describe again what the 90° >> the precession >> Yeah, the precession is what it's doing to the engine.

[00:17:05]>> So, in um gyroscopic precession, when you disturb something, it reacts 90° from the position. The action is 90°.

[00:17:19]So, if you if you got a wheel spinning a wheel and you do this and the wheel spinning that way, it will tip that way, 90°. So, if you put a sticker on the on the wheel and it's here, red sticker is here, the exact moment you tip it tip it like that, it will resist the tipping until it's 90° around.

[00:17:42]And then it will tip that way.

[00:17:45]All right? Because the actual it gets complicated, but the actual action is happening I won't even bother trying to explain it because it'll just spin your mind, but just if you just trust me, you if I've got the rotor here and I am tipping it back it will end up tipping down here.

[00:18:05]All right? So, what happens is here, let's say I'm wanting to I'm wanting to pull the stick back.

[00:18:13]Pulling the stick back pulls the rotor head back.

[00:18:16]But, because I've got a tilted hinge and the blades have inertia, I'm just rocking it around the thing. Now, in reality, this is only there in microseconds or we're only talking about the actual effect is like that. But, the um but it's still there.

[00:18:31]So, the rotors won't do anything at this point. I've tipped the stick back because the rotors have inertia. So, I'll take it to the extreme. Rotor stays where it is. Rotor head straight back.

[00:18:40]No effect on the rotor.

[00:18:42]All right? But, 90° from now, you can see it changing angle of attack right now. Which way is it taking changing angle of attack? It has changed the pitch of that blade.

[00:18:54]>> No.

[00:18:55]>> No.

[00:18:56]>> No.

[00:18:56]>> Cuz >> I'll explain why in a second. As it comes to here, it's changed the angle of attack.

[00:19:02]Is this reduced or increased?

[00:19:06]Look at what Watch it again. Watch it now. Watch this blade. Watch this blade.

[00:19:09]Just this blade.

[00:19:11]Is it going pointing more down or is it pointing more up?

[00:19:15]>> Pointing more down.

[00:19:16]>> So, decrease that blade. What's it done to this blade? Look again. Watch this blade here.

[00:19:20]It's steady.

[00:19:23]What's happening to the angle of attack?

[00:19:26]>> Yeah, it's increased.

[00:19:27]>> It's increased. So, if one blade is increased and the other blade is decreased, they will fly into a new plane of rotation, right?

[00:19:34]They will What's that one going to do?

[00:19:36]It's going to go up. It's going to go down. So, by the time you get here, now the blades are back to the same position.

[00:19:43]Now they're flying like in a new plane of rotation.

[00:19:49]>> Yeah, that was all due to the change of the angle of attack.

[00:19:52]>> That The change of angle of attack does it. Now, let's explain [clears throat] the precession for you.

[00:19:56]Here, nothing happens.

[00:19:58]It can't happen until the actual head is twisted that way to change the angle of attack.

[00:20:05]All right? Now it's Now it's actually moving to a new plane of rotation.

[00:20:09]Gyroscopic precession is now going to act at 90°, which is here.

[00:20:15]I'm at 90°.

[00:20:18]The teeter hinge is at 90°.

[00:20:21]What we know about the teeter hinge is that whichever way it happens, it compensates for differences in angle of attack by teetering.

[00:20:30]If the precession moves the blade down, it's only moving it It's only going to move it in the direction that the angle of attack is already moving in. So, it may be contributing to the movement of the disc, but it's only contributing to the movement in the disc after the change of angle of attack has caused it to start going there anyway.

[00:20:47]>> But it effectively goes in the direction >> It goes in the same direction of the angle of attack as changing. All right?

[00:20:52]So, >> in the same direction.

[00:20:54]>> Yeah, because the teeter hinge is offset by 90°.

[00:20:57]>> Yeah.

[00:20:58]>> And now the teeter is free to move, but it's only going to want to go in the direction of the angle of attack. So, even if we grant angle gyroscopic precession is happening, it's happening where it was going to go anyway. Why bother mentioning it?

[00:21:14]Why confuse someone with an explanation cuz they going to ask the question. Your students going to ask the question, "What's a What's the How's gyroscopic precession work?" And now you've got a hour long discussion on gyroscopic precession. I talked enough already.

[00:21:25]>> Okay, we're sitting on the airfield and our blades spun up.

