designing and builging my gyro

[Victor Duarte]

Hi
i took the decision to build this.
it took me about 10 years of investigation and zig-zag between yes or no.
the building will begin on january with the frame and hull..
prop, rotor for later.
I will update this thread with drawings and calculus if needed, i think some valuable people can help me in some design tips.

comments, questions, recommendations wellcome.
thank you

[Brent_Brown]

Is the motor behind the seats? If not the rotorhead will have to move forward to get it to hang right?

[Victor Duarte]

yes the engine is under the cover, back the seat, back the pylon (dampened) holding the rotor, so, i can adjust the cog, front, back, up and down in a certain way.
the battery will also be used to compensate a little unbalance.

[Brent_Brown]

The rotor looks to far back to me if it lost power it will want to fly backwards.

[Victor Duarte]

some features :
- the hull is made of roving/foam/roving panels, impregnated in a mold.
- the sction of the hull can be compared to a rounded-corners-rectangle, allowing large flat surfaces, so, better resistance.
-the airframe is made with 2 parts : a steel sub-frame around seat-mast-engine.
this subframe is bounded/drowned in the hull.
- the winglets were originally a landing gear comparable to the magnis (negative dhiedral), so, by profiling it, i thought it is worth have a true airfoil allowing a little more lift, this airfoil will have leading edge flapperons to delay stall in vertical descents.
- the "fences you see under the winglets are made to avoid turbulences under the winglets in vertical descents.
- twin rudder with trimmed elevator.
- the transmission shaft goes under the seat to the nose where a belt gear allows reduction.
- the rotor will be prerotated with cold tip jets, allowing also a little de-icing and to sustain a little the rpm in flight.
- the rotor will be (perhaps later) a 3 bladed with a simple cyclic control. that means that if i get enough airmass from the compressor, it can fly in helicopter mode but classified as gyrocopter in the ultralight rules... to be continued, i guess technical inspectors won't be so dumb.

[Al_Hammer]

Looks attractive to me. Hulk says tractor good.

[Victor Duarte]

The rotor looks to far back to me if it lost power it will want to fly backwards.
brent, on the subframe, there willbe a 4 side pylon, the roror will be bolted to this pylon with 4 bolts, 2 lateral, 2 longitudinal, so, the mast inclination will be adjustable, and if i dont get it right, i just need to rebuild a pylon

[Brent_Brown]

My attachment got lost

[Victor Duarte]

Looks attractive to me. Hulk says tractor good.
yes al, i zig-zaged between tractor or pusher, but wanted to keep a little visibility, i think it is not utopic.
thanks for your comments

[Victor Duarte]

Brent, looks nice, you go for a 2 seat ? the blades look very close to the fuselage.. that is why i prefer 2 large rudders shorter tail and a higher mast

Al , on another thread, you had a good discussion (like always) on improvements on blades... that's a good thing, for info :
the rorot is 6m50 diam,
the blades are madeof composites.
the blade will have sereval points :
3 airfoils :
-from a boeing B29 root to a vr7 at 15 % twist 4 degrees. i expect this will allow a better lift at the root, improving hover effect and a thicker blade section allowing to endure a better bending torque.
- the rest of the blade will be from a vr7 to a vr9 at the tip wit 3 ° twist
the taper is not defined, i will define it better depending on the FM optipmisation
-the blade tip will be a BERP-like tip allowing better effificiency and a little inertia (and also a place for the flat nozzle)

[scottessex]

GET BUSY! Build it, I want to see you build it and fly it! :D

Looks cool, I like the design, any engine options at this point? :)

[Victor Duarte]

he he scot.. that's why i asked you about your suzuk , i can easily find one here... so, i wait for some real feedback.
I am limited to 100 hp to keep in the UL rules.
I was considering a Hirth F30, good power, just ideal to fit the mounting behind, sold a good price without gear but with centrifugal clutch..
But i had some bad comments about it so, .. i really stay away from hirth for now, maybe they will fix some problems.. i look at the HKS also.

Yes i will damn build it, fly it will be another mess :D i think someone will fly it for the first hops.. but i will perfom the taxi runs..
what i need now is time to put the drawings on plans...
But in the way i wan to do it, i want i cheap (for the frame at least) and feasable simply.. i will post the how-to.
thanks !!

[scottessex]

The Suzuki should be similar to a Rotax, (I hope) alot of the new snowmobiles and jet-ski's are using 4 stroke engines that have high power-low weight. I'll let you know about the suzuki. Stay away from Italian engines!

You could build a tube frame and the mount the "body" fuselage to it.
Were you planning on making the frame and body one piece, with the steel frame glassed or epoxied in place?

[Victor Duarte]

The Suzuki should be similar to a Rotax, (I hope) alot of the new snowmobiles and jet-ski's are using 4 stroke engines that have high power-low weight. I'll let you know about the suzuki. Stay away from Italian engines!

You could build a tube frame and the mount the "body" fuselage to it.
Were you planning on making the frame and body one piece, with the steel frame glassed or epoxied in place?
just right the subframe willn be "drowned" in the hull while molding.

about italian engines, right also, a good friend had an arrow 80 hp, powerfull, but a disaster in reliability. i think suzu is the best to fit that, because Suzuk sell the engines.. whitch is not easy for other brands.
the body will be one piece (just imagine a box tapered for the tail : simple shape)
in the drawing below i draw the subframe.

