The Unexpected Genius of Contra-Rotating Propellers

Play the incredible War Thunder game and click my link and claim your extra bonuses: playwt.link/ziroth
This video explores the incredible designs of contra-rotating propellers. Although they were mostly popular in military applications of the past, due to the benefits of the toroidal propeller, they might be making an epic return. The toroidal propeller really came into the mainstream last year when MIT and Sharrow gave a new take on an older design. These have been shown to improve efficiency and reduce noise on boats, planes, and drones.
Sources:
www.acsce.edu.in/acsce/wp-con...
en.wikipedia.org/wiki/Contra-...
sharrowmarine.com/products/sh...
Credits:
Producer & Presenter: Ryan Hughes
Research: Ryan Hughes
Video Editing: @aniokukade and Ryan Hughes
Music: Ryan Hughes
#propeller #breakthrough #toroidal

[@ZirothTech]

Play the incredible War Thunder game and click my link and claim your extra bonuses: playwt.link/ziroth Will these new innovations in the world of contra-rotating propellers bring them back to more applications?

[@dimabubnovskyi8000]

Wartunder it's made by russian company Gaijin Entertainment, which, hiding from sanctions, moved russian programmers around the world and hide them as a non-russian company, while paying taxes in russia. So go fuck yourself with this advertising.

[@tonywilson4713]

Aerospace Engineer here: We've chatted a couple of times so I know your engineer and I'll hope you'll take this with the intent it is given. You and others need to stop putting up things like 116% efficiency or the 145% efficiency you had for the Fibonnaci turbine. I have seen a pile of this recently (most notably with heat pumps with insane claims) and we both know that there is simply no way in any engineered system to get mor than 100% efficiency. In fact if you have studied Thermodynamics then you know its fundamentally impossible in a engineered system because there's some loss somewhere that can't be recovered in every cycle. The problem isn't that you and I know what you mean that 116% means 16% above some other standard or reference. The problem is that people who ARE NOT engineers or have forgotten even their high school science class just think its possible. Where this becomes a massive problem is in dealing with the energy crisis. As an engineer I have to deal with it from a very pragmatic perspective. *First and foremost we have to do things RIGHT NOW that we know are going to work.* No matter what project you ever do you must start with something you know will work or have a very high level of confidence it will because the parts you are using are known to work in similar projects. Being honest I haven't always done that and its caused soe serious heart break at times. Here in Australia we are having this insane argument over nuclear power. No matter if we do or don't decide to go with nuclear it wont fix a damn thing RIGHT NOW because it takes time (a lot of time). We have the butt ugly situation of having power stations that we should have closed 5-10 years ago that are limping along because all of the public discussions are shitfests or stupidity fueled by armies of idiots stoking whatever their narratives are. Just this week I have saw a left wing think tanker claim that coal is NOT a mineral with the smuggest of looks on her face and NOBODY to correct it because it was here on her think tanks YT channel On the flip side we have the pro nuclear crowd telling so many lies its impossible to keep track and even more impossible to correct because they have mixed those lies in among actual facts. Do I think we will need nuclear? YES, the question isn't if we'll have it but when and what type and how much. Real Engineering did a great recent video on grid stability issue when you have a lot of wind feeding into a grid. Australia has an insane amount of wind available, but to make it work we need something to absorb the grid disturbances. Nuclear can do that and do it well but we can't even get a sensible discussion going. Just today I watched one of our Senators who was a test pilot and has a technical background in systems engineering and he mixed a staggering array of lie in among some important truths. I have the background to sort the lies from the facts most people don't. A week ago a neighbor of mine told me I had no idea what I was talking about because the Meisner Effect was the answer to everything. He had no idea that even if the Meisner effect (which is the effect of superconductors pushing away from magnets) has NOTHING to do with energy production and until we can use it practically it will have almost zero effect on energy distribution. BUT HE SAW the crap idiotic video by someone (I suspect 2 Bit Da Vinci) and now thinks he's an expert on energy. I have seen Thunderf00t's debunk of the 2 Bit video and its straight forward on how stupid that video was. I don't always agree with Thunderf00t, but most of the time he is spot on because like me he can see the lies through the crap. I think you have a great channel, but like a lot of younger people you haven't yet worked out just how problematic misunderstandings can become. These days we have so many people telling so many things that are simply wrong that its causing a lot of confusion and with that we can't have some of the very important things that need saying.

