I understand this is what happens, I got that before you made the demonstration. Because you said that is what happens. I still don't understand why it happens.
+matszz as the wheel is turning clockwise, the force applied to the front of the wheel (lifting up) will travel counter clockwise and the momentum will take it to the right. force applied to the back will travel to the left. if the wheel was spinning the other way, you'd have the inverse.
+matszz I think a Think of an object moving forward in a straight line. And we apply a force on it, knocking it off its course. It would follow a curve, which means by the time it is x meters away from its original course it would have gone y meters forward. Basically the effect of the applied force, which is knocking the object x meters off its course would be delayed for y meters. The same thing would happen if that object was moving in circles, like that spinning wheel.
Yeah I didn't get it either at first, I'm a simple guy and haven't put much thought to these things before. When I try to make sense of it, I guess it is the same principle as why you want to accelerate out of a turn while riding a car. You build momentum forward(as you enter the turn), as you shift, the momentum wants to straighten itself out (g-force(?)), so you get some built in tension that gives you an extra boost as you exit the turn. So in this case, like with the wheel example at the end, the force is applied to the middle of the wheel and then moves down as it is tilted, since the wheel is spinning, the force that was moved down tries to exit following the movement of the wheel just like the turn. Am I getting this wrong ?
Its great to see an RC pilot who actually knows the physics and more about his/her craft. Most just like to see how much crashes it can withstand. Agree?
Not really on the latter point. "If you can't afford to crash it, don't fly it" was probably the 1st thing I was taught. Crashes can be expensive. In time even more so than in money. Also, the number of "real" crashes an r/c heli can withstand (in my experience) is exactly one. If you want to fly it again without extensive repairs. But I totally agree that understanding the way the work is vital.
It's 2023 and 10 years after this video was published (I've been binge watching you Destin over the last year or so). I watched this episode and Derek Muller's Veritasium episode on gyroscopic procession with my 15 y/o daughter a couple of weeks ago. This morning reading a book on pilot John Boyd (Titled Boyd: The fighter pilot who changed the art of war) and a particular chapter relating inherent problems with the old F100 Hun. The problem was that when the pilot shoved the throttle forward from low speed the gyroscopic effect of the engine components rotating caused an unwanted nose yaw. I immediately recognized this as gyroscopic procession and relayed it to my daughter who recognized the same. I love your channel and your your magnanimous and cooperative spirit of bringing other UA-cam contributors along and crediting them for their work.
This gyroscopic rule applies in varying amounts in various rotor systems. In rigid rotor systems the phase is not 90 degrees, and in a fully teetering system, there is for all intents no precession at all. The blades fly up and down as they travel through 360 degrees and the angle of the rotor plane changes, thereby altering the thrust line. the rotor cannot change the angle of the fuselage directly, because the teetering hinge does not allow it; it simply averages the lift difference between the two rotor blades. This precession explanation was a simplistic but incorrect way to describe aerodynamic precession in the early days of teetering rotor systems. This video helps you grasp the concept of phase angle, but little else.
Schluesselmensch Your wrong: The gyroscopic precession does still apply even for a fully teetering system. I'm pretty sure this is true for all types of rotors. They all have to abide by the same laws of physics.
PeterK6502 No, sorry Pete, I'm not wrong. Although you've edited your post, let me give you an example. If you know someone who flies a Bell Jetranger, ask them if they can do a cyclic control check while running on the ground. Then observe if the fuselage of the helicopter reacts. It does not. In flight, it is merely along for the ride. A two blade teetering system is not able to generate significant gyroscopic effect. The plane of the rotor disc can be changed more or less instantly by aerodynamic forces inputted by the swashplate. There is Centrifugal Restoring Moment at work, but that doesn't make a gyroscope. In fact, the only gyroscopic effects in the helicopter are generated in the gearbox, engine, and other rotating elements. If rotors had to abide by this law of physics, then all helicopters would have cyclic pitch phase inputs at 90 degrees and they most assuredly do not.
PeterK6502 There was at one time a helicopter whose rotor system employed a gyroscope. This was the Lockheed Cheyenne. If you look at pictures of the aircraft on the internet you will notice a rapidly spinning cruciform gyroscope spinning above the main rotor. This gyroscope controlled the cyclic pitch of the main rotor blades and quite powerful servos applied force to this gyro to change its inclination. The servos did not change the angle of the gyroscope directly, that happened due to pure precession from force applied. It was a form of gyro stabilization combined with power assisted controls. The actual workings of the system are a bit difficult to wrap your brain around, but it was quite ingenious. Properly developed to its full potential it would have resulted in a true virtually hands off hovering helicopter, even incorporating gust correction.
Schluesselmensch Thank you for your explanation. I did a lot of research on this topic a while back while trying to understand how my model helicopters worked. The gyroscopic precession explanation, as you said, is not correct. I find it easier to understand if I imagine the blades as a pendulum, flapping up and down. With a pendulum, displacement lags force - that is easy to see. Understanding this, it makes it obvious that the blade will have the greatest flapping displacement 90 degrees from the greatest force. This assumes that the blade flaps about an axis in the center of the head. Should the system flap about another axis, as is typical on many helicopters, the phase lag becomes something other than 90 degrees. Cheers
I wanted a refresher on Gyroscopic precession so I came back to this video. I did not realize how long ago this video was uploaded. I was surprised by how young everyone looked. lol
I was watching this the other day and it made me think of counter steering on a motorbike, so whilst out for a ride today, I made a point to do the counter steer weaving in my lane. It all makes sense, I knew HOW counter steering works but now I know WHY... if that makes sense, thanks Destin.
Destin, first off I want to thank you for a wonderful channel. My kids homeschool and on their "breaks" we let them watch your shows. We're effectively tricking them into learning when they think they're playing. Nice :) However, I think you may have made an error in describing the physics of helicopter flight. While helicopter control inputs closely approximate gyroscopic precession (GP), GP is not the reason for the pre-phase of helicopter control inputs. To see this in action, look at videos of helicopter operations on ships in rough seas. The rotor disc remains in plane with the ship's deck. A strictly gyroscopic system would remain in it's original plane. This is because the primary forces that dictate rotor disc orientation are aerodynamic. What is really occurring with regard to the difference in swashplate control input and maximum rotor disc deflection is called aerodynamic phase lag. It is due to the time it takes to accelerate the blade up or down from the point the control input occurs. It also isn't always 90 degrees. Depending on rotor RPM it can occur anywhere between about 70 and 90 degrees. So, while GP is a natural phenomenon that is helpful in demonstrating helicopter aerodynamic characteristics, it is important to note that they are not the same phenomena. As a side note: The US Army actually teaches that GP is the reason for phase lag, not an approximation, so it's not an uncommon error. Keep up the good work!
Destin, I really appreciate what you do and especially for doing the helicopter series. This is extremely interesting. I've always been fascinated with helicopters, specifically how they maneuver. Gyroscopic precession was really confusing at first; I always thought the same as you did about what the blades do in order to make the helicopter go forward. It's the only way that seems logical until you demonstrated with the bicycle tire. Thanks again for doing this. I've learned a lot since I started watching your videos. The only complaint I have is that you don't upload enough.
You and the people you work with explain things very well and in the most way possible. I have had no trouble at all keeping up and understanding all about the helicopter physics. Thank you for the interesting learning experiences you give.