[Vance]

Hi Victor, are you going to build it for your self, or are you going to go into business? It looks marketable. How long to you think it will take? Ten years is a long time to think about something, you must be itching to get started. What is your first move? It looks like you would be able to see out of it really well, I believe that is a good thing.

I was taking to a fellow last night who flies an Acrosport aerobatic byplane. You can't see down and foward because of the engine and the panel. You can't see down over the side because the wings are in the way, and you can't see up and foward because the wings are in the way. When you are landing you can't see anything. I sugested that Autogiros have a better view and he was in total denial about the short comings of his ship. It looks like you have addressed it very well. After an hour of ranting about rotorcraft, and Autogiros in particular he finaly admited that he always liked the Bell 47 because you could see so much.

Go foward young man!! Thank you, Vance

[Helidev II]

Hey zeeo, good on you mate, go for it!!!
A couple of random thoughts.
I think that the BERP tip is a looser for your application. It adds weight, and reduces the overall efficiency of the rotor. Without the exact planform you may struggle to get it right. The Brits spent a fortune on it, and anything but perfect will reduce performace.
Most of the benefits of the BERP is high AoA on the retreating side for a helicopter, which isnt a large prob for a gyro.
Personally I would go with a simpler blade at first, 1 aerofoil, with small twist, and use that to shake down the rest of your ship. Then take the time to construct the more detailed rotor you mentioned. IMHO this would reduce your initial development costs, while giving you invaluable experience in blade construction.
Im sure youve done your sums and feel confident with it, however going to ambitious initially could leave you with a kiwi (a flightless bird).

[Victor Duarte]

Hi Vance, thank you, you are a part responsible for my decision, thanks again.
If marketable ? maybe, but for now, i do it for me, if i get it working good, it will sell itself, and you know, if going into business, the person(s) that will be at the first places.

10 years, fortunately, i avoided a lot of deceptions when i look back at my first drawings. but i took them back and let them aside also, it was not a full time project.
i as waiting for a trigger.
yes i'm starving to begin and for now, i need a shedule and funds, so the very first step, after plans, will be to build a mock up for ergonomy, visibility and dimensions , then, quickly, the mold, that will also be used to position the subframe elements.
all i need is 4130 tubes, plates, a tig welder (a friend has one), foam, roving, epoxy, sissors, a cutter, a brush, a handsaw and a good mask. i will post it all. thanks again.

Hi christian, happy you went back here, you are right about your thoughts, so, i separate building the frame and the rotor, for now, i can do the tests with a standard rotor as you suggest, the "new" rotor will need more work, but i will build the blades first.
About the berp-type tip : yes, i searched the net and VERY FEW info available.
About its efficiency, i think it will improve efficiency but will cause some extra weight, and i want it..because i want to keep a little inertia, loosing a little efficiency. read the nasa doc.
ideally tip jet blades should be shorter, thinner, lighter and be 3 4 or 5 to gain efficiency. but here, i only plan to use tip jets for pre rotation and power sustain during flight. but if i have a 3 bladed rotor that means a full cyclic-collective control, so.... who knows..

thanks for your comments

berp nasa doc : http://techreports.larc.nasa.gov/ltrs/PDF/1997/tm/NASA-97-tm4754.pdf
it is worth reading it, alla the gains and even tech info (airfoils, twist repartitio, thickness etc are related)
the only BERP doc i found, but good one

[Dean_Dolph]

Victor, I don't know from nothin' but how are you addressing the relatively long drive shaft from the engine to the redrive? It is my understanding that this has been a design problem in pusher fixed wings. But in that application I believe they are a straight drive.

[Victor Duarte]

dean, you know more than me, i m shure of that.

the shaft is comparable to a tail rotor shaft.. i plan to use a dural alu tube or a steel hollow shaft for power drive.
there will be a first twin-belt gear from engine to shaft, and a second from shaft to prop. the shaft is linked wit 2 flexible devices (sorry i miss the english word) at each end.

i need a torsionnal-endurant tube, so, it will have a big diameter (5 cm at least) and 2 mm thick.
i plan to have 2 bearings and a composite bishing close to the middle to avoid vibrations and flexion. the shaf passes in a tunnel that runs on the floor onthe entire aicraft lenght.
i know 2 UL planes using that : "balbuzard" and "isatis" but they use a carbon shaft.
thanks

[Vance]

I am familiar with several plans that used the long shaft, and the ones that had the problems used aircraft engines that didn't have a flywheel. The driveshaft couldn't deal with the torque pulses of conecting the engine with the flywheel (prop). A small auto engine shouldn't have that problem because of it's flywheel, but you will still need some kind of rubber doughnuts to keep it settled down. Suport in the the middle and flex on the two ends is the accepted way to do it, it allows you to keep the shaft lighter. Thank you, Vance

[Victor Duarte]

thank you Vance, so you ll it donuts, i call it "flector", can be a rubber disk or two half "grips" with an elastomeric damper.
your remark about torque peaks is very important, because without a freewheel, power don to up may simply break the shaft.

another point i investigate, still a draft : is to use a differential between the compressor and the prop shaft, this should allow the torque to balance but i think it could also penalize the prop shaft.... solutions appreciated.
thanks

[Vance]

Victor, each part and system adds to the cost and works to keep you on the ground. Part of the alure on an autogiro is less parts and less systems= less cost and development time. I have found it usefull to identify systems and have a living document to track systems creep. If it is just for you, then parts count is not so important.

