Helicopter Drive Systems and Hunting Tooth Gears
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- Опубликовано: 19 май 2024
- A video describing hunting tooth gears used in helicopter drive systems. Hunting tooth designs reduce noise and vibration and improve the longevity of gears. They do this by ensuring that every tooth in a gear pair meshes with every other tooth in the opposing gear.
link to my earlier video on helicopter drive systems: • Helicopter Gear Reduction
References
The Hunting Tooth and its Effect on Break-In, Stadtfeld, 2021, www.geartechnology.com/ext/re...
Prime Numbers are the Secret to Prolonged Gear Life, Lemmy, 2022, shoppress.dormanproducts.com/...
Kish Method for Determination of Hunting Mesh, Kish, 5/1/1997, www.geartechnology.com/articl...
Handbook of practical gear design, Radzevich, Dudley, 1994, books.google.com/books?id=NOq...
Investigation of Advanced Helicopter Structural Designs USAAMRDL-TR-75-59B , Korzun, 1976, apps.dtic.mil/sti/tr/pdf/ADA0...
Design, Manufacture, and Spin Test of High Contact Ratio Helicopter Transmission Utilizing Self-Aligning Bearingless Planetary (SABP), NASA Contractor Report 4155, Technical Report 88-C-009, Folenta and Lebo, 1988, apps.dtic.mil/sti/tr/pdf/ADA1...
Design And Development Requirements for Mechanisms, NASA-STB-5017B, 2022, standards.nasa.gov/sites/defa...
00:00 Intro
00:45 Establishing a Reference
02:10 Wear Pattern in a Non-hunting Tooth Gear
02:57 Wear Pattern in a Prime Hunting Tooth Gear
04:35 Wear Pattern in a Non-factoring Hunting Tooth Gear
05:40 Literature Review 
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Come for the gear animations, stay for the philosophy!
How could anyone talk about gears without drifting into philosophy and metaphysics?
Excellent summary of "team" contributions!
You earned my respect. I always want to work with an engineer willing learn from others, admit an error, then pass it on to others. Good man! Love from Victoria, BC, Canada.
Bravo!! Another great video. And the icing on the cake is the ability to realize that no one is an expert in anything. You Sir have earned my respect, and we need more people such as yourself !!!!
I remember slithering under the old 1948 Ford pickup we had and noticing it had a tag on the differential with the numbers of teeth on the pinion and ring gears: 11/47.
With your explanation of hunting teeth it becomes clear why those numbers were chosen. Ring and Pinion noises are the bane of automotive drive axles.
There is also the consideration that repetitive torsional shock may be coupled into a gearbox from driven machinery, which could wear just a few teeth way before the others. Hunting tooth designs inherently resist forming wear and noise patterns.
That's really cool to hear a real world application of this. Thanks for sharing!
Well, now I know something I didn't know before. Never too old to learn something new.
Excellect presentation. Many yearas ago, as a Diesel Mechanic, we learnt this, as we had a combination of Hunting Tooth and Non-Hunting Tooth Gears in Engine Timing Gear Trains . Where the 2 x Cam Gears would be non-hunting, because they had to mesh exaactly to retain timing at 1:1 Ratio, and the Idler Gear that connected one Cam Gear to the CrankShaft Gear was a Hunting Tooth arrangement to reduce noise and wear.
that's cool to hear the real world application of hunting teeth! thanks for commenting.
Top notch. Love the format, graphics, content, narration, and professional attitude. Thanks.
Much appreciated!
I worked 7 years in a Sikorsky shop overhauling helicopter transmissions on the commercial side. Tear down, evaluation of components, and build up/assembly. S76 and S92. I had the privilege of being trained by an old timer with loads of experience, I remember him explaining hunting gear ratios to me when I was new and i was fascinated from that point on about all the intricacies associated with high performance gear train designs. Very interesting to compare the S76’s relatively simple yet effective central bull design to the much more complex S92’s full planetary design and how they wear during operation, pros and cons of each one. It’s absolutely incredible how the design engineers arrive at the “final version” of any particular component. Now I work in blades/composites manufacturing for the same company. Completely different realm of manufacturing working with composites. Equally as interesting.
BTW, a set of integers which share no common factors other than 1 are also known as "coprimes".
that is a cool fact! Thanks for sharing.
Some people describe them as "relatively prime" to each other, meaning the same thing.
As a fixed wing pilot obviously helicopters are scary magical things that don't make sense, but in all seriousness this is the best animations and explinations of their systems that I have ever seen.
