design of rotor head

[Vance]

Victor, It is easy to imagine that something that is more complex is better, or new is better. This is not always so. Sometimes design inspiration can come from finding a turning point in the past and taking the other path. Questions about why they took the path they did helps to fan the imagination. Aplication of new materials, proceses or tools may revive a dead Idea.

Back to the question, what about a swash plate do you think is better? Thank You, Vance

[Victor Duarte]

vance, i agree, sometimes, the phoenix can revive..

well, vance, as a helicopter wanabee, i began by reading books about how it works, letting aside some complicated equations to catch the essentials...

and if i admit the bensen's design is the one, i just burn the books... so finally dr bensen had a brilliant idea i making "flyable" somethink unperfect.. thats what makes the interest of gyros..
the bensen is a good balance between easy feasability and flyability.

why a swashplate ? ok, let's assume a swplate as a mean to control the disk, so, even bensens have one, i may confuse with "cyclic"
swplate is just a mean to control the disk plan by a "perfect" mean , a pure gimbal, all controls always in-plane. that s academic.

basic advantages i think about : ability to control more than 2 blades, no trimm spring, but ok no feedback, an advantage is also quite no feedback, possibnility to control collective pitch for "hoppers" or in-flight pitch adjustment for heavy loads or performances adjustment..

15 years ago you should have asked.. why an injection system on motos ? it s expensive etc , but now... it s commonly spread..

that s more the way i think , tyres are suitable for a large range of vehicules.. i just think a device like a cyclic/collective/rotor should become a part in gyros, it is yet, you can change blades, hub etc..

i just think the design can really be "actualized" with modern means.. tyres swinged to tubeless...

ok i agree that for very light gyros, the swap is not clearly defendable.

but seeing the need for heavier machines, x country capabilities, or just a comfortable 2 seat aircraft, i think the rotor shoul be most like a r22 or r44 one, why not a mini 500 the rotor is simple.

personally i vote for a 3 bladed...

it s not a matter of revolution, just a matter to take the progresses made in rotors and blades.
talking technically, some examples :

- the blade root, according to your important skills, you should agree that a progressive root is a must - be
- blade tips . it s not that difficult to mold ! and we know the gain in efficiency, noise reduction, i have a doc about BERP blades and some blade tips... if you want i ll make them available.
- if you observe the mini-500 or CH7 in-masts controls, they are simple, i mean as simple as "high-end" classical gyro rotor-heads , i ll post a drawing
- having a mast can allow a powerful pre rotator.. i m not convinced it s a definitive argument...but

at the risk to be shot in flames... i d say roughly the current rotorheads could be compared to a modernized Ford-T...
hey readers and builders, in dont insult you, i just push it a little far.

and as i said gyros share the essential with helicos..excepted the rotor head..

thank you for opening the thread vance

[Victor Duarte]

vance, tell me if i write too much please ;) please feel free to do so, i m pleased

Doug, with your mermission i hope... :
When shopping among the homebuilt gyro designs, the burden is on the shopper (you 'n' me) to inquire what kind of formal engineering review a design has received. Chances are it's ZERO, but there is the occasional exception. If the seller claims to have "engineered" the design himself, ask him where he got his degree. "I have 3000 hours flyin'" is not an engineering qualification. Neither is "school o' hard knocks." This is serious stuff and deserves a serious answer. That seller wants YOU to bet YOUR life on HIS work. It damn well better NOT be guesswork.

thats it ! a lot of designe come from empiric experiments works/fails/works/fails a kind of dichotomy (correct?)

for example the french Xavier AVERSO, now known as THE personality in gyro began to build handmade blades in his personnal workshop.. now he sells blades (i dont like them, but) and is seen as a semi-living god.. ok he s good and has a lot of experience, fortunately...

but look at the pics and tell me your opinion, mine is that this complication is worth to be replaced by an helicopter rotor..
look at the blade root .. i really dont trust that, look at the blade tip... is red paint better for vortexes ? :D look at the rotorhead, a bell UH1 is simpler

thanks

[mceagle]

- if you observe the mini-500 or CH7 in-masts controls, they are simple,

G'day Victor,
As simple as these heads appear to be, they are nowhere near as simple as the offset gimbal head that we currently use, and they only do exactly the same job.
There is further considerable complication at the base of the m-500 and ch7 heads in the mixer controls that actuate the push pull controls up the centre of the mast. Comparatively simple for a helicopter but complicated by Gyroplane standards.

[Vance]

Victor, I feel you are talking about two different things. First is a swash plate controlled rotor as oposed to a tilting rotor head. The swash plate controlled rotor requires pitch adjustment to make it work. This requires the blade grips to have berings so they can rotate and a control system to make them rotate at the correct time. This also puts an interesting twist into the blades twice per revolotion. The tilting rotorhead allows the same action with a simple hub bar. For me the down side of the simple hub bar is that it makes a good pre rotation dificult because you can't flat pitch the blades. I should caution you about embracing the Mini 500 as it's design killed a number of pilots. I agree that it has a good rotor head and swash plate and I would like to see a brakedown drawing of it.

The second thing is lead lag hinges to allow for more that two blades. In my opinion this is a completly different set of requirements. A three blade rotor has a three per rev shake and like most pertibations it decreases the amplitude as it increases the frequency. The response to the disturbance is what says one is better and this has to do with the natural resonance of things. Reducing the weight of the aircraft also reduces the amplitude. One of the down sides to lead lag hinges is the need to keep them from getting out of phase. This is generaly done with some kind of damper which adds to the parts count. The suspension also becomes important to not upset the rotor into ground resonance. Ground resonance can destroy an aircraft in seconds.

I have been interested in helicopter maintinance books as they detail the very high parts count and high maintinance requirements. My limited research leads me to beleive that operating a helicopter is about five times the cost of operating an Autogiro. I also find Autogyros more relaxing to fly because they don't require as much from the pilot if something happens to the engine. The first time my instructor shut off the engine when we were on the down wind leg in an Autogyro it was comic releif compared to doing the same thing in a helicopter. Autogyros are also a little like racing at Bonniville, there is no money in it so there is still lots of room for better ideas. The no money thing also changes the order of the design priorities and once again this opens the door to creative thought and doing it for the love of it and not taking failure to seriously. The no money thing reduces the price to play the game of inovation. Thank You, Vance

[Victor Duarte]

g'day Tim (night here :D)

yes, youre right the offset gimbal do (quite) the same job, no doubt..

ok let's separate the points of improvement, forget the in-mast cyclic, and just keep the hub and blades, that will be a first step as the CH7 (mini 500 ?) were made under much more constraints than the most serious homebuilt gyro... i m not so wrong i guess..

i had the occasion to exemine closely a CH7 ( and get my back in, but not fly it :()
it s feasable. believe me, i ll post a drawing... just let mme work it out..

what i wanna tell, is.. when the simple offset gimbal is getting over-engineered, isnt it worth going to a full cyclic ? avoiding some minor problems due to the bensen design ?
instead of eternally patching something, isnt it worth bying a brand new ?

i think if a pair of manufacturers make available a nex rotor, the other ones will follow, market rules, you must offer much for less everytime, or, better for the same price..

see the GPS, wow, before it was a "star wars" device , one garmin began to offer smaller and cheaper, now you can have it in your pocket and every sports shop..even in a watch !

someone must dare the deal
bensen design was ok for when you had a hansaw and a wrench to build, butyt now who build its own head ? quite no one, manufacturers sell them complete..

thank you tim for participating (c'mon guys let's bash , that will be positive :D)

[Victor Duarte]

accurate , vance

about the need of pitch adjustment, right, i think in it, with NO bearing... damn i must post a drawing...

right, with 3 blades we go for something very different, absolutely agreed..
Dave jackson, here (rotor-rooter) posted a new idea with no need for lead lag damping...i wait for more..., but like the bensen design works with a "tolerance", a small rotor also can "forgive" some effects you must deal with in big choppers (but not ground resonnance, ok)

if only dick degraw could speak of gyrhino here, perhaps i will definitely give it up..

your feeling of gyro "relaxig" make me wonder..positively

about costs, yes choppers are expensive because built under very tight conditions and aproved for flight under heavy conditions... gyros are at the frontier between ultraligh planes and ultralight choppers, i guess if ultrallight choppers could be included in the same category ..the costs should decrease... in a gyro you can "stretch" some maintenance operations such as changing spark plugs..in an helico (almost in france) you must fill the handbook with the part number and show it to the aviation regulators to have the autorisation to fly... not in gyros..

i ve been warned about mini 500 i prefer the italian CH7 or Dragonfly (certified)

vance you re the one person here having a talent to make me re-examine closely my convictions.. positive..

