VTOL Research, Development and Product ~ by Wikinomics

[Dave_Jackson]

The domain of VTOL, specifically that of rotorcraft, has seen limited advancements since the original ones. There are many reasons for this. However, today there are more limitations then there were in the past; additional limitations such as a shortage of ideas and the very high costs of taking the promising ideas on forward into operational products.

The current industry appears to consist of a few well financed companies, which are perhaps putting their financial statements ahead of their product development, plus a number of very small ventures, which lack financing and technical depth.

There may be a new and alternative method. A method that can be participated in by geographically dispersed personnel. A method that can bring together many people from different disciplines, having the common interest of technological pursuit, plus the possibilities of creative satisfaction and financial rewards. :8


The Means: (http://en.wikipedia.org/wiki/Wikinomics)


A book on the subject. (http://www.amazon.com/Wikinomics-Mass-Collaboration-Changes-Everything/dp/1591841380/sr=1-1/qid=1167769102/ref=pd_bbs_sr_1/103-4266018-7542269?ie=UTF8&s=books)

. .

Thoughts?

[slowrotor]

Dave,
Did you read the book?

see this post from Cran, I think its post #18 on this thread http://www.pprune.org/forums/showthread.php?p=1845450&highlight=lets+build+a+helicopter#post1845450

[IFMU]

"The work of the individual still remains the spark that moves mankind ahead, even more than teamwork."

[Dave_Jackson]

slowrotor;

A 5-part newspaper article entitled [Mass collaboration unleashes 'Us' power] said that the book was due out today. I have ordered it.

CRAN's post is a good one. However, I have tried to initiate the same concept in the past, with no luck. It appears that inventors are a proud people with their own ideas and a fear of divulging them. This is unfortunate since a large percentage of ideas are flawed and a polite critique by others allow the individual to adjust his idea or move on to a new one.

A few random thoughts on a proposed methodology;

Projects: The system would not be limited to one project. It would be inclusive of all; from overall concepts to new unique components. It might be a structured forum and repository of technically VTOL related disciplines. Perhaps with a high level of privacy, some engineers at existing helicopter companies might enjoy contributing to the development of novel ideas, which they are unable to pursue at their companies.
Patents: (I think; re US patents) The public disclosure of a new idea stops others from patenting it. However, a patent application must be applied for within a year of the public disclosure. Then a low-cost Patent Application can be obtained. Then there is a year before the start of the conversion to a full patent must be started. The person is therefore protected for a number of years while the 'group' collectively improves the idea or give cause as to its fatal shortcomings.
Renumeration: All viable products might be patented in the name of the 'group' with the members of the group voting on the division ratio of any renumeration received from that product or invention.IFMU;

By 8:45 AM today (Jan 2, 2007) the top 100 CEO's had earned more money than the average worker will earn during the total year.

Perhaps the the Internet is changing the world from yesterday's technological capitalism, and today's fiscal capitalism, to tomorrow's collective capitalism. :ooh:

Dave

[IFMU]

It appears that inventors are a proud people with their own ideas and a fear of divulging them.
Dave
Dave,
Of course, there may be other explanations of equal validity. If you are going to invite the whole world to feast at your table of helicopter design, are the people who are actually capable of designing, building, and flying a helicopter going to want to rub elbows with the guys who want to carve rotor blades out of 2x4's from Home Depot and power it with an Evinrude outboard? Or would they consider that a needless distraction?

The current industry appears to consist of a few well financed companies, which are perhaps putting their financial statements ahead of their product development, plus a number of very small ventures, which lack financing and technical depth.
Have you ever heard the term 90% finished, 90% to go? It is commonly used in the homebuilding scene, meaning that once the project looks like an aircraft you still have a long way to go to all the way finished. If you consider today's helicopters, I would call them 90% evolved. That last 10%, which would yield the ultimate performance and safety that a helicopter could ever achieve, is a bigger job than what it took to get to where we are today. That 10% is a combination of structural, aerodynamic, powerplant, and weird science (like morphing blades and IBC) which is not quite in the realm of practical yet. Nor may it ever be. We push toward the 91% solution with fault tolerant designs, better crashworthiness, better rotor blades, engines with better SFCs, but it is a long way before we even start working on 92%. But, as these technologies mature to the point where it isn't a pipe dream to implement them, you can bet the big dog companies will jump on the bandwagon. After all, each one of those top 100 CEOs wants to beat the average worker by 8:40 next year, and sooner the year after.