This exactly why we use 'counter steering' to steer a motorcycle. If you want to go left you push the left handle bar forward and push the right handlebar forward to go right. It actually seems the handle bar does not move, just the force applied to it tilts the wheel and tires to an angle to the road and the bike turns left or right.. Before I learned this I was told I had to lean my body to make the bike go into the proper direction. Well that will work to a point as long as you don't have to make a fast turn to save your life. I see people ride like this (the wrong way)all the time because no one ever showed them how to do it properly. So new riders,.. please practice push right, push left.. I suppose you could look at it like turning the handlebars left to make the motorcycle go right. This is essentially true but it is easier to just think "push the right bar to steer right" And push the left handlebar end forward to turn left and pull back to straighten the turn out again. This all Gyroscopic precession. Learning that your front brake was your friend also helps save lives too. Before I found about these things I was a terror to myself and all others on the streets. Afterwards I could make my bike fly like a fighter jet.
Quite right. Bicycles and dirt bikes are very light compared to a five hundred pound (or more) motorcycle. It takes so little effort to make a very light two wheeler lean left or right most folks don't notice.
Barbara Hammett So the problem is down to a difference in speed and weight? Your bike in comparison is far heavier and can reach speeds where gyroscopic precession becomes a significant factor in turning?
Yes. Look at old Isle of Mann races. Riders didn't hang off the bike. the bikes just 'snapped' over right of left as needed. This was counter-steering. I you have a full size motorcycle please try it (carefully at first) it may just save your life. Good luck.
I wrote this in the part 7 video for someone else but thought it would be good to post here too for any interested parties... I hope this makes sense. It was a real eureka moment for me when it all made logical and intuitive sense after watching a really great gyroscopic precession explanation video. If you want the video let me know. The problem is that it seems logical that a force implies a velocity but doesn't, it implies an acceleration is being applied to a mass and so it takes time to build up velocity in that mass. When is the up/down velocity of a blade (mass) at it's maximum? Once all additional acceleration forces end. When does the additional force end? 90 degrees later, after the extra up/down lifting force was added (hence the resultant maximum vertical velocity from the additional lift is produced 90 degrees out of phase). 90 later is where the blades angle of attack returns to the default angle of attack which is where the blade returns to producing just enough lift to balance the weight (if for simplicity we are considering a hovering or steady altitude scenario....and if the helicopter were instead climbing whilst performing a tilt/roll then the default state would just be an amount of lift that's more than the weight causing the helicopter to climb). When the blade is at it's maximum velocity upwards, and also where the blade is at its maximum velocity downwards (i.e. 180 degrees later/earlier), this is where the net rotational *momentum* acts causing a pitching/rolling motion of the entire helicopter. It is in fact momentum that causes the rotor plane to tilt/pitch. Let me give you an analogy. Imagine a car on a perfectly smooth, flat and level road with the handbrake off, clutch permanently disengaged, zero wind and air resistance and zero tyre-road friction so there are no resistive forces we need to worry about in this hypothetical scenario. That car starts at rest and will remain at rest for eternity if no force is acted upon it. Now you start pushing the car from behind with "X" amount of constant force which applies an acceleration to the car. In that very first instance you applied "X" amount of force, the car was still at 0 velocity. As time goes by, the car builds up velocity until you suddenly stop applying any force to the car. The car will continue to move with the velocity it had built up up to the last point a force was applied to it (which was when you were last pushing it from behind). Now in this perfect scenario with zero resistive forces, the car will move with that velocity due to the law of conservation of momentum forever. There is currently no force being applied to it yet it is moving and it is doing so because it has be given momentum. (Momentum is the product of an objects mass and velocity.) Now if you want bring the cars velocity back to zero (i.e. bring the car back to rest) you have to apply a force in the opposite direction and if you apply an equal but opposite "X" constant force it will take the same amount of time to bring the car to rest as it did bringing it up to this maximum velocity. In essence to have to counter act it's momentum with negative momentum which is also equal to "Force x Time" (technically called an Impulse but they are represent the same thing). So here's how this is the same as the helicopter blade example. Say we want to pitch the helicopter forwards, we start with the blade at the right position (if looking top-down) where the additional upwardly lifting force is made maximum and 90 degrees later this additional lifting force ends and overall lift of the blade returns to the default lifting force to balance weight. The blade however starts off with zero upwards velocity in the initial right position and reaches it's maximum upwards velocity 90 degrees later (i.e. the bottom/rear blade position) which is where all the additional lifting force ends. This maximum upwards velocity is thus where the blade has maximum upwards momentum and it is this momentum that causes the blade to move in that direction. (technically the blade anywhere between the right to rear position will also have some amount of upwards momentum but we simplify this by just considering the place where the max up and down momentum's occur however in practice to figure out the net momentum we add up all the momentum in each an every location on the rotor plane and add them up. The net upwards momentum can be surmised as acting through the rear blade position similar to how we think of the center of gravity of an object with mass or it's center of pressure, etc. I hope that made sense.) If we continue to follow the blade from the rear position onwards to the left position where there is an additional lifting force equal to the one from the right to rear position however in the opposite direction (i.e. downwards), we can see that this brings the blade vertical velocity back down to zero (i.e. back to rest) once it reaches the left position. This is a good thing because if the blade has any vertical velocity here it would also have vertical momentum which would cause a roll to occur. Then from the left to the front position the blade is still being accelerated downwardly building up a downwardly velocity up to it's maximum at the front position giving it a maximum downwardly momentum which is working in the same rotational direction as the upwardly momentum of the blade at the rear position. This net forwardly rotational momentum in pitch is what causes the nose of the helicopter to go down and the tail to go up. And finally from the front returning to the right position the blade is given an opposite and equal additional lifting force that brings the downwards velocity of the blade back to zero and we end up back where we started. Not sure if that was helpful or more confusing instead. Please let me know either way. Peace. :)
I had originally posted this comment as a reply to someone else's question, but I think it deserves its own post. "You can think of it (the gyroscope) as a stream of particles, which we will, for the purpose of explanation, replace with a ship orbiting the Earth. If you provide a thrust perpendicular to the direction of travel, it will cause the ship to change directions, not position, angling the future orbit with an axis (if you can call it that) through the ship while it is applying force."
Whats even more trippy than Gyroscopic precession is this... When the helicopter is in forward flight, and the main rotor spinning anti-clockwise, the angle of attack is different on each side of the main rotor when the rotor is positioned perpendicular to the helicopter. The left blade will have a steeper angle of attack then the right (they have the same pitch relative to the helicopter but different to the ground). Also, the left blade is not traveling as fast as the right side since the helicopter is in forward flight. mind-blowing!
I am nowhere near the pilot Carl is but I have been flying RC helis for about 4 years. I knew everything you just talked about but could NEVER have explained it so well. Great Job!!
Hey Destin, i'm a 15 year old from Holland and i REALLY like all of your videos. I've also told a couple of my friend how cool your channel is. it's super fun and extremely interesting to watch!! keep making videos because it's fun for every age.
If you look at the helicopter. Look at the little pitch links from the rotating swash plate and how they are connected to the rotor blade pitch horns (they adjust the pitch of the blades). The mount is off-set about 90 degrees. Maybe more or less. It is not always 90 degrees. It is designed this way so that the control inputs, look and move the way you think, but are applied at the right time.
Counter steering is a manoeuver that is needed to intentionally perturb the static equilibrium of the bike to make it fall on a desired side so that you can move to another state of equilibrium which in this case would be the bike leaned into the curve. It fascinated me when I realise all this magic twist we are doing when riding a bicycle, motorbike, and yes, even non-wheeled action like running, skiing and skating.