Design to market is always an interesting excercise even if you will only build one. It starts with defining the mission and moves to why is this better and who will buy it and can they afford it?

I love design, but it is more fun with compensation so making a living doesn't get in the way. Customers never just come because it is better, they need a reson they can understand to buy it. Thank you Vance

[Victor Duarte]

Right Vance.. i must agree.. and let these "prospective thoughts" for very later.
each step wil need to be secured and the first will be to have a flying gyro. and i agree each extra device is more problems, weight, etc etc... just to say that if i do that, i dont close some doors for later..

for the missions specifications, i wont do the list, gyropilots all know what e can do with a gyro, the hardest to convince are those with "old-tales" statements..
I had a discusson with our local aeroclub president and, finally, he could agree gyros have a bad reputation but they have a lot of advantages that must be promoted.

we progress.. years ago,this club would even tak about a gyro , now i learnt there are 2 gyros under construction... i think , knowing a little who builds them, they will be safe and good for the promotion of gyros...

i must also say my sister's friend will help me in building and will start one when the alpha will have, as we say "cleaned the dust"..
cheers

[chuter]

After building my self-designed tractor, which doesn't incorporate any radical designs, I can tell you that no matter how much you try to get everything figured out ahead of time, you will run into problems that you didn't anticipate.

It's called R&D, and your first one is a "prototype".

But sometimes ya just gotta try it. ;)

[Victor Duarte]

thanks michael, i am conscious of that, i love r&d :D, i just hope 10 years of hesitation are enough :(
but your point is interesting, i tried to know more about personnal experiments, your venture seems very interesting.. if you dont mind, you can post come "spicy" details :D
it will help
about "radical designs"... i think people think it, but, looking close... it is not so radical, just packed differently..
Thanks michael

[gyroblackwell]

Good luck with your build. My tips for completeing a design are (even though I am still not finished with my tractor gyro ....)

1. set 1 week goals for yourself, and try to stick to them.
2. show your work to others at the end of your days building, or you will spend much time talking, and little time building.
3. settle on a design, and build it ....change your mind, and your work is wasted.
4. get as many "off-the-shelf" items as you can ... the less you have to machine or fabricate the faster your build will go.
5. Epoxy does NOT compare to standard fiberglassing in any way shape or form .... Epoxy is so much easier to put on. The air-pockets can be a pain, but the end result is a very strong yet light structure.

As a final note , I, as well as Don shoebridge, and others have been thinking about this kind of build for some time. If you want to start an open discission on this design concept,(dedicate a post to concept talk) we (at least I would like to help you with ideas, and solutions to problems) would like to help where we can. I would like to build a 2 seat version of this type of design, as soon as I get my present "bolt-together" ultra light tractor gyro design complete and flying.

Let the build begin!

Tim

[Victor Duarte]

wow, tim an others, i feel the wrenches up ! mine is up !

Tim i fully appreciate your recommendations, and as you see a spend more time talking before than i wil need during the building (i hope :D)

if you wan to talk about this design here, no problem, each tip will help each other and some tricks are useable for 1 or 2 seat.
but a 2 seat is an other mess, i just adapted he design for a one seat.. do you plan a tandum or 2 aside? i think you and don will not cosider the same limitations (hP, weight etc) my limit for now is a 100 HP engine...

yes epoxy is great, and i will avoid air on the frame, here is how it will be built. the hull will be molded in a "simple" mold square, tapered end , rounded corners, constant radius, just flat-n-round.
thank you for participating

[Screw]

Screw-In

Not to sound like a downer or anything, but as I understand that setup of the driveshaft problems you will run into is harmonics and vibration. These thing will effect everything from your engine operations to airframe stresses.

There was a show on TV a few years ago about a guy who set out to design and build an aircraft in 30 days.

He designed a midmount engine long driveshaft to prop, composit material aircraft. There were all sorts of complications just in the pen to paper stage, but mainly with the engine/driveshaft set up.

After abandoning that idea, he still set out to build an aircraft in 30 days. With the help of about 9 other people, they finished a kit bi-plane in the 30 day mark, but didn't fly. Of course, during the show, his relationship with his girlfriend was strained to point of break-up.

It was a funny show to me.

The design looks great and I wish you the best of luck. For simplicity though, do you think you could figure a way to make it a pusher or tractor with the engine placement accordingly?

Screw-Out

[Victor Duarte]

hi John
30 days sounds a world record, but i'm not in a hurry.
yes this shaft can be a cause of vibrations.., but wel driven, with non harmonic intermediate bushings, the shaft won't be a problem, just imagine a wunderlich prerotator flexible wire, it doesnt generate harmonics.
But i think the trick will be on the nose mounting. in an earlier version, the subframe was going until the nose. The prop subframe will be, of course, dampened. I expect an accecptabe level of vibration. The roving/foam/roving doesnt behave like a composite single skin.
BTW, i will try to have a little bending on the shaft, exploiting the elasticity (about 1 or 2 degrees) this little bending will stop the vibrations..but i dont know whether or not it can be destructive.

