Alternative or unusual technical solutions for gyro [Archive]

Victor Duarte

08-26-2004, 08:04 PM

hi everyone, well, i start this new thread because i m curious an hungry about information, but also i would have (some others too perhaps) an overview of some unusual techniques about to be used or considered for rotorcraft design, gyro or helicopter.

i start with these ones :

- has some one experimented an horizontal back rudder to control a gyro, o think this could prevent some negative G situations and make the gyro a little more responsive .. open

- is there an example of a 3 blades semirigid rotor for light gyros, with cyclic control ?

- what about ducted fans ? and about the thrust features ?

- what about twisted blades for gyro ?

- what about blade tips for gyro

- has anyone tried to use mini actuators for rotor controls

- what about push-pull cables for rotor controls

hope it will rise some interest

friendly

victor

Udi

08-26-2004, 08:32 PM

Hello Victor,

- has some one experimented an horizontal back rudder to control a gyro, o think this could prevent some negative G situations and make the gyro a little more responsive .. open

It's called an elevator. Cierva and others used them in the 1920s and 30s. Ron Herron also used them on his LW autogyro. I believe they are less effective than cyclic pitch control, especially at low airspeed. They are also problematic for ground manouvering.

- is there an example of a 3 blades semirigid rotor for light gyros, with cyclic control ?

Again, Cierva et al. They are too heavy, complicated and expensive for small sport gyroplanes.

- what about ducted fans ? and about the thrust features ?

They were tried by a few. All failed to the best of my knowledge.

- what about twisted blades for gyro ?

The most popular twisted blades are the Dragon Wings, by Rotor Flight Dynamics - Florida. They are one of the most efficient blades available for gyros.

- what about blade tips for gyro

Not that I know of. I am sure Chuck B. could chime in with some info.

- has anyone tried to use mini actuators for rotor controls

What for? The simple direct control rods are as reliable as one can get.

- what about push-pull cables for rotor controls

I believe Ron Herron has them installed as backup on one of his LWs.

Udi

gyromike

08-26-2004, 08:38 PM

- has some one experimented an horizontal back rudder to control a gyro, o think this could prevent some negative G situations and make the gyro a little more responsive .. open
Ron Herron's LW-2 Little Wing used an elevator for pitch control.
LittleWing history (http://www.littlewingautogyro.com/history.html)

- is there an example of a 3 blades semirigid rotor for light gyros, with cyclic control ?

McCulloch J2, Air&Space 18A, Chuck Beaty's 3-bladed system...

- what about twisted blades for gyro ?

Dragon Wings (http://www.rotorflightdynamicsinc.com/dragonwings.html) rotor blades. some Australian blades.

- what about blade tips for gyro

Tip weights? Dragon Wings have 'em, among others.

- what about push-pull cables for rotor controls

LittleWing LW-4/5 two-place gyros use dual push-pull cables for pitch and roll control.
LW-5 rotor head (http://www.littlewingautogyro.com/pictures/rotorhead001.jpg)

Victor Duarte

08-28-2004, 09:34 AM

hi and many thanks to you for lighting my candle ..
thanks udi for the right word ;) i must do my homework and learn a bunch of english technical words.

some precisions:
- in fact im going for an ultralight coax helico, the rotor in first. tech data is quite vailable (with some headaches sometimes ;)), but practical data on homebuilders is quite rare and it is in the gyro community that the most homebuilt experiments/techniques can be found. i try to pick some info about that.

- about the use of actuators : i was asking if they could be reliable, cheap? secure?, i agree rods are the simpliest way for light gyros, i was only thinking about the use of mini actuators precisely in the case of and helico cyclic in order of to replace some complicated rods.
In gyros , some use hydraulic motors to pre-rotate, so perhaps some one tried mini-actuators and have a reliable hydro circuit layout.

- about blade tips : i dont mean tip weights but, for example, tapered blade tips, back swept, elliptical, dihedral or anhedral angles etc.. curious about all experiments, wondering if they improve autorot features.

thanks udi and gyromike for your reply!

best regards

victor

Brian Jackson

08-28-2004, 12:46 PM

Zeeoo,

Your ideas are interesting, and I'd truly love to see you progress in your venture. But one thing caught my attention... You've mentioned throughout this discussion using a series of "mini-actuators" from everything from pre-rotation to cyclic control, as opposed to a "complicated" mechanical version.

Unless I'm misunderstanding something (which isn't unusual ;) ), a fundamental error exists. Mechanically controlled systems can provide real-time redundancy, whereas if any one of the many mini-actuators you propose fails, the entire rotor system ceases to function as designed.

Assume any part can fail at any time for any reason. Granted, helicopters are not notorious for having the greatest design emphasis on redundancy of systems, usually because they're ridiculously complicated as is. However, if you were to disassemble a mini-actuator and count the number of individual parts that make them work, and multiply that by how many you'd need, I'd bet that number would be significantly higher than the total number of proven parts on a purely mechanical heli-rotorhead.

As an engineering-type myself, like most on this forum, there is certainly a fascination with simple systems. My point is that many simple systems, in large numbers or in series, become complicated systems. In this case "complicated" does not mean "hard to understand". Quite the opposite... it's an elegant approach to a complicated problem. In this case the complication is derived from the sheer number of individual sub-component parts involved. Let any one fail and a domino effect may ensue.

An old and proven adage among aviation experts is that accidents are ALWAYS the result of several smaller failures happening collectively. Food for thought.

I'm no expert on this, but I've tried to learn all I can from those that are.

