A challenge ~ for those who are not technically challenged.
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
2nd post attempt...
Originally Posted by SR
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.
Originally Posted by MT
think about the cost of the replacement batteries
Originally Posted by DJ
The idea has been modified by moving the propellers further outboard, reducing their diameter, and increasing their pitch.
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
Last edited by Graviman; 22nd Sep 2006 at 17:03. Reason: Had to get some loading calcs to a supplier...
Thread Starter
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Slowrotor,
Thanks for the concept. This idea 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.
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. It is simply the single blade concept modified for two blades. When it comes to cost, one disadvantage it has is the need for two rotors to counteract torque.
Dave
Thanks for the concept. This idea 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.
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. It is simply the single blade concept modified for two blades. When it comes to cost, one disadvantage it has is the need for two rotors to counteract torque.
Dave
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DJ
...one disadvantage it has is the need for two rotors to counteract torque.
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
Last edited by Graviman; 1st Oct 2006 at 09:11.
Thread Starter
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Join Date: Jul 2003
Location: Port Townsend,WA. USA
Posts: 440
Likes: 0
Received 0 Likes
on
0 Posts
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 .
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 .
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DJ
"A motor driving the rotor through a gearbox"
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
Last edited by Graviman; 22nd Sep 2006 at 20:39.
Thread Starter
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
BTW, why not fit two side-by-side pusher props? ...... Intermeshed with differential collective
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DJ
You mean something like this?
Er, no that's going back to beating the air into submission again!
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:
Mart
Last edited by Graviman; 22nd Sep 2006 at 23:24.
Join Date: Jul 2003
Location: Port Townsend,WA. USA
Posts: 440
Likes: 0
Received 0 Likes
on
0 Posts
Radio control helo for under $50. I heard Toys are US has it for $29.
http://www.xheli.com/3rcrarecorcf.html
http://www.xheli.com/3rcrarecorcf.html
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Since i'm too broke to fly the real thing regularly 
, maybe i should get me one of these 
! 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
, maybe i should get me one of these ! 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
Thread Starter
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Mart,
Intermeshing Configuration:
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.
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.]
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.
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
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:
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.
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.]
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.
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
Last edited by Dave_Jackson; 23rd Sep 2006 at 22:47.
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Thread relight, to salvage X2 thread... :)
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...
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)...
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...
Mart
Last edited by Graviman; 26th Sep 2006 at 00:59.
Thread Starter
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Mart,
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
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, a rotor with an attached axial flux motor and no gears
has been added to the web site.
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)
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
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, a rotor with an attached axial flux motor and no gears
has been added to the web site.Dave
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
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
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
Last edited by Graviman; 28th Sep 2006 at 07:59. Reason: Tried crackin' a nut with a sledge hammer! :(
Thread Starter
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Mart,
I would not like to think of it as "protecting the interleaving design".
IMHO, the Intermeshing is the best one (so far ) 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 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
I would not like to think of it as "protecting the interleaving design".
IMHO, the Intermeshing is the best one (so far
) 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 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
Last edited by Dave_Jackson; 27th Sep 2006 at 15:05.
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DJ
IMHO, the Interleaving is the best one (so far) for larger transport craft.
Originally Posted by DJ
.... this web page ... considers the rotor-rotor aerodynamics of an Intermeshing disk. This page is specifically directed at a very light electric helicopter...
Mart
Last edited by Graviman; 27th Sep 2006 at 15:02.
Thread Starter
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Looks interleaving to me -
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..
Last edited by Dave_Jackson; 27th Sep 2006 at 17:31.
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DJ
A very light electric helicopter ...(has)... the need for a high lift-to-power ratio
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?
Mart
Last edited by Graviman; 27th Sep 2006 at 21:50.
Thread Starter
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Mart,
What happened to Side-by-side and Interleaving?
Cause I didn't know whether to recommend a book on rotorcraft or a book on geometry.
________________
OK
Assuming that 'space' means 'area', and by 'area' you are talking about 'disk area', think about your sentence.
Only once?
Perhaps this is the problem. It appears that you think that all 'boxes' [area] must be square.
That's my point Dave, you can only achieve [a high lift-to-power ratio] with either conventional, coaxial or intermeshing.
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?
________________
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 space as the side-by side,
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.
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
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.