[@dfgaJK]

You could've put a huge ad read at the front of the video and I wouldn't have cared... I was too distracted trying to spin my fingers in opposite directions 😂

[@kevindevlieger300]

It's really frustrating. 😛 I tried for a few minutes. I just can't do it. Trying to figure out in my mind how I should do it. Sometimes my one hand suddenly starts spinning the other direction. Sometimes Im not even making circles anymore. 😅

[@PanzerBuyer]

I'm sure it can be done with practice. Reminds me of the guy that could control each of his eyes separately to read two different documents.

[@kevindevlieger300]

@@PanzerBuyer probably. Im getting a little closer to doing it. Right hand small circles. Left hand bigger circles with intervals inbetween. With training it'll possible for sure.

[@lucbloom]

The trick is: make 2 half circles. Really try it. Make a half circle in the opposing direction, stop and repeat but switched. Now keep doing that with shorter stops each time, but keep the 1/2 circle in mind.

[@kensmith5694]

I can do it easily. I can do it where the fingers move at different speeds. That version is hard. Don't look at your fingers. Touch your forefingers together and move your arms up and down. Count off 1,2,1,2 Stop doing that and move your right hand forward and pull in your left like you are punching with alternating fists. Count off 1,2,1,2 Switch back and forth between the two. Then when you can do it easily do both together and there you are.

[@Petriefied0246]

One way to reduce noise with contrarotating propellers is to have one odd and one even numbered prop so they don't pass each other at the same time. Also, the rearmost propeller needs to be slightly smaller so that its tips aren't passing through the tip vortices of the foremost propeller.

[@klausnielsen1537]

That might work. Du you know if this has been done?

[@matthewday7565]

I was thinking the same, just like PC fans have an odd number of blades and an even number of supports (also curved supports) to reduce chop noise

[@kuhhnt]

Came here just for this thought.

[@bartlettdieball2678]

@@klausnielsen1537 Yes it has Look at the AN-70 cargo aircraft out of Ukraine it has 8 and 6 blade combos

[@samsungtvset3398]

@Petriefied0246 That has a conceptual similarity to a vernier scale on a caliper or slide rule.

[@kirkwaggoner7328]

When I joined the Navy back in the '70's there were old torpedoes all over the place. Most that I recall had contra rotating propellers that still turned. The clearance between them was tight enough to do damage to an errant finger in the wrong place, a lesson most only had to learn once before knowing enough to not play with them.

[@jamesoshea580]

They used two propellers to reduce noise I believe.

[@bobsmith3983]

@@jamesoshea580 They used counter rotating propellers to prevent the torpedo from spinning due to the counter torque.

[@mikemondano3624]

Thank God! The voice of a real person using human diction. Guard your health, please.

[@tomscott1159]

Geared reduction drives have proven notoriously difficult on small piston-engine aircraft. Placed between an engine going bang-bang-bang and a propeller with relatively huge rotational inertia, the gearbox walks a fine line between being strong enough to withstand the shocks and light enough to be practical. On electric motors and turbines they may prove much more useful.

[@piconano]

Isn't that what the flywheel is for? Doesn't the prop act like a flywheel by itself?

[@tomscott1159]

@@piconano The prop is a huge flywheel which wants to move steadily round and round. The Pistons go bang-bang-bang. There may be a heavy flywheel on stationary engines, but in airplane engines it's reduced to the barest minimum because of weight. In between are the crankshaft going flex-flex-flex and a reduction box going clank-clank-clank on the smallest lightest possible gear teeth. Long ago Continental (see Tiara engines) realized that 2/1 was a bad reduction ratio because the same teeth were pounded over and over, even with a damper added. By the time all was said and done, the Tiara line was no lighter, enjoyed shorter TBOs, were more expensive to build and overhaul, and burned more fuel. Almost 20 years later Porsche learned similar lessons.

[@piconano]

@@tomscott1159 So all these experimental aircraft home builders are screwed? Some use Mazda rotaries or Subaru engines with reduction gearbox. I've never heard of this and I got my private pilot's license in San Diego in 2000. Where can I read more about what you're saying?