Respectfully,

Brian Jackson

Victor Duarte

08-28-2004, 01:22 PM

thanks Brian,
here is the kind of words i like to read, respectfully.

you re right about "relative" simplicity and failure sources, thats why i need skilled opinions or real life experiments.

about actuators, i do not consider the use of them, but just saw a brochure about them and think"mm why arent they used in microlights?". i ve dropped the idea. :(
see http://zeeoo.free.fr/helico/ sorry(this is not a complete site, only rough drawings to explain some ideas)
as you have seen in my blade desing (for example), i tried to eliminate a significant number of parts by designing all-in-one, i think it is simpler than a conventionnal one, but cheaper than eurocopter unless i dont use elastomeric bearings ($$$) , you know, i just "copy" the EUROCOPTER designs,i dont invent :rolleyes: .
i dont simplify just for performance, look at my rotorhead, i could have a metal plate for rotor like in EUROCOPTER, just cutted to flex, but i complicated my design to make it a little less risky, but keep the original idea.

be shure of my best attention about your opinion, really... the balance of good/bad is not yet to greenlight ... i am not kamikaze. :D

very best regards

victor
"there is no "better pilot", only alive ones" AF

quadrirotor

08-28-2004, 01:29 PM

You can do simpler zeeoo!
Look at the latest design of the Europeen Eurofighter helicopter! (not the Starflex!)
I don't like composite for the critical parts! so!

Victor Duarte

08-28-2004, 01:50 PM

the tiger ? also a source of inspiration... :rolleyes:
if you say it s simpler i have to have a look at that... but mine will not cost 8 million dollars/unit :D

have you go a link to the design?

the use of composites is a debate by it self.
anyway its proven that for blades or reasonnable flexion parts, it is much more resistant-in-fatigue than metal.

i agree about all composite rotors, for a homebuilt it would require to much skills in composites and specific tooling.. i m not convinced. you can cut metal as you want not composites..
homebuilts must have a reasonnable balance between innovation(risky) and safety(proven) ...

i am curious, have you heard about a all composites rotor for a hombuilt gyro ??

best regards

victor
"there is no "better pilot", only alive ones" AF

quadrirotor

08-28-2004, 02:09 PM

MC CUTCHEN SKYWHEELS: (you'd better be more documented if you want to get involved in helico design!!!):
http://www.waitman.com/products.html
http://www.skywheels.com/

Victor Duarte

08-28-2004, 02:42 PM

i agree a lack of info about composites rotorhead for gyros and other domains... :( thx for the link !
be shure i collect LOTS of info, my questions at the moment are more about "is it possible or has it been made yet"
if i knew everything, i couldnt learn from you and others here ;), i said it : i need info to go the right way.

thanks again for your help (et ne vous enervez pas!!!)
amicalement

victor

Aussie_Paul

08-28-2004, 02:50 PM

Andre, both those rotors have alloy spar.

The Austalian rotor blades that I am currently flying are all composite. The spar is a carbon fibre woven rope. The hub bar is alloy, and the blade to hub bar attachment straps are metal. There is a non load supporting rod near the leading edge for 1/4/ chord balancing.

Aussie Paul.:)

Victor Duarte

08-28-2004, 03:09 PM

hi paul ..

"The recreational gyroplane industry is at the stage of needing to use a 3-blade rotor system for the heavier fully enclosed 4 stroke cross-country gyros." :D

interesting to me.... shure there is a gap between 2 and 3 blades rotors, if 2 blades an be very simple using teetering, a 3 bladed needs a cyclic control, but may have advantages in stability/response and vibrations, i may be wrong..

in fact that was the sense of my questions here > is the use of 3 blades rotors going to ultralights ? if not why, if yes, are there examples ? what are the designs in use?
are the helico techs going from heavy aircrafts to ultralights (composites rotorheads/flexible parts/hingeless/bearingless/special blade-tips/advanced blade concept/berp profiles/vertol airfoils etc etc etc)

i think, if so , gyro and heli rotors will be designed quite the same way >>> that means more manufacturers would build 3 blade rotors > possibilities for use in an ultralight of proven rotors.... could be nice :D :D

best regards

(frenchie)victor

Victor Duarte

09-02-2004, 01:44 AM

has some one seen a homebuilt/experimental gyro with a 3 bladed rotor?

Brian Jackson

09-02-2004, 02:26 AM

Yes. There was a 3-bladed enclosed machine the owner/builder dubbed the "GyRhino" at the PRA Mentone Convention this year. Very unusual beast, but man could it perform! If memory serves, it incorporated a jump-takeoff rotor system and had a phenomenally steep climb rate. It was truly a sight to behold.

Perhaps someone here who knows could post a pic or link for Duarte?

Brian Jackson

09-02-2004, 02:32 AM

Ah... here's one...

Caption:
"Karol DeGraw flying husband Dick's jump takeoff 'GyRhino' Bensen Days, Wachula, FL April 2001"

Brian Jackson

StanFoster

09-02-2004, 02:37 AM

Brian: I was at Mentone and the GyRhino is in the back of the picture.

Stan

Victor Duarte

09-02-2004, 02:41 AM

thanks !!!!
i found a few sites showint it.
at first sight, it looked like the "eagles perch" but a close view shown a rotor i could quite recognize... and in fact , ok dick degraw built a synchro called "hummingbird" if im not wrong, it uses the same blade-holders... interesting...

i ll search more about flight capabilities (except jump start), tests or related problems. of what you said, brian, seems to be impressive.
if i think about an helico rotor, i always keep in mind "maybe for gyro too"

thanks brian and stan!!!

victor

rlj4532

05-28-2006, 07:31 PM

Hey Friends,
I"m looking for Diagrams or Blueprints for the cyclic controls for a Gyrocopter,
can anyone Help.

Bob

05-29-2006, 01:47 AM

rlj4532:
you might surch for "pumphandle cyclic"
I don't remember where I found it , perhaps "the lone star gyro site"
also there is documention on the gyrobee site free for the DL
...

Zeeoo:
I beieve your original question on the "Elevator" idea for a gyro is a good one, better control of any aircraft is a good thing not something to be laughed at. if the horizonal stablizer had a elevator attached to it on most gyros... and it was hooked in conjuntion with the rotor controls perhaps better control could be obtained for the avrage gyro I dunno ! but its worth considering !
I think the biggest danger confrunting MOST gyro flyers is the
gyro frame under the rotor swinging arround under the rotor
like a pengulim... I don't think such a elevator could prevent or even lesson the chances of the frame swinging arround in PIO siduations... but if it was hooked up to work against the swing
I would think it could be effective... if you think about it
as the frame swings foward the elevator could be hooked up to point the nose down.... as the frame swings back the Elevator could be hooked to point the nose up.... in effect killing the swing .... if this could be obtained by adding an elevator to the gyro I'ed add one in a hart beat ! because PIO takes out pilots all the time...

