How a Helicopter Works - Part 5

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This is the fifth in a series of videos where I'll create a 3d, animated model, of a helicopter. My intent with this series is to end up with a realistic 3d animation of a helicopter; one that I can use in future videos, to show how a helicopter works.
In this video I explain:
- Motions of the pitch control rods and the pitch change horns in order to cause the blades to change their feathering angle
- Collective and cyclic influence on blade pitch change
- Swashplate advance angle
- How to model blade pitch change in Blender using the drivers and a simplified equation of motion of the swashplate
- modeling of the motion of the pitch change rods and lead-lag dampers using armatures and a damped-tracked constraint
The purpose of doing this as an incremental build is to seek viewer feedback on this model so I can make adjustments to the design and also learn how to better explain the concepts covered in the video.

Опубликовано:

18 сен 2024

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Комментарии : 29

@ofdlttwo 24 дня назад

It is so refreshing to see people share knowledge and look for input to create a better product. That admirable. It's how society and science progresses. It's philanthropic and refreshing given all the dis-information on the internet. I am especially interested because I am a firefighter who has spent the last 15 years flying with the Ca. National Guard in Blackhawks (Uh-60 M, UH-60 L, HH-60G and Ch-47's). I'm the nerdy crew member asking mechanics and pilots if they will show me how something works while we are parked in a field in the middle of nowhere waiting to drop water or hoist someone. Nearly every time we land and shut down, I exit the aircraft and look for the droop stops on the hub. I have stood next to my FE and together, we watch the hub. He or she would point and call, "droops". I just can't see them retract/extend/engage/set. Thanks for your content!!!!

@PetesGuide 24 дня назад

This is an awesome comment! It reminds me of when I was a nerdy bystander who happened upon a firefighting Skycrane up at Chester years ago. I was visiting my nearby rocket scientist mentor (who was better at fighting fires on bulldozers than any of the professional crews), and came across that beautiful beast. I unknowingly and repeatedly insulted him while peppering the pilot with questions, and learned a ton by his responses. Me: “How does she handle compared with smaller choppers?” Him: “Hey kid, I don’t know what you’re talking about-I don’t see any motorcycles around here.” Me (learning quickly): “Why does this _helicopter_ have wheels instead of skids? I would think that skids would be lighter weight and less prone to damage on such a heavy craft.” Him: “Skids are for kids.” I think he might have let me sit in the rear-facing observer seat even after those unintentional insults. But he did throw them back at me because I was twenty-something, not a kid.

@PushyPawn 23 дня назад

Can't offer any advice, just here for the ride, a comment and a 👍.

@sky173 23 дня назад

Another great video on how the the mechanics of helicopters work. Although it might not be the easiest thing, I hope to see how the bearings work in the swash plate, staring from the drive shaft (up and down motion) all the way out to the control horns (rotational motion).

@bzig4929 20 дней назад

I don't know for sure, but given the forces involved in the swashplate (both from the hydraulics pushing up and the rotor forces pushing downward) I'd assume they use a double row, angular contact bearing. I actually did model those, but only in the gearbox; not in the swashplate. I'm working on another video... I'll do a clip of those bearings. Thanks for watching!

@dontyouworryaboutit_ 13 дней назад

just had a newer PI ask me all about phase lag and precession and how it relates to the rotor system, this video explains everything I told him much more eloquently lol, thank you so much

