Both are correct. They both operate in the same direction for completely different reasons. They are not, however, the same thing.

Hat is on point 😂

Why go co-axial when you could go with the proper helicopter scheme?

The problem of phase lag is an interesting one. How do you determine the phase lag angle in a real machine? Calculation? Or experiment? In any case, a coaxial rotor simplifies things by cancelling out all the phenomena.😀

Spot on, Ben! You can actually use the same idea for flywheels even though they are solid. If the flywheel is driven by a CV joint it stays in plane. If you account for shaft stiffness then you get flywheel whirl. This stiffness can also be just because the flywheel is at an angle to the rotation axis so that centrifugal force is trying to flatten it: that's the trick where you spin a plate as you throw it into the air offset from flat and it wobbles due to precession. So what I'm saying is that gyroscopic precession can be thought of as the same thing as a rotating pendulum in resonance with the rotation frequency - you just join all the pendulums together to get a solid disk...

This guy still has no idea.

3:34 Are those training skids or an inherent part of the design?

G'day Ben, I suppose I read a very simplified book on Heligoflopterism., because I never heard of there being any variation of Phase-Lag alteration due to Cierva's Flapping & Drag- Hinges...; it all came under the heading of Gyroscopic Precession - and I understand how that works on Boomerangs & Sopwith Camels... But the effect of adding Soft/Weak/Flappy Bits between the Axis of Rotation and the Blade has always seemed to me to be the sort of thing which is known to be necessary, and can be made to work, then beefed up to prevent the components from failing...; but couldn't ever see how to perfect such a setup, short of building and testing and breaking and tweaking a long succession of failed attempts to make it work, safely and reliably. And I always lacked the skills, tools, time and money to make and break all the wrong ways of trying to get the thing to do as it's told ; before it would ever be likely to behave itself.... If I had to try to express what is going on, I would say that Gyroscopic Precession IS what's happening (happynink...?) ; And adding Hinges Interrupts, Delays Magnifies Accelerates, & Exacerbates the Precession - all Before then reversing the process to permit the various assorted Hinges & Pins to realign themselves with the Blade's-Axis, to achieve a state of Dynamic Balance at least twice per revolution - all while obeying the Pilot's Command-Inputs, and Failing to throw itself all over the Paddock as a sudden violent dispersal of component parts, thrown out in all directions, following Each successive iterative Failure... Igor of the Sikorsky Tribe, he had wealthy Investors & Shareholders, to provide him with a Fire-Hose flowing with money, enabling him to wash away the detritus of every attempt which didn't actually "work" as intended. I never had one of those magic Funding Hosepipes, so I stuck with Boomerangs, Propellers, and Wind-Turbines - which I can carve from Wood, and the whole thing remains quite rigid as it rotates...; unless I count the Mk-1/Mk-2/Mk-5 compound Turbulence Testing Auto-Furling Lawn Ornament - which uses a pair of old badly built Turbine Rotors at 90° to each other on the one Shaft... When the Rotors were bolted together, the whole setup shook and shivered like the proverbial "Wild Woman's Shit"...(!) ; so I replaced the Bolts with Steel Tie-Wire "Stitches", laced through the two Hubs' Bolt-Holes... When the two Sticks were freed up to be able to accelerate/decelerate, relative to each other's RPM...; SUDDENLY the whole Rig began to spin as "Smoothly as the proverbial Turbine...". I accept that it happens, but the intimate details of quite how and precisely WHY shitcanning the precision rigidity of 4 Mild-Steel Bolts for the loosey-goosiness of 4 loops of Hillbilly Tie-Wire - which has run much more smoothly (now for 25 years), in the most turbulent location which I could devise. I accept it, but I'm still grasping at understanding what is happening in the Hub & the Offset Perpendicular Rotational Axes... Which is why making and watching the bloody things is so fascinating..., I suppose. Such is life, Have a good one... Stay safe. ;-p Ciao !