I dunno but the idea has merrit , if anything can stablize the frame under the rotor its going to have to be done by the air !
... how that would effect normal operation is unknown...
someone needs to try it I guess !

Cheers !
Bob........

Ga6riel

05-29-2006, 03:09 AM

castelated blades reduce transverse flow on individual blade elements

devon532

05-29-2006, 04:04 AM

I also thought about an adjustable horizontal stabilizer, or elevator, for use on recovering from a bunt over/PIO/PPO situation. From what I've read, when you get into this situation you lose rotor control for your attitude, so since you're moving through the air anyway, why not have an elevator to assist you in getting into an attitude for the rotors to start picking up some air. It would not be used for normal flight, although I like Bob's idea of using it to help to PREVENT a PIO by maybe some sort of linkage to the stick ....
as the frame swings foward the elevator could be hooked up to point the nose down.... as the frame swings back the Elevator could be hooked to point the nose up.... in effect killing the swing ...

Although, since the airframe is just a pendalum hanging from the rotor, I guess there is a downside that you might fly your yourself into the rotor or chop your tail off.

I also thought of having a Benson type triangular "trapeze bar" connected to the hub that you could grab and fly with if you lose stick control, but that's another story.

devon532

05-29-2006, 04:49 AM

I guess this has been mentioned here already, but if anyone is wondering if someone has thought about their great idea before, the US Patent Office website has a search mode where you can look at any US patent since 1760. Just type in a few search words and any patents with that word in it will show up. If nothing else, it's kind of fun to look up stuff just for the heck of it. There is some really weird and unbelievable patents.

it's http://www.uspto.gov/patft/index.html

Have fun.

Oh, if you have trouble viewing the drawings, go to their HELP section's "How to access Patent full text images". You may have to download a small application, or, if you have it already (and it will tell you when you try to download it) click YES when it asks you to make it the default viewer for TIFF images, then you're set.

Victor Duarte

05-29-2006, 07:35 AM

Bob,
I will try to reply in a simple way about the elevator effect.
My thinking comes from reading how the early La Cierva were controlled : by stub wings , rudders and an elevator...

I thnink that an elevator may have some benefits for safety and efficiency , not for preventing PIO.

I think it would be more efficient :
An elevator would add a direct control on the frame and, doing so, less control on the rotor would be needed, less pitch, less drag, more efficiency.

I think it would be better to prevent Low G situations :
When you dive, the rotor flattens, the frame tends to go "trough" the rotor, THEN the frame follows, but you have lost rrpm.
With an elevator, the frame would dive first or WITH the rotor, loosing less RRPM.

I think it would not prevent PIO because PIO is a synchronized lag in stick imput making the frame oscillate, and you can do it with or without an elevator..

I may be wrong , then, knowledgable people, correct me , please.

In fact the elevator has been tested recently by a friend of mine :
He mounted a Gmeter , an accelerometer and a tach.
The elevator was not linked to the stick but was controlled separately, almost like the collective in a chopper.
The results are clear :
on a dive without the elevator effect : loss of 8 rrpm/min/sec , 1 G
with the elevator : + 12 rrpm/min/sec, 0.5 G

The test are not finished yet but i am starving to see what comes up.

Cheers

REDHORSE556CES

05-29-2006, 09:14 AM

in fact im going for an ultralight coax helico,

coaxial rotors? Wouldn't that call for contrarotating blades? Wouldn't that call for extremely rigid blades to prevent them from impacting each other if there was any significant blade flap?

Victor Duarte

05-29-2006, 12:06 PM

Charlie,
there are 2 solutions, one is extremely rigid blades, hard to achieve, experimented i think with the ABC helicopter.
The other is the existing one : flapping blades but with enough upper/lower rotors clearance (about 20-25% of the diameter).
coaxial rotors also mean less disk loading, less flapping.

cheers

J-SiN

05-29-2006, 02:11 PM

Interesting Gyro

http://img119.imageshack.us/img119/9287/untitled7ne1.jpg

Bob

05-30-2006, 12:05 AM

First let me say that you don't "RECOVER" from a bunt over.
they in one very fast move tumble the gyro foward and the rotor enevitally strikes the tail prop and if theres any rotor left the frame..... a PPO or bunt over is almost alwayse fatel to those unfortionate enough to experience one... However I read a posting where one fell'a almost had a PPO and lived to tell the tale..
that is the only person I know of that ever survived one.
the end results of a PPO or bunt over is ALWAYSE catastrophic
and the air frame (whats left of it after the rotor departs) falls to the ground so waiting to use a moveable HS or elevator to stop or recover from a bunt over won't work... in the 2 tents of a second it takes for a PPO to occur the opertunity is already past to recover from it . that is why You never level out or point down in a gyro at full power... some CTL gyros can do this without fear but with a HTL gyro its a deadly mistake. you might get away with doing it a few times but it will eventually get you.
PIO is a diferent story the way to recover from PIO (thats pilot induced Ossilation) is to power down... and haing on and hope and fight the urge to chase the rotor to stop the swinging
because if you try to stop the swing you will inevitally magnify
the swing due to the rotor lag....
I'm no expert and I just know what I've read but it seams to me an elevator hooked to the control rods just might help stablize the air frame and help prevent PIO...
....
Its important to know what causes PIO and PPO as they are the 2 major killers of gyro pilots....
.......

Its a very interesting idea you have there Zeeoo locking the rotor head ( front to back )and useing the elevator.
turning the rotor disk side to side tilting of the disk would still be needed to be sure , but doing that to an ultralight or conventional gyro could indeed solve some problems.
infact I think it would solve the PIO problem completely as when the air frame noses up the rotor would too , being fixed in its position from the start.... there for the rotor couldn't ever strike the tail ( except with serious Flapping)
.....however a few things would have to be changed i think to do this...the rotor would probly be fixed at about 6 degrees to the level ground. as you proceed down the run way you would fly the tail to get the ballance on the mains and lift off.
.....
its a good idea I'ed love to hear of anyone that has done this.
though you would destroy many of the great atributes that a gyro has by doing this and vurtually turn it into a fixed wing aircraft as far as take off's and landings go .... no more no roll landings I think ..or short take off's .. but you never know it still might be possable <grin> but perhaps the safty of the craft would be worth it ?
its hard to think of my gyro flying like a conventional fixed wing aircraft and ofcorse it never would because its A HTL machine.... but if there is a way to stop PIO it would certainly be worth it....