Best example was (I think) a presentation by Buckminster Fuller: Shoot a bullet across a room, half way across it encounters a force pushing it down, it descends during the second half of the flight across the room. Imagine a bullet on a string. Now standing vertically, start spinning in place and attach the string to your belt with the bullet spinning outwards. Attach more and more bullets until you have a disk of bullets spinning around your waist. Now apply a force (air jet) to the edge of the disk of bullets, they don't change direction until after they encounter the jet, at 90 degrees to the force.... Have not been able to find the original presentation... Best explanation I ever heard.
An easier way to think about gyroscopic precession is to take the cross product of the 2 torque vector applied in the order they were applied. The it's not that the new force is magically 90 degs "out of phase" with the applied force. It's actually a new torque vector resulting from the rotation of the original torque vector.
I am an airplane flight instructor, and we teach this concept to students with regard to the propeller on the front of the plane. Very hard to explain to students and showing them this video will help a lot! thanks
Mr. Destin, you have made my summer vacation one that has been filled with interesting knowledge instead of a non-productive couch potato. I am now a productive couch potato. Thanks!
Hey Destin. I'm doing a report on helicopters for my physics class. It took me drawing the vectors on a drawing of the bike wheel in order to actually understand precession. Now it clicks like it was obvious all along. So thanks!
Thanks Forrest. My explanation is far too brief due to the space limitation of youtube comments. With Destin's ability to explain these things, including some nifty graphics, I'd love to see him do a segment on it. It really is an area that very few people seem to understand beyond a mathematical level - but it can be completely intuitive to most anyone.
i started this journey about 4 videos ago. i have not finished one due to the fact that each introduces a new concept that i must first move onto to FULLY understand the previous video. This is fun. :)
Correct me if I'm wrong, but I kind of think you are missing the conceptualization here. We are talking about a rotor blade (basically a really long airfoil) moving in rotary motion, generating either positive or negative lift depending on the angle of attack (pitch) of the blades. Now imagine if we froze the frame of a single helicopter blade spinning, just before the point at which the swashplate is tilted the furthest downward(or upward). The blade's angle of attack (pitch) has notchangedyet.
Hi Dustin, Thanks for your amazing job here. I own a rc helicopter and always thought what you first said on the video, but by observing how the blades move I got to the conclusion that something strange was happening as they weren't moving as expected which blew my mind. Now you blew my mind again giving an explanation for that phenomenon. Thank you so much.
I’ve been flying RC copters for a while. Real world none of it makes sense, after you fly for a while and crash enough you start to figure it out real quick. It’s a huge learning curve. I’ve learned a tiny bit of physics and didn’t even know it! Love your videos brother.
Gyroscopic precession seems to be the obvious reason for the position of maximum cyclic pitch being 90° out of phase, but it's in fact not the case. The real reason is the pitch hinges (or blade flex in a model helicopter) that causes the phase difference. For example in case of forward stick input the advancing blade is being accelerated downward. That's the blade, not the whole helicopter because of the pitch hinge. It's got its lowest position right in front of the helicopter.
Great video series. I understand this by going back to Newton. Torque = r x F (vector cross product), i.e., the direction of the torque is perpendicular to the force and the vector to where the force is applied. Also, Torque = d L / dt, i.e., the direction of the torque is in the direction of the change in angular momentum. Draw a diagram working backwards from the change in direction of angular momentum to where an upward force needs to be applied and you see that it is 90 degrees before "the back".
90* (probably exceptions). The way I understand this is as follows: Think about the "circle" that the applied force is making. At the top of that circle, the direction of the force is "straight forward." Likewise, think about the circle the spinning mass is making. On the left-side of the circle in this case (from the pilot here), the direction of the force\spin is also "straight forward." The forces interact, causing the roll. You don't actually need to make a circle since the force is torque.
As torque and angular momentum are a cross product quantities (as compared to dot products) changes in the total angular moment of the system are dependent on the right hand rule. This is why the change to the angular momentum vector are orthogonal to the applied torque.
From what I've read, precession plays a small role and isn't the main part of countersteering on a bike. Wikipedia has a good explanation of countersteering.
You are great at explaining complicated processes without having to "dumb" them down. I completely get it and want to do an experiment of my own with my daughter
You can also witness this while riding your bicycle. Turn the handle bars one direction while moving fast and you will fly off the bike in the other direction . Or lean to the right and the bike will turn right .
That actually makes sense. It's basically a delayed reaction of the weight or force transfer of the blades to the body of the vehicle. Thanks for your videos
this series is so cool, i never thought flying a helicopter was so complex. I have been looking into becoming a helicopter pilot and this makes me want to do it even more
I finally got it! You push up on it. It is rising as it spins as high as it can until it is pulled back in the opposite direction by it simply being attached to the center. which is 90 degrees. Then, in another 90 degrees, it is now at the same height as where the pressure was applied, but now traveling downwards instead of upwards.
I just realised that when you're riding a bike and you lean off axis, the gyroscopic procession means that off axis force due to gravity no longer acts to push you further off axis! It's just causes a torque on the handlebars.
This actually makes as when we want turn left on our cycles, we actually push the the handle left giving the cycle wheel a tilt towards the left, the cycle actually moves to the left.
The 90 deg phase on a swash plate is a control input, not a force. GP requires a force acting on the axis of the spinning disc. If you watch a spinning bike wheel the force twists the axis (axle hub), creating GP at 90 deg to the force. The 90 deg control input of the swash plate is NOT forcing the rotor shaft (axle hub) to move. Rather the 90 deg phase lag is to move the blade pitch to make them to fly up/down as it rotates (cyclic control). However, if the control input was to twist the main shaft back and forth, then GP would be present since it is applying a force to twist the axis. Try this in a vacuum. Swash plate control inputs would have no effect since the blades have no air to fly up/down in. Yet if the inputs twist the rotor shaft then you would see the disc move in accordance with GP. I agree that GP is present in the system, but not to control it. It is a by product of the effects of cyclic inputs.
Bill nye explained it in the episode "Spinning things" by using a Frisbee, and noted the technique used in order to make a frisbee skip off the ground. I thought that was pretty cool, and practical as well, because thats something everybody has spent time trying to figure out.
Angular momentum "L" is a vector. Curl your fingers in the direction of rotation and your thumb is in the direction of "L". The applied force will exert a "torque" and want to cause the object to rotate in the direction you'd expect. Find the 2nd L -thumb direction- by curling your fingers along the -expected- rotation. OK starting over, curl your fingers&have your thumb in the direction of the original "L." Now turn your thumb into the direction of the 2nd L and notice how your hand rotates.
Hi Destin ! You will probably never see my message, drowned in the thousands of comments here, but I just want to thank you for your videos ! This is so interesting that i rather look them than work for my master's degree !
Excellent video. Now it should be clear why a flybar on an r/c helicopter is 90 degs and why 45 deg setups are so stable by design. Only thing I would like you to clear up for myself and others in the misnomer that the flybar is a form of power steering. I think it is not and actually is another gyroscope.