[@tomscott1159]

@@piconano Anything can be made to work more or less, but historically, certified geared light general aviation applications have not proven particularly successful. Both Lycoming and Continental brought out geared lines in the 1950s which proved to have no particular weight or performance advantage over slighly larger displacement direct drive competition. The Continental GO-300 in the Cessna 175 would not survive the Lycoming O-360 engines, for instance, because the 300 had shorter TBOs and required a bit more operator finesse to reach them. Likewise in the upscale twin market, the geared Lycoming 480 and 540 series were notorious for demanding smooth and minimal numbers of power changes to preserve gearbox life. Professional corporate pilots fared better at reaching TBO than owner-operators. When small turbines became available they rapidly shrank the market for larger piston twins, with the King Air essentially replacing the Queen Air, for instance. Continental tried a new line of geared engines in the mid 1960s, but they offered no significant advantages to offset greater cost, greater fuel burn, and shorter TBO. Porsche worked with Mooney in the late 1980s to introduce a 200 HP class geared flat six. Less than 50 were installed before Porsche left the market and eventually surrendered the type rating to the FAA. Too heavy, expensive, with short TBO, poor fuel specifics. Today there are several series of small-displacement geared engines available to homebuilders and even a few which are now certified. Most of these are water cooled which makes it a bit easier to build a light-weight high-speed core. Yet by the time the system is complete and installed in an airframe with all accessories and coolant, these rarely offer a huge weight advantage over basic direct-drive air-cooled installations. Smoothness and automated controls are typically the main advantages of these new types. But even in these cases the gearbox is an additional point of failure and a costly component to purchase and overhaul.

[@UncleKennysPlace]

Yep. Torsional vibration is real; designing for maximum torque without considering TV (which forces can be quite spectacular) has caused many a redrive to become scrap.

[@tomduke1297]

now that everything is going electric, i can totally see just 2 motors behind each other turning opposite directions, making the gears unnecessary. 15% higher efficiency is worth quite a bit.

[@TheDerperado]

My thoughts exactly aswell.

[@kittengray9232]

You're losing some efficiency from double the electronics and smaller motors. Benefits have to even that out. Same with mechanics. Turbines just position static blades after rotating ones.

[@dm45lm]

I saw a video recently about a new open rotor jet engine being designed by GE and Safran where they have decided to use a hybrid design. Instead of a second counter rotating propeller they use a set of fixed, adjustable blades that act to straighten out the airflow without creating all the noise.

[@davidmartin3947]

Candela hydrofoiling boats have small, low noise, highly efficient, zero maintenance sea water cooled contra rotating propellors operating right now on their hydrofoils in their C-Pods. Each pod contains two motors, one for each propeller. This seems to me the best and most obvious example of the use of the tech.

[@poneill65]

Sharrow: "Our revolutionary Toroidal propellers greatly increase efficiency and reduce noise" Everyone: "Cool, can we have some figures please?" Sharrow: "No, go away. Here's a promotional video" Color me sceptical, but I smell a monorail salesman.

[@leifvejby8023]

Me too - from the public available data I calculated an efficiency of up to 124%, thought hogwash, and left.

[@gr3g0snz]

yeah and US$9k for a set to go on a existing duo prop legs yeah no thankyou

[@kittengray9232]

There is a video of a guy who tested RC boat with 3D-printed propellers. With GPS, hdr camera and so on... Toroidal designs had no advantage or slight disadvantage. 2 long thin blades has the upper hand!

[@alphaomega154]

a pair of 2 contra rotating propellers would need different aero design each. or the rear one must have lower RPM speed. this is due to how the air get carried into the first propeller's momentum and rotating towards the first propeller direction so it will hit the second propeller with more energy, making the second propeller, albeit it running at the same RPM speed as the first, to seem to have more velocity in relation to the flow coming towards it. and if both propeller have identical design, if the first propeller works the aero perfectly it will be off efficient when the flow hits the second. so the second propeller must have an individual design for its purpose that to deal with the higher velocity coming, and produce efficient flow and thrust. remember, the flow of the air from the first propeller not only faster towards the rear than what the first propeller is feed into, but also rotate the flow in OPPOSITE to the second propeller rotation. i prefer to have a pair of 2 uniformly rotating propeller with each has different aero design purpose. the first propeller act as the "setup" to condition the flow for the second propeller. not to produce power. then the second is acting as the main propulsion which i believe would works better. and the goal design is to produce ultra high RPM without causing any turbulence breaks between the blades. counter rotating propeller in tandem is tricky to make it fully efficient.