[Vance]

Thank You Victor, I take that as a hi complement. I would like you to understand that I am on a fairly low level in understanding rotorcraft. I do know something about design and fabrication. We need to look elsewhere on the forum for people who understand things on a higher level. I have seen Dick's rotorhead and I don't begain to understand it. I have seen it work and it is wonderfull. Thank you, Vance

[Victor Duarte]

vance i would love to see here high skilled aero people taking part to a kind of goal..i try to launch the spark..maybe i (we) ll get some reaction, i would be glad to shut up and learn, learn, just drinking words from real designers..
i think i have not a better knowledge than yours... but a common point we dont give up in front of unknown, thats a good point...

thank you vance, have a good beer or coffee or tea.. my baby needs milk ;)

ps : skilled readers and gods of design, help me to shut up ;)

[quadrirotor]

The Bell concept incorporated an universal joint which released the stress at the root of the blades, and a bar to stabilize the rotor. This concept was reproduced by the Baby Bell (photo underneath) without the stabilising bar. To use this universal joint, you need the swash plate to have the same AOA of the blades as the rotor tilts back and forth (this is a double tilting rotor!) and above all to have a control on the cyclic (and collective by the way). To have the same effect with a Bensen concept, you must have a very flexible mast which keep the same AOA of the blade (as i said in a previous post: the cinematics of the RAF mast is questionable...) the Bensen concept does not need a swash plate, the cyclic is possible due to the precession effect on the rotor disk as we change the angle of the tilting axle ...but for heavy rotor, inertia and flexibility (of all the componants) come into account, so things become more complex...The concept of Sport Copter for heavy rotor, seems efficient.

[Victor Duarte]

yes andre, looks like a built in d3 angle, like on tail rotors.

to have the d3 effect with a bensen design you need a blade pitch axis, linked to the hub and, yes a flexible hub bar, so, as the blade rises too much, the d3 effecty decreases pitch and takes the blade down in the ideal disc.

thanks for participating.

ps : as you re my "official source of rare and unseen stuff" ;) have you something about composite hubs please?

EDIT : you didnt post the pic so i didnt see it...DAMN i really have to draw what i think about...will be easier to tell
i prefer the bell 206 blade grips

[skyguynca]

ON another thread someone posted a picture of Bensen's Little Zipster, a coaxial machine, I have the technical drawings and assembly manual for it. IT had B8 blades, teetering head and a D3 angle of 15 degrees. Pretty neat design so that as the one blade dipped the D3 angle helped correct the flight path so the one rotor system never came into contact with the other even though there are so close together.

[quadrirotor]

two of my favorite rotor heads!
The rotor head of "EL TIGRE" (the best of all for homebuilding)...and the Starflex, both from Eurocopter (the best in the world!!!!) :)

[Victor Duarte]

OI have the technical drawings and assembly manual for it.
hi david, i saw this thread, pretty neat.
do you mind posting some details of what you talk about please ?
thank you

[Victor Duarte]

Andre, i was shure you got something !
but the two last pics are ecureil and dauphin whitch have not a composite hub, but metal alloy, i m shure of that, concerning the tiger, are the x plates made of composites ?

you gona laugh or think i m pretentious, but it looks like the FIRST drawing of a rotor i made 10 years ago, i thought in using spherical bearings to endorse pitch and flap, but after verification, the market parts cant bear such axial efforts (the ball plops out) and the degree of pitch was unsufficient (6 degrees each side)... but THEY are eurocopter, not me, alas..

thanks for you docs andre

[quadrirotor]

Victor, I don't know what the TIGER X are made of, even those photos are difficult to get... But you can make them of what you want if the stress and strain pass...You can consider "forged composite" if you have the expertise to make it...For homebuilding, i prefer metal you can cut and fit at home without complex tools...
For the Starflex, i always thought the flexing Star was made of forged composite...

[Victor Duarte]

andre, you were right and i was wrong, apologizes, the ecureuil hub is made of composites (you can see a broken one here)
http://www.bea-fr.org/docspa/1999/f-gu991215/htm/f-gu991215.htm
i was shure it was made of metal... :eek: silly me i didnt even verify it...
For homebuilding, i prefer metal you can cut and fit at home without complex tools...
not to upset you andre, but ok for tubes and plates, more complex parts at home...mmm you must have a very goood tooling indeeed :D and it s easier to repair a composite hull than a alu one ( i dont talk about critical parts, ok ok) but even on a composite blade you can repair a small impact, but on an extruded alu one ? > dish, on a riveted one ? > special workshop unless you have the skills to do that, i dont.

simple composites now come to the homebuilders... forged composites ? i dont know what it is.. info?

look at the site of the father of magi gyros (dont remenber his name), he just explains how to mold a prop...

but even with metal we can do better.. the advantages of composites being their fatigue features.. the disadvantage is the need of a mold and a precise process for setting up the fibers, impregnation and curing...
my sisters's BF is dental prothesist, he knows a lot about composites and resins, molding, but, alas at a small scale, but he found me some products i didnt even know they existed like an epoxide resin powder that can just be mixed and hardened with water ! did you know?

(for info check this, a new helicopter manufacturer .. http://www.helips.com/CV_rmouille.htm one of the fathers of ecureuil)

thank you

[quadrirotor]

Forged composite is composite formed and cured at high pressure and temp, in a very solid mold!(see the propeller hub underneath). If you don't know what's forged composite, may be you have to stop to play video game and go to school if you want to make an helico from scratch!... :rolleyes:
You can't design and built an helico with a chain saw and pomading every one on this forum!... :p
Many times, i had the feeling to waste my time reading...french diplomacy!!! :D
I don't say that to offend you, but to help you! ;)

"Truth must be told to make things go in the right direction!..." (both J.F.K...;Kennedy and Kerry)

http://www.duc-helices.com/technique/moyeux.htm

[Vance]

Well, so much for Autogyros. Victor, they have made my point, high parts count and complex machining. As an old person, I find elegance in simplicity. It is not hard to move quickly out of affordabilty and that means low production. With the NC equipment we have today it is possible to make wonderfull low production parts and that opens the door to new complex designs but to be a comercial success low parts count and simplicity have value.

I have flown Autogyros that didn't shake, handled well and didn't have maintinance challanges. Always they were more relaxing to fly at low altitudes than any Helicopter I have flown. Everyone I know with a kit helicopter spends at least three hours maintenance for each hour of flight. It may be their personality rather than the design of their aircraft. Thank you, Vance

[Victor Duarte]

well andre, your thoughts have to come out,
sorry but "forged" was a term i didnt know, i know forged notes only, ok next time i l perform a search on google, just to not to tell i dont know something...
well what must i do? stop ? stop trying to be "pleasent" to the people i talk with ?
must i be agressive to be considered ? for what ? i act with others just like i like the others to act with me..
must i definitely shut up and let true designers talk ? ok i ll let engineers together and go back to my toys... you re probably right... but learning technical terms and concepts in english in not really easy...
but come in, true designers !!!!, where are you ? anyone ? ohhh i see ... too busy to hide you "little secrets" or too hight to hear a voice coming from down...

but instead of waiting the occasion to bash, if you know better than me, just tell it, i ask for more knowledge, and i claim it evetime before asking something, im not comparing myself with some genius but one day some men said, we "could fly" and often the good academical engineers said "you re crazy", didnt reynolds said a bumble bee could not fly according to his calculus? maybe my way to write looks "pedant" sorry, try to learn french and i will se how you express yourselves..

must i get on my knees and ask pardon to be missing knowledge? and consider me as trash ? sorry if i am able to recognize my lack and faults, i m not a dumb for shure and wont lay down.. were all the aircrafts built by engineers? was hiller an eng ? Wright Brothers maybe ? Paul Cornu ? a bycicle maker .. averso ? Farman ? Voisin ? Henri MIGNET? i m not comparing to them but some forget that sometime the invention came from enthusiast amateurs... as you say Reflection matter Only!.

ok andre, show me your ideas, let s discuss about that, if we think "all has been done" , what to do ?

all you can blame me for is excess of enthusiasm and will ...
upset ? yes, i just try to bring up something and dont want to be a target for well-intentionned people... for info, designing videogames is NOT playing, you could be surprise by the amount of top-knowledge needed (neuronal networks, multi-agent programming, serializing, AI, dynamics simulations, light shading, BSP, IK, cognitive algorythms, genetic algorythms, motion tracking, plants generators, terrain generators, erosion simulation, human anatomy... ) want some more "wow ! words" ?

sorry if in get a little rough , let me take this out also

thank you

sorry guys, translate it to english, it was said in french..
'' Comme tous les novices, nous débutâmes avec l'hélicoptère mais nous vîmes qu'il n'y avait pas d'avenir et nous l'abandonnâmes. L'hélicoptère effectue à grand-peine, uniquement ce que le ballon fait sans labeur et n'est pas mieux doué que le ballon pour le vol horizontal rapide. Si son moteur s'arrête, il doit tomber avec une violence mortelle puisqu'il ne peut flotter comme le ballon ou planer comme l'aéroplane. L'hélicoptère est plus facile à concevoir que l'avion mais une fois réalisé, il ne vaut rien. ''
WILBUR WRIGHT

[Victor Duarte]

vance, i just see your reply.. yes gyros and helicos are 2 separate way to fly, i also like simplicity.. my will for design is dicated by my poor financial means...

ok, lets say if i ould fly by any means, i d go for a bee or a french guepard, perhaps my goal is to have something i designed and made working, whitch is another different goal...

ok, let me calm dow, (sorry guys, i learned a bad new BTW) excuse my "heat" andre
i didnt have time to do the right drawings but look at this..

count the parts : 10,
and its not finished ok, it misses bolts and about 3 parts, some washers, some bushings....

an its ok for tip jet, full cyclic control

you can easily get some parts for a fixed-pitch 2 bladed rotor, changing the hub, you dont want an articulation ? ok you just need a strong bolt forget about the ball, you want an on-ground adjustable pitch ? keep it...

i think there's something good to take from this...

thank you

[Vance]

Victor, I have found that short people try to make themselves taller by trying to make others shorter. It doesn't work,but it makes my ankles hurt. I hope my meaning doesn't get lost in the translation.

