A challenge ~ for those who are not technically challenged.

[Dave_Jackson]

In January a link to this web page was posted. Hughey Electricopter Corporation (http://www.hecopter.com)

This week the following e-mail was received;"Dave,
I’m flattered that you actually put a message with a link to our “placeholder” web page on a rotary forum.

Frankly, we’re still in stealth mode, but “the cat will be out of the bag” so-to-speak when our first U.S. Patent Application is published by the USPTO in November.

As the name would suggest, the full-size (part 103) flying proof-of-concept prototype is all electric, fly-by-wire, and nothing like anyone has ever seen before.

We won’t be ready for a public demonstration until next spring, as we’re still doing IGE control trimming and the Chicago weather is not kind in the winter.

Since multiple rotors is your thing, I think you’ll want to kick yourself when you see it. :) The miracle is how cheaply we can crank these out (although the production prototype is a year away).

Let the revolution begin!

Regards,

Brad Hughey
Founder & CEO
Hughey Electricopter Corporation"

An all electric craft for $10,000 dollars sounds intriguing.

Based on the limited information, any speculation as to what its features are?

There is (currently) no reward for a winner, :{

Dave


[It is assumed that Mr. Brad Hughey will not find fault with this little bit of advance-promotion.]

[sprocket]

I see they are saying "Investor kits are available".

Dave, why dont you give them some money and see what they send you. :E ;)

[TukTuk BoomBoom]

Im not sure the design is revolutionary, my son has a car that runs on a similar principal.
You grab it by the roof, pull it back on the carpet and let it go....

[OldRookie]

Im not sure the design is revolutionary, my son has a car that runs on a similar principal.
You grab it by the roof, pull it back on the carpet and let it go....

I thought i was cynical, at least have a look first !!!! lol

[Graviman]

Not sure it's such a good thing to be pushing this design into the open yet, Dave, although it's one i'll keep my eyes on. The guys at Hughey are saying next spring for the demo so i would leave it until then. This means that if they have 11th hour bugs to get sorted they haven't got an expectant public clamouring to see, or shareholders banging on the table. Too many projects in engineering fail because they went public before they were absolutely ready, and i'd like to see a success here. :ok:

A general discussion about how such a design might be accomplished is fine though. My take would be that an electric rotorcraft endurance would be at best minutes, so more a weekend hobby thing than application driven. Best powertrain would be a motor running at high RPM with the reduction box driving coaxial rotors. Powerpack would best be NiMH with inbuilt charger/conditioner allowing direct plug in to the mains.

I'm still not convinced that for a given torque output a direct drive pancake motor weights less than a high RPM motor through several epicyclic stages, since even with negligable flux circuit iron you still need a finite amount of copper to pass enough total current in the 1 Tesla B-field that NdFeB magnets generate (2 max if flux concentrated). I don't have time to websurf (revising), but there are plenty of formulas/methods to estimate gearbox size hence mass - epicyclics are the lightest.

Lest Nick show us up again with another napkin calc! ;)

Mart

[Dave_Jackson]

sprocket,why dont you give them some money and see what they send you.
Probably a thank you note.


Graviman,Not sure it's such a good thing to be pushing this design into the open yet,True. However, Mr. Hughey has said next to nothing about his design; other than mentioning a few parameters such as; empty weight under 254 lbs., vertical takeoff and landing capability, all electric power and controls, and under $10,000.00.
A general discussion about how such a design might be accomplished is fine though.True. A discussion could be fun and perhaps rewarding.

Here's my suggestion for the PPRuNemobile;

It's called a PPRuNemobile because the craft will have the same effect as prunes. Partake of either and one will **** their pants. However, I digress.

Take this full set of plans for a Hornet gyrocopter (http://www.ultraligero.net/Sitios/Planos/Hornet/Planos_old.pdf#search=%22Gyrobee%20specifications%22) and disregard the engine, propeller, transmission, fuel tank and most of the control components.