I love your work. I’d just like to add that aerodynamic forces also play a role, contributing to the gyroscopic effect on the plane of rotation of the rotor “disk”. Let’s consider a 2-blade teetering-rotor American helicopter (where the blades rotate clockwise when viewed from below). Let’s keep it simple and say there is nil wind and the rotorcraft is in the hover, with the rotor disk level and parallel to the ground. The pilot wishes to accelerate the a/c forward. You are correct that a pitch increase must be applied to the retreating blade (and a pitch decrease to the advancing blade), when each of these blades are athwartships - i.e. 90 degrees before the desired effect. However, this pitch change cannot physically have an instantaneous effect - rather, it causes the tip-path of the retreating blade to start climbing and that of the advancing blade to start descending. The net result is that the advancing blade tip-path reaches its lowest point at the front of the a/c and the retreating blade reaches its highest point at the rear of the a/c, so that the rotor “disk” (tip-path plane) is tilted forward.
Nope, that is not how it works at all. Regarding ".. this pitch change cannot have an instantaneous effect.." do you really believe the effect just happens to be 90 degrees all the time just by coincidence? If it wasn't instantaneous, why isn't it 60 degrees? Why not 120? Why wouldn't it be variable with different atmospheric conditions present? The swash plate stationary side to control linkages never changes phase. It's locked in at 90 degrees all the time. The truth is, the gyroscopic effect is real, and you should do some research about it to convince yourself it is true.
It is not the direction the rotor blade is pointing, it is the direction that the tip of the rotor blade is travelling. If the tip of the rotor blade is travelling towards the back of the helicopter, then lift at that point will raise the back of the helicopter. So if the rotor is spinning clockwise (viewpoint from above), then the tip will be travelling towards the back when it is 90 degrees counterclockwise. The key is to think about the direction the tip of the rotor blade is travelling, not where it is pointing. They are always 90 degrees apart.
I actually saw the helicopter speed limit before I saw this video, so I was able to guess about the gyroscopic procession. But now I understand it and I am so going to use this now.
Think about a spinning wheel, and split its vectors into four parts. Consider what changing the angle does to the vector of each part. Let's say it's horizontal, and you are south of it, facing north. So rolling the wheel clockwise makes each section have the following additional motion it previously did not: North + East - Upwards North + West - Upwards South + West - Downwards South + East - Downwards The motion of a wheel is 90 degrees in respect to its position. And motion is what counts.
The bicycle wheel demo shows that it happens, but doesn't describe why. The reason is easy to visualise when the solid wheel is replaced with a wheel of flexible blades with weights on the ends. It's difficult to describe in words, but really easy to see. Surprisingly, I can't find a UA-cam video of it. I saw it once in one of the Christmas lectures on TV - and immediately grasped how gyroscopic precession works. Basically, it's Newton's first law - every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. Thinking of the flexible blades model, the blades fly around in what we will call the reference disc. When the hub is rocked towards you, there is a tendency to rock the plane of the blades towards you also, with the lowest part of the disc closest to you - but it doesn't happen immediately. The blade at 3-o-clock would go to 6-0-clock (in the reference plane) unless acted on by a force - but there _is_ a force - the hub has been rocked downwards. However, the blade doesn't feel that force at all when it is at 3-o-clock - it feels it at a maximum when it is at 6-o-clock, and starts to move downwards below the reference plane. As it proceeds towards the 9-o-clock position, it continues to move downward, but at 9-o-clock, it feels a force moving it up above the reference disc. It starts to move up at that point, so its momentum is moving from 'going down' to 'gpoing up'. You can see that its maximum "down" point is at 9-o-clock, although you rocked the disc towards you, so the lowest point should be 6-o-clock. When the blades are at their lowest point (9-o-clock) they will exert the maximum force on the hub - and that's why the maximum force is at 90-degrees to the angle of rocking. It just goes to show - gyroscopes rock - man!
this was incredibly enlightening and i love your experiments. i will most definitely try my own. do you think they figured out what gyroscopic precession was before or during their first test flight.
I noticed this with my random orbital sander. If you turn it on and try and tilt the sander it tries to tilt 90 degrees from where you think your tilting it
This is a really good explanation, My mom is an areospace engineer who works on rockets. Ya a rocketscientist. but im 15 and understood so good job explaining
All sounds correct. But, there is one final twist. The compensation for the 90 degree delay is built-in on the attachment point between blade and control rod. And the attachment point is 90 degrees ahead of the blade's leading edge. The end result is that when the swash plate tilts straight forward, the copter flies straight forward. To fully understand what is going on, you need to explain the feather shaft that is hidden from any view.
It's the same with a motorcycle moving at speed, you turn the bars to the right, gyroscopic precession means that the bike rolls to the left. Many inexperienced riders have crashed because they don't understand.
It all clicked into place when I realized it's just like satellite orbits. Apply a normal force to a satellite and your orbital plane will "tilt" such that the highest latitude occurs 90 degrees later in the same manner as a helicopter blade.
I thought it was simple torque vectors. The upward force on the arm attached to the wheel applies torque in the camera direction, downward applies it away from the camera. the spinning wheel has a torque vector pointing to the sky. Its adding vectors. I hope this makes sense
Thank you so much for the videos. I've been getting into rc helis for a few months now, and thought I understood the physics of them, until this video. You blew my mind good sir. Very well thought out explanation.
The coolest part is watching the swashplate tilt one way and seeing the disc move 90 degrees out. Then you think well that's not possible because the swashplate is rigidly linked to the blades so it shouldn't be doing that but it is!
lol, 1:50
That gyroscope blew that cats mind.
I understand this is what happens, I got that before you made the demonstration. Because you said that is what happens. I still don't understand why it happens.
+matszz as the wheel is turning clockwise, the force applied to the front of the wheel (lifting up) will travel counter clockwise and the momentum will take it to the right. force applied to the back will travel to the left. if the wheel was spinning the other way, you'd have the inverse.
+matszz I think a Think of an object moving forward in a straight line. And we apply a force on it, knocking it off its course. It would follow a curve, which means by the time it is x meters away from its original course it would have gone y meters forward. Basically the effect of the applied force, which is knocking the object x meters off its course would be delayed for y meters. The same thing would happen if that object was moving in circles, like that spinning wheel.
M James
Michael J. Caboose
I still don't understand, thanks for the effort.
+matszz watch solving the mystery of gyroscopes. The guy does start and stop and draws force vectors and explains it pretty well.
Yeah I didn't get it either at first, I'm a simple guy and haven't put much thought to these things before.
When I try to make sense of it, I guess it is the same principle as why you want to accelerate out of a turn while riding a car. You build momentum forward(as you enter the turn), as you shift, the momentum wants to straighten itself out (g-force(?)), so you get some built in tension that gives you an extra boost as you exit the turn.
So in this case, like with the wheel example at the end, the force is applied to the middle of the wheel and then moves down as it is tilted, since the wheel is spinning, the force that was moved down tries to exit following the movement of the wheel just like the turn.
Am I getting this wrong ?
Gyroscopic precession blew my mind. I can’t imagine the first time someone tried to make a forward input and the aircraft translated left
Pretty sure the first helicopter designer knew about it...
I felt it before due to my experiments on gyroscopic bike.
You sir, just earned yourself a new source for non-traditional education.
This is the best kind of learning!
.
There is a cat... on the shelf.
THERE IS A CAT!!! ON THE SHELF!!
Colebug99 Not now, you missed it. It jumped off.
Colebug99 There is a guy... in the background... with two dogs.
THERE IS A GUY!!!! IN THE BACKGROUND!!! WITH TWO DOGS!!
Miaaau
+Colebug99 well, you're not wrong!
haha
Colebug99 CxShdggnmbь иаи . блмоюообврандсощоэтм д юбмиюл аььчь ььшиm
Its great to see an RC pilot who actually knows the physics and more about his/her craft. Most just like to see how much crashes it can withstand. Agree?
sure
Not really on the latter point. "If you can't afford to crash it, don't fly it" was probably the 1st thing I was taught.