-- IFMU

[Graviman]

Dave,

Happy new year. :ok:

While the concept intrigues me, in the real world my time is precious and i imagine most folk fall into the same category. I am about to take a up a project at "the other end of the transportation spectrum", where we are already working with globally distributed engineering design teams. That and still having two more courses to complete my physics degree means that flying already sits uncomfortably on the back burner :{

The real question has to be how serious are you? You have come up with many proposals, since first introducing me to PPrune (thanks for that BTW). I realise you are serious about manufacturing composite blades, but a whole light heli requires a new level of dedication to detail. There is something to be said for having a definate timeline and budget, although i realise the idea is to avoid this. For a start there is a commitment to finding the best idea, then sticking with it until it performs. My real concern is that this would just become an exercise is documenting ideas, but nothing would ever actually fly.

Mart

[slowrotor]

Dave,
I think a group effort is unlikely. I might participate in a group effort but I would be working on my own design as well.

I think we should each work alone, as each project is so different, but get help from the group as needed.
So forming a voluntary design assistance group would be good.

Taking on the challenge of designing and building a rotorcraft is giving me some distress (heartburn). But I feel I have no other choice, nothing else would be as interesting. So my plan now is to break the process into small chewable parts.

got to run now to Home Depot for a 2x4

[Dave_Jackson]

Mart;

I don't think that Wikinomics is globally distributed engineering design teams.

slowrotor;

Based on my limited knowledge, your last post appears to represent the primary feature of Wikinomics. Wikinomics is a collection of people in a common domain who are working on their own projects.

Example are;
~ The thousands of people contributing to the Linux operating system while working on individual projects.
~ IBM employees, clients, business partners and even family members, from 160 countries participating in a wide-open brainstorming session called the InnovationJam.
~ Google employees are required to dedicate 20 percent of their time to personal projects.

Wikinomics appears to be a potential alternative to the improbable 'group effort on a common project'.

Dave

[Graviman]

Mart;
I don't think that Wikinomics is globally distributed engineering design teams...
...Wikinomics appears to be a potential alternative to the improbable 'group effort on a common project'.
Dave

Dave, you got me confused. So the purpose of the Wikinomics exercise is just to share wisdom? Rotorheads already serves exceptionally well as a means of exchanging ideas and discussing designs. The engineering group effort is a means to produce (hopefully) a competetive product in the marketplace. As long as Heliport has no objections, i don't see why you can't go into more technical details on Rotorheads. In fact i suspect going into the nuts and bolts more may be welcome, unless you mean Rotorheads is too open for commercially sensitive material. :confused:

Mart

[Dave_Jackson]

Mart,

Rotorheads is "A haven for professional helicopter pilots to discuss the things that affect them." therefore an excessive amount of technical stuff clogging the bandwidth may not be appreciated. This was the case on Rotary Wing Forum a while back.

I speculate that Wikinomics is more than a forum. The book should clarify things, when it arrives.

Dave

[IFMU]

~ The thousands of people contributing to the Linux operating system while working on individual projects.

Dave
Dave,

How many millions of crashes did they/do they have between stable linux releases? A crash on a PC is not so bad as a crash in a helo. That's a major difference.

-- IFMU

[IFMU]

got to run now to Home Depot for a 2x4
I may be laughing at my own joke, but this really got me going. I hate it when I can't stop laughing at work and people think I'm nuts! Just make sure there aren't too many knots in it, and put them out at the tip! :)
-- IFMU

[Graviman]

IFMU, i used to know a guy in Oxfordshire who was one of the few in the UK qualified to repair wooden gliders. Since he also did composites and aluminium, interesting guy to talk to. I gather that spruce is only considered aero grade from so far above the ground to so far below the first branch!
How the Mosquito was manufactured is anyones guess, considering how many were made. I imagine that they graded wood for suitability in different parts of the airframe - clever chap DeHavilland. :uhoh:

Mart

[slowrotor]

IFMU,
The late B.J. Schramm who founded Rotorway used an Evinrude outboard in his early sport heli designs.