Acquire two Predator motors, their controllers, (http://www.icare-rc.com/document/predator.htm)and a pair of propellers

Install one motor and propeller in each blade, at approximately 1/3 of the blade's span.

Oh, and weld the conventional gyrocopter longitudinal and lateral rotor pivots so that they no longer tilt.

So far the craft is similar to a conventional Ultralight gyrocopter, except that is does not have any controls.


Now for the neat stuff;

Collective control: The pilot's controller has a single throttle, which determines the rotational speed of both the motors and their propellers. As each motor-propeller assemble rotates about the craft's mass, the gyroscopic precession of this assembly wants to pitch it and blade up. In other word, the faster the motors rotate, the faster the rotor will rotate and also the greater the blade pitch will be due to the blade twist that is imparted to it.

Now for neater stuff.

On the retreating side, during forward flight, the propeller does not have to produce as much torque. Its rotational speed therefore increases and this greater rotational inertia results in the retreating blade having a higher pitch than the advancing blade.

Now for neatest stuff.

Cyclic control: To increase the pitch of a blade when it is at a specific azimuth while decreasing the pitch of the opposite blade, simply involves a temporary increase in the rotational speed and inertial of one motor while the other motor experiances a decrease. This is done by temporarily (cyclically) adding a electrical 'spike' to one motor while causing the other to become a generator and thereby slow down.

All in serious fun.

Dave :8

[Graviman]

Well in theory yes. I suspect that in practice getting the pitch return spring to balance each blade tip prop precession in all flight conditions would not be easy, you could use the aerofoil section. With the time lag to accel and deccel the prop it doesn't sound like the most effective control mechanism either. Besides the idea of putting a gyroscopic control system on the end of a flexible blade with aeroflexure makes me very uneasy. Even if you get the blade to behave itself, any departure could be catastrophic.

Remember the Lockheed Electra which crashed due to prop bearing wear allowing precession to match a wing eigenmode? I would keep the original control mech.

The YAK55 model prop looks about ~0.5 meter diam, so with 2 you have ~0.7 m. This is getting on for a microcopter tail rotor diam so efficiency is not so bad. Using the original low disk loading rotor helps, and the prop will help reduce tip vortex strength.

Assuming you can hover at 20kW, and using the Duracell figure of 144Wh/kg (partly since Wikipedia figure of 60Wh/kg for NiMH seems low, and partly because i am too lazy to get proper NiMH figures :} ). This is 8.64 kW-min/kg, so you need 2.3kg of battery for every minute of flight. A 10 minute joyride is already up to 23kg of battery (55 kg if you believe wiki).

Get it wrong and the pilot will not enjoy the experience... :ouch:

Mart

[Dave_Jackson]

Graviman,

The simple [electric&gyroscopic] idea could be kept for the collective control and a conventional gyrocopter cyclic control could be used in lieu of the proposed electric cyclic control. This will make the craft simpler and safer. Web page. (http://www.unicopter.com/1536.html)

However, it deviates from Brad Hughey's " fly-by-wire", and the fun is the challenge to try and guess what his concept might be.


Dave

[Graviman]

This indicates our different approaches to such a problem, Dave! ;)

Since i expect to get shouted at if the design doesn't work, i will go for the simplest solution to the problem. Since your interest is in the technological concept, you will go for a complicated solution which captures a particular mechanism. :8

From Hughey's email i just assumed it was a 4 rotor design, with seperate FBW control motors driving though integral epicyclic gearboxes! I imagine the blades are self aligning to optimum AOA, likely on teetering hubs.

Using the precessing props to control collective pitch won't produce cyclic blade departure. But... don't forget that one design condition has to be failed motors (most likely from flat batteries). You have to allow the pilot to flare from an auto, and no motors means no control (even worse if it was cyclic too). Actually this would also be a failing of the above system too, unless there is a "flare reserve". :\

It's about this point in the project that i expect the shouting to start... :cool:

Mart

[Dave_Jackson]

Mart,

You may very well be describing what Mr. Hughey is developing. Perhaps varying the power of four independent rotors is his intended means of handling all flight control.