[@kittengray9232]

Rear propeller can have different angle at attack. Even different shape and radius might help.

[@BulletproofPastor]

I would like to see some study in applying contra-rotating propellers in a ducted fan configuration. The ducting might reduce tip vortices or perhaps damage the enclosure and prove disastrous. Either way, it would be an interesting study.

[@jamesogden7756]

You might be able to find old Navy research using your described method applied to an older generation of torpedoes.... 😉

[@crazymonkeyVII]

The CFM Rise engine solves the mechanical complexity problem by using static blades with a spinning blade behind it. Possibly interesting for a future video?

[@Sythemn]

For EV, one might be able to just have two smaller motors on one controller which would keep them synchronized. The caveat being if one prop required more torque the motors may need to be different sizes to account for this which would make balancing everything an extra step at the design stage.

[@AJTalks]

Ducted contra-rotating propellers get an even bigger efficiency bump from the ducts removing tip vortices. Studies about the optimized geometry for the ducts claim potentially huge efficiency if the geometry is right. The combination is almost necessary for EVTOLs which need every ounce of thrust they can get to offset the heavy batteries.

[@OliverFLehmann]

The dual-motor Dornier Do 335 was an attempt for a practical implementation with one motor at the front and the other, counter rotating, at the end. Being a development of WW2, it was never sent to the battle theater, but test flights showed its benefits and disadvantages.

[@andrerousseau5730]

What you completely failed to mention was that the trailing propeller in a contra-prop pair is operating in a faster slip-stream and therefore to obtain optimum performance it's design parameters must differ from the one in front, I.e. they're NOT interchangeable.

[@massimomaraziti5595]

Would a second (back) propeller spinning slightly faster that the first (forward) one make sense? The air flow would be accelerated faster by the second propeller, arguably improving efficiency.

[@elonmuskes4874]

There exists a plethora of planes with counter rotating propellers (well almost). Pretty much all turbies use stators in combination with their rotors to counter the rotation of the air flow. It gives (almost) the same efficiency gain without any extra moving parts. In modern jets the stator also act as connecting rods between the casing and the rotor shaft which doubles as a shock dampener af helps with vibration (noise).

[@JoshWalker1]

Also the engine used in the F22 and F35 actually doesn't have static stators (lol). Instead the compressor shaft spins one way and the stator the other, via (afaik) planetary gearbox. This solves a huge problem where rapid changes in thrust or compressor stalls / unstarts jerk the aircraft. This movement was responsible for putting F14 (A model especially) into nearly irrecoverable flat spins

[@ryanjamesloyd6733]

seems to me that as they've already got drones with contra rotating props, printing torroidal props for them would be fairly simple and maybe a good way to test this.

[@nigelwilliams7920]

Great thanks! With electric drives, you would dispense with the gear box, and just run two motors feeding a shaft within a shaft for the two props. There would I am sure be useful benefits in being able to actually rotate the props at different speeds for certain flight regimens and of course stepper motors are king at that sort of duty. Perhaps one prop off for cruise (say the front prop feathered), and differential speeds for assisting or even replacing roll control. For noise reduction a different number of blades on each shaft has helped, but a 2-3 or a 3-4 or 3-7 beat might still be a bit odd.

[@douglee2438]

The Wright Flyer had contra rotating propellers. However they were not coaxial. They were driven off the same engine.

[@Zalex612]

If they are not coaxial they are referred to as counter-rotating.

[@Lord.Kiltridge]

I can contra rotate by hands with ease. I learned how to do it years ago.

[@philleasthouse3791]

I'm always fascinated by new (and not-so-new reused) technology. Your enthusiasm for the obscure is palpable. One personal criticism refers to the "soundtrack" - I'm not sure if I'm the only one who hates the use of "interrupted cadence" "music" (deliberately put inverted commas) as it is hugely distracting and harmonically unbalanced, almost to the extent in my case of wanting to close the video. This is, I know irrelevant to the content😢.