But I see your point about crank inventors. A crank is someone who refuses to review the known data before proceeding. I think I am not a crank but sometimes that's not always clear.

[Dave_Jackson]

If Wikinomics is not the answer then how about the apparently simpler;

Google ~ Docs & Spreadsheets (https://www.google.com/accounts/ServiceLogin?service=writely&passive=true&continue=http%3A%2F%2Fdocs.google.com%2F%3Fhl%3Den_GB&hl=en_GB&ltmpl=homepage&nui=1&utm_source=en_GB-more&utm_medium=more&tm_campaign=en_GB)


Dave

_____________________________


Quick and dirty presentation of an idea for a project for a single device for Improving the Teetering Rotor by;

 Improved Flight-Control;
~ By providing a constant control moment from a 2-bladed teetering rotor when the control-plane is moved out-of-plane from the mast-plane.

 Greater Rotor Inertia;
~ For entry into autorotation and for landing flare, without increasing the centrifugal force on the blades.

 Stability Augmentation System;
~ Somewhat similar to the Bell, Hiller and Lockheed units.

 Gyrocopter Jump-Takeoff;
~ Improved gyrocopter jump-takeoffs; due to the additional rotational inertia that can be developed before takeoff.


Proposed Means:

 Improved Flight-Control:
~ A simple teetering rotor will generate a constant lateral force at the top of the mast when the disk is tipped. However, it cannot create a moment at the top of the mast, which is added to this force.

~ The rotor is modified to include a http://www.unicopter.com/B329.html#Hub_Spring hub spring or http://www.unicopter.com/B329.html#Teetering_Rotor_with_Offset 2-blade teetering rotor w/ offset.

~ The inclusion of one of the above two devices will generate 2/rev moments at the top of the mast when the disk is tipped.

~ A 'gyro-assemblage' is located inline with the rotorhead and it also applies 2/rev moments, which are offset 90º to the rotor's moments.

~ Half of this rotor-generated 2/rev moment will be applied to the mast, for greater control every 180º of rotation.

~ The other half of this 2/rev moment is applied to the gyro-assemblage, to reorient its position.

~ The gyro-assemblage re-orientates at twice the rate that the rotor turns.

~ The end result is that the gyro-assemblage also generates a 2/rev moment at the top of the mast, however, its moments are 90º out of phase with the rotor-disk generated moment.

~ The objective being a constant moment at the top of the mast that is combined with the constant teetering force.

 Stability Augmentation System:
~ Utilizes the gyro-assemblage.

 Greater Rotor Inertia:
~ The gyro-assemblage has;
~ Low mass, high rotational speed.
~ Is rotated by speed-up from the mast or by electric motor(s)

 Gyrocopter Jump-Takeoff:
~ Conventional gyrocopter control system must be changed to swashplate or spider type.
~ Rotating gyro-assemblage will generate very little rotational drag. This eliminates the tendency to rotate the craft on the ground, as does the application of the energy to the rotor.

:8

[slowrotor]

All the RC model helos seem to have moved away from the two-blade teetering in the early days, the current designs are using two-blade without the teetering hinge.
This hingeless(rigid hub) design that models use is virtually the same as your proposed teetering hub with a hub spring, I think.

I have not found any reason why a two-blade rigid hub with flexable blades would not work on a full size(ultralight).

The rigid head has gyro stability in the main rotor.
The rigid head has control moment at the mast.
The rigid head has less parts.
The rigid head has no problems with zero G.

What is wrong with a rigid two-blade rotor?

[Dave_Jackson]

slowrotor,

Operation of Teetering Rotor: A movement of the cyclic stick off of its central position will result in the teetering rotor disk tipping in the direction of the cyclic stick. This causes a constant force at the top of the mast, which pulls the fuselage in the same direction.
Rigid Rotor: Making the 2-bladed rotor rigid will result in a 2/P moment at the top of the mast, The rotor will only apply its full moment when the blades are pointing in the direction of tipping and it applies no moment when the blades are normal to the direction of tipping.
One objective of this idea: To develop a means of eliminate this 2/rev vibration.Dave

[slowrotor]

Dave,
The 2/rev vibration only happens during a roll maneuver, I think.

