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  #91  
Old 10-10-2008, 10:11 AM
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André MARTIN
 
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Quote:
Originally Posted by Rotor Rooter View Post
What about incorporating an automatic pitch-change mechanism?

It would provide advantages for partially and fully powered rotors, plus for propulsors.

There is a lot of material available on the subject. It has been done in the past. It would make for an interesting thread.

It might even make for an interesting group of low cost automatic-pitch projects. A type of Wikinomics by interested forum members to participate in one or more of the steps; requirements, conceptualizations, designing, calculations and prototyping.


Dave
Yes, for a gyro, an automatic pitch actuator can be made like the one of a french gyro, and it works:

http://www.rotaryforum.com/forum/sho...9969#post79969

But for the ULTRALITECOAX, i thought about it and i concluded that it is simpler to have the two (brain) manual-actuated variable collectives. And above all, i don't see anything simpler which could give more pitch at high power setting, and more pitch at low speed and low altitude (just before landing) if the engine quits!...And enabling also to give less pitch if the engine quits at high altitude, during autorotation!...

For the WIKINOMICS, it seems there is not many people interested in this kind of collaboration...
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Nothing is really new under the sun; only new combinations!...
THE TOURINGCOPTER:http://www.rotaryforum.com/forum/att...0&d=1167007089
THE GYROCOAX:http://www.rotaryforum.com/forum/att...4&d=1169478953
THE ULTRALITECOAX:http://www.rotaryforum.com/forum/showthread.php?t=18431
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  #92  
Old 10-10-2008, 11:13 AM
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Andre,

Gyrocopter:
My knowledge of the gyrocopter is very limited (and it may not be much better for the helicopter ) However, I believe that the basic gyrocopter has automatic rotor speed control due to the aerodynamics of autorotation.

The addition of manual or automatic pitch-control is only required on a gyrocopter when jump-takeoff or a partial-powered-rotor is incorporated. Perhaps there is little interest in the community to add these two features to gyrocopters. Perhaps the cost, complexity and minimal benefits are the reasons.

Helicopter:
IMHO, if there is a desire to have a simple, cheap, safe and reliable helicopter 'in every garage' then the piloting difficulty and craft maintenance must be significantly reduced. Whereas current recreational helicopter pilots appreciate the challenges of mastering the skills and maintaining the craft.

An analogy would be the bicycle vs the unicycle.

One idea toward putting a rotorcraft in every garage:
I believe (hope) that torque-pitch and speed-pitch can both be built into a 1-piece hub-bar. This would be achieved by producing the hub-bar out of carbon and fiberglass tow instead of an aluminum plate. The objective is to have torque and centrifugal force (coning angle) effect the pitch of the blades.
One current project; http://www.unicopter.com/0575.html

Dave

Last edited by Rotor Rooter; 10-10-2008 at 11:17 AM.
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  #93  
Old 10-11-2008, 07:24 AM
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Gyro: variable pitch could be desirable in case of low G: the rotor governor, by lowering the pitch, enables the rotor not to slow down to much, and to regain speed more easyly with the coming back G...Then, the gyro gaining speed, the pitch of the blades will be higher as the speed of the rotor gains speed also, so the rotor will tilt forwards, giving more efficiency to the system!...

Helico: In this case, i don't like automatic things which can not be disconnected at once!!! The coaxial helico is very simple to pilot as there is no tail rotor! A journalist took one hour to learn to fly the AIRSCOOTER, alone!!! For the ULTRALITECOAX, the only problem which could remain is the correllation between the collective and the power requirements: a governor must to be used! this governor (as for the MOSQUITO) is a full electric car cruise control (with a lot of settings by micro switches: sensibilty, gain, etc...) which is used in the Hot Rod domain, and can regulate the engine RPM...cost: $250!!!

The problem of the ULTRALITECOAX is not a problem of feasability, but a problem of manufacturing!!! I have no means to make and gather all the pieces and bits, to make this coax a serviceable helico!...
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Nothing is really new under the sun; only new combinations!...
THE TOURINGCOPTER:http://www.rotaryforum.com/forum/att...0&d=1167007089
THE GYROCOAX:http://www.rotaryforum.com/forum/att...4&d=1169478953
THE ULTRALITECOAX:http://www.rotaryforum.com/forum/showthread.php?t=18431

Last edited by quadrirotor; 10-12-2008 at 09:57 AM.
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  #94  
Old 10-22-2008, 06:24 AM
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Have someone more info on the VIKI coaxial helicopter?

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Nothing is really new under the sun; only new combinations!...
THE TOURINGCOPTER:http://www.rotaryforum.com/forum/att...0&d=1167007089
THE GYROCOAX:http://www.rotaryforum.com/forum/att...4&d=1169478953
THE ULTRALITECOAX:http://www.rotaryforum.com/forum/showthread.php?t=18431
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  #95  
Old 10-22-2008, 07:01 AM
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Has anybody more infos on this one? is it on the market? etc...:

http://www.rotor-international.net/h...ry-eaglet.html
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Nothing is really new under the sun; only new combinations!...
THE TOURINGCOPTER:http://www.rotaryforum.com/forum/att...0&d=1167007089
THE GYROCOAX:http://www.rotaryforum.com/forum/att...4&d=1169478953
THE ULTRALITECOAX:http://www.rotaryforum.com/forum/showthread.php?t=18431
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  #96  
Old 10-23-2008, 06:14 AM
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Just came across your postings ...

That VIKI machine, I wonder why they didn't invert the powerplant.