5 years ago i had a flight on an ultra light called "pelican", 100% composites and i found the vibrations where disturbing acousticly, due to the tail resonnance, but appearently, no problem for the engine-prop mount.. just a 4 points chassis and it worked fine. I expect the front of the hull, with a little subframe bolted to plates drowend in the nose skin to absorb gyroscopic prop vibes.. tests will say.. i cant stand firmly i will work fine the first day.

http://www.ultravia.ca/Modèles_ultralégers.htm

i can see their design changed a little.. i cant speak about the new build.

John, my girfriend is already trained for "self-survival" and my new born asks us some kind of maintenance :D :D

John, your last question is surprising, i specially wanted this setup to have the advantages of a tractor with the style and visibility of a pusher.. if i just wanted to fly-on-the-next-hour, i'd just build a bee or a bolts'n-tubes.
Frankly, my earlier constraint was : "what can i build easy, with my a litle tooling and cheap materials ?" .. the materials for the basic airframe will cost me less than a bolted alu one:
- chrome steel tube: about 40 $, welding, nothing.
- foam (insulation blue foam) 40 $ for all,
- roving & epoxy : about 100 -200 $ ... at this point i am about lets'say 300 $ of expense.. to have the hull quite finished. the expenses will begin with the need for alu profiles, nuts,bolts,dampers,bushings, bearings etc etc not speaking about the engine and all the gears.

and i can build it in my bedroom with unexpensive tooling... yes my girlfriend already lives in the bath room :D

your questions make me repeat my thinking, like an examen, and be shure it always make me wonder, but not discourage..
thanks John

centreal shaft links :
http://perso.wanadoo.fr/isatis01/

Details about the fuselage construction.

[Jerseywing]

It looks like a winner. Just a small suggestion...
Put some steel between the shaft and you.
God forbid it comes loose it can become a permanent birth control device sitting between your legs like that.
Best wishes on your build

Mike

[Victor Duarte]

It looks like a winner. Just a small suggestion...
Put some steel between the shaft and you.
God forbid it comes loose it can become a permanent birth control device sitting between your legs like that.
Best wishes on your build
Mike
Thanks mike :D
i will instal a "my balls bearing" :D
it is humour but it is very right, in case of crash or failure the shaft should not be a lethal part, i would have it a little bended (1 degree, this should avoid vibrations and force it to break in the desired direction.
But i must enshure this little bending will not be destructive.
in fact , there will be an alu cover on the tunnel to mount the stick, i expect it to protect me also.
Thanks mike

[Victor Duarte]

About the prop choice :
http://www.duc-helices.com/anglais/windspoon.htm
you will notice the "airspoon" tip, it looks like the main rotor blade "berp-style" tip i plan to use..
i am on a 3 bladed model but the final choice will depend on the engine...
they are damn expensive, but efficient, btw it is a critical part..

[Brian Jackson]

God forbid it comes loose it can become a permanent birth control device sitting between your legs like that.
:D Reminds me of the scene in the chopper in Apocalypse Now where the new guy asks "How come you guys sit on your helmets?"

Victor,
Nice project. Lord knows you've put a lot of thought and research into it. But I echo Tim Blackwell's suggestions. I'll even take it a step further... Have something to show every day. Even if it's only some notes or finishing the edge of some 4130. Speaking purely for myself, few things are more de-motivating than going to bed not having accomplished anything on your project that day. Small goals are paramount. Some days I only have an hour to file the ends of a couple of pieces I'd cut the day before, but those are the times I retire with a smile on my face, knowing that at least the hour I had was fruitful and produced tangible results. I see those small goals like the proverbial "string of pearls." Enough of them end-to-end, uninterrupted, and you finish the cycle with a thing of value. In our case, a living, breathing aircraft.

I wish you all the best my friend, and am anxious to see your ship eventually take form.

Regards,
Brian Jackson

[Victor Duarte]

Brian, thanks for your positive thoughts and wishes.

i read your post carefully, as it is a personnal "hotwire" situation, and i know what you mean.
Yes i must be conscious of the need to have a schedule. For years i have been managing small animation films projects and i kno that de-motivation appears passed the first shots..the rest is only work.. aand sometimes you'd prefer go fishing or walking.. it is human, and i won't hide it to myself..

but, the spring has been so bended that it will have to come out ! watch out :D
and the goal keeps me working... i never lost this goal, i just spotted it in a more "real" way.
my problm will not be a lack of motivation, but a lack of patience, and i have to learn to not file some parts like a beaver :D

Note : this thread helps me to assemble docs and notes..

keep posting your progress, i always read it.
cheers

[Brian Jackson]

Thanks Bro! ("Bro" is a shortened version of the word Brother in English slang, which parallels unity, just in case anything gets lost in translation. :) )

Yes, your springs are bent, (I'd call them "compressed") and eager to launch your project. Mine are too with my GyroBee. That's why I find it so important to get something done every day. That idea is not unique, as it was comforting to see several other GyroBee builders have online construction logs/diaries.

Your journey will be a long one, but so was that of many great innovators. I route for you.