My 2002 book "Advanced Composits by Cindy Foreman" calls what Andre describes "compression molding." I guess she should find something else to do with her time.

I don't see the pitch horns and it is not easy to make the blade attachment part of the blade. I would love to have your skill with computers, but they make my head hurt. I find great pleasure in allowing the metal to become what it wants to become and the feel of it is important to me. Thank You, Vance

[Victor Duarte]

just a funny design after some brainteasing..

if a sphere is defined by at least 4 points in space, theorically you only need 4 points of contact to make a rotula...
so, theorically, you dont need a heavy spherical bearing but just 4 good lubrificated pads..... want to power it ? add 4 sheet of flexing steel ..interesting no ?

[Victor Duarte]

vance, i m ok with drawings, since the beginindg i need an "orthodox" analisis of my propositions... if i didnt need i wouldnt be here and have the pleasure of shouting after andre :D , sorry andre again, i know you wanted to shake me positively and i just wanted to explode a little, but you still my favorite "rare stuff" provider ;)

there's no pitch horn yet, jus because i didnt do it yet, i wait to have my swplate dimensions ok to do it..
how i d love to have a workshop with modern tooling and break some parts ;)

thanks

here is a cross section of my assembly

[Vance]

Victor, I think it is beauitiful. It would be nice to have a dimension or two to get a better feel for the size of it. How much air are you moving and how did you make the first turn? How much air presure? Thank you, Vance

[Victor Duarte]

how did you make the first turn?
vance, sorry i dont get the sense of the question, "moi frenchie" ;)

i forgot : it could fit a 2 bladed rotor, my drawing has 3 but yoy can easily see it in a 2 blades teetering hub;

an idea of dimensions, ok sorry i have them in mind...

the ball is 3 cm diam
the 3 lamina plate 3 cm thick
the height of the blade root is about 12 cm but should change once i will design the metal inclusions in composites for the big bolt..
the blade chord goes from 18 cm to 16 so the blade root "cylinder" wher the big bolt goes is about 7 cm diam..

i must add i think in "quick bolts" to remove blades easily (i asked here if this stuff exists but no answer), so as you can see even with a 3 bladed rotor, removing the blades will be easy (without loosing pitch adjustments)...
at first sight it looks like an amateur idea, but i tried to combine everything to bring advantages...

about the air flow.. it comes from the hollow mast, shared to the 3 blades, i tried to keep te path almost equivalent to a 4cm diam section hose
nb (two lateral ducts will be built in the black rubber part you see, pathing through 2 reinforced air tubes..

ideally i d need 2 bars and about 8-10 m3/ second.. reachable with 2 ROTREX superchargers www.rotrex.com model c15 or just one bigger (to be confirmed, i asked them the power needed to procuce a such air flow with their products, i have no answer yet, i have not their e-mail, so, i tried an all purpose e-mail)

note that a simple turbocharger could be enough for a tip jet pre rotation, or vhy not an in-flight extra power... BTW a supercharger can also e used to gain engine perfs at high altitude, but this is your part, you know it better than me (once someone understood desmodromic distribution, he has a good piece of fine knowledge ;) )

thanks

[Vance]

I feel that tip jets are the best way to reduce the complexity of a Helicopter drive system next to an Autogyro. My opinion has not been born out by the market place. Much of a helicopter pre flight is spent checking the drive system. The tail rotor drive is very complex with bearings and flex joints and gear boxes. The clutch is problematic on many helicopters and the main drive is both heavy and complex. The gearboxes have chip detectors but they still need to be inspected regularly and the fluid levels checked. It would be great to just leave all that stuff on the ground and tip jets are one way to do that. Hiller did some very neat stuff with ram jets to build the everyman helicopter and the French Dijin worked fairly well. Both had a consumption challange. It is not easy to move energy around efficently. The air powering the rotor on an Autogyro is not very efficent.

I never did understand exactly how to calculate thrust but your flow seems a little low to me. How many pounds of thrust are you trying to get? I feel that people don't generally take into account that the rotor acts like a big annular discharge compressor and I suspect that there is value in the centripital force. Thank you, Vance.

[Victor Duarte]

vance you just think like me on this point, getting all the costy stuff off is maybe worth re-exploring the tip-jet, you told about the need for coming back sometimes ;) here we go !

yes consumption is one of the two bad points of tip jets..the other being noise, but i still thinking some ways have to be brought back...(new nozzles, new materials, flow quieteners... well enough work AFTER the rotor flies)

the helicopter is one seat (sea pic below) a central simple 4130 or 25CD4S frame drown in the composite structure..

this structure is NOT molded but an assembly of only flat panels and rounded chamfers
these parts are made of common blue foam between 2 roving skins.... they are molded on the soil by external faces (on an alu sheet with appropriate shape or bending for example) to avoid extra resin and
polishing, ready to paint... the bottom of the fuselage is flat, these pannels are assembled on a wood shape-frame around the central frame , grooves will be done to bind and drown the frame, then bounded between them by a groove parallel to the surface, linked by a ready made epoxy+roving tape and an exterior roving tape to link the exterior borders interior also (perhaps some finition needed on external joint)

the engine is on the rear up of the central frame mounted on dampers..

the mast is mounted on a welded steel pyramidal pylon mounted on the basic frame by 4 crossed dampers focused to the top of the mast (like in some lycoming engines mounts)

the cap will be made of a foam block with a light roving skin, the near air intakes may serve for comp air, carburation, the back of the cap is hollow maybe for oil cooler and exhaust, depends on engine..

fuel tank and controls links are in the central room, under the CoG, there are 2 cloisons made of these same panels in front and hebind the pilot, the seat being made the same way.
a tunnel runs on the floor from the front to the rear, for controls and electrical (and it hardens the structure...

laterally, 4 holes with a screw will allow the mount of extra tanks or any kind of stuff (camera etc bombs ? ;))

ok the rotor i planned is about 6m diam, a little large for a light heli but enough close to gyro specs,

i evaluated the mass bill to (empty) 160 kgs, a rough evaluation , it may be a little more depends on engine, turbos, wheels or skids also..

about the air needs i interpolated it from the djinn, ok i take your remark as a must-do-that... to be confirmed or precised

my thought was : a little crazy, : if the tip jet doesnt work, just keep the roto, the engine and add two aside lateral props (as shown in a thread here)..yeah i m scared to loose my work, so, i think every part to be re-usable..in case of...

other thing, i will use a sweptback blade tip and a little neg diedral to gain a little efficiency (BERP tips allow 6% of gain... i need data but blackout about it)

well i m glad to give an overview of what i ve been thinking aboust a few time...

thanks

[Vance]

One way that I can tell if a project is going to be special is how much stuff I throw away. For me, the answers emerge as I am building and I need to be ready to scrap what I just made. My friends have seen me saw things up that were nearly done in order to make something better. I believe that saving your airframe has merit.

I wonder why you question yourself. Perhaps the first will work. An Airframe to support a drive system has to be much stronger than something with tip jets. That actualy reads heaver. If you are going to use an ineficent drive system (tip jets) you should do everything you can to take atvantage of the bennifits of the design (less weight) there by mitigating the down side (inefficent).

Hiller used a tilting rudder at about 45 degrees to control yaw and he told me it was fine. The only reason the military version had a tail rotor is because that is what the customer asked for. Thank You, Vance

P.S. I have to take my wife to the hospital in Los Angles now, so I will be gone for a couple of days.

[Victor Duarte]

vance, to be continued with pleasure,
i hope nothing serious for your wife, whish you good health..and be careful
i whish to read you later with a smile
cheers

[pwendell]

sorry guys, translate it to english, it was said in french..
'' Comme tous les novices, nous débutâmes avec l'hélicoptère mais nous vîmes qu'il n'y avait pas d'avenir et nous l'abandonnâmes. L'hélicoptère effectue à grand-peine, uniquement ce que le ballon fait sans labeur et n'est pas mieux doué que le ballon pour le vol horizontal rapide. Si son moteur s'arrête, il doit tomber avec une violence mortelle puisqu'il ne peut flotter comme le ballon ou planer comme l'aéroplane. L'hélicoptère est plus facile à concevoir que l'avion mais une fois réalisé, il ne vaut rien. ''
WILBUR WRIGHT

I'll have a go:

"Like all novices, we started with the Helicopter, but we saw that it had no future and abandoned it. The Helicopter achieves with great effort just what a ballon does effortlessly, and is no better than a ballon at high speed horizontal flight. If it's motor fails, it falls from the sky with deadly violence since it is unable to float like a ballon or glide like an airplane. The Helicopter is easier to conceive than the airplane, but, one conceived, it is worthless."

Wilbur Wright

[Victor Duarte]

Not bad Peter ;)
what to take from that ? personnally, i keep that every firm statement can be true/false depending on the context/time.
and i wanted to quote two famous american amateurs who had a tight story with france...and just dared..
thanks !