I understand PIO is PILOT induced ossilation so it would never STOP it completely because a Pilot is involved in the first place. normal FW aircraft ossilate up and down all the time
but I am concerned with the rotor comeing in contact with the dangleing frame.... with the frame swing wildly .... the frame couldn't swing wildly if it was fixed in place to the rotor.
there for that part of the problem would be eleminated wouldn't it ?

thanks for the ideas and info guys !
Bob.......

devon532

05-30-2006, 02:43 AM

I'm running out the door to work but I took a minute to read the last few posts about basically fixing the hub to the airframe and using the theoretical elevator on the airframe to pitch the rotor forward and backwards, and I wanted to get my thought out before I go.

When you try to tilt a gyroscope (or spinning rotor) forward, lets say, by tilting it forward, the result of that force actually shows up 90 degrees further around the disk in the direction of the disk's rotation (gyroscopic precession).

So, my thought is that if the hub is rigidly attached to the airframe, and you try to use the airframe to tilt the rotor forward, lets say, the resultant rotor force would actually be to bank to the left, and vice versa. The reason that when you pull the stick back and the rotor tilts back is NOT due to pitching the hub back directly, but rather that you are creating more lift on the advancing blade to your right, and that resultant force is being applied 90 degrees further forward in rotation, or directly in front of you, and THAT is what is pitching the rotor backwards, so I don't think that you the fixed hub idea will work.

Wish I had more time to clarify my thoughts, but have to run, but I hope you get the idea, and please correct me if I'm wrong.

devon532

05-30-2006, 02:50 AM

Correction on my last post, --- the gyro would bank TO THE RIGHT in the scenario I described above. By pulling the stick back with the fixed airframe/hub, you would be trying to force the front of the rotor disk UP , but that force would actually be pushing the rotor up 90 degrees to your LEFT, banking you to the right.

I should'nt try to post so early in the morning!!!

Victor Duarte

05-30-2006, 03:18 AM

Vince, Bob,
i never stated that the rotor should be fixed in pitch..no no... just a normal rotor. But i think the stick imput with an elevator should be less than without elevator.

Vince, i wonder if there is not something wrong inyour statement ..
if the rotor was fixed, your frame would just act like the gimbal .. or an overhead control..the rotor is still a teetering rotor, or am i wrong ? maybe you and i need some coffee :D

Bob

05-30-2006, 11:45 PM

well, the old timers that developed the first gyro's used the very same method I discribed if I'm not mistaken, and it worked for them
quite well, and I believe the little wing gyro still uses this same method front to back is fixed in place on the rotor head but the rotor head can move from side to side....
.... I know Zeeoo I was just takeing it a step further is all

the tetering rotor is there to alow the rotor to fly... it for all intents and purposes acts like a disk though the path the rotor tips carve are not a flat disk as you all already know.
with the gyroscopic forces on the rotor head the frame would see a ridgid disk in this case sense its fixed in place front to back, so the tennancy to DANGLE or swing wildly under the rotor wouldn't happen.... if i am not forgetting to consider something
... anyway.... its something to consider... might lead to a safer gyro , who knows !

Bob....

gyromike

05-31-2006, 03:15 AM

.... if i am not forgetting to consider something

Bob....

Only that gyroplanes are not pendulums.
They don't swing or dangle below the rotors like a bobweight on a stick.

Bob

05-31-2006, 11:55 PM

Hi Mike !
unfortionately in PIO siduations the do, that is how the rotor can come in contact with verious parts...
but thats my opinion <grin>
Bob......

C. Beaty

06-01-2006, 03:55 AM

Bob, if you decided to built yourself a swing, one way might be to use a length of rope tied to an oak tree limb with an old tire tied to the bottom. Then you would have both a swing and a pendulum.

If instead of an oak tree limb, you tied your rope to an overhead trolley with ball bearing wheels, you’d have neither a swing or a pendulum. In order to have either, you need a stationary attachment point for your rope.

A rotor isn’t a stationary attachment point.

Bob

06-02-2006, 08:10 AM

Duh state the obvious !
being trchnical on the words now are we ? then what do you call the action of a weight swinging beneth something that is moveing...a gyro ???????
its still a pendulum.... that hapens to be moving through space !
You know and I know that there are all kinds of forces effecting the frame of the conventional gyro copter one of those forces happens to be that the frame can and does swing back and forth under the rotor.... this doesn't happen much or often usually,
but some times when conditions are right it can be catastrophic.
Most of the time the Swinging motion is held in check by the thrust of the engine, the pilots hand on the stick , wind resistance on the frame and all that...
but make no mistake , what happens in a PIO siduation is the frame swings back and forth ... and can continue to do so , amplifying each stroke until the frame comes in contact with the rotor. its basic stuff... don't attribute it to some hocus pokis bull that is misterious... if you swing a weight on a string far enough it will hit the half way point... that half way point is into the rotors on a gyro .
...
ok I'll shuddup ! wasn't my intention to hijack this thred.
c ya !
Bob......

C. Beaty

06-02-2006, 08:41 AM

A rotor behaves more like a hockey puck on ice than like an oak tree, Bob.

In the sketch below, do you think you could get the cannon ball swinging like a pendulum in the plane of the sketch? Whether it was moving to the right or not?

There are other factors that give rise to oscillatory response but that’s not in the context under discussion here.

Vance

06-02-2006, 09:04 AM

Duh state the obvious !

its still a pendulum.... that hapens to be moving through space !
You know and I know that there are all kinds of forces effecting the frame of the conventional gyro copter one of those forces happens to be that the frame can and does swing back and forth under the rotor.... this doesn't happen much or often usually,
but some times when conditions are right it can be catastrophic.
Most of the time the Swinging motion is held in check by the thrust of the engine, the pilots hand on the stick , wind resistance on the frame and all that...
but make no mistake , what happens in a PIO siduation is the frame swings back and forth ... and can continue to do so , amplifying each stroke until the frame comes in contact with the rotor. its basic stuff... don't attribute it to some hocus pokis bull that is misterious... if you swing a weight on a string far enough it will hit the half way point... that half way point is into the rotors on a gyro .