[Dave_Jackson]

slowrotor,

IMHO, there should not be any significant difference between a roll maneuver and a pitch maneuver. The fuselage moment and the HS will offer a greater resistance to pitch than to roll and this might result in the 2/rev pulse during pitch being a little less noticeable.

I have not found any reason why a two-blade rigid hub with flexible blades would not work on a full size(ultralight).

The hub spring will act similar to a rigid hub with flexible blades. This page give information related to the hub spring and attempts by others, such as Bell, to overcome the 2/rev vibration. http://www.unicopter.com/1230.html

Dave

[Heliport]

Dave Jackson Rotorheads is "A haven for professional helicopter pilots to discuss the things that affect them." therefore an excessive amount of technical stuff clogging the bandwidth may not be appreciated.
:confused:


I don't see any problem.


Heliport

[Graviman]

Slowrotor,

2P will happen everytime the cyclic is moved off-centre. Models get away with it because they carry no useful payload (and bending moments don't scale linearly) - so structure can withstand the vibration. The batteries don't scale up too well either. ;)


Dave,

Interesting concept. My first thought would be why even allow hub compliance, if the gyro is there to remove 2P vibration. The only advantage i can think of is the convenient hangerage of a 2-blader. Probably once the gyro mass was taken into account, an additional blade or two works out lighter. Then again the hub compliance does allow a smaller gyro, at the expense of some zero-zero control loss (bladestrike? :uhoh: ).

Agree about designing in a system for dynamic stab aug though. A gyro could force helo to follow cyclic, giving linear displacement roll/pitch rate. The gyro could thus be embedded within the airframe (this is effectively how electromechanical SAS works).

Mart

[slowrotor]

Dave,
The 2/rev vibration may occur with pitch change also as you suggest. But should we care. If the pitch change or roll is done slowly, the vibration would be minimal.
The advantage of restricting the flapping with a rigid head would be worth the effort in spite of the additional issues. For a coaxial or intermesh the rigid head would be best I think, to avoid blade contact.
My point is:
The models work very well with rigid hubs. I dont see any vibration. The vibration would be hard to see on a model, I admit, but I certainly see other types of vibrations in my model. A model cannot be compared with a full size in some respects of course, but the models show the way for simpler design.

[Dave_Jackson]

Heliport,

Thanks.
It's looking like the 'bandwidth' usage ain't going to be too large. ;)


Slowrotor,

I think that two, or more, recreational coaxial helicopters have rigid (no teetering or flapping) hubs with 2 blades each, as you suggest. However, I really question this approach. In addition, one of these coaxials has no ability to autorotate.

The following is a quick 'cut and past' from a UniCopter web page;
__________________________
Hiller Rigid Rotors: Hiller X-2-235 (http://avia.russian.ee/vertigo/hiller_x-2-235-r.html), Hiller XH-44 (http://avia.russian.ee/vertigo/hiller_xh-44-r.html)

"... the extremely rigid rotor of the Hiller lead to "Vibration problems curtailed these tests for fear of damaging the wind tunnel" When you worry about the aircraft wiping out the tunnel, you have problems! ~ Nick Lappos on RAR

Dual rotors with two blades each will result in a lateral vibration when longitudinal cyclic is applied. See: DESIGN: SynchroLite ~ Rotor - Disk - Lift Distribution re: Vibration (http://www.unicopter.com/1142.html) ~ DBJ
___________________

This submitted idea may not work and it is not intended for any of my projects. It just seems like an idea where one device might satisfy 3 or 4 requirements and be fun for a number of people to work through.


Mart,

Would you elaborate on 'hub compliance' and on 'zero-zero control loss'. Thanks.