[Victor Duarte]

i ve read videogames is fun!!!
ok... making them is NOT PLAYING, is not that easy.. and may give real headaches..
just a sample of the main software i use : 3dsmax (i dont even show third part sofrtwares and middlewares !!!)

what you can see is the workspace and, under, a VERY VERY small SAMPLE of the kind of parameters i handle...

i d say the soft has about 20 or 40 times these parameters... solidworks, compared to this is a baby toy...

so, making a video game, even a little one, needs amost 1000 or 1500 this complexity..

just in case of some think i cant understand more than a,b,c ;) or think that videogame is making "fancy", we sweat to bring you some fancy..

[Cobra Doc]

The AH-1 Cobra has the most elegant two-blade head of any helicopter. It also has a stability augmentation system. Since gyros fly by drag-induced-lift, I don't think messing around with blade angle is a good idea. Blade stall is an ugly concept. A Gyro isn't a helicopter. A helicopter in autogyro mode is a lot work very suddenly. What a gryrocraft pilots does with out effort on every landing can cause a helicopter pilot to lose 5 pounds and most of his (remaining) sanity. ;)

[Victor Duarte]

i love the cobra, it inspired me a lot and the super cobra also
but if i m not wrong the first ah1 came from a fitting of the uh1 for viet nam isnt it?

well a 2 bladed bensen rotor is fine for light gyros... ( if a ful options RAF can be called "light"), but for heavier machines or combined ?

doc, yes, i target a small chopper, not a gyro yet, i just throw "why cant gyros benefit from recent technology improvements ?.."

ok a chopper is not intended to fly like a gyro and autorot is an emergency procedure, i didnt perform one by myself but was in 4 , made by my "trainer", yes impressive the first time, and the end is critical..

this thread was more created after the "RAF bub cracks" thread, to have some propositions, but i m the one (mad enough) to make some...

anyway, thanks for your opinion,
look under, dont you see i LOVE cobras ;)
cheers

[Cobra Doc]

My beloved "Snake" never had the Huey's fly-bar. The prototype did, but it was abandoned in favor of the SCAS, resulting in the very clean but not quite simple head/grip design.

[Victor Duarte]

allright, i meant it was derived from a huey, but they kept the blades no ? the "clapping" blades ;)
yes the design is clean, you really cant imagine that for a heavy or light gyro ?
there was a variant of the cobra ah1z i think 4 bladed, but did it fly ?
i love the color scheme of the marine cobra (or the russian blue/grey..mm with a red star, looks neat)

thanks doc

[Cobra Doc]

The Cobra still has the teetering head. It looks like the "Z" aka Viper may soon go into production.

[Victor Duarte]

then maybe, this time, it will win the contracts he lost vs apache, but the tiger looks a better challenger for foreign sales ;) :D
i had a look to your site... not bad, if i lived in US , it s a kind of place i would get in..
i think about doing the same, but on the net.. to concentrare knowledge, exchange mech tips and parts, tooling , all these sports can bring a lot to each other if "unified".. you just forgot hovercrafts (fun, easy to build, cross-interests with aero)
good luck in your venture Cody
thanks
(ps : remembers me my zz times when i was 17 :D)

[Cobra Doc]

Too bad hovercraft aren't as popular in the US as they ar in Europe. Maybe that can be changed.

[Brian Jackson]

i ve read videogames is fun!!!
ok... making them is NOT PLAYING, is not that easy.. and may give real headaches..
just a sample of the main software i use : 3dsmax (i dont even show third part sofrtwares and middlewares !!!)

what you can see is the workspace and, under, a VERY VERY small SAMPLE of the kind of parameters i handle...

i d say the soft has about 20 or 40 times these parameters... solidworks, compared to this is a baby toy...

so, making a video game, even a little one, needs amost 1000 or 1500 this complexity..

just in case of some think i cant understand more than a,b,c ;) or think that videogame is making "fancy", we sweat to bring you some fancy..
I run 3DS MAX at work. Like you, I import the geometry from a NURBS/solids modeling program. MAX is great for renderings but its modeling "features" positively suck.

SolidWorks and MAX are built for totally different ends. Personally I like Rhino 3.0 for modeling, but MAX is geared more for rendering. It's cool to pass geometry to MAX, but I loathe its interface. I wish they'd make MAX more standard with CAD commands for pan/zoom/spin. Love the program otherwise though.

I recently got MAX version 7, which has some very cool walk-throuth features incorporated as part of the pan/zoom view parameters. You can place keyframes at various points from right inside the viewport and modify their spline curves, each affecting a specific camera angle XYZ. Nice stuff.

Cheers,
Brian Jackson

[Victor Duarte]

brian,
max has a weak point : NURBS, forget it, RHINO IS the good choice for that kind of modeling, but nurbs are more suitable for CAD than for video, then you must handle meshes, and in this point, MAX IS the good soft..

passing geometry to max ...mmmm i tried, dxf, ase etc... a weak point.

solidworks is just amazing by the workflow, it looks like a well organized workshop (not like mine :D) the right tool is just ther, where and when you need, but you must at least have a basic kowledge of machining, SW doesnt allow fancy, but as i am not an real eng, i rate SW VERY WELL (knowing Max helped a little...ok)

you know what i dream of ? just have some mechanical eng features in Max such as dimensions,materials physical properties, some stress analisis, plan drawing etc and it would be a hit.. BTW the prices are the same.
what i miss in SW is a kind of utilities library, like ergonomic setups, but i love it

you have a plugin for max called "glider" allowing to create airfoils and get their aero behaviour..

cheers

[Victor Duarte]

Too bad hovercraft aren't as popular in the US as they ar in Europe. Maybe that can be changed.

wow ! with the AMOUNT of flat spaces you have, the swamps and deserts... it s a shame !! i had the occasion to try one... very very fun, just imagine racing a quad on ice with slick tyres :D, thats great and much easier to build than an aircraft, but using the same parts, BTW the hover fans have really good tricks to get the best from ducted props... you must try one, even kids can practice hover in small ones

but go on with your idea, sympathical... a kind of "hard shock café" :D :D

cheers

[Cobra Doc]

You would really be envious over the Hovercraft I got to try my hand at at Ft. Story, Virginia. I've been fortunate in that I have been in the diver's of an amazing array unique, huge, powerful, simple, exotic, fast, slow and complex machines. The only type of machine I've never operated is a submarine, but it will happen.
As for a hovercraft in my particular desert, my son's old '71 Yamaha 125 works better than any hovercraft could. This desert isn't very flat (or soft!!). My SR500 stays on the asphalt.
The shopping malls will happen. It's going slow right now, but it is going. N'est pas? (Oui, je parle en francais, un petite)
Back to blade hubs, you have to admit Enstrom has an asthetic design. May not be the most efficient, but it is nice to look at. I'm not sold on the idea of making gyros more complex. The biggest problem with helicopters is that there is a lot to go wrong with them. I would like to see a gyro with a Garret APU turbine for power. The greatest mechanical marriages ever: diesel engine/turbocharger, helicopters/turboshaft engines.

[Vance]

I think that it would be nice to think about what would make a teeter tower and a hub bar work better and shake less. They are simple and the forces involved are not too complex. We should probably start with definitions of what they do now and what would be termed better performance.

Rotor blades would be fun to define also. Thank you, Vance

[Victor Duarte]

hi vance, everything's ok i hope ?
yes, thanks for straightening the thread, and it s still an interesting one, a lot of brainstorming to be done...
i ve been trying to work on several designs :
to the simpler, from just replacing actual hubs , adding some "design tips" to go to a more "elaborated" one (yes, means complex, but not so)

so, yes, maybe a precise definition of the forces and effects in action is the good base for a start. also a list of the defaults of actual designs...

perhaps the blades should be thought in a parallel way, always keeping in mind that the link is also source of failure...

ok, vance are you ok to list the real problems to overcome ? as a pilot would do..

thanks vance (for keeping the line ;) )

[Victor Duarte]

N'est pas? (Oui, je parle en francais, un petite)
Cody, not bad and thanks for the effort ;)

Back to blade hubs, you have to admit Enstrom has an asthetic design. May not be the most efficient, but it is nice to look at. I'm not sold on the idea of making gyros more complex. The biggest problem with helicopters is that there is a lot to go wrong with them. I would like to see a gyro with a Garret APU turbine for power. The greatest mechanical marriages ever: diesel engine/turbocharger, helicopters/turboshaft engines.

what enstrom model ? i had the occasion to have a flight in one (280 i think) whth the galet clutch and a creepy noise !

personally i think the Eurocopter ecureuil or astar is a smart design, the lynx also has a simple-in-theory design just bending titane plates..world record..

about an APU ? i asked here if we couldnt gate a serie of old generation, even, but think about maintenance pb, a piston engine can be unmounted on the table, a turbine...mmm.. bucks bucks

a small chopper had one (predator) did you see it?

i think diesel is perhaps a better way (i dont forget diesel engines can run faster than gasoline ones and the first very hight speed record was won by a Mercedes with a diesel engine !) cheaper fuel (or kero) can be supercharged.. common parts.. high torque, smooth curve of power..

if you dont know VANCE, let me say for him, we have a very accurate eye about power sports... so i must shut up before saying something wrong :D

thanks cody

[quadrirotor]

The world record holder rotor :eek: and Enstrom design. :)
Diesel fuel is desirable in helicopters, above all and like in a boat, because it is less prone to EXPLODE during a crash!... :cool:

[Victor Duarte]

right, fuel is safer, BIG advantage

in the lynx hub, i saw a slightly different design, there was a vertical bending zone after the pitch horn for lag.... changed?

enstrom, ok thats this one i saw... there are hydraulic dampers..

cody, apperently you like the one-bolt blades with retainer rods... it works fine.

i m also for a one-axle blade..