It’s amazing how numbers are used to calculate anything known to man. Impressive!
I was working for 9 years in a design department for gearboxes and drive trains in the steel business calculating and designing all kind of large high loaded gearboxes, drive spindles and couplings. The theory for hunting gear tooth combinations seems to be logical. The kicker is the counter-evidence: The hunting gear pair concept can not be applied e.g. at mill pinion gearboxes or mixing gearboxes and other cases where it’s a must to have a 1:1 gear ratio (each teeth is meshing all the time with one other teeth) to achieve the same speed on each output shaft. And trust me the 1:1 gear ratio is required in really many cases. The practical experience at non-hunting high loaded gearboxes over 30-40 years of operation shows that the wear does not necessarily have to be higher compared to hunting gear pair designs (odd number of teeth). So in fact the hunting gear pair philosophy can be totally ignored in modern designs. There are several other factors which are much more important and can accelerate the wear at gears much faster like regular overloads, oil quality (purity, particles, water, temperature), bad gear material combination, wrong hardening process etc. compared to the non-hunting gear pair concept. Hope this practical experience feedback helps! Finally: Big like on your mind-blowing good animations and top notch content!
This is an awesome explanation. The Stadtfeld article tried to say the same thing, but you were much more succinct and easier to understand. Thank you for taking the time to write this.
Great, but "can get away with it" and "there are other important factors" are not the same as "hunting ratio doesn't matter".
Noise doesn’t sound (sic) like a factor in your designs. 😁
If it were really necessary an idler gear set could be used but would be more complex. 😎
Courses for horses- n stuff..
@michaelgarrow3239 true... a 1:1 (or any integer) ratio is not often needed in a single stage. Every 4-stroke engine crankshaft to camshaft drive must be exactly 2:1, but they very rarely use a 2:1 gear set - they have idlers, or chains or belts.
I think that this was about imperfections from manufacturing. With all teeth meeting each other, we get some average surface which is supposed to be smoother. Like wheels on a rail. Of course high precision gears, much harder then the load, will not change shape. No burn in.
I like the humility, I feel like you are doing a great job and putting so much effort into your videos. I greatly appreciate your work!
Thanks! I'd love to do more of these... The day job keeps getting in the way 🙂
Thankyou very much for taking all this trouble to share this with us.
This may explain the patterns on machine finishes on lathe work.
Different ratios of gears produce different speeds, and feeds.
Even though everything is clamped, and tight. You can end up with a variety of patterns which you do not want.
There are other effects as well such as the material it's self. It's shape, and mass. And the cutting tool geometry, and so on.
Steel atoms all vibrate, and we are putting energy into a series of components.
This was why all the early machines were so massive. To cut down on vibration, by using mass damping.
Kind regards, and greetings from Africa.
Thank you for your comment. I'm flattered that you watched my video intently enough to draw a conclusion for an unrelated discipline. Another example may be the brinelling wear patterns that develop in bearings over time. It's fascinating to see patterns emerge from seemingly events!
A fantastic explanation and graphics. I’m looking forward to seeing more posts. Thank you.
Spot on about why we work in teams! Showing wonderful humility in how you responded to the original comments, to the benefit of us all! Many people would have ignored such comments, perhaps writing them off as pedantic or minor distractions compared to the giant accomplishment of animating and explaining a helicopter transmission overall. Instead, you used it a an opportunity to learn and teach - well done.
I just wanted you to know that you’ve gained amount of respect & admiration from me for just simply being able to admit a fault & a slight gap in your knowledge of helicopters, especially having the vast knowledge of them that you already have. It takes a lot for one to swallow their pride & put that out there for the worlds critics.
If it weren’t for you & your beautifully animated video explanations, I’d never have what limited understanding that I do now about how helicopters power transfer works. It’s been something Ive always wondered about how it works, then suddenly one day, the YT algorithm blessed me w/ the last video you referenced in this vid aaannd-down-the-rabbit-hole-I-fell into everything helicopters. So, I thank you as well!
Thanks for this comment! I'm planning a few more videos in the helicopter series.
Asmr voice and mathematical model details is oddly satisfying
I love this comment! A few others have said my voice is so boring they can't watch. I think ASMR means I'm boring but you're still watching. Thanks! I appreciate anyone watching my vids!
I oversee engineering for the housing of the first gear reduction set; hunting gears extend maintenance intervals by a factor of 50. I'd say that's pretty significant.
cool! thanks for adding that context.