Respectfully,
Brian Jackson

[Victor Duarte]

Thanks Brian for the vocabulary. ok for bro, bro.
you are so perfectionnist that i wonder if you used a "perth" diagram to plan your job ? seriously ! ? i began to build a schedule with excel but i know perfectly that a schedule is essentially made to be useless :D :D.
thanks

[quadrirotor]

If someone has any solution, would you be kind to help them, they seem to be stuck with that problem...(B12, B14)

[Victor Duarte]

stuck ?
a lot of bd 5 fly very well.. i use this aircraft as source for tech details.
http://www.bd5.com/
http://www.bd5.com/expo2002.htm

and what about helicopters tail rotors ? long transmissions work fine
http://www.kiwiaircraftimages.com/pages/a01b4704.html

thanks

[quadrirotor]

Beautifull expo of R/C, no one flying!!!! :D :D :D :)

[Victor Duarte]

no one flying ?
http://www.bd5.com/manning.htm

test flight notes : nothing about shaft problems
http://www.bd5.com/testberven.htm

if you speak of non flying prototypes, ok, the laflamme helico also doesnt fly :D

[Al_Hammer]

Victor, just be careful to avoid whirl modes and you should be ok. The following is from an accident report involving an R22 in which the tail rotor driveshaft was oversped and entered one of the whirl modes.

Tail rotor drive shaft whirl modes

Information supplied by the manufacturer indicated that the tail rotor drive shaft design featured whirl modes, which occur at 15%, 40%, 60% and 132% RPM respectively. The shaft fundamental (at 15%) is normally damped by the presence of the damper bearing, which is positioned reasonably close to the anti-node for this whirl mode. The mode at 40% is a fundamental whirling of the section between the damper bearing and the rear coupling. The second order whirl of the whole shaft length occurs at 60% RPM and should again be effectively damped by the bearing which falls close to an anti-node under these conditions.


However, since the drive is normally engaged when the engine is operating above these rpm figures, the shaft both accelerates and decelerates rapidly through these speeds leaving insufficient time for significant amplitude of vibration to develop even if the damping at 15% and 60% rpm proves ineffective.


Should the shaft reach a speed of 132% however, a further whirl mode will be encountered. In this instance, the damper bearing has no effect since its position coincides with a node of the shaft. The shaft deflects to form three anti-nodes, the two rearmost of which fall close to the planes of two frames, whilst the intervening node falls almost in the plane of another frame. The third and most forward anti-node coincides approximately with the plane of a frame of large internal diameter towards the forward end of the tail boom.


I think the Bell47 has many bearings along the shaft. The Helicycle uses a larger diameter shaft and has only a couple of bearings. I'm sure it's possible to calculate the resonant frequencies if you can find the formula somewhere.

[Brian Jackson]

Al, That sounds like the same physics that govern guitar string harmonics. Pretty amazing... I didn't realize the shafts were subject to this kind of harmonic vibration. The Bell 47 I fly in does have many pillow blocks down the shaft, which I'd always presumed was overkill until I read your post. Probably has nothing to do with the Harmonic Time Cube (http://www.timecube.com) theory. :D

[Victor Duarte]

Al, thank you for this very useful info.
they talk about "decelerate-acelerate" ? a kind of torsionnal eigenmode?

On B47 (i spent 3 years in a ag workers family with 6 B47, a B206, a shweitzer and an enstrom), the partitionned b47 shafts are linked between them with a kind of teeth gear, i was amazed of their lightness. mounted on bearings.
If i remember, this shaft allows a torsionnal damping of about 60 degrees, absorbing the little torque peak each time you start the lyco.

What do you think about the idea of gently holding the shaft sligtly flexed ? i think it can quiten it.

i dont think full stiffness is a solution, the stiffnes only transmitts vibrations better. the ideal would be a plain fiberglass bar.

thank you

[Al_Hammer]

Victor, stiffness can be important, I think. Notice how the Helicycle gets away with only 2 bearings. The shaft is made up of several segments of thin walled aluminum tube. The vibratory modes are apparently much different than for a small diameter solid shaft. I think your diagram shows the right approach to placing nodes.
I don't know about the eigenmode thing. The acceleration -decelleration was referring to not spending time at those rpms, so it was safe to accelerate past them.

Brian, that time cube stuff is really on the lunatic fringe- amazing. :D

[Victor Duarte]

Al, by eigenmode i mean resonnance, maybe i don't use the right word.
the helicycle sounds interesting ... just thinking two coaxial tubes seperated by an elastomeric tube could dampen high freq vibes and maybe some low freq...
the sandwich Skin/elastomeric/skin is used in airliners to damper vibes in the room.
(see PAULSTRA HUTCHINSON).
to be investigated... i can do it easily, i just need to replace the shaft..
thanks al

[quadrirotor]

http://www.prime-mover.org/Engines/Torsional/contact1/contact1.html

[Victor Duarte]

Thank you andre, finally a good reading indeed. usefull .
a quote (among many others):

" I know of many who have tried using a freewheel clutch in a hard system as the solution to the torsional resonance problem, but I do not know any who have succeeded in the long term. For these reasons, I can not recommend the use of a freewheel clutch with a torsionally hard system "

and the entire text is full of rich points.
thanks you

[Victor Duarte]

Air production :
tip jets require from 2.5 to 4 bar pressure and about 10 m3/s air.


a basic formula to balance tip jet propulsion forces is :
Fj = q(Vj-U)

Fj being the blade tip thrust
q : airmass (kg/s)
Vj : air flow speed ( here i take 500 m/s)
U : peripheral tip airspeed ( here i take 350 m/s)