But... don't forget that one design condition has to be failed motors. Why? The highly promoted AirScooter (http://www.airscooter.com/) doesn't even have the ability to Autorotate. :eek:

Meanwhile back in the land of practicality. My previous mention of conventional gyrocopter cyclical control may not work. This is because the pilot would probably be required to exert strong forces on the cyclic stick to overcome the motor&prop's gyroscopic resistance to change. So, it's back to the earlier mentioned electric cyclic control.

Reliability should not be a concern if redundancy was incorporated in everything electrical; from the batter-packs, to controllers, to the windings within the motors.


Dave

[aeromys]

Won't fly-by-wire severely limit it's range?
I'll get my coat.....

[Dave_Jackson]

aeromysI'll get my coat.....Why? Are you trying to get beyond the range of the craft? ;)

I don't think that fly-by-wire will have any detrimental effect on the range. The control circuit should be insignificant because it will only be 5 or 12 volts.

The power circuit will not be expending any power on electro-mechanical blade-pitch devices. All power will go into rotating the rotor, via the two propellers, The power to change the pitch of the blades will just be an increasing and decreasing of the mean rotational power.

If this is not a satisfactory answer to your concern, http://www.unicopter.com/Please.gif say so.
_____________________________________

Sketches add to web page (http://www.unicopter.com/1536.html) to show two alternative means of effecting blade pitch.

Dave

[Graviman]

The highly promoted AirScooter doesn't even have the ability to Autorotate.

:uhoh:

My previous mention of conventional gyrocopter cyclical control may not work. This is because the pilot would probably be required to exert strong forces on the cyclic stick to overcome the motor&prop's gyroscopic resistance to change. So, it's back to the earlier mentioned electric cyclic control.

This is where my professional displeasure of being shouted at makes me question whether the whole approach is flawed. There was an MIL which had jets on the tips, which may have had high control forces. I had thought to mention counterrotating props, but this means g/box - so why not bite the bullet and design one g/box to reduce high a RPM motor to low RRPM?

Besides high mass 1/3 along a finite section blade? You were championing rigid rotors at one point! I am not an expert aerodynamicist, but one immediate concern is the velocity gradient across the prop. The solution is too much of a leap into the unknown, unless the benefit justifies the investment.

Above a certain rotor size RRPM reduction (for tip speed) makes blade jets/props more weight effective. For a one man machine i just don't think it is worth the complexity. By trying to avoid a tail rotor, or counterrotation, you are introducing all sorts of new problems.


Mart

[Graviman]

Dave, since you seem adverse to epicylic g/boxes in your motor concepts: ;)

http://www.uts.com/ResourceCenter/TutorialsandExamples/IntegratedGearSoftware/DesignEpicyclicGearSystems_JimMarsch.pdf#search=%22epicyclic %20gearbox%20torque%20calculation%22

http://www.roymech.co.uk/Useful_Tables/Drive/Gears.html


Software:

http://www.uts.com/ResourceCenter/ProductLiterature/ProductBrochure_IntegratedGearSoftware.pdf#search=%22epicycl ic%20gearbox%20torque%20calculation%20radius%22


Useful resource maybe:

http://www.powertransmission.com/gtforums/qanda/


Far too technical for concept evaluation:

http://gltrs.grc.nasa.gov/reports/1996/TM-107201.pdf#search=%22epicyclic%20gearbox%20torque%20calculat ion%20radius%22

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900014958_1990014958.pdf#search=%22epicyclic%20gearbox%20t orque%20calculation%20radius%22


General:

http://scholar.lib.vt.edu/theses/available/etd-05102004-214649/unrestricted/Wolff_Thesis.pdf#search=%22epicyclic%20gearbox%20torque%20ca lculation%20radius%22

http://www.bga.org.uk/publish/techpub/biblio/Noise-vib-Biblio.htm


The point is that this is a well established technology. Apart from investment in time and tooling (or use standard parts), a concept using this will work - otherwise i had better start designing toasters for a living!