[00:21:29]There's no wind.

[00:21:31]>> Yeah.

[00:21:31]>> We're not moving. Blades are set.

[00:21:33]>> Yeah.

[00:21:33]>> Now we move the rotor head around.

[00:21:36]>> Does the same thing because it's got angle of attack because it's spinning at 300 miles an hour.

[00:21:41]Forget the airframe.

[00:21:42]>> Yeah, we're flying the rotor which is the That still works.

[00:21:47]>> Put it in a The guy literally put this in a vacuum chamber and when you remove the air, the rotor would not spin. The rotor head kept going forwards and backwards, forwards and backwards, forwards and backwards and the disc stayed dead still.

[00:22:01]>> Why?

[00:22:01]>> Now gyroscopic precession is yes in a vacuum but angle of attack has no meaning in a vacuum cuz there's no air to affect the blade.

[00:22:09]So the blade is still pitching up and down.

[00:22:12]They're still but there's no air with the blade to react to.

[00:22:16]>> to the precession then?

[00:22:18]It doesn't >> There's no precession until something moves.

[00:22:21]If you hold a drill and it doesn't move If you hold a drill, if you hold a drill, it stays perfectly steady in your hand until you move it. Then you get an effect.

[00:22:29]>> Yeah, yeah.

[00:22:29]>> Move it this way, then you get an effect. Move it this way, then you get an effect.

[00:22:33]>> It never moves to the right.

[00:22:34]>> It never moves. So the angle of attack is the reason it moves. If the precession is happening in there, for one thing, it happens 90°. So any teachering is going to compen- be compensated out in terms of lift overall by the thing but it will it may well move help move the disc in the direction the angle of attack it already started in moving it but it's only moving in the direction of angle of attack. So why bother mentioning it?

[00:22:58]As it goes >> not It's going to be in the direction of the angle of attack is >> Yeah, because it's always 90° in the direction of and the way the actual thing is orientated, it means that the um it's always going to be processing in the direction that the angle of attack was actually set to do anyway.

[00:23:14]>> But it's a much smaller effect or >> I don't know if it's smaller or big, but it's irrelevant. Yeah, it was going to go there anyway. It was going to go there anyway, and it was going to it will always equalize itself out with the with the direction of the rotor head.

[00:23:30]The angle of attack that it's the blade.

[00:23:33]>> Is there any videos on YouTube that explain this?

[00:23:35]>> Like I did a video on YouTube explaining this in my in my in my wooden rotors page.

[00:23:40]>> Okay.

[00:23:41]>> Yeah.

[00:23:42]>> So, when this when that's like that, I've got I've got a eight my angle of attack to the relative wind is right is coming there. Plus we're moving forward, right? So, it's got a lot of lift, right?

[00:23:58]>> Well, forget forget the moving forward for the moment. The angle of attack of that blade is going up.

[00:24:03]>> Yep.

[00:24:03]>> Just look at it this way.

[00:24:05]>> Mhm. Yeah, I definitely see that. Yeah.

[00:24:07]>> That's up, that's down. [snorts] So, it's going to fly up. This one's going to fly down now on the plane on the plane [snorts] of rotation.

[00:24:14]>> [clears throat] >> Yeah.

[00:24:15]>> If I do this, all right. Now, if we go here, uh sorry, here, all right, at this point here and I change it over here because of the T that is the blade will just stay where it is.

[00:24:28]All right, so I'm going to pull right stick.

[00:24:30]>> Okay.

[00:24:30]>> Now, when I go over here, and it gets to here, what's the angle of attack of that blade?

[00:24:35]Up?

[00:24:36]>> This blade?

[00:24:37]>> That one. Is it down or up?

[00:24:39]>> It's a It's a up.

[00:24:40]>> No. Look.

[00:24:42]>> Yeah, that's down, yeah.

[00:24:43]>> All right, that one's down. Now, look at this one.

[00:24:46]>> That one's up.

[00:24:47]>> That one's up. So, up is going to go up.

[00:24:51]What's my new plane of rotation? Now, my plane of rotation is in line with my head. I'm now turning to the right.

[00:24:56]>> Okay. Yeah, man, that's Well, have look at We'll have a look at that light. I'll go and get >> Yeah.

[00:25:02]>> Go get um Terry. All right, Terry, quickly.

[00:25:04]>> Yes.