Dave

[slowrotor]

Dave,
The Hiller had super rigid blades. I am talking about flexible blades with a rigid hub.
The rigid hub works fine with models. We might find it would work with very small and slow helicopters.
If you know of any two blade single rotor with rigid hub, please let me know.
Thanks
slowrotor

[Graviman]

Dave,

'hub compliance' - 1/stiffness of hub spring. If spring is stiff, does it need to be there?

'zero-zero control loss' - reduced g rotor unloading and reduced foward speed tailplane surface ineffectiveness (just quicker to type).

Perhaps not relevent to this thread, i have been reconsidering reason for Lockheed blade forward sweep. Since flapback is natural to any rotorhead, the forward sweep was really there to compensate the tendancy for a hingeless to roll left (US rotation) in forward flight.


Slowrotor,

Hiller X-2-235 blades were super rigid for their day, but in the absence of data outside of that PR shot i would conservatively estimate offset to 15%. If pushed i might be convinced of 30%, but you really have to be careful how much engineering data you read into a PR photo...

Mart

[Dave_Jackson]

Mart,

Thanks for clarifications.

If spring is stiff, does it need to be there?The intention is that the physical movement of a teetering rotorhub with a hub spring (http://www.unicopter.com/1535.html), or the shifting of the tie bar on a teetering hub with offset hinges (http://www.unicopter.com/1127.html) provide the force to 'reset' the orientation of the gyro-assemblage; twice per rotor revolution.


Dave

[Graviman]

Dave, OK so a 21st century Hiller paddle system (with CVJ hub). In this forum i learned that the Hiller system is flawed, because the delay of a teetering rotor means pilot has to think a second or so ahead - pilot is flying the rotor rather than the machine which swings underneath.

An alternative objective might be to give the zero-zero control authority of hingeless rotors to a 2 bladed design. You could achieve this by having a gyro cyclically moved to minimise hub moment vibration (ie moving in opposition to blade cyclic 90' out of phase to blades). So the gyro could simply be put inside the fuselage as a motor driven vibration adsorbing/cancelling device.

IMHO the whole setup is too complex unless the benefit is improved pilot machine interface. Lockheed got closest to ideal for a mechanical only solution, using a hingeless rotor. The achilles heel was the blade flap feedback via the pitchlink, needed to stop roll towards retreating side (blades were forward swept). This pitch feedback does not suit modern aerofoils, while its removal would result in some control asymmetry. Maybe a small amount of hub compliance would allow flapback to trim gyro directly (without risk of control divergence).

I can see why SAS systems have developed the way they have...

Mart

[forget]

The public disclosure of a new idea stops others from patenting it. However, a patent application must be applied for within a year of the public disclosure.

Dave, I'd say you are wrong here. Only the first part is correct. The public disclosure of a new idea stops others from patenting it.

Second part - once an idea is publically disclosed but without an issued Patent or application, you've no chance of stopping anyone, worldwide, from using the idea.

[Dave_Jackson]

forget,

The primary objective is to stop the ideas from being patented. This way all can freely use these basic ideas. However, an individual still has the ability to patent related or subordinate ideas, which he/she develops.


The second part of your posting could be a concern for 'open group inventions'.

The following is from a patent lawyer. "In Canada and the United States, you may still apply for a patent if such public use, sale, disclosure, etc. occurred no more than a year ago, and if a patent application can be prepared and filed within a year of the first such public use, disclosure, sale, etc."

The fact that he uses the word 'etc.' may make his statement questionable. :)

Any additional information that you can offer on this subject will be appreciated.

Thanks,
Dave
____________

Mart,

Will get back to your posting.

D

[Dave_Jackson]

OK forget the gyro ~ for a moment.
Another idea added to the stack.

The following regards a 2-blade coaxial configuration that incorporates any means and amount of 'rotor rigidity' (IE. not a simple teetering rotor).

For a given amount of cyclic input, it appears that the amplitude of the vibration will differ when the direction of the cyclic input is the same as one of the blade crossing azimuths from when the direction of the cyclic input is midway between two of the blade crossing azimuths.

It therefore appears that the vibration may be lessened if the blade-crossing azimuths can be actively varied so that they always have a constant relationship with the ever-changing cyclical input azimuth.

This coaxial transmission should be able to change the crossing azimuths. (http://www.unicopter.com/0954.html)

Just a wild idea.

