Helicopter Physics Series #6 – LASER HELICOPTER BLADES – Smarter Every Day 49
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Helicopter Physics Series #6 – LASER HELICOPTER BLADES – Smarter Every Day 49

October 14, 2019


(Carl) We have our bolt and thread here to balance and we can run the nut in and out to get the perfect balance.
(Destin) That’s pretty smart. I bet a smart guy came up with that.
(Carl) oh.. a.. brilliant person.
[laugh] Oh hey. Yeah. You see that? You see how awesome this is? Hey it’s me Destin. Welcome to Smarter Every Day. We’re continuing our study of helicopters and we have just come up with my best invention since the chicken powered steady cam. Well.. Carl helped too. [laugh] You know, the whole helicopter thing. It is one of the more dangerous things and you know you’re living right if you need laser goggles and a helmet.
(Carl) And where’s my helmet?
[chuckle] I only have one. He can hide in the toy closet. We’re in my son’s bedroom. Alright so let’s explain what we’ve got here.
(Carl) Alright. We’ve put a laser in place of our blades.
(Destin) Lasers are like bacon they make everything better.
(Carl) Oh yeah. We’ve balanced it out here with our high-tech little gadget and ah we’re going to show how collective and cyclic pitch changes as a disc.
(Destin) What we do with this is we are measuring the pitch output on this rotor grip. Excuse me, is that am I saying that correctly?
(Carl) Yep correct.
(Destin) So we are measuring the realtime pitch as it goes around a revolution.
(Carl) Getting a nice visual representation of it.
(Destin) Sweet. OK where do you want me?
(Carl) Alright how about we ah you get right behind it.
(Destin) Over here? (Carl) Yep right here. and ah we’ll project it against the wall.
Here we go. (Destin) We’ll shut the ah shut the closet. Oh another thing we made it so when it spins up it turns it on using the ah gyro force ah excuse me the centrifugal force. Ready.
(Carl) Here we go.
[Rotor spinning up] (Carl) Alright.
(Destin) [unintelligible excited] (Carl) So ah here we’ve got zero pitch, all round. and if we give a collective input, our line goes up positive collective, negative collective it will go down. If we give any cyclic input the disc will or the line will tilt, right left forward, back. (Destin) So to be clear, we’re measuring the pitch, so the rotor shaft is not changing at all, other than rotation, correct. (Carl) Yes.
(Destin) Alright so the pitch of the blade is changing as we go around a revolution because the swashplate input (Carl) the ah grip changes from positive to negative pitch every revolution.
(Destin) That’s awesome. I am extremely excited about this. This is the best visual representation I’ve ever.. oh there’s one more thing. It’s also pointing 90 degrees out of phase right? (Carl) Well, yes but that puts it in the phase that it would normally operate. (Destin) Alright hold on. I don’t understand how you’re gonna do this without a helmet. Alright, so if you think about, OK, when you say it’s in the phase that it would normally operate, the laser is shining 90 degrees off
(Carl) The laser is pointing this direction and as we get a forward cyclic input tilts down and that transitions to take effect 90 degrees when the (Destin) That’s gyroscopic precession.
(Carl) Gyroscopic precession.
(Destin) Alright, so let’s zoom in on the swashplate ah just for people who don’t know what swashplates do, give me a (Carl) This is the swash plate.
(Destin) Collective input up.
(Carl) Collective up.
(Destin) Collective down. (Carl) and it can tilt forward back left or right.
(Destin) That’s your cyclic input. Alright you can give collective, and you can see the light goes up, and that would pull the helicopter up [unintelligible] negative, and if we get cyclic, it changes the tilt of our line.
(Destin) OK what is the front of the helicopter towards you or towards this wall over here?
(Carl) The front of the helicopter is towards the camera’s left.
(Destin) Got it, so let me go back over here and try to get it on the wall here. Alright do it again. (Carl) Alright here we go. Left, forward, Right, back, up and down. (Destin) This is so awesome I want to cry. I think our contribution to science for the day is done.
(Carl) Alright! I’m Destin.
You’re getting Smarter Every Day. [ Captions by Andrew Jackson ] Captioning in different languages welcome.
Please contact Destin if you can help.

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  1. Great series this just blows me away. So the chopping sound comes from the blades changing pitch with each rotation?

  2. Your videos about the helicopters made me understand most of how the helicopter rotor works. I am kind of an inventor so I am going to try to make a new generation helicopters. As small as a bike that you can ride on in air 😀

  3. Destin if you had used a smoke machine in the room it would have blown your mind completely! Please please please try it once. Lasers and smoke machines. That too on a rotor!