Mart

[Dave_Jackson]

Mart,

There is no adversity to epicylic gearboxes. They have a good power/weight ratio and are used in many helicopters. In fact, the SynchroLite (http://www.unicopter.com/SynchroLite.html) uses a pair of them in its final reductions. [Final Reduction] (http://www.unicopter.com/SecondaryReduction.html)

My proposal is just one idea. The intent of this thread was for a number of ideas to be proposed, and discussed.

From Hughey's email i just assumed it was a 4 rotor design. You may be correct. Brad Hughey has just placed his first two posts to a thread (on a different forum). He provides a link to Towards Dynamically-Favourable Quad-Rotor Aerial Robots (http://www.araa.asn.au/acra/acra2004/papers/pounds.pdf)

_____________________

Forget my idea. ~ The aerodynamic inefficiencies of a propeller mounted on a rotating blade, combined with the intrinsic inefficiency of the rotating blade probably make my idea unattractive. Its efficiency is far less than that of mounting a propeller on the non-rotating wing of an airplane.


More ideas needed. http://www.unicopter.com/Help.gif


Dave

[Graviman]

More ideas needed.

A prop tip rotor drives the blade tip prop? :}

Seriously, if the purpose of this concept is e-drive, go with conventional or coaxial. The smart part is in the g/box and powertrain. As an aiming point go for 10 mins flight per batt pack.

Mart

[slowrotor]

Back about 1975 there was model helicopter with an unusual rotor drive.
It had a vertical gas engine bolted on top of the rotor head with a large prop above. The torque from the engine turned the main rotor and the prop blast straight down added thrust also. In effect, it worked like a gearbox and clutch without the parts.
And no tail rotor Dave.

[Dave_Jackson]

A prop tip rotor drives the blade tip prop?Back about 1975 there was model helicopter with an unusual rotor drive.........

OK
The idea has been modified by moving the propellers further outboard, reducing their diameter, and increasing their pitch.
This should improve the efficiency. :ok:

[maxtork]

Hi Guys,

I've been watching this thread for a bit and thought I would chime in with a question. I like the idea of a $10k helicopter I can't help but think about the cost of the replacement batteries. If we are looking at 2.3 Kg of battery per minute of flight as Graviman suggested and we want to fly more than 10-15 minutes we would have to have a pretty good size battery pack I'm guessing. How many charge/discharge cycles are NiMH batteries good for before requiring replacement? It would really suck to have a $10K helicopter that flies for 30 minutes on every charge but you have to spend $100K on batteries after 10 flights! I'm sure it wouldn't be that bad but I figured I would bring it up and see what you all thought. I know most of this thread has been about how to make the thing fly and not how to make it practical but I think it is an added aspect to the challenge.

Max

[Dave_Jackson]

Max,

There are a number of people who are working toward producing an Ultralight electric recreational helicopter. The motivation appears to be the challenge, combined with the belief that electrical storage technology will see significant improvements over the next decade or two.

This is probably going to be a staged growth that parallels the electrical storage improvements. First the designer/developers. Then the hobbyists, who enjoy building, taking short test flights and discussing their craft. And finally, those who consider the flying as their primary interest.

IMHO, electric propulsion and control may well be a reincarnation of the exciting early days of helicopters.

Dave

[Graviman]

It had a vertical gas engine bolted on top of the rotor head with a large prop above. The torque from the engine turned the main rotor and the prop blast straight down added thrust also.

There have been many variations on the tipjet theme (this is not really one of them if i understand correctly). Efficiency generally suffers, so tip jet only becomes an advantage on large flying cranes due to required g/box mass.

think about the cost of the replacement batteries

Diesel, kerosine or even gasoline are cheaper...

The idea has been modified by moving the propellers further outboard, reducing their diameter, and increasing their pitch.