Dave

[forget]

Any additional information that you can offer on this subject will be appreciated.

I'm right - and I'm wrong, depending on which side of the Atlantic you're sitting. The US has unilaterally gone sideways on this, despite Patents being very much an International thing.

From US Patent Office web

http://www.uspto.gov/web/offices/pac/provapp.htm

Provisional Application for Patent Filing Date Requirements

The provisional application must be made in the name(s) of all of the inventor(s). It can be filed up to 12 months following the date of first sale, offer for sale, public use, or publication of the invention. (These pre-filing disclosures, although protected in the United States, may preclude patenting in foreign countries.)

Such as the rest of the world. :hmm:

[slowrotor]

Dave,
The Yamaha RMAX helo has two-blade hingeless hub.
see page 6 at this site: http://controls.ae.gatech.edu/papers/schrage_erf_99.pdf

I don't think the hiller paddle control would be needed with a manned helo.
The Mosquito ultralight apparently does not need a hiller system.
slowrotor

[Graviman]

OK forget the gyro ~ for a moment.


Still worth considering, Dave. Flapback provides static stability, but a gyro is perfect for dynamic (ie transient input) stability.

One concept i have often wondered about is designing a 4-blade hingeless rotor with hiller bars. Basically two 2-blade designs at 90 degrees. Again complexity of this concept tells me that Lockheed got it right with final system (perfected after cancellation :rolleyes: ).


It therefore appears that the vibration may be lessened if the blade-crossing azimuths can be actively varied so that they always have a constant relationship with the ever-changing cyclical input azimuth.


My concern here is that you are introducing complexity for an otherwise simple to solve problem (extra blades). Ignoring the control complexity problems, the real headache is that every time you move the cyclic around the box you will perform an unrequested turn! The solution would simply be to provide additional drive to a smaller yaw control rotor, fitted aft of the main rotor. ;)

Vibration is best cured from source, which to my mind means designing a main rotor assy which does not respond to frequencies to which it might be exposed. Continuously trimmable RPM rotors are feasible, but may increase the problem of rotor resonances (active or internal damping clearly helps - more complexity). Combine this with possible problems associated with high speed and it looks more daunting.

Mart

[Dave_Jackson]

forget,

Thanks for the information related to foreign patentability.
_______________________

slowrotor,

IMIgnorantO, the RMAX may have good stability. However, like the Mosquito it may not have good controllability.

IMO, the stiffer the RMAX blades are, the greater the 2/rev vibration is. Perhaps in models the rotor speed is so fast that the high frequency is not considered detrimental.
_______________________

Mart,

I'm not giving up on the gyro, it's just that the mind got temporarily side tracked.

Your last two paragraphs are very valid.
_______________________

The thinking behind a small light gyro with an exceptionally fast RPM, is that it might be justifiable if it (a single item) can satisfy more than one or two rotorcraft shortcomings.
Hopefully, stability and controllability are two of them.
http://www.unicopter.com/Think.gif


Dave

[Graviman]

IMO, the stiffer the RMAX blades are, the greater the 2/rev vibration is. Perhaps in models the rotor speed is so fast that the high frequency is not considered detrimental.


The model can be strengthened against the resonance and fatigue failure which would occur if it had to carry a useful payload. Besides the pilot has no direct feedback of the vibration.


The thinking behind a small light gyro with an exceptionally fast RPM, is that it might be justifiable if it (a single item) can satisfy more than one or two rotorcraft shortcomings.
Hopefully, stability and controllability are two of them.


Agreed. With a rigid rotor the gyro can force a pitch/roll velocity response from the cyclic. With feedback of flapback you can maintain the speed/sideslip displacement response too. Sounds flyable to me.

----

At times i feel helidynamics is like quicksand - you think it all makes sense then explaining it to someone causes you to reconsider. Thinking about whether the response of a teetering is acceleration response to cyclic, until fuselage drag and flapback make it velocity (maybe) then displacement response, has made me reconsider Robinson "wee-wa". If the rotor was changing attitude, i can see how the relative upflow in one half and downflow in the other would cause an azimuthal reduction in lead angle from 90 degrees.