  4. Am I right in saying, that because the laser is mounted 90' out of phase, we see the movement 'in phase' e.g. to go forward, tilt the blades forward. But really to move forward, the blades tilt left (right side up)

  5. Awesome video! Could you maybe make a new version of this experiment with a low laying fog in the room?
    I'd be curious to see it

  6. The cone of light from the spinning laser is projected onto a plane that runs parallel to the central axis of the cone so the shape produced is a hyperbola. If the plane was instead parallel to the surface of the cone on the other side of it (hard to explain in words) the shape would be a parabola.

  7. Someone should really use schlierin optics at high speed to photograph the change in pitch of the helicopter blades so in that way we should be able to see the actual real time transfer of energy from the blades to the air AFTER the 90 degree phase shift due to gyroscopic procession so in theory, instead of being a whole step behind in the analytical process when it comes to gyroscopic procession we should be able to see the physical manifestation of this event as the reaction occurs

  8. I did not understand how the right and left movement of rotor (laser here) relates to the gyroscopic precision? Please explain. Thanks 

  9. Destin, another awesome video – but I have 2 questions (really one) how do the controls work – both for this remote controlled helicopter, and in the full sized version – they use their feet don't they?
    I'm still working through these in chronological order, so I may yet get an answer to this.
    -Shawn

  10. :O wut if he put his cat in the room while they were doing this and the cat started chasing the laser beam

  11. How do you know which side the gyroscopic precession leans towards.

    Left or right. Clock or counterclockwise.

    I hope you understand the question am asking.

  12. So a helicopter works by many small amounts of force? Like small nudges in one direction? 
    Since it can only apply, say, the forward motion once every 360deg?

  13. I know I'm way behind but the curve is a hyperbola. The cone of laser light is being sliced perpendicularly by the walls. It can only be a parabola if the rotor axis is tilted to a specific angle relative to the wall (90 minus the angle of the pitch).

  14. If you had attached another, different colored laser on the other mounting point, would it have shown the reciprocal motion?

  15. I have a hard time understanding the explanation given at time 2:51 to 3:07. Don't really understand what it is meant by this sentence'When you say it's in the phase the laser the laser normally operate , the laser is shining 90 degree off', also, I have a hard time linking this to precession. I don't know if anyone could rephrase that for me , so I could understand :)?(this is probably because of language barriers , sorry)

  16. You could add some smoke or fog to make the laser plane visible. That way you could show that the plane tilts forward, backward, left or right, and for up and down the plane becomes conic. That would be more awesome.

  17. Destin, you're just way too cool! Thank you for this awesome series. This is at least the second time I'm watching it and having just recently started playing Battlefield 4 on my console, I most certainly applied this knowledge to practicing some helicopter flight. Keep it up! Your channel is the one I'm always looking forward to new videos. I hope all is well with you. Stay blessed!

  18. the laser setup was a fantastic idea. I've been trying to explain this to my brother for the past hour and he didn't get any of it till he watched this video.

  19. Yeah I gotta tell ya, really appreciate these videos. I've always loved this stuff, used to draw pix of remote controls when we were kids, but you guys clearly have some sound physics and engineering backgrounds and are very effective communicators of these principles. I rate these free on line videos above some that state colleges (which I've wasted thousands $$) offer. So yeah, maybe not wasted because I understand what you are telling me and I feel like I could build one of these things and eventually master flying one, even the real ones, thank you! Nothing to do on a cold January day, might as well learn to fly, so much depends on the weather, that extension of the universe that is relatively uncontrollable on earth, that can kill ya in the air though, extreme downdraft /microburst stuff, other than that physics does what it does, w no surprises, coming down is the hardest thing

  20. That was Awesome! But there's one thing you could have added to this demonstration, that would have helped show the effects even more. Now most are probably going to suggest a fogger or fog machine. The proper tool for this is going to be what we in the live event industry call a hazer. You will need to turn off the fire detector in the room. Run it for about a minute, then turn it off and turn on the helicopter laser.

  21. I think the the imaginary rotor disc does not tilt (always perpendicular with the rotor shaft) when we put cyclic pitch control, beccause cyclic input only changes the angle of attack of each blade depend on where the blade is on the cycle of rotor disc (due to the previous videos of this series). But in this video, it looks like the rotor disc tilts when we put cyclic input. I am so confused

  22. This is just amazing, this series allowed me to understand in less than half an hour how a helicopter works! And this was so interesting, thank you so much

  23. By far the best videos on how these work.
    I bought a RC Heli for my daughter for Christmas. And noticed it operates in a totally different way. Less mobility. But its has a dual blade system that rotates in opposite directions. Making it fly 100% stable. And able to turn electronically from the shaft itself. Forwards and back is achieved by a smaller blade on a horizontal axis.