These vids are exceptional. Thanks for the considerable effort you put into them. You need to bottle this stuff and sell it to every ground school in every country - maybe throw in a complimentary subscription to Gear Technology to sweeten the deal 😂
I love the comment! The learning resources available in the 21 century are so amazing! I'm making these with (mostly) free software. The young folks today have no excuses! I was supposed to have a flying car by now and, apparently, my generation let you down.
@@bzig4929 ב''ה, this is so well done that I just want to point out making your index mark across the two non-hunting gears would "bury the lede" less even if it takes time to finish explaining the concept, and demonstrate that common mechanics' technique.
@josephkanowitz6875 I think you mean to let the video play until all of the teeth mesh... I thought about that, but I did the narration first, so it would have been a lot of quiet time. Or I could have made the gears spin a lot faster. Or I could have done the math ahead of time. I always think of what i could have done better afterwards... thanks for the comment!
Top notch work. Animations are great, and your voice and speaking style works well for it. Looking forward to the next episodes.
I really appreciate that comment... The narration piece is the hardest part of this for me. I've been working to improve.
Excellent, both this video and your concept of an intelligent way of working and consistently increasing knowledge!
Love to learn new things!
Thanks mate!
That's an excellent presentation sir. Thank you 👍🙏
I spent 12 years in Army Aviation as a helicopter engine mechanic. New sub.
LOVE the channel! Awesome work!
I spent A LOT of time just below and above everything at the start of the video...
Ahh the Iraq flashbacks..
"Stay in formation. Target's just ahead. Target should be clear if you go in low enough. You'll have to decide. You'll have to decide. You'll have to decide."
Wait... That's not right. Humm
Indeed, giants sit right next to us at our jobs, well said
Bravo my dude. I didn't think anything of the tooth ratios mainly because I knew it was supposed to be a simple explanation of a complex idea and not a how to guide on how to build a helicopter drivetrain system. I worked on this stuff for close to two decades and still enjoy your animations because the whole knowing how things work and seeing it in action is why I got into aircraft maintenance in the first place. As an instructor it was hard to explain something these things to people because while I could visualize how it worked in my head(I have an uncanny ability to understand things by seeing them in my mind's eye), it is often difficult to put those thoughts into words. A lot of students couldn't understand how a collapsing magnetic field could create electricity in a coil inside a magneto, and I just wished I could put my understanding into their heads. haha
Thanks for the comment! I appreciate that you took so much time to reply. I know what you mean about understanding something but not being able to explain it. I feel like the way I'm mixing CAD with the animation software give me the chance to finally explain things the way I wanted to when I started working with helicopters.
What a great video!! I have now learned something amazing that I had never come across. I also love the way you also explained how we all learn from each other. I taught in a school for 33 years, and during that time, learned piles of new things every single day, from my colleagues and more importantly, my students. We train and learn and hold and convey, so much information, but it's never 'done'. It's never over, and every new day is a chance to come home with new knowledge and experience. We only do that if we are open to listening to those around us. Not hearing; listening.
I love your animations and as you might have guessed, am a self confessed helicopter nerd!! 😊
Exceptional work!
Hello Bzig,
You're totally right considering yourself as an expert ! Why ? You brillantly explain concepts you "admit" not knowing about an iteration before ;-)
Nice words! Thank you.
Thanks for the explanation and the excellent illustrations. I was aware that there was such a thing as hunting and non-hunting, but your explanation of the factors involved with teeth numbers was the missing piece of the puzzle. My interest lies in automotive ring and pinion gears, and why some manufacturers chose to go non- hunting for some reason.
Never stop learning 👍
Your videos are fascinating.Thank you.
Thanks!
Excellent job sir!
Respect, thanks for another nice video
So well done! Great post.
Thank you very very much for share your knowledge ❤
you're welcome! Thanks for taking the time to comment.
Great video
Excellent explanation
Awesome attitude
🫡
Thank you for the video
Absolutely useful and educational. Thanks sir!
Yes sir...Just what he said.
This hunting gear application is also used believe it or not on tracked equipment. Excavators- bulldozers The drive sprocket always lands on a different track chain pin. I was always told it was for wear mitigation
that was crazy interesting!
Awesome video. Thank you!
Thank you too!
Great explanation thanks.
You're welcome!
Love this content!
Very Good. Thanks
Teamwork makes the dream work 🙂
I'm studying for PPL(H) and this series has made a few things click for me. Had a few "a ha" moments. Thank you.
that's awesome to hear. An upcoming video will be on forward flight dissymmetry of lift, blow-back and some of those other flapping/feathering topics.