Fj = 0,5 * (150) = 75

Power generated by one blade thrust :

P = q * U(Vj-U) = 0,5 * 350(150) = 26250 w ,
in HP : 26250*0,0013 = 34,125 hp
(could be roughly divided by 3, but i think i should perform this calculus for each blade as the numbers are not scalar)

"pleinitude" expected pl = nb of blades * airfoil chord at 0.7R /Pi*R = 3 * 1.7 / pi*32.5
pl = 0.04 whitch is just fine
Info : ideal values
powered rotor : 0.05< pl < 0.1
tip jet : 0.02 < pl < 0.05).

notes :
- the efficiency is estimated roughly to 0,4
- to have a better efficiency i should have thinner blades and a fast tip.
- the blade is 3 m long, the hub about 50 cm so, the diameter is about 6,50 meters.


SUPERCHARGER :
_______________

ROTREX supercharger C38.
comp ratio : 4
airflow : 0.5 kg/s

they are pretty compact and simple to setup, the oil circuit is independant.
Note : i would mount a second Magnetic filter before the oil reserve toi avoid chips to concentrate in the tank.
i would mount a radiator .

each weight about 10 lbs

Actually, i asked rotrex what should be the HP necessary to run 2 twin c38 compressors, still have no answer.

[Victor Duarte]

Wanted :
a light coaxial differential system to share torque between compressor and prop shaft.
thank you

something like this :

[Victor Duarte]

Some more details About the rudders design .
Why flapperons :
If i intend to use comp air for prerotation, i will also use it for a better yaw control by ejecting comp air over the flaperon (air knife).
Opinions, comments, shots wellcome.
thanks

[Victor Duarte]

Posted by Doug on another thread, i found it very accurate.
Victor: An "H-tail" design is a perfectly fine concept. The vertical fins will assist the HS by acting as end plates. You don't need a moveable elevator on the HS, unless (1) you use it as a trim device and/or (2) you use a fixed rotorhead and emply the elevator as your primary pitch control.

If your prop thrustline is above the CG, the HS should be at least partially immersed in the propeller slipstream. If it is not immersed at all, it will not work at slow airspeeds.

If the prop thrustline is above the CG, you also must set the HS so that it creates a variable down-load on the tail, proportional to the thrust of the prop. This can be tricky to achieve for all airspeeds and throttle settings. Again, it will require that the HS be partly immersed in the slipstream. It will also require that the HS have either negative camber (elevator up) or negative incidence.

As Don pointed out, there are other sources of pitching moments than the propeller on most gyros. For example, the drag of the landing gear and the aerodynamic effects of pods and windshields can produce pitching moments, too. These effects can be compensated for by the HS as well. However, a portion of the HS should be OUTSIDE the prop slipstream for best results in performing this task. That's because you want the portion of the HS force that compensates for these items to vary with (freestream) airspeed, not with throttle setting. If the entire HS is inside the prop slipstream, its total force will vary with throttle setting. For example, a fully immersed HS's force may be relatively low in a high-speed dive at idle power. Yet the drag and moment of the wheels/windslield and so on would be at their peak in just such a dive.


Thanks a lot Doug,
Allow me to report this post on "my design" thread as it may be of interest for others.
nb : yes i plan to have an in-flight elevator/trim mix, i plan to use a semi-rigid rotor, so, as you said, i will try to use the HS to avoid the pendulum behaviour to favour a direct control.
If I feel it too risky, i can finally disable it and just use it as a trim and use it's dissymetry of lift to have a down moment.
Thank you again.

[Victor Duarte]

Hi ,
i just delt today my future hangar place .
The flights, building and training will be on the same location, that is cool, but the tests will be on a second place : a wonderful brand new strip built with our money by and for a local politician's private use. a shame, but i hope the strip will be available for tests as the DZ is not officially aproved by the french DGAC (note that no demand has been done for that).

Note the shape of the airport site and the cliff after the strip, a don't fail, it is rated as "altiport". (that is not my jet :D)

Thanks

[Victor Duarte]

What i expect it to look like when (when.. ?) finished

[chuter]

Looks like it may be nose heavy? If you notice other 2 seat tandems, the rotorhead is usually over the rear seat. :confused:

[Victor Duarte]

Hi michael,
Your comment is right but it is a single seat, whatever, i must be careful on the nose balance, for that, i will put in the tail some devices like the battery, a small oil reserve etc.. I think when i will have the weight bill complete, i will have a very precise idea of the future CoG, BTW, the mast can be adjusted rear and fwd (2 bolts nearside, 2 rear/fwd side) to compensate a little.
thank you , every comment rises questions and makes me check if i am not that wrong.
Thanks
ps : the big nose impression is due to the camera FOV a little too wide, it makes things closer bigger..
attached : pylon mounted mast

[chuter]

Sorry Zeeoo, I was thinking it was a 2 seater. That makes more sense, looks a lot better. ;)

[Victor Duarte]

That"s ok Michael, thank you and don't stop to view and bring critics, that is why i made this thread.
cheers

[Mike Hook]

Victor

Here in the US there is several rubber couplings one is by dodge and the other is by faulk both do a great job in transmitting power and as well as helping in alignment problems on shafting. Did you think on putting the psru on the engine and then the drive shaft would be at a much lower rpm and they will help on vibiration and harmonics.