Returning to the problem of blade flexure and control difficulties with prop RPM lag. It is not impossible, i am just saying that an epicyclic gearbox is a known solution. Tips will also be in compressible flow, so high mass flow suggests ducted fan.

You need to understand any development issues assciated with this aircraft:
http://avia.russian.ee/helicopters_eng/mi-7-r.html
There doesn't seem to be much on the web, but i'm sure the tip jets were turbojets not ramjets.


Mart

[Dave_Jackson]

Slowrotor,

Thanks for the concept. This idea (http://www.unicopter.com/0812.html) may be similar to what you are describing. The differences being, an axial flux electric motor replaces the reciprocating engine and the rotors are of the same diameter.


Max,

While discussing the future of electrical storage, have a look at Europositron (www.europositron.com).
They claim to be developing "rechargeable aluminum batteries, providing up to 20 times more capacity than the types currently available on the market."


Mart,

For those who like epicyclic gearboxes. ;)
Here is another idea. (http://www.unicopter.com/A119.html) It is simply the single blade concept (http://www.unicopter.com/ElectroRotor.html) modified for two blades. When it comes to cost, one disadvantage it has is the need for two rotors to counteract torque.


Dave

[Graviman]

...one disadvantage it has is the need for two rotors to counteract torque.

I don't understand why this offers any advantage over a static motor. The need to supply power (using say transformer coil slip rings) is a distinct disadvantage. Why not just design a motor driving the rotor through a gearbox?


A good habit to get into is to compare a new concept to a known solution. The advantages and disadvantages over the known solution should be documented. It does actually provide a good reality check to see whether the concept is worth considering or not - you'd be suprised how looking at the details sorts out the good from the bad...


Mart

[Dave_Jackson]

OK.
"A motor driving the rotor through a gearbox" (http://www.unicopter.com/Electric_UniCopter.html) ;)

[slowrotor]

Dave,
Your drawing is close to the concept I described.
The model had a large lower rotor turning slow, and a small upper rotor (prop) that turned thousands of rpm. The large rotor was cut out in the center where the small rotor could better use the center area .

[Graviman]

"A motor driving the rotor through a gearbox"

Now you're talking! Put a gyro in the control system and i think it's there. :}

BTW, why not fit two side-by-side pusher props? Gives good yaw control and would package better (Nick commented that S69 lacked positive yaw authority). Intermeshed with differential collective, or even cyclic, pitch would work well...


Mart

[Dave_Jackson]

BTW, why not fit two side-by-side pusher props? ...... Intermeshed with differential collective

You mean something like this (http://www.unicopter.com/1512.html). :)

[Graviman]

You mean something like this?

:eek:

Er, no that's going back to beating the air into submission again! :ooh: Remember i've never been a fan of interleavers, and this one just looks too complex. The intermeshing concept is sound, but just replace the single pusher prop with a side-by-side counterrotating system - so the spinner axes can be horizontal.

If piloted flight is being considered:http://www.unicopter.com/Index_4-blade.jpg http://www.unicopter.com/Closed.gif

Mart

[Dave_Jackson]

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

[slowrotor]

Radio control helo for under $50. I heard Toys are US has it for $29.
http://www.xheli.com/3rcrarecorcf.html

[Graviman]

Since i'm too broke to fly the real thing regularly :( , maybe i should get me one of these :ok: ! Real helis have 4 channels, so what does 6 and 7 channels get you?

I notice it only has 7 mins flight time, doesn't bode well if you scale it up to carry pilot & pax...

Mart

[Dave_Jackson]

Mart,

The intermeshing concept is sound, but just replace the single pusher prop with a side-by-side counterrotating system - so the spinner axes can be horizontal.


Intermeshing Configuration:

http://www.unicopter.com/1097.gif

Your statement is a valid one. It was, and still is, under consideration.