[@properlyinactive]

contra rotating my fingers makes my brain go numb

[@mrxmry3264]

years ago i went to a museum in germany where they have an antonov 22. i took one look at that bird and i knew that it had counter-rotating props. on one engine the blades were spaced out evenly, one blade every 45 degrees. but on the other engine it was more like 30-60-30.

[@mikemondano3624]

Not sure what that means. A degree is not a measurement of space.

[@mrxmry3264]

@@mikemondano3624 degrees can be a measurement of temperature or, in this case, angle.

[@mikemondano3624]

@@mrxmry3264 Indeed. But the angles need to begin somewhere, have an origin. And angles have nothing to do with spacing. From where are they being measured?

[@mrxmry3264]

@@mikemondano3624 where do you think they are being measured? From one blade to the next, of course,

[@mikemondano3624]

@@mrxmry3264 In a box on the floor?

[@diGritz1]

Not sure what the increase in decibels for a smaller plane would be. But in the Tu-95, AKA: Bear, it was substantial. US fighter pilots would regularly intercept them flying up around the arctic circle, and could hear them before seeing them. An impressive feat, especially when you consider how loud a fighter can be. Had a low flying F-16 from the 180th FW and you could feel the sound in your chest. If I'm remembering correctly they were also able to track them using acoustic sensors used to track subs.

[@garywhite2050]

Props👍🏼

[@loisplayer2658]

Thanks for another great video!!

[@catherinesarah5831]

When talking about propeller efficiency, another interesting topic you may wish to entertain is increasing the efficiency of full displacement hulls. As it was for the Wright Bros to overcome gravity by increasing lift & thrust, I’m sure it’s only a matter of time someone will break the 1.48 constant on full displacement hulls. Thank you. 🙏

[@mm-yt8sf]

toroidal-contra-rotating propellers would look so strange on a plane....or does the difference in air/water density make the best design very different for one rather than the other?

[@elonmuskes4874]

I dont know if they are currently possible on jets due to the massive g loading. Modern turbines need to be made out of carbon fiber and titanium alloys just to withstand the force so adding a large chunk of material at the very tip might make them explode... boats have MUCH lower rpm and tip speed so dont have the same problems.

[@RagtimeMikeinSD]

Why not have two electric motors so the phase difference of the props is computer controlled.

[@Kargoneth]

Non-loopy propellers. Preview image gives me more confidence now.

[@FreekHoekstra]

Note most commercial planes use turbofan/props which have counter rotating fans

[@e7yu]

Simply amazing!

[@dandare1001]

The first time I ever flew as a child was on one of the Tupolevs. I still remember it being noisy. People should accept the slower speed of propellor-driven planes for environmental reasons. The airlines can supply us with noise-cancelling headphones to make it easier.

[@nunya___]

Increase the speed of the second prop.

[@lukecreamer8426]

I want to see this combined with toroidal propellers yesterday.

[@haxi52]

When talking about single engine (single prop) airplanes, P-Factor has a much greater effect on left turning tendencies than torque or slipstream.

[@tuberroot1112]

Why will there be a increased interest in the future as we are using less propeller driven aircraft ?

[@billberg1264]

I think most drones still use propellers.

[@wobby1516]

With the onslaught of batteries in aviation and the need for efficiency these contra rotating propellers make a great deal of sense.

[@joes8473]

Volvo has had counter rotating props on outlived for over 25 years with reliability and ease of manuering and backing.

[@joes8473]

Out drives - damn Google keyboard!

[@chrissmith7669]

I’ve seen lots of theoretical stuff saying they’re more efficient but reality rarely does the maths.

[@MAviation_com]

Can be produced with electric motors without using gears

[@bui340]

We had the same comment🙂

[@janno1177]

Contra-rotating (or "coaxial") props have become a common sight in the drone industry for quite some time now. Also you missed some downsides. 1. You can't just add another prop and the efficiency increases, you also need to install a more powerful engine. If you just install another prop the engine has to work against more drag with the same amount of power which will cancel the added efficiency. 2. if there is enough space, it is even more efficient (about 15-20%) to install the same amount of props side by side instead of coaxial. -> combining these two: since you have to replace motors anyway, installing another set of props in the same plane as the already existing ones gives you an improvement of about 35-40% in efficiency (given your weight stays the same) 3. (drone specific) however for another set of props you need another set of motors, increasing the weight and cancelling the efficiency bonus. So for drones coaxial is only viable if there are very tight space constraints.