Mike

[Victor Duarte]

Oh Mike, interesting indeed... could you give more info please?
I as thinking in making the reduction in the nose (to avoid a big pulley near the gas tank)
I found this about "psru" but your remark is new to me.
http://www.epi-eng.com/GBX-WhyaPSRU.htm
Is there something there you know well ?

Thank you for making me finding some new great sites ;)

[Vance]

Hi Victor, why does it have five tires? Thank you, Vance

[Victor Duarte]

Vance, I think the wheels dimensions are not perfectly right, just to show I will use 2 lighter wheels instead of a bulk one (i call this mounting "diabolo") . Do you think it may rise a problem ?
Cheers

[Vance]

Hi Victor, no problems I can see. It seems to me that it is heavier than it needs to be and it raises the parts count. I am not sure that I understand the benifit. The load ratings in the catilog would sugest that three wheels would be plenty. Many of the Gyros that I have seen also have a tail wheel that is raised about 10 degrees up. It doesn't have to be very strong. Even a skate wheel will do. Thank you, Vance

[Victor Duarte]

Vance : i thought in using 2 thinner wheels instead of one to gain weight and to avoid torsionnal moments on the landing strut... what would you recommend ?
Thanks

[Vance]

Victor, a lot of unpredictible things happen when you add contact points. You will get vertical bending loads on bumps that only hit one wheel and a lever arm on tracking. More structure usualy adds weight. Smaller wheels see the world as bigger bumps. That does not make your wheels bad, it only raises questions because it is not like everyone else. Your creativity and originality is part of what makes it interesting. For someone like you, following is not the goal. thank you, Vance

[Victor Duarte]

Vance, i get what you mean, i will see if i can simplify..
Thank you Vance

[Mike Hook]

Victor

Here is one of the better coupling manufacturers for flexable couplings.
http://www.dodge-pt.com/products/pt_components/couplings/gear_coupling.html

The offer high torque and high RPM without vibiration. This may be what you need for your drive shaft from engine to PRSU.

Mike

[Victor Duarte]

Thanks mike, i found interesting componants on Dodge, a litthe heavy btw.

Have look a that also : http://www.acces.ac/catalogue/achat/produit-173.html
also : http://www.ktr.com/katalog/rotexgs_zr3_en.pdf

Thanks a lot

[Mike Hook]

Victor

I looked at the site but I can't read french. LOL Guess when I was thrown out of french class in high school for shooting the teacher with a rubber band ended the french.

Here is a US company that has all kinds of power transmission procucts.
www.grainger.com

another good sales catalog is McMaster-Carr Supply Company
their email is cle.sales@mcmaster.com thier catalog is on cd so they could send you one.

[quadrirotor]

Go direct to the manufacturer:
http://bostongear.com/products/enclosed/ra.html

[Mike Hook]

Victor

Have you any data on the torque required for a spin-up for the rotor. That will determine what size gear case you will need. The higher the rpm the lower the torque. Just a thought your installing a drive shaft thru the center of your gyro. Is it possible to install a gear box inline on your shaft with two outputs so that you will have a psru as well as a output for your pre-rotor. Just brainstormin here this morning.

Mike

[Victor Duarte]

Mike, very pertinent.. look back on my posts, i searched a kind of coaxial differential gearbox, one output for the prop, the other for the prerotator, but the problem is to share the torque/reduction on the 2 outputs, one at almost 2000 rpm, high torque for the prop, the other at aprox 10000 low torque for the compressor.. i didn't find this device yet..
andre, good link
thanks to all

[gyromike]

Victor

another good sales catalog is McMaster-Carr Supply Company
their email is cle.sales@mcmaster.com thier catalog is on cd so they could send you one.

McMaster-Carr also has their entire catalog online (http://www.mcmaster.com).

[Victor Duarte]

Mike thanks ! what a catalog ! thats incredible.
thanks

[Vance]

Hi Victor, It has been my observation that most long drives to the prop in aircraft have suffered because they were running an aircraft engine with little or no flywheel. They use the prop for the flywheel. I have also seen conventional u joints that have angular acceleration challanges of their own. Supporting a long shaft is also very imoportant. The drive that you propose can probably be done with automotive constant velocity joints just like the drive under your car. If you have a flywheel on the engine and it is realitivly high speed it should be fairly simple. It is less dificult that the tail rotor drive on a helicopter. Thank you, Vance

[gyroguy]

Overall your proposed design looks good. I've got a few comments, and I'll put them all in one post because I don't get on the conference that often.

1-- Driveshaft. In the early days of ultralights, we experimented with engines on top of the wing and pusher props at the end of the root tube. One design had a driveshaft from engine to reduction drive mounted on the end of the root tube. Driveshaft failures resulted from high modulus of elasticity due to unsupported length of driveshaft. When this occurred over your head it was quite exciting. Second design bolted reduction drive to the engine, with driveshaft turning about 60 percent slower, to a pillow block bearing mounted on end of root tube. This had no failures. The principle may be useful in your design. FYI, we counted on the 2-inch by 2-inch root tube to keep the driveshaft away from the pilot. It worked.

2-- Rotor configuration. As I understand it, you can have a smaller rotor diameter with three blades. Disadvantage is the potential for ground resonance with three-blade rotor. Disadvantage is more complicated rotorhead and weight of an additional blade. The two-blade teetering system is about as simple as it gets.