I think this goes under the theory vs experience folder...

Mart

[Dave_Jackson]

This is my thinking on the subject; :8 subject to objections or improvements by others. :ouch:


Objective:

To create a constant moment at the top of the mast when the cyclic stick of a 2-bladed rotor is moved off of center.


Physical Layout:

The rotor is a teetering rotor with a hub spring.

The gyro-assemblage consists of two counter-rotating gyros. Their rotational inertia is obtained from high rotational speeds and not from large masses. The two gyros are independently gimbaled on the mast, just below the rotor-hub. The two gyros are linked together so that they tip in unison. Their rotation is provided by electric motors. Perhaps the mass of the gyro is the rotor of its axial flux motor.

Description of Operation:

When the rotor disk is tilted down, the aerodynamic force that applies this tilting is partially resisted when the blades are in the rotor disk's two quadrants of tilt. Half of this resistance comes from the hub spring and therefore a moment is created at the top of the mast. The other half of this resistance comes from the act of tilting the gyro-assemblage in the same direction.

When the blades have rotated 90-deg and are in the two other quadrants, a cam-follower device at the bottom of the rotor-hub applies a force to the gyro-assemblage. This force reorients the gyro-assemblage to its normal position. The opposing force of this reorientation on the cam followers applies a moment at the top of the mast.

Theoretically, The moment on the hub spring from the teetered blades and the moment from the normalizing of the gyro-assemblage create an equal and constant moment at the top of the mast.

[Graviman]

Dave, gyros will need to be actuated out of phase or forces cancel. Otherwise the principle is sound. My question remains why would you want to add this additional complexity to the design of a helo? Additional blades are mechanically much simpler, at the cost of increased hanger space.

The reason i ask is that helos are driven by cost, which reflects on us mortals as $/hour. Introducing additional mechanical componentry increases both the initial outlay and the maintenance cost (inspections even if parts have infinite life). I'm not against the use of gyros, far from it since i believe that significant handling improvements are possible, but preference is to use them sparingly and for good reason.

The only real reason i champion the unpopular view of a mechanical SAS over electromechanical systems like the Honeywell SPZ 7600 is that for a light heli a mechanical system will be less likely to be overlooked. Combine this with the fact that failure is likely to be a progressive reduction in performance by wear and it strikes me as a good engineering soln. It does not allow all the advanced features that a full FBW system would, and naturally i accept that FBW will be the long term winner.

Mart

[slowrotor]

Dave,
I agree with Mart about keeping design simple. Two blades is simple, partly the reason for the large sales of Robinson compared with Enstrom and S-300 with the complication and cost of three blades.

Mart,
The Yamaha RMAX is more than a model( at 128lbs). It has also carried a videocam, no reports of vibration on the camera. More than 1200 have been sold mostly for crop dusting by non-pilot farmers in Japan. It has automatic hover. Pretty impressive.

[Dave_Jackson]

Yes, the 2-blade w/ gyro will have pros and cons and 3-blade rotors have their own pros and cons. God knows which could be the best. Its just that the desire to remove the 2P vibration from a 2-blade rotor, which has some amount of rigidity, has bugged me for years.

Mart,gyros will need to be actuated out of phase or forces cancel.Correct me if this is wrong but I think that having 2 gyros counter-rotating about the same axis, but having their own independent gimbals should work.

The rotating members would be linked by 3 tie-rods, with spherical bearings at both ends of each rod. This way the two gyro disks always tip in the same direction, by the same amount.

Because they are counter-rotating, the opposing gyroscopic moments should be canceling each other in the tie-rods and not in their common axle (mast).

Hopefully, this will will result in a gyro-assemblage with only a resistance to a tipping of it's plane. It is this resistance that provides the foundation of the moment when the two blades are not providing it.

If you find that this is flawed, please say so.


Dave

[slowrotor]

Dave and Mart,
I just tested my two blade hingeless model and found there is a vibration with cyclic input. It seems to be about the same magnitude as the other normal vibrations.
So Dave, I hope your invention works.