@@bzig4929 Ace. And if you could just extend your fabulous teaching and presentation skills to air law too, that would be fab 😝 (joke)
Awesome 👌
You're humble. That says a lot about your character.
Iv always been fascinated by how planetary gears work but haven't had much chance to visualize them in action.
Awesome!
Brilliant
You're doing a great job with these videos. Don't entertain the pendants. 👍
Works for car axles too . Thanks
you mentioned the coupling of 2 engines in your last video. As far as I could see both engines where considered basically the same.
SO my question would be if you know or know any literature that explains the coupling of 2 engines with different power output and probably RPM.
Thanks in advance and your videos are great m8
I'm not aware of any helicopter that does this. The closest thing might be aircraft such as the lynx or the H-3 that have an accessory drive feature where one of the main engines powers the accessories during start via a separate gearbox. While it's doing this, it operates at a higher rpm than the main rotor. If the pilot switches to the main gearbox in this condition... Damage will happen.
The pilot has to accelerate the rotor above the acc drive before switching over.
I'm not sure if this fits the example you were looking for, but I think its a positive example that engine speeds are always matched in two engine aircraft.
Toyota synergy drive. Turbo compound aero engine
Gestalt is the German principle that says the whole is greater than sum of its parts. In biology it would be emergence, like with ants or bees that have behavior a single member does not have. This video will help when I want to change pinion gears...oh epiphany! thanks
Would you consider making a video about the intermeshing system ability to move inputs from the mast into the rotor blade? Some sort of magic happens up near the blade root. Somehow Kaman gets the inputs down the inside of the blade bypassing the effects caused by actual flight. I can find nothing.
Cool idea. Kaman uses servo tabs on the blades instead of pitch links. I don't know for sure, but I think there's a swashplate in the system to control the blades, but then the control rods are passed inside the rotor most. Enstrom also has a crazy design where it appears like there are no controls going to the rotor.
They use something called an azimuth plate, it does not actually touch the outer surface of the mast. The bearings and tilt mechanisms sit below the masts. I am really curious about the mechanics of getting the control inputs from the top of the shaft into the roof of the blades. No hydraulics.
Superb dissection of a chopper's inner organs - can you please share with us the name of this software package?
I made the 3d models in Autodesk Fusion. And I used Blender for the materials, lighting and animations.
Oh yeah also fine Cad n Rendering,
What software?
Fusion for the CAD and Blender for the animation and rendering.
Every gear system has integers as the basis of their gearing. One cannot have a partial tooth. If we expand the 10:19 gear system to a 100:190 system, we get a common factor of 10 and the wear will be uneven after time. The 10:19 gearing is selected for economic and weight factors, as well as the hunting tooth feature.
Can you Please explain the tail rotor and pedal system and what is the cable tension impact on pedal !!!
Most helicopters maintain tension in the cables that control the pedals via springs. Slop would create a deadband in the control system.
Some Sikorsky products have a cable break system that allows full control even if one of the tail rotor cables brakes. They do this with the spring tension so that when one cable breaks, the other pulls, or relaxes the pull of spring tension and the let's the pilot move the tail rotor in both directions.
I suspect that this sort of detail about gearing is not well known among helicopter operators and enthusiasts because they are never in the position of choosing gear ratios. In contrast, automotive enthusiasts routinely choose gear ratios (typically in final drives, but sometimes in transmissions), so most are aware that gear ratios are never simple integers... even if they don't understand why. There are probably some auto enthusiasts watching this and saying something like "so _that's_ why they're always weird numbers".
This is a great observation. I've used machines for years and suddenly had ah-ha moments where I suddenly understood how a particular thing worked.
Learned Something New, I would have liked it a little better, if hunting gear was specifically designed first, but could have lost interest.
Animation was good too, once the second gear set is shown with differences of contact it really starts gearing you up!
I love the gear pun!
W video
4:10 but you haven't explained why this would cause wear.
Oh. That's what the part about differences in micro geometry and repetitive wear with a unchanging tooth mesh was supposed to be. I see your point... It could have been more clear.
Yes, some helis have heavy, expensive, maintenance hungry gearboxes. Others have tip jets. Gyroplanes need nothing.
I agree... Gyro planes/gyro copters have much more potential than the commercial markets have allowed.
This is what Steve Jobs was talking about. Instead of standing on their shoulders, you talk to them via an AI that was trained on their life's work.