    Buy a RC chopper and check it out and make a video!!!! They are 20$ and have a totally different flight mechanism as for stability.

  24. destin i can youst say that without you i wouldnt be half as interested in phisics than i am now cause i was watching you for some time now 😀 thank you man for giving my brain a purpose 😀

  25. The arc of the laser is because there is more distance for the light to travel before it reaches the walls in the corners. If it was placed in the middle of a round room there would be no arc. 😉

  26. Fisrt of all how do you get your son to keep his room so clean?
    Question, when you increase the pitch to go up don't you have to increase engine power ?

  27. I think I can explain why the light arcs during collective input. Put simply, it is because of the fact that the room is rectangular. The corners are farther away from the axis of rotation (spinning blades) and the light can travel farther before it hits the wall. This allows the light to be the highest at the corners and lowest between the corners.

    To understand this on a deeper level, try visualizing the light beam on a 2D platform at any given point in time (meaning freeze time). When you have no collective input, the light beam is completely horizontal (no y component) and you get a straight line all the way through the rotation. When you add collective input, the light beam is pointing up or down from the rotational plane (the horizontal/straight line from earlier) with an angle θ. Now, the rotational plane and light beam create a right triangle with the wall.

    The rotational plane is the x component, how high the beam is up or down the wall is the y component, and the light beam itself is the magnitude (hypotenuse of right triangle). As the light beam maintains its angle (θ) with the rotational plane, the distance of the x component (how far the blades are from the wall) affects the y component (how high the light goes up the wall). Say, a large distance (x) would mean a bigger height (y). That is why the light beam is higher (or lower) in the corners compared to the middle of the wall.

    The reason why it is hyperbolic is because if we were able to see the physical light beams itself during collective input (would've been made possible with a fog machine), then the beams would've created a single cone. The wall is your plane that is cutting into your cone, which is why the line you see on the wall is a hyperbola (half of it at least). If we had two lasers (one of them opposing the laser in this video), then the second laser would make a second cone opposite to the first cone. The end result would be a double-mapped cone and a full hyperbola. This took me a while to figure out.

    I don't have any drawings to help you visualize what I'm trying to say, sorry. If you read this far, may I say you are a wonderful and patient human being.

    Conclusion(s): If you did this demonstration in a cylindrical room, then the line should remain straight during any collective input. The wall is the plane that is cutting into the cone the light beam creates when there is collective input into the helicopter which is the reason why the line is hyperbolic.

  28. So is the 90degree difference compensated for by the hardware, or is the pilot responsible for it? My guess is the hardware does the compensation, else the pilot really would have a very confusing time learning how to fly.

  29. Did he put air quotes around "lazer?!" If so, he is the new ambassador for his generation! Bring on the ill-tempered sea bass!!

  30. I'd say that the line is curved for collective due to the fact that an angled line (the LASER) hits a flat surface (the wall) at different heights. If the LASER rotates around itself, the shape of the LASER on the wall would be hyperbolic. The laser however does not rotate round itself but I still think it's hyperbolic. Anyways, that's just a shot in the dark. Have a nice day.

  31. Destin.. Smart is not the knowledge you have… but the seeking of knowledge.
    YOU are the smartest man in the world 👍 Inquiring mind is what makes us smart. (dummies dont care)
    Thank you for all you do.
    I'm addicted. 😀

  32. So I have to know, for cyclic pitch the swash plate is tilted causing the blade pitch to be down at one point and up 180 deg then back down again when it comes around. So, this creates a piston like movement on THAT blade right? Wouldn't there be some crazy vibration? Aaaand if there is, is it canceled out by the opposite blade, and if so what about copters with 3 blades?

  33. The cyclic pitch control input and the laser beam orientation are in phase because the pointer is mechanically pointed 90 deg. ahead of the blade. This implies the blade pitch is changed 90 deg. in advance. This is not necessitated entirely by gyroscopic effect, but due to blade flapping.

  34. The swash plate is so cool. The helicopter seems like it moves how the swash plate moves. The swash plate tilts the perpendicular blades the same way as the swash plate tilt. If the swash plate tilts front of helicopter side up, then when the blades are perpendicular to the front of the helicopter, they will also be tilting front of helicopter side up. Applying lift to the front side of the helicopter. The gyroscopic precession is engineered into the swash plate and it makes controlling the helicopter tilt so simple and awesome. Way simpler on the pilot!

  35. Because the laser was mounted at a 90* angle it corrected for the 90*-out-of-phase application of the collective and thus appeared in phase with the control inputs, correct?

  36. Pretty cool! But if you were to take a opaque piece of plastic strip that is about 14" x (radius of the regular rotor blade when installed) and place it around that helicopter, you can better picture the rotor disc.

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