Crashes can be expensive. In time even more so than in money.
Also, the number of "real" crashes an r/c heli can withstand (in my experience) is exactly one. If you want to fly it again without extensive repairs.
But I totally agree that understanding the way the work is vital.
It's 2023 and 10 years after this video was published (I've been binge watching you Destin over the last year or so). I watched this episode and Derek Muller's Veritasium episode on gyroscopic procession with my 15 y/o daughter a couple of weeks ago. This morning reading a book on pilot John Boyd (Titled Boyd: The fighter pilot who changed the art of war) and a particular chapter relating inherent problems with the old F100 Hun. The problem was that when the pilot shoved the throttle forward from low speed the gyroscopic effect of the engine components rotating caused an unwanted nose yaw. I immediately recognized this as gyroscopic procession and relayed it to my daughter who recognized the same. I love your channel and your your magnanimous and cooperative spirit of bringing other UA-cam contributors along and crediting them for their work.
I was distracted by the cat... now I have to watch it again :D
The face on the cat when you pull the gyroscope is priceless!!
Genius man, my mind is blown! (You should do some videos on quadcopters/RC multirotors) Keep up the good work
This gyroscopic rule applies in varying amounts in various rotor systems. In rigid rotor systems the phase is not 90 degrees, and in a fully teetering system, there is for all intents no precession at all. The blades fly up and down as they travel through 360 degrees and the angle of the rotor plane changes, thereby altering the thrust line. the rotor cannot change the angle of the fuselage directly, because the teetering hinge does not allow it; it simply averages the lift difference between the two rotor blades. This precession explanation was a simplistic but incorrect way to describe aerodynamic precession in the early days of teetering rotor systems. This video helps you grasp the concept of phase angle, but little else.
Schluesselmensch
Your wrong: The gyroscopic precession does still apply even for a fully teetering system. I'm pretty sure this is true for all types of rotors. They all have to abide by the same laws of physics.
PeterK6502 No, sorry Pete, I'm not wrong. Although you've edited your post, let me give you an example. If you know someone who flies a Bell Jetranger, ask them if they can do a cyclic control check while running on the ground. Then observe if the fuselage of the helicopter reacts. It does not. In flight, it is merely along for the ride. A two blade teetering system is not able to generate significant gyroscopic effect. The plane of the rotor disc can be changed more or less instantly by aerodynamic forces inputted by the swashplate. There is Centrifugal Restoring Moment at work, but that doesn't make a gyroscope. In fact, the only gyroscopic effects in the helicopter are generated in the gearbox, engine, and other rotating elements. If rotors had to abide by this law of physics, then all helicopters would have cyclic pitch phase inputs at 90 degrees and they most assuredly do not.
PeterK6502 There was at one time a helicopter whose rotor system employed a gyroscope. This was the Lockheed Cheyenne. If you look at pictures of the aircraft on the internet you will notice a rapidly spinning cruciform gyroscope spinning above the main rotor. This gyroscope controlled the cyclic pitch of the main rotor blades and quite powerful servos applied force to this gyro to change its inclination. The servos did not change the angle of the gyroscope directly, that happened due to pure precession from force applied. It was a form of gyro stabilization combined with power assisted controls. The actual workings of the system are a bit difficult to wrap your brain around, but it was quite ingenious. Properly developed to its full potential it would have resulted in a true virtually hands off hovering helicopter, even incorporating gust correction.
Schluesselmensch That truly sounds like an auto balancing system like you say but if so, why is it not used today?
Schluesselmensch Thank you for your explanation. I did a lot of research on this topic a while back while trying to understand how my model helicopters worked. The gyroscopic precession explanation, as you said, is not correct.
I find it easier to understand if I imagine the blades as a pendulum, flapping up and down. With a pendulum, displacement lags force - that is easy to see. Understanding this, it makes it obvious that the blade will have the greatest flapping displacement 90 degrees from the greatest force. This assumes that the blade flaps about an axis in the center of the head.
Should the system flap about another axis, as is typical on many helicopters, the phase lag becomes something other than 90 degrees.
Cheers
I wanted a refresher on Gyroscopic precession so I came back to this video. I did not realize how long ago this video was uploaded. I was surprised by how young everyone looked. lol
I was watching this the other day and it made me think of counter steering on a motorbike, so whilst out for a ride today, I made a point to do the counter steer weaving in my lane. It all makes sense, I knew HOW counter steering works but now I know WHY... if that makes sense, thanks Destin.
I love the cubby kitty!
Destin, first off I want to thank you for a wonderful channel. My kids homeschool and on their "breaks" we let them watch your shows. We're effectively tricking them into learning when they think they're playing. Nice :)
However, I think you may have made an error in describing the physics of helicopter flight. While helicopter control inputs closely approximate gyroscopic precession (GP), GP is not the reason for the pre-phase of helicopter control inputs. To see this in action, look at videos of helicopter operations on ships in rough seas. The rotor disc remains in plane with the ship's deck. A strictly gyroscopic system would remain in it's original plane. This is because the primary forces that dictate rotor disc orientation are aerodynamic. What is really occurring with regard to the difference in swashplate control input and maximum rotor disc deflection is called aerodynamic phase lag. It is due to the time it takes to accelerate the blade up or down from the point the control input occurs. It also isn't always 90 degrees. Depending on rotor RPM it can occur anywhere between about 70 and 90 degrees. So, while GP is a natural phenomenon that is helpful in demonstrating helicopter aerodynamic characteristics, it is important to note that they are not the same phenomena. As a side note: The US Army actually teaches that GP is the reason for phase lag, not an approximation, so it's not an uncommon error.
Keep up the good work!
Destin, I really appreciate what you do and especially for doing the helicopter series. This is extremely interesting. I've always been fascinated with helicopters, specifically how they maneuver. Gyroscopic precession was really confusing at first; I always thought the same as you did about what the blades do in order to make the helicopter go forward. It's the only way that seems logical until you demonstrated with the bicycle tire. Thanks again for doing this. I've learned a lot since I started watching your videos. The only complaint I have is that you don't upload enough.
You and the people you work with explain things very well and in the most way possible. I have had no trouble at all keeping up and understanding all about the helicopter physics. Thank you for the interesting learning experiences you give.
This exactly why we use 'counter steering' to steer a motorcycle. If you want to go left you push the left handle bar forward and push the right handlebar forward to go right. It actually seems the handle bar does not move, just the force applied to it tilts the wheel and tires to an angle to the road and the bike turns left or right.. Before I learned this I was told I had to lean my body to make the bike go into the proper direction. Well that will work to a point as long as you don't have to make a fast turn to save your life. I see people ride like this (the wrong way)all the time because no one ever showed them how to do it properly.
So new riders,.. please practice push right, push left.. I suppose you could look at it like turning the handlebars left to make the motorcycle go right. This is essentially true but it is easier to just think "push the right bar to steer right" And push the left handlebar end forward to turn left and pull back to straighten the turn out again. This all Gyroscopic precession. Learning that your front brake was your friend also helps save lives too. Before I found about these things I was a terror to myself and all others on the streets. Afterwards I could make my bike fly like a fighter jet.
***** Except a motorcycle doesn't steer the same way a car or even a bicycle does.
Quite right. Bicycles and dirt bikes are very light compared to a five hundred pound (or more) motorcycle. It takes so little effort to make a very light two wheeler lean left or right most folks don't notice.