Bob......

Hello Bob,

I am trying to understand your position.

If I took a pendulum from a clock and hurled it as far as I could would it still be a pendulum as it tumbled through the air?

At what point does that clocks pendulum stop swinging like a pendulum?

How does the ship turn upside down if it swinging under the rotor?

It is my understanding that all things in space rotate around the center of gravity. This seems in conflict with the picture I imagine as I read your words.

The spinning rotor seems to me to be particularly willing to diverge from a fixed attitude. I am not able to imagine swinging under it without accidentally telling it to diverge.

I am trying to understand your position, not change your mind, so please be gentle in your response.

Thank you, Vance

Al_Hammer

06-02-2006, 09:28 AM

the tetering rotor is there to alow the rotor to fly... it for all intents and purposes acts like a disk though the path the rotor tips carve are not a flat disk as you all already know.
That is a myth, Bob. The rotor tips move in a flat plane. Flapping does not move the tips up and down out of this plane- it tilts the plane relative to the plane of the rotor head. In other words, stick could be neutral, yet the rotor plane might be tilted back 2 degrees from level due to flapping.

with the gyroscopic forces on the rotor head the frame would see a ridgid disk in this case sense its fixed in place front to back, so the tennancy to DANGLE or swing wildly under the rotor wouldn't happen.... if i am not forgetting to consider something
... anyway.... its something to consider... might lead to a safer gyro , who knows !

Even if the head is rigidly attached to the body, the body is still dangling from the teeter bolt, isn't it? The disk does not appear rigid at all. Also, any force that tilts the body will also tilt the rotor because that is how the rotor is controlled- by tilting the rotor head, whether it is rigidly attached to something doesn't change this. control inputs don't tilt the rotor, they tilt the blades as you can see on the ground if you put the blades in the broadside position and move the stick fore-aft.
Having a rigid head merely simplifies the controls, since the elevator now does the work instead of the pitch gimbal. It loses effectiveness at slow speed when the stab stalls and that's the weakness of the idea.

its still a pendulum.... that hapens to be moving through space !

Yes and no is all I can say to that statement.
A pendulum obviously isn't a gyro. If you strap a Rotax to a 1000 lb bowling ball and hang it from a tree it can only swing, but never go anywhere.
At some angle the Rotax no longer has enough power to increase the swing angle against the force of gravity.

Hang the same contraption from a trolley and the thing will take off down the track when you add power and it will not swing except a very small amount.
The thrust is through the ball which is also the location of the CG.

The problem comes when you try to stop. The prop could be reversed, but that's not how you stop a gyro. We use the rotor. If you try to stop the trolley by putting the brakes on, the bowling ball will swing forward.

If you try to accelerate by driving the trolley, again, the ball will swing behind.

In this sense, the gyro acts as sort of a pendulum whenever the rotor movements get out of sync with the body.
The pilot has to be in the loop to do this and thats why its called PIO. Its a problem of overcontrolling.

Having a rigidly mounted head probably would reduce the lag factor due to the damping of the tail, so a tractor with elevator control is less PIO prone, I think, and you raised a good point.

Bob

06-02-2006, 12:13 PM

Humm ...
Ok Al I will conceed to your wisdome on the flapping blades...
thats not how I learned it but it seams to be exactly what you say it is , the tips move in the same plane .. I figured the faster you moved the rotor foward the bigger the seperation or Flap but I guess thats not the case. interesting !
Chuck: I could get the bolling ball swinging wildly in many ways... moving the trolly up and down would do for a start.
speeding up and slowing down would do for another...
...Perhaps I don't undersatnd the mechanics of the rotor system
as well as I thought I did !
.... So my question to you fellas is what then causes PIO if it isn't the frame under the rotor swinging wildly ?
PIO isn't alwayse caused by a Pilot chaseing the up and down movement...and therefore amplifing the movement , PIO can also be caused by turbulant winds....
... if that doesn't discribe a ball on a string going through space then what does ?

as Al stated its "Sort of a Pendulum when ever the rotor movement gets out of synk with the body" the human agravates the motion and amplifies it because his inputs are in sync with the swing ...
.... we know all that, and I would asume that a tractor gyro could get into a PIO siduation as well but you would probly have to work hard at it ! <GRIN>

where the Spinning gyro of the rotor imparts stability to the gyro frame is information i am missing because from all accounts
it looks as if the frame is just dangleing under the rotor and realy is just along for the ride.... the only stability that I can see that the rotor imparts to the frame is the upward lift
and the slower side to side drift . other than that its mostly gyrosopic forces at play of the weight under the rotor.
as a Pengulum.
Bob.......

Bob

06-02-2006, 06:22 PM

A friend of mine tells me that the little wing gyro has a fully articulated head just like most gyros and the elevator is fixed in place, so I stand corrected...
I do know that back way back when , there was a "little wing looking " type gyro that used the rotor only to tilt side to side and the rest was conventional airplane of the day ... it was quite interesting indeed. though Al's statement ofthe elevator stalling ( which makes perfect sense at low speeds)
sorta leaves the evelator idea out cold for conventional gyros
...Personally I'ed rather have the head moveable in all directions but it just might be a diferent way to apply what we know to our gyros and come up with something safer than the original ? stranger things have happened ! <GRIN>
Bob........

Al_Hammer

06-02-2006, 06:45 PM

If you want diferent, how about the idea of using a servo flap as invented by Charles Kaman.
Then, if it could be combined with modern electronic drive control you could eliminate virtually all the mechanical controls, or have a safety (and low speed) backup to existing controls, which could be of conventional or elevator type.

http://www.helis.com/howflies/servo.php

Hiller paddles could also do the same thing and they could similarly be controlled with electronic actuators. This is often done on RC gyro models, by the way. In some, they eliminate the teetering hinge and the rotor is only free to move about the "feathering" axis. The hiller paddles provide enough control and stability that flapping is not required.