[quadrirotor]

Years ago, i thought of a design which could be built only with yokes and spicers!
(directly from the car industry...that's cheaper not to make them oneself...)
http://www.markwilliams.com/

[Victor Duarte]

he he how do you think i went to that ?
dont you see a kind of yoke? ;)

[quadrirotor]

The Starflex is simpler to make for me!

[Victor Duarte]

my first version was a copy of starflex, i just took the articulation from the root to the end to have a smaller hub...

ok maybe considering aa composite hub i could work this out, you told about metal vs composites, thats why i designed it like this, just keep metal where composites are not needed

[quadrirotor]

Zeeoo, it seems to me that you are a hoax!

[Victor Duarte]

maybe ! fun ! isnt it ?

look under, it was my first drafts doesnt it look like the starflex? it was posted on another forum

[Vance]

You are coming up on something that makes me wonder. I feel that a hinge is a way to make something bend if you don't know how much or where to make it bend and you beleive that making it bend in a certain direction has value. In rotors for helicopters usually they have some device to limit the movement or slow it down. It would seem to me that with the tools we have now we could build something the flexed in the corect place at the corect time and direction. I beleive that the Germans are going down this path. Victor is also moving down this path by adding elastomeric bushings to his rotorhub.

Taking this toward autogyros, there would apear to be some forces that are not being delt with by a simple hub bar. It is acting like a spring and aluminum is a poor spring so it may be the movement is being limited in order to reduce the cycles or keep the blades more in line. As soon as we go to more than two blades we need lead lag hinges. This would sugest to me that there are forces that are not being addresed well even in the hub bar and maybe hinges in the rotor hub are not the best solution for a multi blade rotor.

Historicaly we are told that the flaping hinges were introduced to deal with the disemitry of lift and the lead lag hinges to reduce the bending moment on the blades. This seems like an invitation to re-adress the problem with our new materials and annalisis tools. I would like to see someone with more skill and knoledge run a little down this path. I don't think that hinges are the best solution and I think that a hub bar and teeter tower might benifit from from some study. If nothing else we will emerge with a better appreation for just what an elegant solution we have. Thank you, Vance

[Victor Duarte]

Historicaly we are told that the flaping hinges were introduced to deal with the disemitry of lift and the lead lag hinges to reduce the bending moment on the blades. This seems like an invitation to re-adress the problem with our new materials and annalisis tools. I would like to see someone with more skill and knoledge run a little down this path. I don't think that hinges are the best solution and I think that a hub bar and teeter tower might benifit from from some study. If nothing else we will emerge with a better appreation for just what an elegant solution we have. Thank you, Vance

vance, it was a parenthesis.. let me work out some propositions about what you created this thread for : teetering tower hubs for light gyros.. forget flapping plates for a 2 bladed...
just a remark : lead lag are also usefull do reduce the drag of the advancing blade and the torque induced on the mast..

i think if it is used to reduce the bending moment, that's because the pitch axis, instead of being always pointed trough the 25% chord line, tends to stay aligned with the expected initial axis, this way, there is a up rear bending moment.
but if the pitch axis moves as the blade moves, the pitch horn will always input through the real blade axis... it lessens the bending..

yes some more skilled people expected...
but i ll still, with your permission , posting my mad ideas, maybe one will hit ;)

thanks

[quadrirotor]

Victor, your rotor design is nothing more than the one of the Cabri:
http://avia.russian.ee/vertigo/guimbal_cabri-r.html

[skyguynca]

My question is, since this discussion started as a way to carry heavier loaded gyros (ie 2 or more people) and it was said Bensen's teetering rotor was fine until it was loaded more, then it started to shake more......Bensen did a 4 bladed rotor at 24ft span, that carried two people very well, it even had the weight of 2 engines....so what is wrong with doing a 4 bladed double teetering system, it is still simple, easy enough to make and still affordable????

[Victor Duarte]

andre > you re right andre, i saw the guimbal's Cabri and thought it was possible to have this kind of rotor on a small chopper... there is worst inspiration tnah that no?

david > andre posted pics of this rotor... i dont know how it behaves, i just wonder if a higher tower doens generate more skake... more control efforts, do you know some details about that ?

thanks

[Vance]

David, Design is about improving things that work or making things that arn't posible happen. High parts count and complexity are the down side of Igor Bensen's solution. He didn't have our tools and materials so maybe we can come up with a better answer.

Victor, In my opinion you have captured one of the keys to good design. Take a good solution and apply it to other challanges. I once patented a quick errect radio antenna and made a good profit on it, by sawing up a camera tripod. Thank you, Vance

[quadrirotor]

My question is, since this discussion started as a way to carry heavier loaded gyros (ie 2 or more people) and it was said Bensen's teetering rotor was fine until it was loaded more, then it started to shake more......Bensen did a 4 bladed rotor at 24ft span, that carried two people very well, it even had the weight of 2 engines....so what is wrong with doing a 4 bladed double teetering system, it is still simple, easy enough to make and still affordable????

Nothing! but by double teetering, you mean this one!

[Vance]

I was wondering what are the avantages of the four blade rotor that justifys it's complexity on a light Autogyro? Thank you, Vance

[quadrirotor]

This was a post of 03-22-2004
Re:Best rotor ?

--------------------------------------------------------------------------------

Actually, the question is: what is the best rotor?
and the answer is: the quadrirotor(four blades rotor!)...
ref:
The performances and efficiency are documented:
Boyette: Rotocraft dec-jan 97-98 p.44.
Magni: Rotocraft dec-jan 00-01 p.27.
and others...
conclusions: better efficiency, better lift, less drag, less (no) vibrations, better flares, stiffer and cheaper blades, less fatigue, better sound and so on etc...
The scisor effect is not well documented, it seems not to be a big issue for semi-rigid rotors.
Sportcopter solved this problem that exists even with two blades rotor...

Price:
Sportcopter 25' 7"----> 1700$ X 2 = 3400$
Sportcopter 30' 8"----> 3900$ X 1 = 3900$

500$ cheaper with four blades! ok use them to have a heavier and more complex rotor head...


and to improve this rotor, you must add some power to the rotor: the BIRD of Dick Degraw---> 90mph cruise on a ea81 stock!...(10% power on the rotor)
and Bensen has done it before!...

AND TO HAVE THE BEST GYRO CONFIGURATION:
to solve the C.G. problem: put the engine behind the seats but the prop in tractor position...

[Vance]

If they tried four blades and it worked so well, why don't they promote them and sell them?

I thought that Dicks machine had three blades?

What CG problem? How would that fix it? Thank you, Vance

[Victor Duarte]

andre you have all right,
but opinion about 3,4 or 5 blades if dicussable.. since you go over 2 blades, it s another kind of design.. you say the blades are cheaper, i m not convinced, they are shorter, thinner, but even with 20 pounds less, it stills the same work to mold etc... i think it is not proportionnal...

and thanks to aprove a design i proposed for a tractive gyro in one of my first threads ;)

[Vance]

I seem to remember that particular PA was roadable with a powered rear wheel. I understood that, and pilot view had more to do with the configuration than cg. It seemed that everyone liked it but It was abandoned with no production. Thank you, Vance

[Victor Duarte]

it seems the 3 bladed rotor has been also abandonned because of parking place... but now we can do quick bolts...

[Vance]

In the USA the three blade rotor is quite popular and from the begining they folded. Some of them even have a mechinism that folds them. Thank you, Vance

[Victor Duarte]

i didnt knew they are that popular, vance, so, why not more gyros with them, i guess we get back to complex/costy/risky vs simple/cheaper/proven design..

the matter is we can keep the good points : simplicity but make it with actual solutions, or some improvements , as you told..

so what to improve on your opinion ?

thanks

[skyguynca]

Yes, the Magni is a direct copy of Bensen's four bladed system. It does not have a high part count and is not hard to make. Bensen's notes on its flights show it to be a great improvement but the only problem he had was he tried it with two engines, that was a mistake and he dropped it because one engine out was a nightmare due to the asyimetic thrust. The rotor system worked though, the reason it was not done until now was people's misconception that it did not work but as you can see Magni has rebirthed it and they like it alot, smaller rotor diameter, standard blades really since each blade will be loaded about the same as a single seat operation. It is a great idea.

[Vance]

Victor, I was trying to be clear in post 56. I beleive that there are better ways to make things work as far as vibration, blade stress, weight, cost and control. I'm not saying that what we are using now doesn't work, only, given our new tools (computers), materials and manufacturing processes we might do better. Composits have such posibilities. For instance, I always liked the way Stanley Hiller used his stack of plates to hold the blades together. To me this solution begs for composites. Thank you, Vance

[Victor Duarte]

David > i trust your opinion, makes me get into a brain storm... positively, thanks for details, sometimes all we need to know is that it works..