Hi there, I'm afraid that I don't fully agree with your explaination. If I may offer the following description: There are three key principles that need to be taken into account, Phase Lag, Flapping to Equality and Advance Angle. Firstly to rule out the gryroscope, consider a fully articulated head (ie each blade has 3 degrees of freedom (flap, lead-lag and pitch). The blades are therefore not linked to one another and follow their own path. Phase Lag will always occur 90 degrees after where the input is applied relative to the blade axis, no matter the rotor system. This is due to the effect termed Flapping to Equality, whereby the maximim change in pitch of the blade occurs at the point where the input is applied. At this point the blade will have the maximum rate of flap, either up or down, coming to zero rate 90 degrees later and then reversing. The effect is similar to that of gyroscopic precession, however it is not gyroscopic precession The second important point is Advance Angle and this is the difference between the control orbit and the rotor orbit. If your control arms (and by extension the pitch change links) are 30 degrees ahead of the rotor blade axis, then the advance angle would be 30 degrees. The effect is that the input on the pitch control arm will occur 60 (ie 90 - 30) degrees before where it will be experienced on the rotor. This affects the offset that would be applied to the swashplate. The model helicopter shown has a advance angle of 90 degrees and with a Phase Lag of 90 degrees, the result there is no difference between the swash plate orbit and the rotor orbit (ie when you tilt the swash plate forward the disc tilts forward.) One of the best references that describes the above is AP3456 Pages 5 to 10. The document can be downloaded here assets.publishing.service.gov.uk/media/5e18b9c3ed915d3b0c0848e0/Volume_12_Helicopters.pdf. If the link doesn't work, search for AP3456, Volume 12. The AP3456 manuals are one of the best available. With the above said, the helicopter in the video looks as though it has either a rigid or semi rigid heads. There are no contol inputs made directly to the rotor blades, but rather by applying a change to the axis of rotation of the main rotor shaft. In this case I believe the effect would be gyroscopic rather than in accordance with the description above, but stand corrected. My 2c.

Phase lag and gyroscopic precession are the same thing. Think of it like this, Phase Lag: varies as a result of an imperfect gyro with many moving parts, and will be different from one rotor system design to another. Hunting & Dragging, Flapping, coning, etc. as well as the physical design of the rotor system. Gyroscopic Precession: does not vary, due to being a rigid spinning object.

Finally I get to read about a thing I never heard of before lol

I love your kit car. But Unfortunately this is illegal in China. I was studying the Hiller control method today. Because I have a huge rotor that needs to be driven.Do you know anything about Hiller system?

Even minor damage to moving mechanical parts caused by stress and strain on the parts. It leads you to death. Rigorous engineering testing is required. Hope you don't take off.

Hi Ben , with your fixed pitch rotors, is there a flapping hinge at the hubs? Also how did you determine the vertical distance between the rotor hubs??

Hi all, I think I was wrong to say the Smarter everyday video was wrong, for the moment think of the information in this video as another way to understand whats going on. Gyroscopic preccession and phase lag could be two ways of saying the same thing.

*_Do you know how to say ZERO? Instead of naught? It's what the entire world does BTW._*

Lovely Ben! Reading all comments with great interest!

Ben. To sum it all up you've had the most hands on experience with this setup, if somone came to you and was thinking of going down this road building a machine, fully tilting head etc ,would you spur them on or put them off. ?

That is a beeeeeautiful Seven!

Very good strait to the point Outstanding

My rotors phase lag is phasing out as my helicopter transitions to a new parallel universe.

This is super interesting because I have never comprehended phase lag, even as a very experienced R-22 pilot, and even so with your explanation, I am still not sure. You say blades always want to align themselves with the rotor shaft at 4:53 , but I think specifically loaded blades which have a counter to gravity force upwards, because a unloaded R-22 disk becomes un-oriented to the shaft, and made worse by aerodynamic (pilot) inputs. Autogyros appear to have a 'joystick' which is fixed to the rotor disk, which appears to be the same as your coaxial machine; pushing forward on the joystick raises the front of the rotor disk, moving it left lowers the RH side of the disk; I wonder why this seems to not apply to the gyroscopic precession. In a autogyro, I would think, if you applied a force directly to the rotor disk, say raising the front via the joystick, the force would act 90 degrees later in the disk raising it there? I understand how it works with an R-22 with swashpate inputs 90 degrees before, say increasing pitch on the blade at the RH position creates a force raising the front of the rotor disk, the cyclic linkage taking this into account; but is an autogyro different somehow? Wow, hearing you added a hinge to the exhaust to change resonance is very interesting.

Im not sure I fully agree with this. Phase lag exists but I am convinced cyclic inputs are adjusted so min/max AOA still occurs 90 degrees out from the desired rotor disc effect. I know appealing to authority is a fallacy so I'm not going to lean on it, but all of my textbooks and resources for my certifications explain it that way so I just have a difficult time believing they're all wrong. My instructor was an accomplished Boeing engineer and a IA A&P and taught it that way, so I didn't dig too deep into the details.