[Graviman]

Slow, Yamaha RMAX sounds pretty good. I must admit to getting myself a Sabre RC helo with a similar control system (although RPM controlled collective and TR - so no autos). I just wanted to find a way to keep something airborn while i study Quantum Phys (yes seriously). The blades are hingeless, but very far from rigid - fortunately RC blade strike is not serious (relief nut on root).


Dave, the fact that the gyro moments cancel undoes the gyro torque reaction - unless i have missed something. Are the rods changing length to actuate the required moment?

In truth you could just use one gyro for the effect you are after. The gyro mounting would need to have forces in opposition to the blade, but free to gimbol in what would otherwise be the teetering axis (ie 90 degrees out). It still strikes me as overly complex given that the general view is that many weaker tip vortices are better than a few strong ones. Even Prouty was suprisingly vague on the subject of blade number, so i suspect cost and rotor dynamics are a bigger factor.

Mart

[Dave_Jackson]

Mart,

Yes, you are no doubt correct. The two counter-rotating gyros will probably act the same as if they have no gimbals and are on a common axle.

The problem ~ Assume that the pilot causes the rotor disk to tip down at 180-deg azimuth. Can you come up with a simple linkage arraignment where; 1/ when the two blades are between 45 - 135-deg and 225 - 315-deg, the gyro applies a downward moment to the mast at 180-deg and, 2/ when the two blades are between 135 - 225-deg and 315 - 45-deg, the aerodynamic teetering force of the blades applies a moment to the mast at 180-deg plus restoring the gyro to its 'home' position?

There must be a mechanical way.

Dave

__________________________________


The following could be a potential application for this idea.

The sketch comes from Intermeshing - Dragonfly - Principal Assembly (http://www.unicopter.com/0986.html), which has 3-blade teetering rotors. The objective would be to replace the complexity of 3-blade rotors with 2-blade rotors and a gyro.

http://www.unicopter.com/GyroMoments.gif

The gyro could be drive at 5,250 RPM from a pinion identical to the pinion on the input shaft, Alternatively, it could be drive by a small seperate crown and pinion with a 6:1 ratio, which would turn the gyro at over 15,000 rpm.
The moment of the gyro is in the same vicinity as those of the two rotor hubs.
I think that the two rotorhubs will create a more complex vibration then a single rotorhub but its amplitude might be smaller.Just ideas.

[Graviman]

Dave, in some respects a counterrotating application would simplify the design. The gyro in your picture would not need it's gimbal to rotate with either rotor. The gimble would simply tip as the rotors passed each other with the tip axis at 90 degrees to the rotor crossing line. As long as the gimbal was rigidly linked to the rotor system, to avoid unwanted movement, then the tipping action would not require any significant forces. It would tip one way then at 90 degrees the other way etc - direction would depend on gyro direction.

Could i concieve of a swash/cam mechanism to do this? Probably, but i just find the whole system unecessarily complex. Vibrations are just best cured at source, and since counterotating rotors will not cross above the fuselage this set up doesn't even offer improved hanger usage. Considering that it takes 17mins (i think that was the figure, including 12 bolts for bifilar removal) to fold up the S-92 head for transport, then multiple stowable blades make more sense to me.

IMHO gyros really are better off being used to improve dynamic stability, by forcing roll/pitch velocity control. I admit to understanding where you are coming from with your interleaver design, since this also has natural roll velocity control (horizontal stabiliser and flapback would help pitch to be velocity control). It's just that a combination of more complicated drivetrain and a wider machine would push up outlay and running costs, when a gyro would be just as effective. It also doesn't really help with the retreating blade stall adversely affecting downwash distribution either, but avoids lift imbalance.

Like i say, i suspect we will seldom agree but it does force me to think about rotorcraft design from all perspectives...

Mart

[Dave_Jackson]

Mart ,

It is looking difficult and it's not only the linkage. The rotor and the gyro actions are out of phase with each other. It just seems that the use of a gyro to eliminate 2-blade vibration might not have been considered before, particularly in respect to twin main rotors.

The interest would be to see if; 1/ it can be done, 2/ the complexity can be reduced, and 3/ it is viable from a practical perspective.

OK Its back on the shelf; for now.
So is Wikinomics. :)

Dave