[@ZirothTech]

This is super interesting, thanks for these insights. I should have thought more about the surrounding systems, the need for a larger engine is a really important consideration

[@andym4695]

The P-38 used counter-rotating props, though one engine drove each prop. This keyboard fighter jock loves the P-38. As far as the 110 dB of the Tu-114, I bring you the C-5, which I got to ride back from Europe. it doesn't have the niceties of sound insulation (that weighs a lot), and sounds an awful lot like being trapped inside a giant vacuum cleaner.

[@ZirothTech]

Sounds like quite the ride! Bet it was an awesome experience, even if your ears needed a rest afterwards 😂

[@thekinginyellow1744]

To contrarotate your fingers, start with one high and one low and then think about moving your fingers towards you then away. Makes it much easier ( though not easy)

[@toi_techno]

I remember flying from Dublin to Frankfurt on a propellor plane in '93 It was unbelievably loud and turbulent (and kind of scary)

[@Petriefied0246]

That wouldn't have been a contrarotating propeller though. Lots of regional airlines are propeller driven because they're more efficient in short journeys.

[@ChrisTaylor-NEP]

I guess we're going to see more and more of these, however, one disadvantage with big ships using this will be the loss of transverse thrust, which is very useful for manoeuvring.

[@Llyd_ApDicta]

Don't big ship usually have maneuvering thrusters?

[@michiganengineer8621]

Well, perhaps Veem will put out some numbers in a year or so since they're now milling Sharrow designed props in Oz. I know the NautiStyle channel is putting them on their new Bering. One surprise to me was seeing a Sharrow toroidal as a contra-rotating prop, those on a Merc 600 would be NUTS!

[@BluespotKneeClinic]

Thank you

[@1jotun136]

He should not be portrayed with the crown until after he meets the monk Ta Sheng.

[@samsungtvset3398]

I wonder if the two propellers would benefit by being driven from a differential gear setup so that they each received equal torque despite possibly seeing different loads. Any unequal load would make them rotate at unequal speeds, the sum of the two speeds being unchanged. Would help the torque reaction problem on a plane, but might partially undo the smoothed airflow exiting the rear prop.

[@moxie_ST]

You did not mention everybody favorite Wyvern 😂❤🎉

[@richardfinnigan7458]

Turning your fingers in the opposite direction after turning them together is hard for a dyslexic person but really quite doable.

[@pbasswil]

Efficiency quotients above 100% make for enticing video taglines! (As do perpetual motion machines and the Tooth Fairy.)

[@tsclly2377]

Penta-Volvo has made counter rotating marine propeller inboard and outboards designs for over 20 years.. the problem I deducted with these toroidal propeller designs work best in a small speed range on marine drives. So maybe for and ocean going tug or fast (17-19knots) bulk cargo ship of the twin shaft design..

[@Ucceah]

there's a simple trick to rotating your fingers in opposite directions: do half circles, meeting again at the top and bottom, and repeat. fun to watch folks try without knowing. but once you internalised this trick, you cant unlearn it.

[@Allan_aka_RocKITEman]

Great video...👍

[@mr.normalguy69]

I love contra-rotating propellers, they look futuristic, until you realize that they are a very old tech.

[@richardwallinger1683]

great info as usual .. keep up the / your excellent presentation video,s

[@Zalex612]

CFM RISE open fan architecture enters the chat.

[@Skylancer727]

From what I've seen from people testing toroidal propellers, it really doesn't seem the claims hold up under third party testing. There are many videos here on youtube testing the design and the toroidal propellers just tend to do pretty poorly. The MIT report was a bit misleading as they claimed at the same rotational speed the toroidal fans are quieter; but they are also much weaker at the same RPM. I follow computer building all the time and there are many who build PCs with closed off front panels to reduce noise from fans. The issue is now your fans have to run faster resulting in them making even more noise. The end result is having an open meshed case will still be the quietest even if you're directly exposed to the fans.