Vance > as i am a curious person, i can also see we can have a great advantage in using composites .... but if i aproximatively know how to set them up, at the same time i think they need a lot of experience and tries to master them.... not in their setup or sizing, their strenght is easy to understand, but curing them is really a piece of hazard.

i ve been looking for "shure" processes on the net, and due to the variety of fibers/resins there is not ONE way to cure them but quite one way for each usage..

going into composites (for us, amateurs) may need a lot of losses before getting somethin good, and we are not even shure it will still good the nex time...
knowledge needed..

thanks

[Vance]

Victor, I believe that is what they said to Columbus. Thank you, Vance

[Victor Duarte]

well... let s get at work!

[Al_Hammer]

if two teetering rotors are combined, I believe there is a problem related to the fact that a flapping rotor is not moving in the same plane as the rotor hub. It is inclined relative to the plane of the hub by a few degrees in forward flight. This leads to the hooke's joint effect. The rotor has inertia and will tend to rotate at a constant rpm in it's plane, while the hub changes speed twice per rev as the rotor constantly crosses in and out of the plane of the hub.
With one rotor, this is not a problem. It is not noticeable and causes no stress on the hub, only a very slight variation in rpm of the hub which of course is free rotating in a gyro.
But when you mount two teetering rotors on one hub, one rotor is now trying to slow down and speed up the hub while the other rotor is doing the same , but 90 degrees later in the cycle. The rotor hub bars are now forced out of their 90 degree relationship by a slight amount which varies with flapping angle.
It seems that this problem could be solved by mounting the teeter bearings in an elastomeric sleeve. It only takes a few ten thousands of an inch of compliance to absorb the calculated movement.

[Victor Duarte]

al
wellcome and thanks, for the explanation... so , your opinion about it ? is it an improvment ? is the offset hub still a good control system?
if te two rotors are not in the same plane, the effort to change pitch on each is not the same isnt it? the upper being "harder" to teeter ?

if you mount elastomeric sleeves dont you fear a kind of misadjutment ? at the frontal azimuth the blades getting the max drag, it could induce a little lever under the tower, so lower a little the angle of the advancing blade ... or am i overkill ?

thank you al

[Vance]

Hi Al, It is nice to hear from you. I have learned so much from you and your no nonsense approch to things. In case you don't rember you were able, with your animation, to confuse me on a much higer level about such things as teeter rotors. I know you are realy a helicopter guy now so it is very nice of you to visit.

I would think that the rotor head would get a little tall and I would think that is a bad thing in a tilting mast. Am I being oversensitive about teeter height above the tilting pivot for the mast? Thank you, Vance

[Al_Hammer]

Victor,

Thanks. I have not flown such a system, but, yes, it seems it might be somewhat stiffer on the controls. The reports I read of Ernie's system were that it was very smooth (and made a nice sound.)

Since the rotors can teeter independently, I don't think that one rotor can influence the other in the way you describe. I hope I am understanding you correctly.
Overall, the 4 bladed idea sounds like it is worth looking into...

[Al_Hammer]

Hello again Vance,

somehow you don't sound quite as confused these days..congratulations.
I am not so much a helicopter guy as I had hoped now that my machine is up for sale.
Maybe I'll rebuild my gyro one of these days.

I think you are right about the height of the rotor. I don't recall whether this has been reported on in the flight reports that were posted on the old forum at the time Ernie was trying out his system. I always thought my dominator felt a bit stiff due to the double bearing rotor head and tall towers, but it was nothing compared to a non boosted R44 that I got some stick time in one day.

[Victor Duarte]

vance and al, i just realized something....
thinking to a gyro rotor is a very different way to think, as an helicopter fan, i tend to think "cycles".. "control the blade angle" "ease" "damper" "effortless" "smooth" "keep the center of lift on the mast"...
... i must "imprint" that the main concerns are slightly different

andre is also convinced by a 4 bladed, the 90 degrees allowing a cyclical synchronized teetering, right

but coming back to the initial subject vance launched, the 2 hubs or main hub need to be revisited with modern means... we were wondering about composites hubs.. have you some nuggets for us ? ;)

thanks

[skyguynca]

Ok so Ernie and the guys at Magni and the first guy Igor Bensen pulled it off. I have read Bensen's info on the smooth operation, do you guys know where I can read about the other two?

[Al_Hammer]

Click here (http://www.magnigyro.com/USA/magniday2000.htm) and scroll down for a brief description of the magni system.

Ernie's system below.

[Victor Duarte]

al, they say the purpose it s made for is crop spraying and heavy works..BTW they say the price will be much higher than a 2 bladed. logical
but apparently smoother controls and best turns, quite chuckable ;)

is it worth going that way ? whats your opinion on a 3 or 4 bladed semi rigid?
we are approaching this kind of complexity...

thanks !

[skyguynca]

to me, to get smoother flight and yet the ease of building it verses a rotor head with lead/lag hinges, flap hinges and pitch control with swashplate....that seems so very complex and way away from the homebuilders capabilities, but the head like Bensen or magni......possible

[skyguynca]

thanks for the picture and the Magni page Al, can you tell me do you think it is possible to build this and fly it without the fracture problems Boyette saw?

[skyguynca]

one more thing Al, could a extra pivot be in the upper teeter assy, limited to just 1 to 3 degrees but 90 degrees out from the teeter assy to allow for the scissor effect and prevent the excess load of the blades trying to speed up out of phase from each other?

[Al_Hammer]

Here is another- The Heliplane.
4-blade system comprised of two 2-bladed teetering rotors utilizing a common tilting spindle.

http://www.cartercopters.com/heliplane_overview.htm
http://www.cartercopters.com/heliplane_desc.htm


The cracking problem doesn't seem insurmountable. More experimentation is needed.

An " extra pivot be in the upper teeter assy" sounds like something that should be investigated. Allowing one rotor freedom to move, but not the other. hmmmm...

Also, DeBird was mentioned before. It has only 2 blades according to this photo. And the Gyrhino has 3....

[Victor Duarte]

david i must agree the 4 blades "as seen" are impler than a 4 blades "as seen in common set ups" but no investigation has been made to "simplify" correctly .
bensen had the idea to get this simplicity "you just need pivots and hub bars, ok"

it s not to bash or upset, it s not aimed to you, but i ve a feeling that this design need an eternal patching to erase defaults that are inherent to this design like trying to have 4 wheels on a bycicle !

the gyrhino has my vote, has someone more details aboout the rotorhead, i think d degraw derivated it from an intermesher he built...

another thing : theres a way to eliminate the need for a complex swashplate as long as you need a fixed pitch , theres a way to simplify a swashplate, theres a way to simplify flapping lead lag hinges,
david, did you have a look at my first posts here? i d just like to have your opinion..

we still going away from the initial thread : designing a correct hub bar

thanks you

here some "wild" investigations

[Victor Duarte]

another batch

[Vance]

Victor, your drawings come up a little too small for me to read the print. I'm not clear on the relationship of the pitch pivot to the airfoil on the blade itself. I am also not clear on balance. It looks to me like there is a sudden a change in section at the blade root and I would guess that making the transition from the blade to the fork would call for a change in your lay up process. I don't know enough about it to understand the impact on cost. I have found when I test things to distruction that when I to keep changes in section slow that fatigue challanges are reduced.

To everyone, I would like to see an Autogiro rotor head with about 4 degrees of in flight pitch adjustment to allow faster prerotation and shorter take off roll. In the ship I usually fly, I pre-rotate to around 200 rpm, tilt the rotor full back, and accelerate with the rotor working against me. It feels like the brakes are on. Once the rotor is going fast enough the front wheel lifts and I balance on the mains. Thats when I really began to accelerate. It lifts off at around 55 miles per hour. All this takes around 500 feet. I beleive it would be nice to flat pitch the blades and bring the rotor up close to flight rpm before begining the take off roll. It seems to me that I could accelerate a lot faster, for a shorter take off roll, if I wasn't trying to accelerate the rotor at the same time. I am not trying for a jump take off because I don't want to fly behind the power curve and I want to be going fast enough for the control surfaces to work. It seems like if you were only trying for four degrees pitch change it could be a fairly simple device. Any thoughts???

I have watched jump take offs by two different Autogiros and they were both things of beauity. I have also seen a number of Autogiros on their sides after making a jump takeoff that didn't work out. I may be worried about things that aren't really a problem in my effort to keep things easy. Both pilots that I watched had vastly better flying skills to mine. I am sure we have some divergant thoughts on shortening the take off roll or jump take offs???? Thank you, Vance

[skyguynca]

Ok, here is something taken from Al's suggestion of elastromeric sleeve in the teeter....we can keep both blades in the same plane like Boyette did but how each blade bolts to the hub bar different. Use 2 single bolts inline with elastromeric bearings on the inside bolt and the outter bolt in a bearing to allow the blade to lead and lag but leaving in the normal teetering system. Since it is the blade speeding up catching up and passing the hub out of phase with the other blade 90degrees behind it, this system will allow each blade to move some in the horizontal plane allowing the scissoring effect and releiving the stress from the hub and the teetering hub will still handle its normal function unmodified???????? What do you think???? The way I figure the tip of the blade would probably max move 1 inch from center line forward or back.