As for that second one, by chance, isn't that the VIKI machine?

tyc
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  #97  
Old 10-27-2008, 03:46 AM
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Quote:
Originally Posted by tyc View Post
Just came across your postings ...

That VIKI machine, I wonder why they didn't invert the powerplant.

As for that second one, by chance, isn't that the VIKI machine?

tyc

Tyc,

I think the rotor system in the latter differs from the VIKI as is the engine placement and the tail I guess.

It could be though that the second helicopter is a developped prototype from the proposed VIKI drawing.

Inverting an engine which is not designed to operate in that "new mode" can be a very tricky thing and I know from first hand information that Rotax for example will not permitt use from their engines in manned craft,other than the postion to operate in they are designed for.

Cita

Last edited by Sita; 10-27-2008 at 03:50 AM.
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  #98  
Old 12-05-2008, 06:29 AM
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Just so happens I have a picture of this very helicopter I'll post it (I hope)


Doug S

Last edited by Doug Schwochert; 12-05-2008 at 06:34 AM. Reason: put picture in:)
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  #99  
Old 12-05-2008, 09:33 AM
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Thanks Doug. Have you any info on this one? location? is she flying? what about this helico?
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Nothing is really new under the sun; only new combinations!...
THE TOURINGCOPTER:http://www.rotaryforum.com/forum/att...0&d=1167007089
THE GYROCOAX:http://www.rotaryforum.com/forum/att...4&d=1169478953
THE ULTRALITECOAX:http://www.rotaryforum.com/forum/showthread.php?t=18431
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  #100  
Old 12-05-2008, 06:46 PM
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Hahahaha at first glance I thought it had a blue tail rotor with yellow tips.

Then I saw it was a ladder... I need new glasses.

Looks real nice, did it ever fly ?

A company in Australia is building something like this, I believe got orders from Thailand, singapore etc.
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  #101  
Old 12-15-2008, 10:16 AM
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News from EASYCOPTER!

http://www.ezycopter.biz
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__________________
Nothing is really new under the sun; only new combinations!...
THE TOURINGCOPTER:http://www.rotaryforum.com/forum/att...0&d=1167007089
THE GYROCOAX:http://www.rotaryforum.com/forum/att...4&d=1169478953
THE ULTRALITECOAX:http://www.rotaryforum.com/forum/showthread.php?t=18431
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  #102  
Old 01-01-2009, 03:12 AM
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I have to plead my igorance on rotor tip brakes. Looking at the pictures of the small coax helos I see the tip brake...how do they work?
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  #103  
Old 01-01-2009, 04:40 AM
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Quote:
Originally Posted by joe nelson View Post
I have to plead my igorance on rotor tip brakes. Looking at the pictures of the small coax helos I see the tip brake...how do they work?

Good morning Joe.

From memory in one of my old helicopter design and data manuals (by Stanley Dzik ) he showed a tip brake drawing.

I think it was used on the Hiller Rotorcycle one man co-axial developed for the Army. In order to control yaw each set of blades had small flap on the end to create drag. The 1" square flap simply folded out into the airstream at the rotor tip.

It used a small rod down the length of the inner blade to control the small flap . Each set of blades had these flaps and the controls were almost like an additional swashplate in amongst all the other linkages (complicated)

They were connected to the rudder pedals. The idea was to create more drag on one set of the (co-axial) blades by opening the flaps into the airstream and the extra drag caused the fuselage to rotate. Opposite pedal and flaps opening on the other blades to rotate the other way.

In other words , the torque free co-axial rotor now required more torque on one set of blades than the other and the fuselage would have rotate. Hope that makes sense.

Some experimenters use a small brake band at the hub of each rotor to do the same thing. Mostly they were trying to eliminate an actual rudder in the downwash behind the helicopter for yaw control.

Some experimenters use a system to apply slightly more collective to one set of blades than the other which also works.

C0-axial blades and controls are complicated enough , and with the added yaw control it gets even worse. For this reason most designers see the single rotor helicopter with a tail rotor a much simpler solution .

Even if you look at the production Kaman Husky , they had to use a huge ungainly set of downwash rudders at the rear for yaw control. All this to eliminate a small tail rotor. Not very practical in the end.

Happy new year Joe.

Arnie

ps: I am glad you saw the strap pack on the Ukrainian built helicopter I posted elsewhere. I was thinking of you when I saw it. It sure would be nice to have a machine shop like those guys .....

Last edited by Arnie Madsen; 01-01-2009 at 05:10 AM.
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  #104  
Old 01-01-2009, 04:41 AM
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They add more drag when extended, then the basic rules of physics apply - if one rotor has more drag than the other, you'll yaw.
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  #105  
Old 01-01-2009, 06:37 AM
C. Beaty C. Beaty is offline
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Traditionally, yaw has been controlled by differential collective pitch in coaxial helicopters. The problem then is that yaw pedals reverse in autorotation unless some type of automatic linkage is introduced to prevent reversal. Syncopters have the same problem. Dick DeGraw has pedal reversing linkage coupled to collective pitch on his syncopter. .

Tip brakes do not reverse yaw direction.

The Nolan Bros. helicopter had fixed collective pitch with blades ground adjusted for torque balance; in-flight yaw being controlled by a canted rudder in the rotor downwash. The lower rotor needs more collective than the top rotor for torque balance.

Bensen interposed a differential between engine and rotors, eliminating airframe torque reaction altogether. He also used canted rudders or on at least one occasion, a chain saw engine and torque rotor mounted on the tail.
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