[@mrvn000]

Awesome....

[@nimoadder]

the RISE engine gets most of the benfits using a static 2nd propellor.

[@bobgreen9980]

*Contra-Rotating Propellers are LOUD!!!!!*

[@ZirothTech]

What's that?? I can't hear you over the propellers!

[@bobgreen9980]

@@ZirothTech *Hey Ziroth. There is an option you did not know about. Only about 2 years ago a few people in the quad copter industry have had great luck with the rear propeller on it's own FREE spinning bearing. The Rear blade spins at the same speed as the front driven propeller and does all the same things: No more tip vortices and no strange torque with the mass of the rear blade spinning the opposite way to offset forces. Also if the free spinning blade is given a small "kick-twist" on the rear tip like a turbo charger most of the air stream shots straight back just like a jet engine. Much work is needed but it looks promising. Time to throw all those messy gear drives away. Look for a NASA report by end of this year.*

[@zvenlin]

@majorhardware can't wait for the contrafan video

[@jaspertell6764]

You never talked about drones. A pretty famous counter rotating design would be ingenuity on Mars. Also I'm curious why there isn't a dual electric motor design? the axle could house the stator and the blade the rotor, something similar to what verge motorcycles is doing with their electric drive. I know there's added weight by having a second electric motor but eliminating the gear box, increasing reliability, and the potential for some interesting vortices precision control mechanics sounds like it'd be an interesting experiment in the least.. yet the internet hasn't shown me any examples.. why?

[@koiyujo1543]

I thought about this too before this vid came out

[@kenreynolds1000]

Do a big circle with one hand and a counter rotating big circle of small circles. Can be done but swapping is super difficult

[@antoniopacelli]

<a href="#" class="seekto" data-time="14">0:14</a> You already had me over the Fact that you cannot do that as Any Normal People without Psychotic Personalities.. Or Drum Players, but for them would be Fine because the Differential Rithm they have to Keep..

[@CC-iq2pe]

It is really interesting that these two technologies haven’t met with windmills to produce higher efficiency windmills which are more quiet and have impact due to low frequency sound waves.

[@darthnihilus511]

I doubt there is anything you can do to a windmill to make it a viable, reliable source of energy, we are finding out the hard way after all of that money wasted 😢

[@dianapennepacker6854]

​@@darthnihilus511lol, have you been living under a rock since 2000? Work for the oil industry? I don't think you know what you're talking about. Clearly you are ignorant on the subject. Wind is the cheapest form of new energy production now, and only getting cheaper. The percentage of total wind will rise significantly. There are literal swathes of areas running off of offshore or land based wind across the world. Any failures happen due to operator error or poorly designed grids. Like in Texas - but wind didn't just fail. Their gas plants also failed. Practical Engineering has a break down on what happened. Stop getting your information off tiktok or Fox News.

[@dianapennepacker6854]

When 3d printing becomes better then definitely for smaller blades. For grid? Right now cost is everything... It just wouldn't make sense when you can purchase much larger designs of a less efficent design for the same price. Afterall the bigger/taller the blade the more power you get by a big factor. It is why we've constantly pushed for bigger standard designs. For example the world's biggest design is coming out at 140m. Just making the blades 10m bigger of the previous record holder netted you 2 more megawatts. Once we hit the limit where going bigger is no longer feasible or wanted then definitely. When that happens I have no idea. China will launch a turbine with some truly monstrous blades at 140m and over 50 tons a piece. Generating like I said 18 megawatts total. Soon we will have ones that are skyscraper tall at 150m plus! Wild.

[@entelechy00]

​@@dianapennepacker6854a more feasible alternative would be a different approach to solar: instead of light changed to direct current electricity with a lot of heat inefficiency and about 5 years life, pull heat directly off man made objects creating the Urban Heat Island Effect (UHI), such as buildings and roads, and storing heat in heat batteries. A heat battery's life is measured in decades, not years, and the side effect of lower temperatures is what climate change activists want, right?

[@The8blackwidow8]

windturbines can only have a maximum efficiency of about 59% and the current designs are getting quite close to that. Having two rotors would be much more challenging and costly than the efficiency gains would ever yield.

