Helicopter with coaxial rotors

[ArneCRosenfeldt]

Like in my car plan, a (non-stealth) helicopter allows to combine a nice body with some interesting mechanics which can be shown off in an image sequence zooming in on specific parts and hiding some others (unlike in a real video at worst with hard lightning). I have read that the coaxial helicopters are less loud, can fly faster, are more compact and less likely to hit something with their tail rotor than helicopters with a tail rotor.
Due to their height they seem to be unsuited for combat in the army. That is okay, I like peace. More importantly they need two albeit small
swash-plates. But hey in Blender swash-plates are cheap. For a stiff control of blade angle these indirect actuation of the upper rotor in Kamov helicopters is not suitable and I will not model them. I thought about placing the drive gear between the rotors, but then the conflict between aerodynamic resistance and gears with a large safety margin is unresolvable. Thus the single stage gear is placed in the body. Aerodynamic large gears may double as fans for some increased lift. You know because in this rendering everything is open anyway. For a real helicopter I would place them in
a gearbox.

Since I like symmetry both rotors get identical heads stacked over each other. This means that all bearings for the shaft of the top rotor
are located on top of the lower rotor. Also the servos for the swash-plate are placed there. For the servo assembly to be firmly connected to the
body, the lower rotor shaft needs to have a thin walled large radius tube as a shaft. Consequently the lower rotor needs large radius thrust bearings.
This breaks the symmetry a bit, but I would not burden both rotors with the high friction due to oversized bearings. It may look better to place both
swash-plates between both rotors placing 4 servos in a single place. Each servo implementation could be explicitly modeled as a sector of a gear
driven by an electric motor and connected to the swash-plate by … ah scrap that, the swash plate is held inside a Cardan joint and each axis of that
is driven by an electric motor on a gear. I am all for electronic mixers and gyro stabilization, which could be indicated by drawing 3 gyros or
Foucault pendulums inside the body. Known from small RC helicopters and auto-gyros are tethering rotor-heads, where the opposing blades of a rigidly
connected, keeping lever amplified forces away from the joints which are turned on every rotation in straight forward flight reducing friction losses.

Two dedicated gears allow to change collective pitch. Each blade passes the drive shaft and is connected to the other blade on the other side in order to reduce the load on the pitch bearing. I have no idea how to replace the simple but symmetry-braking mechanics which rotate the track of the swash-plate. In an image sequence some arrows could be added to indicate lift and forward thrust given by the blades. For example the drone grabs a post box, rises, cruises, turns around a high building and lands. Auto-rotation is important for me thus I would like to show it too. It is a pity
that the Osprey cannot do that.

Attachments

heli20141122.blend (139 KB)

[ArneCRosenfeldt]

But failed because I cannot instruct blender to first dupliVert and then arrayMod. It is kind of missing parentheses which allow me in formulas to change the order between multiplication. Anyway here is what I’ve got. Now i probably end up with two meshes with seams between them. If both faces of a seam share the same vertices, no light can get through. If I fake it and have internally separate vertices all kind of rendering (and boolean modifierer) nonsense ensures.

Somehow Window preview and BA have problems with png and jpg from Blender. I had to mangle it through gimp!?

And of course, in modelling a torus using Array.Mod there are 999 ways to get one rotation wrong and one way to do it right. I will have to give it another try. Try out different orders of parenting.

Attachments

dupliVerts20141223.blend (102 KB)

[ArneCRosenfeldt]

I modeled raceways like marble raceways and in the end the stator ended upside down. Rotors can be modeled similar. stator has to be scaled -1, and I did it this time after I took the screenshot.

Uses this modifiers:
Array.object
Mirror.object
Shrinkwrap.projection
Decimate.planar

Attachments

20150111ArrayOfArray.blend (138 KB)

[ArneCRosenfeldt]

The construction of the body of rotation needed to much concentration to be fun. I have come up with a second project: ornithopter as a stealth (silent) drone to take aerial photo for openstreetmap (I like models with a story around them . It is supposed to have two fuselages placed at a distance from the center where the wing does not move. Canard which detects up-winds. I want to show off bondary layer magic at the joints using an electric vent. Like for the heli the final model is supposed to support a “view”, where it shows of the low friction mechanics (large gear). How can this be done in an aerodynamic way? Fuselages all over the wing. The trailing edge of the wing is coated with a transparent foil (Kryptopterus vitreolus). Angle of attack is set actively (also needed for sharp turns). Animation of crash landing with disintegration at predefined magnetic joints. One wheel per fuselage.

[ArneCRosenfeldt]

I wanted to create a look of an unbreakable rotation. As long as the rotor turns, a heli flies. It does not need an engine for that. Unfortunately the rotor-head is of a small scale. The balls are hidden. With bikes it bothers me when they make noise. I like clean bikes where a quick look can identify any part touching the wheel. Balls are touching, then going to the outside, the clearance gets bigger. Same for clocks with 3 indices. My intention just does not show in the renderings.