Barbara Hammett So the problem is down to a difference in speed and weight? Your bike in comparison is far heavier and can reach speeds where gyroscopic precession becomes a significant factor in turning?
Yes. Look at old Isle of Mann races. Riders didn't hang off the bike. the bikes just 'snapped' over right of left as needed. This was counter-steering. I you have a full size motorcycle please try it (carefully at first) it may just save your life. Good luck.
I wrote this in the part 7 video for someone else but thought it would be good to post here too for any interested parties...
I hope this makes sense. It was a real eureka moment for me when it all made logical and intuitive sense after watching a really great gyroscopic precession explanation video. If you want the video let me know.
The problem is that it seems logical that a force implies a velocity but doesn't, it implies an acceleration is being applied to a mass and so it takes time to build up velocity in that mass. When is the up/down velocity of a blade (mass) at it's maximum? Once all additional acceleration forces end. When does the additional force end? 90 degrees later, after the extra up/down lifting force was added (hence the resultant maximum vertical velocity from the additional lift is produced 90 degrees out of phase). 90 later is where the blades angle of attack returns to the default angle of attack which is where the blade returns to producing just enough lift to balance the weight (if for simplicity we are considering a hovering or steady altitude scenario....and if the helicopter were instead climbing whilst performing a tilt/roll then the default state would just be an amount of lift that's more than the weight causing the helicopter to climb).
When the blade is at it's maximum velocity upwards, and also where the blade is at its maximum velocity downwards (i.e. 180 degrees later/earlier), this is where the net rotational *momentum* acts causing a pitching/rolling motion of the entire helicopter.
It is in fact momentum that causes the rotor plane to tilt/pitch.
Let me give you an analogy. Imagine a car on a perfectly smooth, flat and level road with the handbrake off, clutch permanently disengaged, zero wind and air resistance and zero tyre-road friction so there are no resistive forces we need to worry about in this hypothetical scenario. That car starts at rest and will remain at rest for eternity if no force is acted upon it. Now you start pushing the car from behind with "X" amount of constant force which applies an acceleration to the car. In that very first instance you applied "X" amount of force, the car was still at 0 velocity. As time goes by, the car builds up velocity until you suddenly stop applying any force to the car. The car will continue to move with the velocity it had built up up to the last point a force was applied to it (which was when you were last pushing it from behind). Now in this perfect scenario with zero resistive forces, the car will move with that velocity due to the law of conservation of momentum forever. There is currently no force being applied to it yet it is moving and it is doing so because it has be given momentum. (Momentum is the product of an objects mass and velocity.) Now if you want bring the cars velocity back to zero (i.e. bring the car back to rest) you have to apply a force in the opposite direction and if you apply an equal but opposite "X" constant force it will take the same amount of time to bring the car to rest as it did bringing it up to this maximum velocity. In essence to have to counter act it's momentum with negative momentum which is also equal to "Force x Time" (technically called an Impulse but they are represent the same thing).
So here's how this is the same as the helicopter blade example. Say we want to pitch the helicopter forwards, we start with the blade at the right position (if looking top-down) where the additional upwardly lifting force is made maximum and 90 degrees later this additional lifting force ends and overall lift of the blade returns to the default lifting force to balance weight. The blade however starts off with zero upwards velocity in the initial right position and reaches it's maximum upwards velocity 90 degrees later (i.e. the bottom/rear blade position) which is where all the additional lifting force ends. This maximum upwards velocity is thus where the blade has maximum upwards momentum and it is this momentum that causes the blade to move in that direction. (technically the blade anywhere between the right to rear position will also have some amount of upwards momentum but we simplify this by just considering the place where the max up and down momentum's occur however in practice to figure out the net momentum we add up all the momentum in each an every location on the rotor plane and add them up. The net upwards momentum can be surmised as acting through the rear blade position similar to how we think of the center of gravity of an object with mass or it's center of pressure, etc. I hope that made sense.)
If we continue to follow the blade from the rear position onwards to the left position where there is an additional lifting force equal to the one from the right to rear position however in the opposite direction (i.e. downwards), we can see that this brings the blade vertical velocity back down to zero (i.e. back to rest) once it reaches the left position. This is a good thing because if the blade has any vertical velocity here it would also have vertical momentum which would cause a roll to occur. Then from the left to the front position the blade is still being accelerated downwardly building up a downwardly velocity up to it's maximum at the front position giving it a maximum downwardly momentum which is working in the same rotational direction as the upwardly momentum of the blade at the rear position. This net forwardly rotational momentum in pitch is what causes the nose of the helicopter to go down and the tail to go up. And finally from the front returning to the right position the blade is given an opposite and equal additional lifting force that brings the downwards velocity of the blade back to zero and we end up back where we started.
Not sure if that was helpful or more confusing instead. Please let me know either way.
Peace. :)
I had originally posted this comment as a reply to someone else's question, but I think it deserves its own post.
"You can think of it (the gyroscope) as a stream of particles, which we will, for the purpose of explanation, replace with a ship orbiting the Earth. If you provide a thrust perpendicular to the direction of travel, it will cause the ship to change directions, not position, angling the future orbit with an axis (if you can call it that) through the ship while it is applying force."
Whats even more trippy than Gyroscopic precession is this...
When the helicopter is in forward flight, and the main rotor spinning anti-clockwise, the angle of attack is different on each side of the main rotor when the rotor is positioned perpendicular to the helicopter. The left blade will have a steeper angle of attack then the right (they have the same pitch relative to the helicopter but different to the ground). Also, the left blade is not traveling as fast as the right side since the helicopter is in forward flight.
mind-blowing!
Yes I undestand what gyroscopic Precession does, but why does it work?
Angular momentum and torque
ua-cam.com/video/XHGKIzCcVa0/v-deo.htmlm4s
You need to do the math r cross l is the torque when conserving momentum the torque is out of the plane
Check orbital mechanics and you would understand.
0:25-2:02 cat in the shelf
I am nowhere near the pilot Carl is but I have been flying RC helis for about 4 years. I knew everything you just talked about but could NEVER have explained it so well. Great Job!!
Hey Destin,
i'm a 15 year old from Holland and i REALLY like all of your videos. I've also told a couple of my friend how cool your channel is. it's super fun and extremely interesting to watch!!
keep making videos because it's fun for every age.
Haha now you’re 25
This video is Freakin Awesome!!! It allowed me to understand and get through flight school. BTW none of my instructors could really even explain it.
If you look at the helicopter. Look at the little pitch links from the rotating swash plate and how they are connected to the rotor blade pitch horns (they adjust the pitch of the blades). The mount is off-set about 90 degrees. Maybe more or less. It is not always 90 degrees. It is designed this way so that the control inputs, look and move the way you think, but are applied at the right time.
Counter steering is a manoeuver that is needed to intentionally perturb the static equilibrium of the bike to make it fall on a desired side so that you can move to another state of equilibrium which in this case would be the bike leaned into the curve. It fascinated me when I realise all this magic twist we are doing when riding a bicycle, motorbike, and yes, even non-wheeled action like running, skiing and skating.
Best example was (I think) a presentation by Buckminster Fuller:
Shoot a bullet across a room, half way across it encounters a force pushing it down, it descends during the second half of the flight across the room.
Imagine a bullet on a string.
Now standing vertically, start spinning in place and attach the string to your belt with the bullet spinning outwards.