[@bui340]

With an electric powered plane you don't need the complex mechanical stuff to make the props spin equally fast

[@Llyd_ApDicta]

Yea, I was thinking the same. You could even go further and - for example - reduce or even eliminated the need for ailerons since you can rotate the propellers at different speeds and use that to induce a rotation along the roll axis. Kamov has been using coaxial rotors for decades now and that is how they completely negate the need for a tail rotor for yaw control.

[@bui340]

@@Llyd_ApDicta fascinating! Thanks for sharing😀

[@harrygoldhagen2732]

Interesting! How about a video about noise in our environment and how to reduce it. Road noise, fan noise, you name it!

[@BenjaminGarcia-ol3bh]

cool vid dude :)

[@indralaljayathilaka645]

nice drone

[@WMCloseProtection85]

Anyone else just spent the whole video trying to rotate fingers... gonna restart the video now and desperately try not to fall into the same trap 😂

[@ghostshadow9046]

counter rotating props require MORE power, moving parts and expense that is why it is not frequently used.

[@bwuepper439]

I wonder about the noise when the blades pass by each other. I wondered if either the front or back could have one more blade which would make the blades front to back pass by each other at slightly different times. Just a thought.

[@kristinaF54]

I thought bladeless propulsion (somewhat like Dyson bladeless air-dryers) and electric atmospheric thrust (ionic vector) pods were the future, no?

[@DanFrederiksen]

They are exotically noisy, at least configurations tried so far. In reality stator vanes are used instead

[@joseveintegenario-nisu1928]

Would a CounterPropeller, after the turning propeller, same concept as fixed vanes in turbines, improve ordinary simple propellers?

[@dallebull]

I remember the old Delta (PC Server) fans, thicc bois with dual props. Moves a ridicolus amount of air...

[@peetsnort]

The old Shackleton used those

[@JohnBoen]

<a href="#" class="seekto" data-time="22">0:22</a> Haha - that is easy. I finally got value from my martial arts classes :)

[@user-fl2wn5zr5z]

propellers are antique technology

[@BenWillBarrows]

Yes and also cutting edge😂

[@darthnihilus511]

Great, now I will be walking around trying to spin my hands around, looking like Im having a seizure 😂

[@kittengray9232]

Differential gearbox lose quite a lot efficiency. Benefits from optimized air stream have to even that out. One could just put static blades after single rotor to get laminar flow. Turbines do that. And calculated winglets on tips.

[@sottonk]

What effect does running the two propellers at different speeds have?

[@mishapsrus]

Where does the extra 16% come from?

[@MrTiti]

we can have these toroidal (is that correct?) propellers to reduce noise. if we have a 3 and 4 balde propeelr behind, the tips wont past at the same time. what about a faster spinning rear propeller with lesser pressure difference and smaller diameter? and a shape that focuses the stream of the fluid whilst the first naturally expands it? also, what about more "blades" to have lesser noise? with that combination we might get over 10% efficiency. also the two gears for the rear propeller are quite a lot of friction, wouldnt it better to use a planetary gear? you might also get the higher rpm that way , like 15-20%

[@itsrachelfish]

No link to the 3d print model in the video description? 😢 Please hook me up I want to print this 😭

[@Jkend199]

yea... modern props are constant speed, variable pitch, they are VERY complicated, when you throw in counter rotation gearing it gets MESSY. Are there benefits, sure, but it's so expensive that no one outside the military can afford it.

[@KhamusSolo]

Hey, if Warthunder wanted me and my money back, all they have to do is re-enable rudder usages in arcade mode. They had it, and took it away years ago. I'm not budging.

[@colindonoghue6120]

Is contra-rotating propellers really needed on commercial airlines, doesn’t the stators in the jet engine serve the same function?

[@mitchellambro4347]

Please Test the Propellers used in St@rW0rs episode

[@poepflater]

wonder if it would work in a PC case to stack two fans...

[@jdsahr]

Maybe the clocks rotate in different directions in the UK (see <a href="#" class="seekto" data-time="20">00:20</a>)

[@viniciusbrito7512]

Great vid! What about 4 propellers in the same axis? Makes any sense?

[@UndulatingOlive]

What about the reverse application, wind turbines, too much resistance?