@jakerabinz9411 23 дня назад

Hi there. I appreciate your work here. It illustrates well the concepts of the UH-60 power train to the rotor head. As a now retired electro mechanical repair tech III, working on devices used by the top research labs in the world. I will give you an insider's perspective. The difference between what makes a very complex device operate well, and fail completely is known as " build up of tolerances". That is why many tolerances are called out in a single thousandth of an inch. The resaon being is each consecutive jointing interface, being more than the specified call out, results in an compounding sloppiness in the system . That at the end critical point makes the difference between a 5 thousandth functional tolerance and a ten thousandth inch dysfunctioning failure mode. These critical tolerances are generally proprietary to the engineering departments of the manufacturer. They have done all the experimentation research as to what tolerances are consistenly functional, and what tolerance build ups result in " epic fail." In my case, semi skilled builders assembled a very complex electro- mechanical widget worth thousands of dollars, as certifiable sourcing to NIST standards. One out of 3-5 widgets failed repeatability final testing. It was up to me to rebuild those widgets so their repeatability was 100%, on a 30 repeat final test. And to repair used product returned for service back to 100% repeatability. In Aviation, Helicopter mechanical systems, and any aircraft turbine power systems, have the tightest tolerances. This is why total rebuilds costing tens to 100s of thousand for such systems. You make top drawer conceptual renderings. But.... you do not have the thousandths of an inch proprietary data that makes everything fit together and work perfectly. Nor will any of the engineers or repair techs disclose that. Most being under Non Disclosure Agreements. Thereis an interesting " gossip" that the Russians also built a Space Shuttle. But it never flew. Because the espionage data they were fed was intentionaly false. So your conceptions of dynamics modelling is educationally good. But without the blueprinted real world manufacturers tolerances you can never expect everthing to fit together perfectly. Yet still your conceptual flow is indeed educational. The caveat being , " these are for conceptual flow use only. The actual detailed to thousandths of an inch build tolerances is proprietary to the manufacturers."

@bzig4929 20 дней назад

Here's a funny story about the Russian space shuttle. Although they never flew it, they did enough work to know they planned to roll the aircraft prior to orbital insertion... just like the American's did; the Russians copied NASA. NASA rolled the shuttle because they reused the Apollo launch pad and the only way the shuttle would fit was backwards.... they had to roll or else it would have been in the wrong attitude for orbital entry. Touche on the tolerances. I'd doing this because I find it fun and I hope to educate. Speaking of tolerances, I found the drive-train data (module, helix angle, pressure angle etc.) in a NASA technical report. After I modeled it, I see there is less than 1mm of clearance between the planet gears. It's not like I could have screwed that up... gear math is pretty easy. I'm surprised they would have that little clearance. Or maybe, as you said, the real numbers are proprietary. Thanks for watching and commenting!

@jakerabinz9411 20 дней назад

@@bzig4929 I think what you are doing is excellent endeavour. It shows quite adequarely the power flow concepts. And also shows the limitations to complex dynamic components modeling. Virtual Reality, and real world practicality can be very close correspondence but seldom exact to each other. In the proprietary work I did. When the line, which used several jigs, produced a widget, that failed the repeatability standard required by NIST cert. These were micro level devices. They would be handed over to me, to either tweek electronically or gravitationally to repeatability standard. Then environmentally cycled hot to cold performance specs for two weeks. Then retested and if still out of spec. A total tear down of the widget and it's 45 mechanical components and 12 electro- mechanical, components. When 10 of these would accumulate, I would just randomize the 10 of each component and reassemble. Typically 7 to 10 of these rebuilds would pass all tests, and ship. During the prototyping of these devices over 2 years, there was plenty of trial and error re-engineering. In real world that's why engines are not shipped without some sort of factory run in. To make sure all the components mesh well enough to not immediately fail. What I'm try to say is, it my be a perpetual exercise in frustration to get all your interfaces in perfect mesh. Keep up the modeling. When you are done you could even market to A and P schools. It appears your first module was based on the Astar 355 combining transmission and three blade rotorhead. The UH-60 appears to simplify the reductions to far less interfaces. It would be interesting to see the intial turning motor/ generator. The Allison C series turbo shafts could be another challenging project to show, as the transmission is integral to the turbine. Good Work.

@PetesGuide 24 дня назад

One thing that confuses me in this video is the part about how the control inputs need to be mechanically input about 90° ahead of the desired direction change. Well, several things actually. I know I can use the tail rotor drive shaft as the 180° reference relative to forward flight, but I’m still getting lost when you start drawing on the model. Can you add some sort of visual reference with the cardinal angles, plus the slight variations you’re talking about? And can you increase the visibility of your annotations? Maybe wide translucent “highlighter marker” strokes? I easily saw the 270° green lines mentioned at 3:31 , but not the short one at 3:42, and had to replay it several times to see it. While doing so, I realized that your presenting the system from several different camera positions is why I was confused about where the nose of the helicopter was. Some sort of helicopter-specific compass rose would definitely help! And this is getting ahead of your planned curriculum, but I don’t understand why the inputs need to be 90° ahead. I think a very brief bullet point explanation of why would help the next time you animate this assembly. Lastly, I do think we all would appreciate you modeling the non-rotating swashplate before moving on to other topics. I’d like a complete description of this mechanism before learning something else.