With the single prop the intermeshing UniCopter is intended to have a slight forward tip during forward flight. This is so that the rotors provide most of the lift and a little propulsion while the propeller is providing most of the propulsion and a little lift. The intention, rightly or wrongly, is that the prop will only remove (and diminish) rotor induced thrust from under the front quadrant of the rotor. In addition, some of the prop's incoming air will be drawn through the inefficient center of the rotor disk.


Coaxial Configuration:

Sikorsky has the prop horizontal and at the tail.

http://www.sikorsky.com/Images/SAC_Sikorsky_Aircraft_Corporation/US-en/X2_Demonstrator_Aircraft.jpg

This arraignment will remove air from under the front and rear quadrants of the rotor disk and I suspect that it will diminish the induced thrust from both quadrants.


Interleaving Configuration:

This subject shows up one of the advantages of the Interleaving configuration over Sikorsky's Coaxial. The following sketch show that having two rotor disks, instead of one, allows the prop to be slightly closer to the craft's CG. [In the following sketch, the propeller should be invisioned as being back close to the HS.]

http://www.unicopter.com/1368-C.gif

Much more importantly, the propeller on the Interleaving is drawing air from the area of the retreating blades. With the inclusion of the Advancing Blade Concept, it can be see from figure 6 in the following sketch that there is very little rotor/propeller interaction.

http://www.unicopter.com/1372.gif
The upper frontal view is hover and the lower frontal view is forward flight.
The 2 circles on both sides of the fuselage are the turbofans, which are intended for larger transport Interleaving helicopters.


slowrotor,

It's too bad that the price of full-size helicopters don't come down like that. Must have something to do with mass production.

A friend has just produced a simple rubber-band model of the Interleaving. He is pleased with it and is now making an electrically power one from an RC coaxial that hit a wall one time too many.


Dave

[Graviman]

Dave,

Having a single prop spinning one way is not symmetrical, but two props would be (and offers good yaw authority in a neat package)... ;)

The reason i am not convinced about interleaving is that for a given disk loading the interleaver requires more ground profile. Helicopers trade on versatility, so the less ground profile the better. A larger ground profile will also cost weight, since it implies additional structure. If you are trying to make the most of the battery mass you need low weight and high efficiency.

Intermeshing is a much better concept, since hubs sit on outboard corners of fuselage. This has to be best for aerodynamic efficiency, since reverse flow is over fuselage and ABC / IRAT will improve airflow further. I am not really interested in UAVs, since the discussion was originally about piloted recreational flight and UAVs have none of the constraints imposed on a piloted machine. If stability is the concern, i remain absolutely convinced that gyro augmented stability is the solution (aerodynamic input for dihedral is easy to implement).

But at least the motor is now going through a gearbox... :ok:

Mart

[Dave_Jackson]

Mart,Having a single prop spinning one way is not symmetrical, but two props would be (and offers good yaw authority in a neat package)It is said by many that it is not necessary to have counterrotating props on an airplane with twin engines. However, as you say, it MIGHT be an advantage for the helicopter, due to its high blade loading. (not disk loading).

Twin props will definitely give strong yaw control.
_____________________

A little 'sale pitch' on the Interleaving.

The most efficient rotorcraft configuration (thrust/ power) is the Side-by-side configuration. The Coaxial would have the same efficiency if its two disks could be located at a very large distance from each other.

The next most efficient (thrust/ power) configuration must be the Interleaving. Forgetting the fuselage and struts for a moment, the blades of one Interleaving rotor do not place a downwash on the blades of the other rotor, whereas the Interleaving and the Coaxial rotor blades do.

In respect to 'footprint', the large total disk area of the Interleaving could be reduced if it was required to match the disk loading of the Intermeshing or Coaxial. In addition, the spars of the interleaving could be folded back for 'parking'.

By adding the Advancing Blade Concept and Active Blade Twist, particularly to the Interleaving, the downwash on the fuselage and struts should become relatively insignificant. The aerodynamic drag of the struts could be minimized by; reducing their size through the use of composite construction and a slight weigh penalty for the addition of extra composite (so to speak).