So I could settle for an animation. Show the rotor in close-up and uncovered, then move to a realistic view. I may need to make a long sequence, show steady flight, close-up: low friction in the bearings. Then show maneuvers and then auto-rotation. This maybe interesting in the future, but I do not have a work-flow set up for this nor do I have the time budget.

I need a hull for the heli. I like hulls with this lifting body style. But then this is a heli, so cruise is just one use case. The coaxial heli has no tail rotor. Thus the tail … can only be justified by cruise. Ever seen a quadro-copter with a tail? In the end the body probably looks like a drop of water with exhaust to the lower back (if not electric driven). Very boring.

So what about an airplane? As a kid I though a plane hangs under a wing and liked kites and Chessnas. Then I landed in a low wing plane which did a hard turn still at high speed (from landing) to get the shortest path to the terminal. Planes have to land, they need to carry their weight on their wheels. Wheels, fuselage and wing need all meet at the same point. But then there is wing-fuselage interference. That high efficiency solar plane has a high mounted wing.

As a kid I would say a pusher prop is better then a prop at the front. Now I know that a prop makes the most of wind far away from the center and is less noisy. And like 2 bladed very large props at the front where the heavy engine is, and where is more ground clearance at take of.

As a kid I would say engine on the wing is better, now I like a clean wing. As a kid I would say counter-rotating propellers are better. The A400 has these and the thunderbolt has them. But now I like it (in real life) to only have a limited amount of spare parts, which fit everywhere. This all screams compromise.

So here comes the fan. Above I wrote: Two blade propeller is best (like biplanes are bad). And now I like fans, which have about 20 blades. I am just stressing this because large ships have a single pusher propeller with 5 blades and the constructor does not want to got to 6 blade. But hey, ships are ships and planes are planes. Fans run in front of a stator which takes all angular momentum out of the pushed air. Perfect. No need to have counter-rotating anything.

The problem with fans is, if the engine is off, the air should go around the housing of the fan. This can best be done with the fan inside the fuselage (or wing, or wing-root). Then the engine is no easy bolt-on device anymore. On a modern plane I cannot place the fan in the tip because there is the radar. How does a radar deal with a propeller? What about a radar in the spinner? What if the engine blows up?

I have read that large planes can glide 200 km. I want to model a futuristic plane. Not a historic one. Futuristic means less fuel, less noise. A short haul plane ( for example to an island or on land where is no train track), could climb for 40 km and then glide. This type of plane is then allowed to land late at night. Less traffic makes sail plane mode safe enough.

Furthermore I like super-sonic stuff. What a about a sailplane with transonic wings. I would like to model a complex wing root for a high mounted wing. The upper side of the wing should be totally clean, and disturbance by things hanging below minimized. Boundary layer suction in front of the wing. In this way I get a clean accentuated pressure profile in the center, which spreads out over the sleek 40° swept wings. I would like to model the super-sonic region above the wing on one side of the plane (modeled after calculations). Here it is again, the high mounted wing. There will be intrusions into the passenger room. Turning engines of and moving them inside like landing gear - while flying at top speed - sounds like a bad idea. Motivation gone Flaps to divert air to the engine or pose the risk of leaks, weight.

Experimenting with model planes and reading stuff I found that swept wings are bad below 200 m/s. So for short haul planes, why not just obey the speed limit and use straight wings? Not going that high and that fast and thus not gliding far enough to make that mode worthwhile. NOT FUTURE.

Another place I already modeled in Blender using curves with bevel is a supersonic plane like the Concorde. I’d like to capture the shockwave by means of a tube around the fuselage behind the cockpit. Like the engines on the SRB 72 blackbird. I figured out that such a tube would be very large and need to be placed close to the nose of the plane and acts like a tail, but on the face and necessitates an even larger “real” tail to counter that effect. That plane looks ugly. NO FUTURE.

Using the original Buseman biplane idea is better in this respect. But it has other problems. A tube is thin walled and long and not a big obstruction to the air. A second wing is much more of a problem. A biplane like 2d intakes are more prone to choke than the circular (3d) intake on the blackbird.

Having one tube for the passengers on top of one tube for the captured air looks weird. I want that pancake look of modern fighters for civil flight. Passengers want windows. Solution: Tubes as leading edge extensions of the wings. These are too small for the shockwave, but large enough to supply the air for the engines. Skin-friction? Skin needs to be made irrelevant by scale. 3*2 seats.

I want a silent supersonic airplane, but any idea to silence the fuselage and the engines leads to more weight and thus larger wings and thus larger shockwaves by them. I wonder if there is any way to get a new concorde. The original is such a beauty, I do not feel like I can do some small improvements. There already exists models of the concorde…