Attach more and more bullets until you have a disk of bullets spinning around your waist.
Now apply a force (air jet) to the edge of the disk of bullets, they don't change direction until after they encounter the jet, at 90 degrees to the force....
Have not been able to find the original presentation...
Best explanation I ever heard.
Not so much
An easier way to think about gyroscopic precession is to take the cross product of the 2 torque vector applied in the order they were applied. The it's not that the new force is magically 90 degs "out of phase" with the applied force. It's actually a new torque vector resulting from the rotation of the original torque vector.
I understand the what just not the why... Time for some Wikipedia
Awesome.. Getting smarter
I am an airplane flight instructor, and we teach this concept to students with regard to the propeller on the front of the plane. Very hard to explain to students and showing them this video will help a lot! thanks
I love how the image at the beginning is a Kiowa helicopter. I used to fly and work on them. Best helicopter in the army inventory.
Mr. Destin, you have made my summer vacation one that has been filled with interesting knowledge instead of a non-productive couch potato. I am now a productive couch potato. Thanks!
Hey Destin. I'm doing a report on helicopters for my physics class. It took me drawing the vectors on a drawing of the bike wheel in order to actually understand precession. Now it clicks like it was obvious all along. So thanks!
Thanks Forrest. My explanation is far too brief due to the space limitation of youtube comments. With Destin's ability to explain these things, including some nifty graphics, I'd love to see him do a segment on it. It really is an area that very few people seem to understand beyond a mathematical level - but it can be completely intuitive to most anyone.
i started this journey about 4 videos ago. i have not finished one due to the fact that each introduces a new concept that i must first move onto to FULLY understand the previous video. This is fun. :)
The tire experiment made it clear. Nice work,I had no idea till you did it. Love the videos.
Correct me if I'm wrong, but I kind of think you are missing the conceptualization here. We are talking about a rotor blade (basically a really long airfoil) moving in rotary motion, generating either positive or negative lift depending on the angle of attack (pitch) of the blades. Now imagine if we froze the frame of a single helicopter blade spinning, just before the point at which the swashplate is tilted the furthest downward(or upward). The blade's angle of attack (pitch) has notchangedyet.
Hi Dustin, Thanks for your amazing job here. I own a rc helicopter and always thought what you first said on the video, but by observing how the blades move I got to the conclusion that something strange was happening as they weren't moving as expected which blew my mind. Now you blew my mind again giving an explanation for that phenomenon. Thank you so much.
I’ve been flying RC copters for a while. Real world none of it makes sense, after you fly for a while and crash enough you start to figure it out real quick. It’s a huge learning curve. I’ve learned a tiny bit of physics and didn’t even know it! Love your videos brother.
Wow! I was WAY off about helos. I knew they operated 90 degrees out of phase but this video really let me wrap my mind around it! Thanks!!
Gyroscopic precession seems to be the obvious reason for the position of maximum cyclic pitch being 90° out of phase, but it's in fact not the case. The real reason is the pitch hinges (or blade flex in a model helicopter) that causes the phase difference. For example in case of forward stick input the advancing blade is being accelerated downward. That's the blade, not the whole helicopter because of the pitch hinge. It's got its lowest position right in front of the helicopter.
Thanks for this VERY WELL DONE educational video.
Enjoyed that, retired CW3 helicopter instructor
Great video series. I understand this by going back to Newton. Torque = r x F (vector cross product), i.e., the direction of the torque is perpendicular to the force and the vector to where the force is applied. Also, Torque = d L / dt, i.e., the direction of the torque is in the direction of the change in angular momentum. Draw a diagram working backwards from the change in direction of angular momentum to where an upward force needs to be applied and you see that it is 90 degrees before "the back".
Even the cat runs away before the subscribe bit.. 5:30
90* (probably exceptions). The way I understand this is as follows: Think about the "circle" that the applied force is making. At the top of that circle, the direction of the force is "straight forward." Likewise, think about the circle the spinning mass is making. On the left-side of the circle in this case (from the pilot here), the direction of the force\spin is also "straight forward." The forces interact, causing the roll. You don't actually need to make a circle since the force is torque.
It was actually Carl's explanation that explained it best to me. It was one of those moments where suddenly a lot of things made sense.
As torque and angular momentum are a cross product quantities (as compared to dot products) changes in the total angular moment of the system are dependent on the right hand rule. This is why the change to the angular momentum vector are orthogonal to the applied torque.
Veritasium makes a great video about gyroscopic precession that explains it very simply.
Do you have a link? Search seems to be failing me.
Colin Richardson its in the helicopter deep dive playlist. Check Smarter Everyday Playlists
Colin Richardson /watch?v=ty9QSiVC2g0
From what I've read, precession plays a small role and isn't the main part of countersteering on a bike. Wikipedia has a good explanation of countersteering.
You are great at explaining complicated processes without having to "dumb" them down. I completely get it and want to do an experiment of my own with my daughter
Perfect explanation, never seen in specialistic videos about helicopters!!!!!!
You can also witness this while riding your bicycle. Turn the handle bars one direction while moving fast and you will fly off the bike in the other direction . Or lean to the right and the bike will turn right .
I agree on that, maybe make another video to explain that in detail? Very cool video series over all, love it, shared it.
Nice video. I love the Destin area. I was station at Hurlburt Field and Eglin AFB for years!!!
i like how in the beginning when you are all building you can see you take all the tinker toy parts to finish your 'copter
I finally got it with the bike tire experiment!!! Love the vids, keep 'em up!
That actually makes sense. It's basically a delayed reaction of the weight or force transfer of the blades to the body of the vehicle. Thanks for your videos
thank you, your's explanation is easier to imagine/ understand
All those years as a youngster I was baffled when I applied force laterally and the wheel banked horizontally... IT ALL MAKES SENSE NOW
Made sense to me...good demonstration.
really liked the experiment with the camera and bicycle rig. Garage style academic
this series is so cool, i never thought flying a helicopter was so complex. I have been looking into becoming a helicopter pilot and this makes me want to do it even more
"What are you going to build out of tinker toys?" She says, "the sunset." Awesome, I wish I was unhindered by logic clouding my creativity.
I finally got it! You push up on it. It is rising as it spins as high as it can until it is pulled back in the opposite direction by it simply being attached to the center. which is 90 degrees. Then, in another 90 degrees, it is now at the same height as where the pressure was applied, but now traveling downwards instead of upwards.
I just realised that when you're riding a bike and you lean off axis, the gyroscopic procession means that off axis force due to gravity no longer acts to push you further off axis! It's just causes a torque on the handlebars.
This actually makes as when we want turn left on our cycles, we actually push the the handle left giving the cycle wheel a tilt towards the left, the cycle actually moves to the left.
The 90 deg phase on a swash plate is a control input, not a force.
GP requires a force acting on the axis of the spinning disc. If you watch a spinning bike wheel the force twists the axis (axle hub), creating GP at 90 deg to the force.
The 90 deg control input of the swash plate is NOT forcing the rotor shaft (axle hub) to move. Rather the 90 deg phase lag is to move the blade pitch to make them to fly up/down as it rotates (cyclic control).
However, if the control input was to twist the main shaft back and forth, then GP would be present since it is applying a force to twist the axis.
Try this in a vacuum. Swash plate control inputs would have no effect since the blades have no air to fly up/down in. Yet if the inputs twist the rotor shaft then you would see the disc move in accordance with GP.
I agree that GP is present in the system, but not to control it. It is a by product of the effects of cyclic inputs.