The struts could also have aerodynamic profile skins, which rotate to suit the airflow. In fact, with slats, they might even contribute to lift during forward flight.

The Interleaving might not be as well suited to highly maneuverable flight as the Intermeshing, and to a lesser degree :O the Coaxial, will be. However for transport requirements and for maneuverability beyond today's rotorcraft, I really suspect that the Interleaving may be the best answer.
__________

Maybe all the gears will never go, but for interest and perhaps future development, a group of pages on the ELECTROTOR (http://www.unicopter.com/ELECTROTOR.html), a rotor with an attached axial flux motor and no gears http://www.unicopter.com/Chairshot.gif has been added to the web site.


Dave

[Graviman]

Dave,

I see why you are protecting the interleaving design so. The trouble is i'm not sure i agree with your reasoning. For good lift to power you need low disk loading.

Disk loading is simply the weight of the aircraft divided by the projected swept area of the rotors. For a coaxial this means that the projected area is effectively one rotor disk, while side-by-side would be two disks. This means that for the same rotor diameter the coaxial would have twice the disk loading as the side-by-side. However, if the coaxial rotor diameter was doubled to fit into the same landing width as the side-by side, then the coaxial disk loading would be quartered. The final result is that the coaxial offers half the disk loading of the side-by-side for a given landing space requirement.

The interference of coaxial blades on airflow is a necessary evil. Lift is obtained by accelerating a given column of air towards the ground. This means that the lower rotor operates at higher pitch due to the upper rotor downwash, so for equal torque the upper rotor ends up lifting more than it's share - remember we are discussing hover here not forward flight.

When a design brief for a new helicopter is established it is the concept teams job to package as much rotor planform into the ground box as possible. Intermeshing will come a close second to coaxial, but may actually have aerodynamic advantages since there does not need to be flow interference. Naturally an ABC IRAT intermesher would need some serious study for the numbers to compete with X2.

Since an electric helicopter needs to operate as efficiently as possible, i naturally suggest starting with low disk loading. In truth the only real reason to consider counterrotating is to avoid retreating blade stall, so conventional actually still gets a look in.

Mart

[Dave_Jackson]

Mart,

I would not like to think of it as "protecting the interleaving design".
IMHO, the Intermeshing is the best one (so far :eek: ) for small agile craft.
IMHO, the Interleaving is the best one (so far) for larger transport craft.

No single solution is likely to be best for all applications.


In regard to this thread's topic, this web page (http://www.unicopter.com/1525.html) might be of interest. It considers the rotor-rotor aerodynamics of an Interleaving disk. This page is specifically directed at a very light electric helicopter. The downwash on the pilot is not considered.


Dave

[Graviman]

IMHO, the Interleaving is the best one (so far) for larger transport craft.

I can see this. Since for large rotor assemblies the limiting factor is the size of gearbox required to get high engine powers into very low RRPM. Doubling up (or quadrupling) the rotors is the best way to keep the total gearbox mass sensible - it is again a necessary compromise. Worth noting that the MI-26 has as much air flow through the gearbox as each engine. This suggests the rotor diameter must be on the limit of design for a large transport aircraft, but then again it can lift 20 tonnes... ;)

.... this web page ... considers the rotor-rotor aerodynamics of an Intermeshing disk. This page is specifically directed at a very light electric helicopter...

Looks interleaving to me - this is where i do get bothered. We are agreed that interleavers are suited to very large transport aircraft. All of the interleavers you concept layout on your site show one or two crewmen, so are only about the size of an R22 or R44. A very light electric helicopter is not a large transport aircraft...

Mart

[Dave_Jackson]

Looks interleaving to me -
It does to me too. Thanks. The error has been changed.

All of the interleavers you concept layout on your site show one or two crewmen, so are only about the size of an R22 or R44 This one looks fairly big. (http://www.unicopter.com/1121.html)

A very light electric helicopter is not a large transport aircraft.. No, but they both have the need for a high lift-to-power ratio.