Bob

06-03-2006, 01:38 AM

Vance:
No offence taken as you stated your understanding without name calling ! <GRIN> good man !
... You give a good example with the pengulum of the clock in free space... but don't forget that the frame is not "DISCONECTED" as it is attached to the lifting device ...the rotor.
sense it is, it will haing below the disk of the rotor ( obviously)
.... Now I know for the most part the frame of a gyro is constantly moveing under the rotor , by moveing it is Swinging sense it has a long moment arm of the mast to the COG... or as I call it Dangleing
under the rotor ... the frame moves when ever the input to the rotor changes or external forces act upon it like wind or thrust changes. in my mind the gyro is not solidly connected to the ROTOR
infact it is very Loosly connected, thats what gives it its menoverability. if the rotor was solidly affixed to the mast head as in a Helicopter its a entirely diferent story... but its not
where the helicopter changes the AOA of the individual blades to obtain directional control the gyro tilts the disk of the rotor... there is a big diference in the idea and outcome of doing it this way... though both have directional stability if all goes well.
that is why I am saying that the gyro is nothing but a weight dangleing from the rotor disk or a Pengulum under the rotor.
remember you fly the DISK and the frame follows ?
thats my point is all.
sense the gyro is nothing but a pengulum as I see it it explains PIO to a "T" and why it is so darn dangerous
combatting PIO is something I feel can be beaten and I am trying to think of ways to do just that ! ... if a Elevator added to a Gyro could accomplish this one task and stop all PIO incidents it would be worth it wouldn't it ?
I personally doubt that would happen , but its worth exploreing the idea as thinking is cheep ! at least in my world <GRIN>
...
Bob.......

P.s. INteresting Idea Al... a person could change the amount of lift from the rotors to sute the conditions ! no doubt a great asset.... somehow I can't imagen that set up on an Ultralight gyro but... it definately has possabilities !
.

Vance

06-03-2006, 04:47 AM

Hello Bob, Thank you for your patience.

It sounds to me like you are trying to take the Pilot out of the PIO.

I learned to fly a Helicopter in gusting winds in Augusta, Kansas. As I was learning to hover into the wind, the wind would hit the front of the helicopter and move me back, I would apply a little forward cyclic and would continue to move back. I would apply more forward cyclic and the helicopter would start to respond. I would apply still more and the helicopter would leap forward. I would apply rearward cyclic and the helicopter would continue to move forward, so I would apply more and still I had not arrested my forward speed, a little more an off to the rear I would go at some considerable velocity. The cycle would begin again, only with more helicopter displacement. Usually around the third complete cycle I would precede rearward with considerable velocity. I would reach translational lift and up I would go. The hanger was to the rear and I could not see it, so I found this intimidating. Fortunately my instructor was there to take control of the ship before I hit the hanger or the oscillation became unrecoverable. A Robinson 22 helicopters have a teeter rotor and also cut off their tails.

The point is, I was not operating at the control frequency of the helicopter, and because of this I induced an oscillation that I was not able to arrest. I had this epiphany, as I lay awake at 0400 hours after the second day of what I felt was abject failure. The next morning I was able to hover and I couldn’t understand how I had so much trouble.

In a gyroplane that is not pitch stable, an inexperienced pilot may get out of step with the aircraft. The oscillations become worse until it becomes a non-recoverable event. There are many unexpected things that can begin this process.

In most fixed wing aircraft there has been considerable effort expended to make it pitch stable so usually just letting go of the controls will restore stability, so a fixed wing pilot is particularly susceptible to PIO in a gyroplane.

It feels as though the helicopter or gyroplane is swinging under the rotor, but I believe it is just trying to rotate around its center of gravity and the rotor, like everything else is just along for the ride. If it was swinging under the rotor, than I believe that each swing would likely cause a control input to the rotor that would cause the rotor to diverge. I believe that the relation ship of the rotor to the pilot is the place that control commands start.

That is my understanding of PIO. The tools to make a gyroplane more pitch stable are well known. The main tool to make the pilot less PIO prone is practice.

I am not educated in aeronautical engineering; so all this is just my observation. I hope someone will correct me if these observations are flawed.

Thank you, Vance

gyromike

06-03-2006, 07:20 AM

.... Now I know for the most part the frame of a gyro is constantly moveing under the rotor , by moveing it is Swinging sense it has a long moment arm of the mast to the COG... or as I call it Dangleing
under the rotor ... the frame moves when ever the input to the rotor changes or external forces act upon it like wind or thrust changes. in my mind the gyro is not solidly connected to the ROTOR
infact it is very Loosly connected, thats what gives it its menoverability. if the rotor was solidly affixed to the mast head as in a Helicopter its a entirely diferent story... but its not

The gyro rotor is as solidly fixed to the frame as a helicopter's rotor. A 2-bladed teetering rotor system on a Robinson R22 is free to tilt left, right, fore, and aft just like our gyros. It will re-orient the frame in the same manner as our gyros.
A left cyclic input will cause the blades to fly to a new position, making the Rotor Thrust Vector pass to the right of the fuselage. This then pulls on the frame, rolling it to the left.

Thrust Vector Orientation.

where the helicopter changes the AOA of the individual blades to obtain directional control the gyro tilts the disk of the rotor... there is a big diference in the idea and outcome of doing it this way... though both have directional stability if all goes well.

Actually Bob,

It's the same for both the helicopter and the gyro.
When we tilit the head of our gyros, we apply a cyclic input to the blades (add pitch on one side, depitch on the other side), and the blades fly themselves to the commanded position. Same as a helicopter, except they use a swash plate and feathering hinges.

that is why I am saying that the gyro is nothing but a weight dangleing from the rotor disk or a Pengulum under the rotor.
remember you fly the DISK and the frame follows ?
thats my point is all.
sense the gyro is nothing but a pengulum as I see it it explains PIO to a "T" and why it is so darn dangerous

Bob,

As has been pointed out to you, the gyro is not a pendulum. You cannot have a pendulum when you have 500lbs. of gyro hanging from a 50 lb. set of rotors. The frame does not swing around beneath the rotors. You shouldn't even think of it that way. It's not a set of rotors and an airframe, it's a single unit moving through space.

