Hello!

Somebody did autogyro under 26сс the gasoline engine? What blades can be used for a rotor and in what quantity?

I wish to use 3 blades from 90 class heli in length about 710-720 mm(63 mm width).

Model parameters:
Fuselage length - 1200 mm
Main rotor with a direct drive gear
Tail uncontrollable
Take-off weight to 3.7-4.2 kg
Engine thrust - 6 kg


Whether such blades will suffice me that the model has flied up? Or it is necessary to do blades most? Whether there are any design procedures of the main rotor?

WBR, Alexander

Alexandria,
Don't use Heli blades..
I would use Aero Balsa Blades if I could. Other wise use a Clark Y flat bottom blade. I work in pounds so don't know kg.. Maybe 36" blades almost one meter.

Jim

I have in mind something like that for a 30cc gasser.... I made some numbers a few time ago, but I can't find them.

Well, I'm not the best person to speak, but just to give an idea... Rotor loading and rotor size vs engine size seem like the main things to watch out for, since they are quite different from those on a plane. While a plane can usually fly with low/excess power/wing area, autogyros are more critical to that. In my experience, a very low rotor loading is advisable, as excess weight soon "kills" the gyro capabilities and behaves similarly to a plane; the machine has to fly fast to have enough lift and you virtually lose all the low speed advantatges they have. You can't just cure a heavy craft by adding rotorspan, as it also adds drag and other forces which your frame/components might not withstand.
I think you can get a basic idea of dimensions by finding cessna-type planes which use your same engine, but keep in mind that your craft must be even lighter, so you'll likely keep the wing (rotor area) and shorten somewhat the other dimensions.

Using heli blades isn't a good idea, IMHO. You need lift, lots of it. A symmetrical blade will give you very poor performance; Jim is very right about that.

By the way, what do you mean with "main roto with a direct drive gear" and "uncontrollable tail"?
Anyways, I wish you luck with your project!

Thanks for interest to the project!

I will begin the project of autogyro since June-July (after I will complete Sopwith
Camel 1/4), and by this time I assemble the various information on a design of
details and methods of prerotation of a rotor.


While I tend to a rotor design here at this autogyro.
http://www.rcuniverse.com/forum/m_7213200/tm.htm


Also I was issued with rotor blades. They will be self-made and length 1000 mm (3,28 ft).
The profile is a NACA 8-H-12. Anyway to me it was advised by one of our gurus in autogyro.

Total diameter of a rotor turns out 2150 mm that at take-off weight in 5 kg (11 lb, but I
think will be a little smaller) will give loading on a rotor in 12g/dm2 (~4 oz/sq. feet)
that is comprehensible as me the aforementioned guru has prompted.

Still not clear while the moment with blades - what to choose a blade chord?
While the parity 8:1 or 9:1 is supposed that will give a chord of 125(~10 in) mm or 115.


The rudder will be on the area big, and on appearance of the classical scheme,
here I have already understood that experiments not to spend better

Rotor details will be made of aluminium.


While I have two not clear moments:
- What servos to establish on a rotor drive gear? While I assume on 33 kg effort Turnigy S8166M Servo.
- How to do rotor prerotation? While two variants: the electromotor 480 classes and a toothed
belt from the electrotool (as on the aforementioned reference) or prorotation at the expense of a
deviation of an air flow from the engine upwards on a rotor.


Blades I will make of a beech and balsa. From a beech will be first 1/3 of chord of the blade
and a root part, and from balsa the others 2/3 chords of the blade and from above it will be
covered by fiber glass. The beechen part will be made most likely on CNC.



I hope by August-September it to realise!

If you have to machine your rotor, which I think is a must for such a big craft, I'd try to add some kind of mechanical limiters for the blades. Something, such as a set screw, which limits the flapping in each way, at least on lower side, to avoid blade strikes and (if you add on the top side too) excessive blade flapping during takeoff and particularly hard maneuvers.
Your numbers seem to make sense, and such rotor loading is very good. BTW, which guru are you referring to?
For the blade chord, generally speking, the larger the craft gets, the higher aspect ratio you need. Smaller craft tend to work better with wider blades, but as size goes up, they seem to like thinner chords. I'd start with something like ~10:1, which seem a good middle point.
Be careful with the rudder! If your fuselage isn't long enough to put the rudder after the rotor, then you may have problems to have enough area and rotor clearance (some people use small rudders under the craft to avoid this, even historic aircraft).

I can't help you with servos, but as you may know, use powerful stuff there. An average servo may even break under certain loads.
For the rotor prerotation, you have several choices. The air flow idea has been tried before, at least in full size craft, with not so good results. I personally dislike it.
- For small craft, a flat spring wound around the rotor can do the trick. It can be installed so that it releases it's energy only when you tilt the rotor full back and then it doesn't affect the spin during flight.
- For medium-big craft, a small motor seems to be the best solution, but it adds weight where you don't want it. Perhaps you could even mod a strong outrunner motor so that it shares tha axle with the rotor, and spins it during prerotation without any external gears.
- For big autogiros, you can use a flexible coupling from the engine. A very realistic method, perhaps even lighter, but not an easy one. For the coupling, you can try one of those that come with chinese dremel-like tools (they cost like 15€ or 20$, so you can give it a chance) and include a flexible coupling which might be shoul be more than enough to move
I hope this is of some help.

I welcome all fans autogyros!


At last business has moved from a dead point and construction of mine autogyro has begun.
At present to me make details of a rotor and the rotary hinge of duralumin.


Also other colleague does plywood details of a fuselage and rotor blades on a CNC-milling cutter.
Next week I plan to assemble together a fuselage, a rotor mast which not so long ago has welded
in car-care centre.

Before manufacture of blades of a rotor, I have decided to make some sample (short pieces) blades
With a different design for a choice of the blade with the most favourable position of the CG.

Drawings I finish on a construction course so all of them time vary in trifles.

Prerotation I will use at first from electromotor GreatPlanes 42-40-800 through a belt drive.
If wind and a place on a runway will be enough for prerotation - the electric motor I will clean
that will positively affect balancing of autogyro and its total loading on a rotor.

Looking forward to seeing how you progress with your large autogyro, I have started building a large gyro to be powered using a Laser 150 vee twin. Unfortunatly due to other projects and financial reasons (large powerful servos needed) so this has been shelved for the time being. My only advice at this moment in time is to keep it as light as you possibly can for good flight peformance...every gramme saved in weight is worth it..Im not sure how long your blades are? the largest I have built to date have been 100" span and these are constructed of bass wood and balsa, they use a flat bottomed clarke y aerofiol and seem to work well.
Im looking forward to how your build unfolds.

Regards Rich

rotor span 85.5", and length of the blade 40.55".

On steering of a rotor I have bought on www.HobbyCity.com giant servos with strength of 33 kg for $30 that rather cheaply.

Those servos should work out fine, on my 75" rotor spanned tractor model I use two 12kg torque servos using a push pull system and these work ok, on my larger 100" pusher I use two 25kg servos in a load share system so in theory I have 50kg of hold torque. This one uses a teetering head so I dont think the forces are as great.

Regards Rich