Should I have just said nothing? Yes. I just can't let this go because misinformation on the internet travels faster than truth. This vid indicates the seriousness with which you misunderstand this topic. How about you build a coaxial RC helicopter model version of your project and try to get it to fly before espousing your insights. Me? I'm just a 5000 Hr turbine helicopter owner/pilot with a PhD in physics.

GOOD JOB ...I always have respect for persons who spread the knowledge Regards .....CAD designer..... Have Nice Day :)

Phase lag is a special case of gyroscopic precession. Consider the dynamics/cause of gyroscopic precession and that of phase lag. They are fundamentally the same thing. The fact that we have a complex system involving two or more blades rather than a rigid disk, offset hinges, etc. does not eliminate the basic cause. It complicates the result for the reasons you describe.

As an afterthought Ben, in the case of your machine the whole rotor head and gear box and drive shafts are doind the tilting, wouldn't gyroscopic forces act on this, as a conventional machine the forces are coming from the blades themselves by cycilc pitch change. Thus tilting the disc the direction you want to go. ?

Еще зависит от типа втулки несущего винта. Если втулка несущего винта выполнена по жесткой схеме, усилия от лопастей непосредственно передаются на вал редуктора и конструкцию вертолета, имеет почти нулевое запаздывание по фазе. Если втулка шарнирная, то там иной механизм передачи усилия от лопастей к валу редуктора. Он принципиально отличается от механизма передачи усилия жесткой системы, имеет звено компенсатора взмаха, который вносит значительное запаздывание по фазе. Чтобы управлять такой системой, они управляют положением конуса винта, которое отклоняется ручкой, а непосредственное воздействие на вертолет происходит косвенным путем через баланс центробежной силы и плеча, одна сторона которого равна радиусу между осями шарниров.

Greatly explained

One might also Google up Flap natural frequency of a helicopter rotor blade which has a strong bearing on the phase lag angle and therefore on control system design

يا ممكن اسأل كيف تقلع الطائره من الأرض بمعنى زاوية المحور

Good Job MAN .......Ps. All THE BET FOR YOU

Did you get the engine built in charge winding and an external regulator / rectifier contributing to your cooling fan and so reducing or hopefully eliminating the need for external alternator? Many older original equipment outboard charge regulator rectifiers are inefficient. So a later single phase reg rectifier is likely to give you more output. I'm guessing your electrical requirements are around 10 amp so within the ability of the outboard charge winding.

I wonder if you have considered making the gearbox with one fwd and one reverse output attached and driving the rotor shafts directly with the auto one way on the gearbox input end. This will allow for drive belt or engine failure while still maintaining ability to auto rotate. Of course this depends on a collective pitch upgrade.

Amazing mate - just amazing the thought that goes into your projects, the skill and confidence to go forth with it - Max respect Ben. Lookin' forward to meetin you pal.

Single element failure....although most heli stick forces are light.

@7:45 sharpie marker leaves a coating almost .001" thick, definitely enough to mess with bearing press fit. In fact its an old machinist trick, if your bearing isnt snug, you can use sharpie on both surfaces and get a friction fit.

Relying on parts not failing because they are ‘well built’ is idiotic. For example, that top rotor shaft looks like it would fail in an instant if you lost a blade to a bird strike. Nothing is ever built well enough to negate failure.

Is it not possible to add additional rivets ?

Thanks for the update and bonus knowledge about chain drive.. I was always curious why it was always belt. I would have felt safer with double roller wide chain,or 2 belts with chain drive in the middle for extra safety..

Adding chain's increase Murphy's law Ben. Stay safe.

interesting

Perhaps a bevel gear set to get the reduction and to correct the chain orientation.

Hallo, danke für dein sehr gutes video und gute arbeit. Ich möchte aber sagen, das die lager , für die umlenkrollen am antrieb, zu schwach sind . Die laufen trocken und dann gibts probleme. Größere rollen und stärkere kugellager , wäre die lösung..

Consider also the tortional vibration situation as well. See how motorcycles resolve it with a cush drive in the rear, and the clutch basket springs up front - and even then there will be an "avoid" rev range.

There’s quite a bit of energy lost using a chain. Up to 30% as opposed to the belt. Belts are far more efficient and more than strong enough to handle the load. Not to mention lighter, quieter and require far less maintenance.

I love your thoughtful designs. I'm looking forward to seeing what improvements you make!😀

Probanly find Ben, De lackners flying platforms were fixed pitch but were flying in the ground effect all the time.

Listening to keyboard engineers on youtube comments have led many to their demise....

Hayyyyy Ben glad to see you flying it for longer time. Will write you more soon. Wow