[Victor Duarte]

vance, you may have trouble viewing the pics if they are not full screen,
your browser (internet explorer) reduces then in order to fit the window, so the quality and lisibility will be bad..

look at the right botttom corner of the picture, if you can see a square icon like shown under, click it , it will show the picture full size.

thanks

[Vance]

David, I think that is a fine idea. I am not able to imagine the layout. how do you keep the elastomeric intact against the centripital force. Thank you, Vance

[Vance]

Well Victor, I am showing my ignorance once again. Your drawings don't have the little icon, but when I went back and looked again they came up individualy. I don't see what has changed?? My questions are still the same as post 91. Thank You, Vance

[Al_Hammer]

To be accurate, as I see it, the blades would not actually lead and lag. The towers would lead relative to each blade hub twice per revolution as a result of the kinematics of the rotor head.
The effect is the same as if the blades were to lead and lag. The two rotors would move in a uniform manner with the tips neither advancing nor retreating relative to their own centerline.
This is not the scissors effect of Chuck Beaty(does it exist?), but rather a hookes joint effect and it is somewhat difficult to visualize without a little practice.

I found this equation below for calculating the max angular displacement of a hooke's joint. The rotor hub is one half of a hooke's joint so I divided the result in half.
The "B" in the formula is the flapping angle.

Using a max flapping angle of 9 degrees, I get about 0.17 deg displacement with normal in flight values much less than this; about 0.04 degrees (Flapping angle of 2 degrees)

David: Could you post a drawing of the inner and outer bolt idea?

Vance: I'd like to know more about your patent that you mentioned. Did you write it up yourself? I'm thinking of applying for a patent myself and could use any advice you might have. Thanks. PM me if you want.


A four bladed R/C teetering rotor:
http://www.autogyro.com/technic/pstah.htm

[Vance]

Al, I just love it when you share your knoledge. I will pm you on the patent.. Thank you for being you!, Vance

[Victor Duarte]

al, right on the hookes joint called here "cardan"..
fortunately, 4 blades share the 90 ° precession with 2 blades, that s why this kind of setup works.. according to that, even a fully rigid 4 bladed rotor should work, every pair of blades flapping without disturbing the other.

you state about 9 degrees flapping angle.. just sounds low to me, what worries me is the case of a larger teeter, wind gust, a shock on landing gear, a little neg G, i dont know, how does it behave ?

thanks

[Victor Duarte]

here is a proposition to have a variable pitch on a classical rotorhub..
comments ?

thanks

[Al_Hammer]

Victor, are you familiar with the CH-7 (Angel) helicopter? It uses a similar concept.

[Victor Duarte]

yes al, i had the occasion to see it very close, i like the concept, appearently simplier but not so... BTW in my design, i kept the mast hollow to allow air path..
the CH7 has an elegant design but very small levers , IMHO, may be soon source of problens, once they get some play... but i like this way to investigate aside classical solutions..

correction : in the pic i posted, the upper "ball" should be a bearing or a bushing

thanks

[Al_Hammer]

Thanks for the pic, Victor. The swashplate looks different from the one in the Angel.
(It is a Kompress, right?) Your idea looks good also.

[Victor Duarte]

hi al,
yes this is a pic of the Kompress, the angel i saw in 1995, was one of the first.
, about the idea, take you drill and do it ;)
cheers

[skyguynca]

4 blade head teetering with this hub bar design. Simple and should take care of the lead/lag movement of the blades. Al said that it did not need to be much and this will allow a little movement. What do you think Al? Simple yet effective without complex machining. Now I did this drawing quickly on Delta cad and exported as a bmp, writting may be a bit blurry until you zoom in. Come on guys, let me hear your ideas, rejections.....etc


David

[quadrirotor]

Why don't you use something which looks like the SportCopter system but without the pitch setting device...you could get off the small bolt to fold the blades.

[skyguynca]

This does not use a pitch setting device the small block is to act as a stop during lead/lag movement to limit it. The material between the end of the hub bar and the stop block is a dense rubberized material to add resistence and return to center and stop buffering. With the single bolt pivot the blades should remove and install quickly.

[Victor Duarte]

David, i can't read allthe labels, (bolt font) if you can have a better definition (and a front view). is the bushing the only link of is there another link hub/blade grip ?
Allow my opinion please.
1 - if you use an elastomeric bushing to lead/flap, so close of the blade grip, i feel there could be huge efforts in it, if it works for a chopper, that is because the pitch angle is stabilized by the pitch control, but here, nothing forces the pitch, i wonder if it is not going for a kind of flutter... each degree is about one inch at least on the blade tip.
2 - personnally i dont like this kind of blade grip, i told why.
3 - are they custom blades or an existing model ?

thanks

EDIT : david i posted before your last post, ok you answered one question.
but the arm betweenthe bushing and the rubber is very short... you should give a little more lenght.

i had designed a hub like yours but with a kneecap instead of your bushing, a rubber like you to allow lead/lag/flap, but it appeared the axial force on the sphere could "plop" it out.. enshure your bushing will not degrade too fast.

if you look we are not far on our respective designs

[skyguynca]

OK, hang on a bit. I will post a new drawing with more details of what I have planned. I will still be using a 4 bladed head, with two teetering hub bars at 90 degrees to each other. The upper one will bring the second set of blades into the same plane as the first. Just like Ernies 4 blade head except I am making lead/lag hinge into the hub bar. This should handle the scissor or Hook joint so the head is not stressed nor are the blades.

[quadrirotor]

The blades have not to be exactly in the same plane.

[skyguynca]

I know, but looks good doesn't it?????

[skyguynca]

Ok, I took a few minutes longer on this one, take a look and let me know. The overall hub bar length is adjustable and yes the pitch blocks are still in there with pivot pins. But I think this will take care of the Hook Joint or Scissor Effect. Ok lets have comments, recommendations and of course objections...let me hear it..........remember now it is supposed to be a way for the common everyday guy to have a more efficient 4 bladed rotor system not high tech must be machined one that is why I am trying to keep the lead/lag hinge simple. The high density block will act like a buffer along with the friction washers. Keeping it between the hub bar and the intermediate bar will help the return to center function and buffer the intermediate bar which is really more a stop to prevent the blade from going to far. So the gap is directly porportional to the amount of lead/lag needed. If you need any explinations of working or parts just ask.

[skyguynca]

Hmmmm, 5 hours and nothing....now I am worried........are all those calculators and slide rules running numbers???????? Is it possible that I may have done it right??????? Naw you guys are just asleep. Well I guess I will find out tomorrow

[Victor Duarte]

David, wait ! i 'm havin my morning coffee and your drawing calls for a better reflexion, !
one thing to think : yoyr set up with the rubber strap and the axis so close will create a tend to tear the bolt outwards, your rubber stoppers should work better is laterally placed .

David : what kind/brand of blade are you gonna use
what is your schedule ? connditions etc, what do you want to obtain ? var pitch ?

thanks... finishing morning coffee

[skyguynca]

Hmmm, no this will only lead or lag the blade.........I thought I posted that some where up there........this is a lead/lag hinge to help with the Scissor or Hook Joint effect of flying 4 blades on two teeter joints on the same head. The whole idea is for you to use what ever blade you want. Trying to keep it cheap. The only rubberized material is a buffer between the hub bar and intermediate bar to prevent the two metal sufaces from direct contact, heck I know rubber won't work it will wear out in a few seconds but something denser will work. I don't have a schedule right now just thinking before I build. The bolt is in shear, the metal plates should hold up fine along with the bolt and the friction is set by torque on the bolt. If you want to use blades like Ernie's then the pitch blocks are not used and you instead drill the intermediate bar for his strap attachments. If you want some like Bensen/Brock you use the pitch block attachment.

[skyguynca]

Messed up on my math, new pic. I changed the .250 4130 plates for .50 6061 aluminum. The wear on the 4130 bushing would have been only about 5000 cycles before the bushings would have been trashed. Going with the .50 6061 should give a tremendous life with bushings, atleast 100hrs flight time before changing the blocks.

[Victor Duarte]

Hi david, after a few thinking :

you drawing may work but let's get a little paranoid, i prefer

1 - i still thinking the bolt so close to the border and rubber may produce a strong moment and tear the hole off... draw a line between the point of contact of rubber and the bolt you wil see a lever to shred the alu hole... you have a 3 meters lever to produce effort on a small 3 cm line ! and ideal can-opener. ther can be a little "percussion" on your blade leading edge.

2 - you should "enshure" the bending zone of the hub, in your drawing, there may be a little stress at the bolt hole while bending..

3 - your rubber may pop out if not correctly bounded, and BTW degrade if not oiled.
it should work laterally and not in the long direction. why not another elastomeric bushing ?

here is a proposition... to be discussed...
note : this proposition allows an adjustable pitch ( add a screw adjutment)
beware : i didnt draw it, but you should avoid metal/metal wear between the dark grey part and the blade grip plates, perhaps taper the dark part a little, around the steel rod .

we get close to my design ;)

cheers

[quadrirotor]

Zeeoo, too complex and all the centrifuge force is taken by the small left bolt!!!! Why don't you take the SportCopter design (as I already said...) without the possibility to set the pitch. The pitch is set as usual (Bensen type)or built in. This allows to fold the blades by getting off the small bolt which goes through a rubber bushing. Due to liability issue i can't tell you, David, that this will work or withstand the stresses, you must expect to use strain gauges to know what's going on; you must make your homeworks, that's for reflection only.