The gyro will rotate about it's Center of Gravity, not around the teeter bolt or gimball assembly.

When a pitch input is made, say to climb, the rotors will fly to a new position, tilting the disk up. The RTV will pass ahead of the CG pulling the nose up as the gyro rotates around the CG. As this happens the RTV will move back closer to the CG (unless you're doing a loop). Because it has mass and inertia, the gyro will continue to rotate beyond the commanded input and the RTV will pass close to or even behind the CG, causing a nose-down pitching moment. This cycle will tend to repeat itself because of inertia. Once it starts to rotate it wants to continue until some other force stops it. Trying to damp out this pitching using the control stick is what can get people in trouble.

That's where the horizontal stabilizer comes in. It damps out uncommanded pitching, allowing the gyro to respond to the cyclic input the pilot commands, without lagging or overshooting the input.

combatting PIO is something I feel can be beaten and I am trying to think of ways to do just that ! ...
.

Already been done.
With a direct-control head like we use, a horizontal stabilizer will damp out the oscillations. No extra control surfaces are needed.

C. Beaty

06-03-2006, 07:58 AM

If our gyro “pendulum” really was a pendulum and the distance from teeter bolt to CG was 5 feet, it would complete a cycle in ~2.5 seconds.

A cycle would consist of swinging from center, left, back to center, right and back to center again in 2.5 seconds.

A grandfather’s clock has a 39” pendulum and is said to have a one second “beat.” A complete cycle requires 2 seconds.

Thank goodness it’s not a pendulum; no mortal could fly one.

Time for one cycle = 2 x pi x (L/g)^0.5

Vance

06-03-2006, 08:02 AM

I love it when you speak that way Chuck. I always feel less ignorant when the pain stops.

Thank you, Vance

C. Beaty

06-03-2006, 08:27 AM

The pain in your belly from laughing or the pain in your head from thinking?

Vance

06-03-2006, 08:29 AM

Thinking Chuck, I didn't know it was funny.

Thank you, Vance

C. Beaty

06-03-2006, 08:37 AM

It’s obvious some people don’t appreciate my humor.

Vance

06-03-2006, 08:48 AM

Sorry Chuck!

I appreciate your humor. I just don’t understand it.

I try to picture your examples and it makes my head hurt, I try to work your math and I am reminded of the tragedy of my education. This may be too intense an experience to include laughter.

I will try to recognize the levity in your posts and expand my appreciation of you intellect.

Thank you, Vance

Al_Hammer

06-03-2006, 09:29 AM

Just to jump in amidst the laughter guys...

A rotor which controls by tilting the thrust line away from the CG(vectored thrust) does not have the same response in roll and pitch as the stick in an airplane. The stick or yoke in an airplane usually conrols the rate of roll, or pitch, whereas the stick in the gyro alters the rate of acceleration. Because of damping, this is not strictly true, but there is enough of an effect to create problems for the pilot who is inexperienced.

The nose does not go up or down as fast as the pilot wants, at first, so she adds more stick. By this time the acceleration has allowed the velocity to increase and she gets overshoot.

Its a time lag problem, as it always is with PIO.

Adding a horizontal stab causes the nose to track into the relative wind and this has the effect of reducing the time lag between input and result. Pull the stick back and the rotor immediately changes the trajectory of the gyro upwards.

The airflow is now from above and the gyro weathervanes into the wind due to the tail, so the nose rises faster than it would without the stab.

You still might have a lateral PIO problem, even with a stab. Doug Riley said he encountered lateral PIO on one of his first flights, but it is much more common for students to have problems with pitch PIO.

The gyro rotates about its cg, of course, but the fact that the weight is hanging from the rotor does make a difference. While its not a pendulum and doesn't have the same period of swing, as Chuck says, its still the reason there is a lag in the first place.

The gyro is moving forward and pilot wants to slow down- the body swings forward(relative to the rotor)while it rotates about the cg and now gravity wants to make it hang straight beneath the rotor again.

The gyro moves about the cg and not the teeter bolt, but because the pilot responds based on perceived attitude and body motions, the result can look a lot like pendulum motion. Its the human in the loop again, not the physics of rotation that is the problem.

If the rotor were of the fully articulated , offset hinge type, the torque on the mast would cause an immediate response.

I am not sure, but my guess is that PIO is more of a problem in helicopter training when a teetering rotor is involved as compared to say a hughes 300, or Eurocopter.

Vance's description of lunging forward and backwards while trying to hold a hover is typical.

There's no doubt that Vance Breese's inherent motor skills are far sharper than mine, yet
I had only a single cycle of forward and back PIO on my first helicopter lesson.
I immediately recognized it due to my previous simulator training at home and was luckily able to get my timing in sync with the machine and damp out the PIO. Sometimes I think sim training ought to be required now that the sims are to the point of real usefullness.

gyromike

06-03-2006, 10:07 AM

To use one of Chuck's favorite words...
Much more succint than my explanation, Al.

Would you agree that part of the PIO problem in pitch is that the gyro has a greater mass moment of inertia in the longitudinal axis, than in the lateral?

As to PIO in helicopters, I recently got some stick time in an R22 and there is a noticable lag and overshoot in response to the control inputs vs. a Hughes 269. It took a few moments to get the feel of it.

Al_Hammer

06-03-2006, 10:12 AM

If succint means blithering on for half a page , than, ok, I guess it was.
I still can't bake 30 minute brownies in 20 minutes, though, Mike. :D

Thanks for your observations about the Hughes, which confirms my suspicions.

As for moment of inertia in the different axes, could be, but my guess is its more of human factors thing. Some people might just be more prone to lateral PIO.

gyromike

06-03-2006, 10:15 AM

I try to picture your examples and it makes my head hurt, I try to work your math and I am reminded of the tragedy of my education. This may be too intense an experience to include laughter.

Don't feel like the Lone Ranger, Vance.

I've felt that dull thumping in my skull on occasion, trying to keep up with Chuck, Al, Doug, et.al.

It is fun to do the experiments though, and see the results first hand.