Bill nye explained it in the episode "Spinning things" by using a Frisbee, and noted the technique used in order to make a frisbee skip off the ground.
I thought that was pretty cool, and practical as well, because thats something everybody has spent time trying to figure out.
Angular momentum "L" is a vector. Curl your fingers in the direction of rotation and your thumb is in the direction of "L". The applied force will exert a "torque" and want to cause the object to rotate in the direction you'd expect. Find the 2nd L -thumb direction- by curling your fingers along the -expected- rotation. OK starting over, curl your fingers&have your thumb in the direction of the original "L." Now turn your thumb into the direction of the 2nd L and notice how your hand rotates.
thanh you, I have confused about cyclic pitch long time, now I understand.
I can't get enough of your videos.
Hey Destin, ever thought of explaining bicycle rake and how that effects control at low and high speeds.
Hi Destin ! You will probably never see my message, drowned in the thousands of comments here, but I just want to thank you for your videos ! This is so interesting that i rather look them than work for my master's degree !
Excellent video. Now it should be clear why a flybar on an r/c helicopter is 90 degs and why 45 deg setups are so stable by design. Only thing I would like you to clear up for myself and others in the misnomer that the flybar is a form of power steering. I think it is not and actually is another gyroscope.
I love your channel. You can never stop learning!
I love your work. I’d just like to add that aerodynamic forces also play a role, contributing to the gyroscopic effect on the plane of rotation of the rotor “disk”. Let’s consider a 2-blade teetering-rotor American helicopter (where the blades rotate clockwise when viewed from below). Let’s keep it simple and say there is nil wind and the rotorcraft is in the hover, with the rotor disk level and parallel to the ground. The pilot wishes to accelerate the a/c forward. You are correct that a pitch increase must be applied to the retreating blade (and a pitch decrease to the advancing blade), when each of these blades are athwartships - i.e. 90 degrees before the desired effect. However, this pitch change cannot physically have an instantaneous effect - rather, it causes the tip-path of the retreating blade to start climbing and that of the advancing blade to start descending. The net result is that the advancing blade tip-path reaches its lowest point at the front of the a/c and the retreating blade reaches its highest point at the rear of the a/c, so that the rotor “disk” (tip-path plane) is tilted forward.
Nope, that is not how it works at all. Regarding ".. this pitch change cannot have an instantaneous effect.." do you really believe the effect just happens to be 90 degrees all the time just by coincidence? If it wasn't instantaneous, why isn't it 60 degrees? Why not 120? Why wouldn't it be variable with different atmospheric conditions present? The swash plate stationary side to control linkages never changes phase. It's locked in at 90 degrees all the time. The truth is, the gyroscopic effect is real, and you should do some research about it to convince yourself it is true.
@@byugrad1024 As I wrote (correctly) “Aerodynamic forces ALSO play a role…”.
It is not the direction the rotor blade is pointing, it is the direction that the tip of the rotor blade is travelling. If the tip of the rotor blade is travelling towards the back of the helicopter, then lift at that point will raise the back of the helicopter. So if the rotor is spinning clockwise (viewpoint from above), then the tip will be travelling towards the back when it is 90 degrees counterclockwise. The key is to think about the direction the tip of the rotor blade is travelling, not where it is pointing. They are always 90 degrees apart.
Hey cool! Are you going through my backlog?
I just found out about your channels I've been binge-watching you and trying to get smarter every day
i was amazed when i kind of understand how gyroscopic precession works..amazing!
Thanks Destin I'm working on testing an invention a gyroscope that counters the force applied to it so this was very helpful.
I actually saw the helicopter speed limit before I saw this video, so I was able to guess about the gyroscopic procession. But now I understand it and I am so going to use this now.
Think about a spinning wheel, and split its vectors into four parts. Consider what changing the angle does to the vector of each part. Let's say it's horizontal, and you are south of it, facing north.
So rolling the wheel clockwise makes each section have the following additional motion it previously did not:
North + East - Upwards
North + West - Upwards
South + West - Downwards
South + East - Downwards
The motion of a wheel is 90 degrees in respect to its position. And motion is what counts.
The bicycle wheel demo shows that it happens, but doesn't describe why. The reason is easy to visualise when the solid wheel is replaced with a wheel of flexible blades with weights on the ends. It's difficult to describe in words, but really easy to see. Surprisingly, I can't find a UA-cam video of it. I saw it once in one of the Christmas lectures on TV - and immediately grasped how gyroscopic precession works.
Basically, it's Newton's first law - every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. Thinking of the flexible blades model, the blades fly around in what we will call the reference disc. When the hub is rocked towards you, there is a tendency to rock the plane of the blades towards you also, with the lowest part of the disc closest to you - but it doesn't happen immediately. The blade at 3-o-clock would go to 6-0-clock (in the reference plane) unless acted on by a force - but there _is_ a force - the hub has been rocked downwards. However, the blade doesn't feel that force at all when it is at 3-o-clock - it feels it at a maximum when it is at 6-o-clock, and starts to move downwards below the reference plane. As it proceeds towards the 9-o-clock position, it continues to move downward, but at 9-o-clock, it feels a force moving it up above the reference disc. It starts to move up at that point, so its momentum is moving from 'going down' to 'gpoing up'. You can see that its maximum "down" point is at 9-o-clock, although you rocked the disc towards you, so the lowest point should be 6-o-clock. When the blades are at their lowest point (9-o-clock) they will exert the maximum force on the hub - and that's why the maximum force is at 90-degrees to the angle of rocking.
It just goes to show - gyroscopes rock - man!
this was incredibly enlightening and i love your experiments. i will most definitely try my own. do you think they figured out what gyroscopic precession was before or during their first test flight.
I noticed this with my random orbital sander. If you turn it on and try and tilt the sander it tries to tilt 90 degrees from where you think your tilting it
This is a really good explanation, My mom is an areospace engineer who works on rockets. Ya a rocketscientist. but im 15 and understood so good job explaining
All sounds correct. But, there is one final twist. The compensation for the 90 degree delay is built-in on the attachment point between blade and control rod. And the attachment point is 90 degrees ahead of the blade's leading edge. The end result is that when the swash plate tilts straight forward, the copter flies straight forward. To fully understand what is going on, you need to explain the feather shaft that is hidden from any view.
At 1:50 the cat's mind is blown!!
It's the same with a motorcycle moving at speed, you turn the bars to the right, gyroscopic precession means that the bike rolls to the left. Many inexperienced riders have crashed because they don't understand.
excellent video - you made a complicated subject very understandable.
It all clicked into place when I realized it's just like satellite orbits. Apply a normal force to a satellite and your orbital plane will "tilt" such that the highest latitude occurs 90 degrees later in the same manner as a helicopter blade.
I thought it was simple torque vectors. The upward force on the arm attached to the wheel applies torque in the camera direction, downward applies it away from the camera. the spinning wheel has a torque vector pointing to the sky. Its adding vectors. I hope this makes sense
Thumbs up for the cat in the background not caring that its on camera
Thank you so much for the videos. I've been getting into rc helis for a few months now, and thought I understood the physics of them, until this video. You blew my mind good sir. Very well thought out explanation.
Blown away COMPLETELY
The coolest part is watching the swashplate tilt one way and seeing the disc move 90 degrees out. Then you think well that's not possible because the swashplate is rigidly linked to the blades so it shouldn't be doing that but it is!
At 4:20 the neighbor is like, "WTF are they doing over there?"