[Victor Duarte]

andre,
1 - there are not 1 but 3 small bolts (can be 4)
2 - depends on how the bushing is set up, if as long as the bolt, the centrifugal efforts will be shared, and he small bolts only play a role of holding the plate
3 - too complex ? with pich adj and lead lag ? maybe we should compare apples with apples, and compare the parts count of other "elaborated" hubs
4 - everything could be simplified, but david lauched a design, we just follow his idea...nor, better have a new design..

rotor hubs
http://www.rotaryforum.com/forum/showthread.php?t=2739&page=2&pp=15

thank you

[quadrirotor]

Too many parts, the rubber bushing of the big bolt is not hold if you say that the small left bolt hold the "black peace"...Take the SportCopter design...It works and a aeronautical engineer has worked on it!!!

[Victor Duarte]

andre, please, read my post and read the plan. 8 parts excepted the bolts, yeahh of course we can have 2 ! just put a plain bar with one huge bolt and ok.
perhaps david doesnt want to pay something like 2x2000$ for hub bars ? and build his own. what's wrong ?
If gyros waited for "aero engineered" parts, none should fly now...
tell me every gyro built has been designed by an aero eng...
RAF also says aero eng worked on their machine :D
and please.... improving or criticizing doesnt mean say "Bull...t" everytime.
thanks

[quadrirotor]

Sorry Victor, take your pills...

[Victor Duarte]

andre , if there is something wrong, mail me , you have my mail. thx

[quadrirotor]

no need to mail you!

[Vance]

David, you have done several things particularly well. I would expect the loads on your bar to be in the neighborhoos of 10,000 pounds. Your selection of .750 bolt is capibal of handling the load. Your choice of steel .250 thick is also good because both the upper and lower steel plates should be able to handle the loads individusly and I beleive your material and thickness is correct. If it was me I would use a larger hollow pin of similar strengthand make the hub bar wider where the hole is to not create a stress riser. any time you increase the diameter of the pivot it is easyer on all the parts, But rember missing material (hole) is mising. Your Idea of using friction washers to dampen the lead/lab action is good, but it is very hard to get friction washers to actualy produce the dampening you are looking for because of a thing called static friction. This is where a thing resists begining to slide, but once it slides, it slides freely. Tempeture also affects friction.

I liked the way you used the resiliant material to center the blade. You may be able to find some material that does not release eneger in the typical way. We played with this kind of stuff while trying to deal with high amplitude, low frequency vibration. You could hit it with a hammer and the hammer wouldn't bounce back. You also have to deal with the flaping movement and I asume you are doing that elsewhere. I have never like the four bolts in tension, but it seems to work well. It is just not best practice. I beleive that you have a fine demonstration of thinking there. I have a time bind now so if I screwed this up I don't have time to proof it. I will do it later. I don't type or spell well. Thank You, Vance

[skyguynca]

Thanks Vance, your opinion is deeply appreciated as is all.

[quadrirotor]

One of the main drawbacks of the four bladed rotor is space storage, but with foldable blades (same space that with two blades)...The SportCopter hub doesn't allow this!...and the pitch setting device of the SportCopter hub could be questionable anyway!...

David, can you give me the parameters of the projected gyro (4 bladed), i am gone a try to figure out the performances. If this is a modification of one existing gyro, give me also the parameters of this gyro with some figures about its performances...
cheers.

[skyguynca]

It is a project from scratch. I will give you all the figures tonight. Right now I have to head to work. I work 7 days a week right now so time is limited. Thanks guys

[Victor Duarte]

David, what i wanted to underline, is the lever effet in your blade pivot..
i joined a drawing, hope it explains what i wanted to say.
thanks

[skyguynca]

No I understand your point, and since that piece is rated at 64,000 psi in tension it should hold fine barring a blade striking the ground and most hub bars can not take that. Now what is the math for that little steel pin shearing off???? last I figured it was 8000 psi in shear applied to it max which would be only about 400 psi less than its ultimate strength.

[Victor Duarte]

david, ok, glad you understood me ; then you know your numbers. why not to add an inch lenght, just to be safe.. your rubber damper will work the same.

BTW i stand by Vance's opinion : you could give more mater around the pivot... just in case (in my proposition, the steel holder was supposed to replace that)

for the pin shear ? what pin please..
if you talk about rods, they are comparable to bolts.. I , right or wrong, obtain the resistance by taking 60 % of the bolt resistance in traction.. depends the bolt grade of course.. what is your opinion ?.
thanks

[skyguynca]

We are thinking along the same lines. I have already made the hub bar taper from 2.5 in the center to when it clears the tower out to 3.75 and rounded to the stop portion which remains flat. that area is already 3.25 inches thick between the pivot bolt and the flat stop area. Shear is usually figured at .58 of tensile usually on AN bolts and .62 on Grade 12 bolts so your calculations are pretty close.

[Vance]

You two are going down a path in a very instructive way. You will be confused on a higher level. Thank You, Vance

[skyguynca]

????????????????????????????????

[Victor Duarte]

David, i think Vance means that we take every little "understandable" design problem and try to resolve it by an "understandable" explanation, helpfull for us, and others, i hope. doing so, we may get further.. and Vance also has an acurate eye.
thanks, correct me if i'm wrong Vance

[Vance]

Victor, I think that David got it. As I learn I always expand my questions faster than my answers. I don't mean to be dificult to understand. I was admireing your aproach and the way you challanged each other and resolved things. In my opinion it helps everyone who sees it understand the creative process better.

Victor, I am e mailing you some updated pictures of the model that my wife took. I beleive that her camera has better resolution than mine and takes up more space. The first time I tried to send them it choked my server to a stop. I hope I don't choke your machine. Let me know if it is a problem and I won't do it again. Thank You, Vance

[skyguynca]

hence all the ?????????????????????????

[Victor Duarte]

oookay ! you got me David !

here are 2 links related to polymeric lubed bushings and elastomeric dampers :
2 worldwide manufacturers

for the polymeric bushings : SKF
http://www.skf.com/portal/skf/home/...ng=en&newlink=3
a nice parts browser, with all dimensions etc, but miss some infos (ex: rod ends tear off limit), but browse them and you'll be ammazed by all the bearings . BtW CAD models/data downloadable.

for the elastomeric dampers : PAULSTRA-HUTCHINSON (they build all the elastomeric bearings for Eurocopter .. a must)
http://www.paulstra-vibrachoc.com
sorry, no direct link but choose english language, then bushes, download the full catalog, all models and dimensions, and calculus to size a damper.
Also a lot of interesting solutions ... look the spherical damper...and the pivoting damper.

No pricing for both..alas

[quadrirotor]

In North America, elastomeric stuff
http://www.lord.com/

[Victor Duarte]

Interesting. closer to US

[quadrirotor]

Lord worldwide.

[quadrirotor]

David, you have almost exactly what you want to design in the PRA ROTOCRAFT MAG. October 1994, that's the folding blades of a Barnett J4B2!...
Many other examples, like the C.Beaty rotor (september 1994) and of course the Rhinogyro of D.Degraw...

[skyguynca]

hmmm, I will have to see if I can find those issues. I have been flying gyros for quite a while but just recently joined PRA.

[quadrirotor]

You must zoom a lot! David.

[Victor Duarte]

David, i forgot one thing in my calculus, you go for a 4 bladed, so, blades would be shorter, thinner, lighter. what do you expect ?(size speaking) are you going to shorten existing blades or make them by your own ? Is this why you asked for wooden blades plans?
If you go for your own building, let me know, i have info about how a "famous" blade manufacturer does them, and guess you can improve it.
I m starving for your late design, like a dog with a bone :D
let us know.
thanks

[skyguynca]

Yes I am making the blades, wood but with the aft face of the spar with carbon fiber laminates, 2 full length, 1 @75% 1@50% 1@25% and then the outer skin of plywood with one layer 5.8 oz biaxial cloth 90 degress to span and then all remaining layers at 75%, then 50% then 25% on the 45 degrees to span. Should stiffen the blade and if I don't mess up the layups then should be able to balance then with the same center of mass and 25% cord. Practicing with the single place 3drv with 24ft span 7 in cord 3/4 in thickness and for the 4 blade I come up with 6in cord with a 1/2in thickness at 24 ft span for the 2 place. Whatcha think????

[skyguynca]

Thanks for the page Andre'....new ideas are great!!!

[Victor Duarte]

David, honestly, i have no skills, so no opinion on wooden blades :(, just begining to overview the composites thing.. i think you got this shceme working from your experience. If i dont misunderstand you, you go for thinner blades but wit the same diameter ? I'd really love to see someone working on wooden blades, sounds like an old knowledge owned by old wizzards...;)
thanks david

[quadrirotor]

Newest of oldest ideas!

[skyguynca]

Well the same diameter but for a 2 place. For the 3DRV it is 24ft span 7 inch and for the 2 Place Modified Parsons it will be 4 blades at 24 ft span and 6 inch cord for a faster rotor but alot more lift....well in theroy anyways that is the way it is supposed to work, because for most 2 place machines it is 28 to 32 ft span with 8 inch cord.