[Graviman]

A very light electric helicopter ...(has)... the need for a high lift-to-power ratio

:ugh: :ugh: :ugh: :ugh: :ugh: :ugh: :ugh: :ugh: :ugh: :ugh: :ugh: :ugh: :ugh: :ugh:

That's my point Dave, you can only achieve this with either conventional, coaxial or intermeshing. And the intermeshing needs some development.

I layed out the reasoning very clearly in post #35. Why ask for constructive criticism then ignore it?
http://www.unicopter.com/Chairshot.gif

Mart

[Dave_Jackson]

Mart,That's my point Dave, you can only achieve [a high lift-to-power ratio] with either conventional, coaxial or intermeshing.:confused: :confused: What happened to Side-by-side and Interleaving?


I layed out the reasoning very clearly in post #35. Why ask for constructive criticism then ignore it?
Cause I didn't know whether to recommend a book on rotorcraft or a book on geometry. :ugh:
________________


Disk loading is simply the weight of the aircraft divided by the projected swept area of the rotors. For a coaxial this means that the projected area is effectively one rotor disk, while side-by-side would be two disks. This means that for the same rotor diameter the coaxial would have twice the disk loading as the side-by-side. OK


However, if the coaxial rotor diameter was doubled to fit into the same landing space as the side-by side, Assuming that 'space' means 'area', and by 'area' you are talking about 'disk area', think about your sentence.


The interference of coaxial blades on airflow is a necessary evil. Lift is obtained by accelerating a given mass flow rate of air at the ground, and clearly that column of air can only be accelerated once. Only once? :confused: :confused:


This means that the lower rotor operates at higher pitch due to the upper rotor downwash, so for equal torque the upper rotor ends up lifting more than it's share :confused: :confused:


When a design brief for a new helicopter is established it is the concept teams job to package as much rotor planform into the ground box as possible. Perhaps this is the problem. It appears that you think that all 'boxes' [area] must be square. http://www.unicopter.com/Chairshot.gif

[Graviman]

Assuming that 'space' means 'area', and by 'area' you are talking about 'disk area', think about your sentence.

Perhaps this is the problem. It appears that you think that all 'boxes' [area] must be square.

I'm considering the width of the aircraft as the main constraint to a pilots decision on where to put down - the thread was for a piloted electric rotorcraft. The front-to-back length is less of a concern since the heli will approach it's landing area with some forward speed.

The FW-61 and FA-223 machines could not be described as compact. To ignore pilot requirements for the sake of "design principles" is just wrong.

Other side by side concerns: I accept that the outriggers can have fairing that rotates about a cylindical spar, but this adds weight. Even a faired outrigger will suffer drag, so contribute to downwash penalty. You will need a distributed drive system to maintain indexing, this adds weight. So you have taken a "design principle", then introduced all sorts of compromises to get the thing to fly.

If the symmetrical helicopter is so perfect, why have there been so many posts bemoaning the limited payload capability of the V22? You ask for constructive criticism, and this is what i give (i actually recommended the intermesher). I can't be blamed if my engineering knowledge does not fit your design ideal.

Mart

[Dave_Jackson]

Mart,

This thread is about the possibility of getting an electric helicopter off of the ground ~ for the first time.

Disk loading is very important. Keeping it compact is ................

[Graviman]

Impasse! :rolleyes: Nick, you hold 'im i'll hit 'im. :}

OK Dave. For a one off helicopter where there is no practical constraint on landing width, side by side is easier to do with motor drive than conventional, coaxial or intermeshing or interleaving. Like the FW-61, design it with pylons rather than try to outsmart the air. If "the possibility of getting an electric helicopter off of the ground" is truly the goal then 3 or 4 rotors makes much more sense than two, since you can use the motors for cyclic and collective.

I expect i have just described the Hughey. If the concept takes off see how long it takes for the next generation to become either coaxial or conventional, with motor driving through a reduction gearbox.

Mart