Considering a planetary, the number of planets, and the number of teeth on the sun, planet, and ring must share a common integer. I don’t think a hunting tooth planetary is possible, though mistaken I may be.
So... I looked up the technical drawings on the S58 helicopter. It uses 46 tooth planets (factors are 23 and 2). A 39 tooth sun (factors are 13 and 3). And a 131 tooth ring (prime). So it appears it is possible to make a hunting tooth planetary. Thanks for the comment.
@@bzig4929 Thanks. Some years back designed a planetary with off the shelf spur gears. They needed a common denominator to fit. It’s not just the number of gear teeth, it is also the number of planets.
Spur Gears are formulaic requiring selecting pressure angle and ‘Diametral Pitch’ (English) or ‘module’ (metric). Helical gears, which would be used in aero applications, have to select the helix angle as well. Once these parameters chosen, all the gearing in the set uses them. However, the designer may choose not to use book DP or module and use his own as long as gear laws obeyed
Gears can and are modified by thinning the tooth. Thus more teeth on the same pitch diameter…say 130 tooth ring gear cut with 131 teeth. In addition, helical gears can slide axially which, due to the helix, changes where the contact. Sufficient axial will get the hunting tooth to work.
The P&W 4360 gearbox’s planet gears are configured so. The planets are counterbalanced by engine oil pressure. By this the planets equally share load and damp vibes.
Still, it’s a mystery! Cheers
Designers who ignore all known concerns as just an option 😮
There are no giants, only drudges.
Show how much simpler a gyrocopter is.
Agree! It's a shame there are not more gyrocopters flying.
How about Juan de la Cierva? He started it all. In fact if Sikorsky had not "borrowed" Harold Pitcairn's jump start autogyro collective pitch design head, he would have not be successful with the control of his first helicopter. Pitcarin was a licensee of De la Cierva but had improved the design allowing jump take offs by de-pitching the rotor blades and pre-rotating the rotors by 150% of the normal RRPM needed to sustain flight. He had figured out the swath plate and the cyclic. Sikorsky was urged by Uncle Sam to become a licensee of Pitcairn because of his struggle to control his helicopter. Pitcairn sued Sikorsky but the government would not allow the suit to go forward, claiming National security. In 1976 the Pitcairn family did win the patent encroachment lawsuit. Harold Pitcairn shot himself over this. Think of all of the millions of dollars that Sikorsky, Hughes, Bell and others profited by the 70's. The Pitcarin estate was awarded 60 million. Sikorsky was a genius no doubt but well, now you know the rest of the story.
I just read about Jaun de la Cierva... Fascinating history! The autogyro is an amazing invention and there's no doubt the early pioneers of the helicopter learned from and relied on the work done developing autogyros. Thanks for commenting!
Why not speed up the animation so we can see that the tooth does in fact contact every one of the meshing gear's teeth? You have created an unscratchable itch in my brain!
So if you don't know about gearbox then what do you know what part of the helicopter do you specialize in Mr engineer because this hunting to design is used in a lot of cars and trucks I take apart a lot of stuff when it comes to Motorcycles Cars and heavy duty trucks what kind of engineer doesn't get his hands dirty before he even goes into college you should have already learned this manual labor you know in Romania an engineer always start off to learn how to use the shovel and hoe if you cannot engineer your own garden you should not attend to go to college for other engineering you're going to be too lazy to learn outside of your books just think about it your engineer you got the brain power
I’m guessing English is not your primary language; although your spelling is good, your use of punctuation and grammar is not. What you’re trying to say is completely lost to this reader.
@@ronjon7942 hahahahaha that's so funny your brain can't put it together just because of some punctuation what the hell did you go to school for if you can't use your brain at least this much
My areas have been ops, flight test, stability and control, flying qualities and flight control systems.
Your point about experiential learning is a consideration. Some of the most valuable team contributors I've worked with have been those who can walk in both worlds... The hands dirty world and the white shirt and tie engineering world. I believe complex programs need a robust workforce that has a spectrum of experience and qualifications.
If you ever get the chance to sit in on a flight test brief for an aircraft in early development, you'll see the most eclectic mix of people in the organization... The mechanic on the shop floor has as much to contribute as the lead design engineer. And every person on the educational spectrum is needed to safely produce aircraft.
@@bzig4929 if I can only get to that level of punctuation and knowledge expertise I would definitely join the Aviation Group I'm all about rocket science and I like building fpv drones problem is I'm afraid of heights but if I'm the one flying I'm not so scared I hope no one's afraid of heights while I'm flying
Wtf? 👎