3-- Construction planning. I write gyroplane assembly manuals. One thing I do is to pre-plan the construction sequence using a PERT chart. An example of PERT charting with house construction would be: 1) Pour concrete slab, 2) Frame walls, 3) Install roof trusses, 4) Install roof. Each of these items must be done in sequence for the project to be a success. The PERT chart also identifies events that can occur simultaneously: 2a) Frame interior walls, 2b) Frame interior doorways, 2c) Frame interior window portals. On a real PERT chart you would estimate how much time was needed to complete each item, with the longest time requirement for simultaneous items counting as the minimum time for that segment. For example, 1 day for framing interior window portals vs. 2 days for framing interior doorways means a 2-day minimum. Finally, the PERT chart identifies the CRITICAL PATH of things that MUST be done, in sequence, and determines the shortest possible completion time for the project. Recommend you look at your construction project in this way to identify in advance as many conflicts as possible.

4-- Rudder bottoms. Recommend you consider some kind of flexible skid on the bottoms of your rudders to prevent damage if you flared a great deal and contacted the bottom of your rudders. Another option would be to build an inline skating wheel into the bottom trailing edge of the rudder.

5-- Airframe design. Mooney builds airplanes with steel fuselages inside the aluminum sheet metal. Basically they have a roll cage like a racing car. Your design could work in a similar way for pilot protection. For example, the joint where your windshield meets the canopy could be a roll bar, and another could be placed over your instrument panel,etc. Pilot safety can be designed in cheaply if you plan ahead for it.

6-- Main landing gear width. Your proposed design would make a very stable landing gear on the side-to-side axis. Many people in the U.S. transport their gyros on trailers behind cars/trucks. Just looking at the design, it appears your landing gear will be wider than the 8 feet width allowed on a standard trailer. If so, getting your gyro to the airport would be difficult.

Hope these comments will be helpful, as I like what you are trying to do.

Now, go cut some foam!

--Kerry Cartier

[Victor Duarte]

Kerry,
Your comments aare very accurate and useful, thanks for the time you took to write them. Here are some replies to your remarks :

1 - i think, on other people recommendations also, that i will do the first reduction on the engine, in fact , i am working out to find a differential that could be used to share power between the engine and a compressor or hydraulic pump, and, so, acting as a reductor... nothing fixed, proposals are open. I think the shaft won't be a problem and there will be a sufficient protection for the pilot'balls : a tunnel + an alu cover.

2 - the rotor will be, for the first version a classical 2 bladed teetering rotor...
the pylon mount will allow to develop another rotor and to fit it with minor mounting changes.. the "other rotor has not been decided, but i work on an alternative design, a 4 bladed hingeless, more complex but more lift and more "forgiving" neg G.

3 - I know how to work with PERT but i find that this kind of planning is more suitable for a true production process, You know as well as i that every hasard can turn the PERT useless.. and in an amateur build, a lot of hazards can occur ;) alas
But instead, i plan to have a weekly-shedule, easier to change in case.
For organisation, i actually build a database for all the design/build elements and sub-elements, doing so, i can have a precise nomenclature and all infos about progress with cost/design/buy/weight infos.

4 - you are right about the skids, my renders don't show it but it will have a "S" flexible skid on the tail , i hope the ridders won't need one but you may be right... BTW i plan to have a little flexible antenna on each rudder to "alarm" on an eventual blade touch..the upper mart of the riddders will be "breakable" in case of touch, then there will not have a loss of control (i expect).

5 - I din't think in roll cages for pilot protection, more in the fact that the foam hull can crumple and absorb a small crash. In this case, the mast pylon should act as a roll cage...

6 - about the landig gear width : yes i favour the stability and the possibility to mount something under the winglets (a camera for example). the actual width is actually about 1.80 meter (about 6 ft). should be ok.

I am starving to cut some foam :D, and some steel too... but for now i will cut some plywood to buid the assembly frame/mold.
Thank you Kerry,
cheers

[Victor Duarte]

Hi all, a litle time since my last post, That doesn't mean hat i am unemployed at all .
I work on making my plans "clean" to build the main mold.
Actually i worked to estimate the hull's weight and i get a 40 lbs with the wing and spar.
I also worked on the rotor design for later, his weight is about 62 lbs without the swplate and the controls (i expect it to be about 20 lbs only).

My first step in buillding will be the wings (epoxy over foam), the spar (molded composites).
I meet the composited dealer tomorrow to choose and eventually order the materials.
the next steps will be
- to fit the landing gear.
- build the main mold.
- build the subframe.

Thank you for your interest.

[Brent_Brown]

go to this website and see how he made the foldaplane Vision airplane. I think this is what you should do for the body. glassin the spar and bolt on meat and motor.
http://www.visionaircraft.com/foldaplane/

[Victor Duarte]

Brent You're THE man ...happy Bday :D

Yes that's exactly what i was planning to do.
In fact , years ago, i wanted to build a bassboat based in the same principle, a flat shape folded and bended to obtain a hull, so, i went to imagine a method to build a fuselage.. the drawing you see is made to obtain the unfolded shape i will make of plywood+a sheet of plastic.my hull will be made with a 30 mm thick foam.

I must have a minimal subframe for the mast and engine.
it will be bounded to the hull b this kind of part.

Thanks again Brent