I did the one experiment with a piece of broomstick hanging from a string to demonstrate thrustline offset vs. CG.
I must have pushed, poked, and sailed that broomstick around the hangar for an hour...
all the while hoping no one walked in on me!:)

gyromike

06-03-2006, 10:26 AM

If succint means blithering on for half a page , than, ok, I guess it was.

succinct \suhk-SINGKT\, adjective:
Characterized by compressed precise expression with no wasted words.

It would have taken me 3 pages and six hours to write what you did, Al.;)

Back to the helicopters,

Although the Robbie was a little more of a handful than the 269, it was not as squirrely as I had expected. I guess knowing ahead of time that there was going to be some lag in the controls helped me to deal with it better.

It was a lot more fun than I thought it would be.

Al_Hammer

06-03-2006, 11:39 AM

Mike, the famous R22 tri-hinge rotor head might make it feel different than some other teetering types. There is a delta-3 effect which reduces flapping and may speed up, or crispen the response.

When switching types, it can be a rude awakening as I discovered when a friend let me try out the controls of his R44.

Much bigger ship and I was not used to sitting in the left seat. The guy was evil and challenged me to try doing 360 deg. nose-in turns about a point while he and his wife sat back and laughed at my attempt.

This was an old model without hydraulic boost and it felt like a dump truck. His wife then told me that it took her hubby a year before he could do what he was asking me to do with less than 30 seconds of time in the ship.

brett s

06-03-2006, 01:05 PM

For a real eye-opener try a Hiller 12 - the first few minutes hovering felt like I was starting all over again.

Bob

06-04-2006, 09:46 PM

Al :
I have thought long and hard on Gyro Mikes comments concerning several factors.... lets see if I can word my thoughts correctly.and see if you agree.
One and the most important is a gyro does not and cannot rotate arround its COG.... I know lot of you think that is wrong but this is why I say that... the COG of a mass in space where no other effects are applied to the mass will indeed rotate upon that point of COG ... BUT we are not IN SPACE ! for that statement to be true the gyro would have to be in a vacume !
so we have the force of AIR reacting as a resistance to turning
on the rotor and air frame and there fore changes the point at which the aircraft rotates... it will be at some point but NEVER at the COG it simply cannot be ! with the rotor on such a long moment arm and the rotor pushing against so much volum of air it will likely be quite a ways from the COG ofcorse all the rest of the surface airea of the entire craft would be needed to take into account and all to be acurate on the turning points where abouts, but its obvious that it cannot be at the COG if you think your gyro alwayse turns on the COG just because your in the air you are mistaken thrust from the prop,lift from the rotor, force from the HS , drag on the frame and you ALL play their part in determining the where-abouts of the turning point.
...now... what diference does that observation make Not much right? for all intents and purposes it can be said to rotate somewhere arround the COG... Untill you start thinking about the odd setup of the gyro itself it is a disk with a weight tied by a string to the center in the crudest of illistrations.
turn the disk from horizonal and the weight stays where it was
obviously because it is a pengulum moveing the disk through the air does not change this fact, it only changes the outcome of how the pengulum swings and where
the Rotor Loosly coupled or not is the lifting device and directional control for the most part there are a dozen diferent rotor head types on many diferent craft but the idea is the same
its the primary lifting device of the gyro in this case.
if you denie that the frame of a gyro acts as a pengulum you hide its actual behaviour in gobblygoop ! when its plane to see to anyone that it dangles below the rotor in flight if this were not so incidents like PIO would not happen weather its a helicopter or a gyro its still acting like a swing object on a string.... by the observations of vance and others its still a pengulum because it acts as one ... not because I took the swing part out of the grandfather clock and tied it to the mast !
its its mechanical set up, it can be no other way !
now granted, you can haing a fixed wing by the prop and it will react like a pengulum as well but that is an odd case most of the time the fixed wing aircraft doesn't have this problem but the fusague is actually a pengulum under the wing , it doesn't revolve arround the COG eather contary to what you've been tought because there are forces acting on it such as air , thrust and drag as well, just like the gyro....
but we are getting away from the point , and the point was diferent things to try on a gyro, and would they work or not.
I don't know weather an elevator on a gyro would be a good thing or not, but I suspect so. as someone pointed out controling a gyro by the HS and elevator alone for pitch control might be a bit hadzardous if the speed is slow and the elevator stalls and a loss of control results . so if this method was used I amagon that a larger than usual HS and elevator would be needed, because that is a very good point !
as usual I seam to see things diferently than most which can be good or bad, depending on your outlook.
it is in my mind Dangerous to think of a gyro as one unit and not think of the individual parts that make up the whole craft
but each to their own. if you think of a gyro as one unit you could easily get into a PIO siduation... if you think of the gyro as a pengulum your less likely to have that problem.
for what its worth .
Bob.........

Al_Hammer

06-04-2006, 11:26 PM

Bob, I can only point out that the various forces acting on a mass can be on long or short moment arms and all you have to do is add up all the forces and moment arms and this will give you a single moment of force about the CG. This has been well proven and you just need to pop open any book on mechanics or google on the subject to see for yourself.

To get back to the pendulum business, The gyro and rotor are part of one larger mass and they always rotate together about the cg.

However, the rotor can also move within that system because its on a hinge and so it adds a bit of complication to our nice model.

You can get the rotor moving out of phase with the body and this is what happens in PIO. The body is not a pendulum, but when the rotor is moving one way and the body is moving the other way it gives the appearance that the body is swinging from a point like a yo-yo when you walk the dog or whatever that trick is.
The yo-yo does swing like a pendulum under your hand and the difference is that you are anchored to the ground.
If the yo-yo was lifted by a kite, the system would rotate about its cg, somewere bertween the yo-yo and the kite wing. Just like a gyro.

The advantage of a tail is that it keeps the body tracking into the wind and this reduces any tendency for the rotor and body to be out of phase. More effective on a tractor because of the long moment arm.

I did say that the gyro can be sort of a pendulum, and I only meant that you can get the rotor tilting one way and the body swinging the other way- only, once again let me repeat that it isn't ever swinging from the teeter- its just out of phase and the mechanics is different than a pendulum as Chuck pointed out. The period is not calculated the same way , etc.