@bzig4929 20 дней назад

I'm actually learning how to use Davinci Resolve for the video editing part of this (I've been using Blender to edit the videos, but it's really optimized for animation, and not video production) I hope to learn some better techniques for annotating videos in Davinci.

@PetesGuide 20 дней назад

@@bzig4929 Interesting comment. I have some experience in both fields. I started using AutoCAD in 1989, and was later the technical editor for CADENCE magazine for a decade. A sister publication was DV Magazine. It’s been a while, but I’m not aware of video editors that can do 3D matching. What is Davinci capable of these days? Can you create a 2D plane in Davinci and have it match the rotations in Blender?

@ofdlttwo 24 дня назад

Awesome. so looking forward to all your content

@bzig4929 24 дня назад

Thanks! I appreciate you.

@user-us3dp7tb3m 24 дня назад

You are truly amazing.

@user-ii4su2sn2w 24 дня назад

Хорошая работа

@roystevenson9632 24 дня назад

Gyroscopic precession for the first thing.

@RyanPlate 23 дня назад

This 👆 @PetesGuide The force (increased angle of attack [AOA] and therefore lift on the 6 o'clock rotor) on a spinning disc (rotor) is applied 90° in the direction of rotation (counter clockwise results in the 3 o'clock position). Lots of great videos about this, but the best physical demonstration is to hold bicycle wheel by the hub, spin it, and apply a force and see what happens. This results in the right hand side of the rotor rising and the left falling, resulting in a left turn. You can see the 12 o'clock rotor blade reduces AOA to compensate for the increase on its counterpart - much like ailerons do in an airplane. Full disclosure, I'm a fixed wing pilot with about 3 hours of helicopter time so I may have outkicked my coverage here; I welcome the more qualified folks to correct/augment as needed without going too far into the weeds.

@rekov 18 дней назад

Two thoughts. 1: I think you could probably use inverse kinematic constraints to drive your pitch arms and pitch links. They can be a bit confusing to set up if you're unfamiliar with them though. 2: How did you rig the rotating swashplate? I cannot figure out a good way to have the rotating swashplate follow the rotation of the shaft while also staying aligned with the non-rotating swashplate.

@bzig4929 18 дней назад

My next video will have IK for the non-rotating flight contrila. that was a mind bender to figure out. It took awhile to figure out what has to be done in pose, edit and object modes. Now that I know... I think you're right, the rotor head couod have been done, easier, with IKs. The swashplate has three parent levels. The first does not rotate... It fixes the location in space. The second is a child of the first and has tilt plus z axis change. The 3rd is a child of the second and this adds rotor rotation.

@PetesGuide 24 дня назад

Quick suggestions before I watch past the first 18 seconds. For the model in your thumbnail, please highlight the changes and additions in two separate manners. Maybe a red highlighter for deletions, a yellow highlighter for changed, and a green highlighter for additions? Or part coloring instead of highlighter strokes. Look at how change bars and strike through are used in legal/MS Word documents. Also, please add some bold text title that highlights the update. Keep out of the lower right corner video length time stamp.

@bzig4929 24 дня назад

Good ideas!

@MohamedAhmed-gh6cs 24 дня назад

Awesome, Génial, Genial, Fantastico, Καταπληκτικός (Katapliktikós), 棒极了 (Bàng jíle) , رائع

@TheSakzzz 20 дней назад

6:07 Never noticed that the blade mounts isnt aligned with the centre. Is the centre axis of the blade aligned with the center point when looking from the top?

@bzig4929 20 дней назад

Nice observation. The aerodynamic center of the blade, which is at 1/4 chord, aligns with the center of rotation. This is also the center of feathering rotation in the spindle and it keeps forces nice and balanced.

@bzig4929 20 дней назад

wait... that didn't make sense. The aerodynamic center is aligned with the center of the spindle rotation, but this is forward of the hub's center of rotation. Maybe it's to keep the blade cg in line with the center of rotation?? I know the real hub as this offset, but now I can't recall if I wondered why as I was modeling this. It's hard to see IRL because of the bifilar.