ottogiro58

Hi Gang !!! I am very interested in developing a two-bladed rotor head for my gyroplane, and was wondering if any of you have had success in flying one. Please post your success stories here on this forum. I would like to hear about them. Thanx !!! Charlie Anderson

Lizard

I have seen and flew two bladed model, but has anyone seen a flying single bladed model with a counter weight I'v read they used single bladed propellers in control line models in early days. Would that method work with autogyro's blades?

ottogiro58

Hi Lizard !! I checked out your two-bladed flapping head and was impressed. The single bladed head would work, but there would be a great loss of efficiency. There is a single bladed free-flight helicopter called the Charybdis, or something to that effect (another version called the Rotoriser). I think someone has even made an R/C version of it. The rotor blade would have to be thick and wide for use on a gyroplane, in order to gain some level of efficiency. Please keep me posted on any new developments of your two-blader. I will be resuming experiments soon with my teeter head. Good luck and happy landings !!! Charlie Anderson

Hal deBolt

Hi ya'll,]
Two blade rotors? Yes they work fine. perhaps not as efficent as 3 blades
but do the job.
Advantage is with the blades, 1/3 less rffort. Rotor head very simple from aluminum angle and maplr engine mount stock.
The '77 MAN Trainer did well with 2 blades. Coming Giro Plane trainer features two blades and does fine.
Note that all Gyroplanes do well with 2 blades.
Good luck, have fun!

Hal [email protected]

Spindizzy

Hi Otto

I have used two bladed hubs on a couple of my gyros. Personally speaking I find they are not as efficient or stable as 3 blades. The rpm was a lot higher and vibration then becomes a problem unless the balance is perfect. I did use a two blade hub (attached image) on one of my early winged gyros and it worked just fine however I would not recommend a two blade for use on a non winged direct control gyro.
I have seen some gyros that use only two blades with direct control to great effect though...I think Emery Wayman made a lightweight electric gyro that flew best with thwo blades rather than 3 so I guess it depends on how well you design it !!!!

Sean

ottogiro58

Hi Sean !!! Thanx for the pix of your two-bladed head. Looks good. I have yet to start working on my two-blader due to other obligations. It will be soon, however. The key to success, in my opinion, is to use thicker and wider blades. I may try some foam blades with ply or hardwood spars. Rotor RPM can be significantly reduced with the use of thick blades. My early experiments verified this. Using helicopter blades, the rpm was well over twice that of my homemade 7/8" thick airfoils, and it didn't have nearly as much lift. I have some foam wings from an airplane kit, and will convert those into rotor blades. I believe the teeter head (as opposed to the flapping head) runs much more smoothly (less vibration when balanced). I hope to get some extra time soon and resume my experiments. If you have the time (and the gumption !!), give some lightweight thick/wide blades a try on your 2-blade hub. You may be pleasantly surprised !!! Happy Flying !!! Charlie Anderson

Spindizzy

I might just try those thicker chord blades

If you are planning to use a teeter hub on a gyro that does not have a wing for stability you may find that you will have stability problems. The problem is that full size teeter gyros get the flapping effect from the flexibility of the blades so unless your blades are very flexible you may have problems........also a teeter hub with rigid blades tends to precess rearwards a lot.
I wish you every success and if you manage to fly a gyro with just a teeter hinge and rigid blades I will be very impressed not to mention asking you for design drawings so I can make one !!!

The only successful model with a teeter hub that I know of is the Whistler and that will NOT fly without the wing for stability.

If your teeter doesnt work and I hope you do succeed with it , try a two blade hub with offset hinges.

Sean

tintrax

I have a small `Gyro Kite` which has been on the market for several years. (Not to be confused with the `GyroRaptor). It has a teetering head. The plastic head broke within five seconds of the first attempt to fly! I made my own teetering system from ply & tubing. This kite does fly, but needs a stiff breeze. Probably heavy for its size. There is provision for adjusting the head to one side or the other, and provided early test flights don`t result in a broken kite it does fly quite stably. However sooner or later it hits the ground and the plastic fuselage, or rotor mast, breaks.
Anyone tried this kite? I am thinking of making another, scratchbuilt, but bigger and lighter, with a teeterhead. Perhaps a good way to gain experience of teetering heads before going to a more valuable r/c model.
Colin

Hal deBolt

Hi Tintrax,
Good to see someone investigating rotors. so much of what has been done has been follow the piper. What that is may work OK but is there
something better, simplier? The only way to get proper data is to test all
aspects?
This requires effort, fabrication? To bring this to a minimum a method was
developed which produces precise blades quickly without labor per sey.
This is detailed on the Model Airplane News web site under "Quick and
Dirty Wings-Blades" address> modelairplanenews.com
Also of interest> in recent times I have been investigating 2 blade rotor
systems,relative to 3 bladers. Thought being that of importance could be
the area of the blades. Perhaps if the area of two blades was equal to that
considered proper for 3 blades that would be a major aspect. So that is
the design I have used.
Also other experience has shown that airfoil chords of less than 7" are
very inefficent. For that reason wider than normal chords have been tried.
Also investigation showed that chords of 7 to 8% of the span were most
desireable. Reasons if desired another time.
Results> Flights of equal to 3 blade performance in all respects were seen. These findings plus past experience say a 2 blade rotor is adequet
It could be that 3 blades are more efficent but if so the added bit does not seem necessary.
Known> Drag increases as he quadruple of frontal area increase.
Airfoils used have been 10% thick regardless of chord. Obviously the
wider the chord he greater t he frontal area?
Perhaps tthis accounts for the same flight RPM seen with 2 or 3 blades.
Finally> for me at least it is an advantage to test action without flights,
wind tunnel? I found a way to do this which is so simple it is pathetic!
I use a "car tunnel", attach the Gyro or my test fixture to the hood of my car and drive down the road.. With this mehod I get COMPARATIVE
RPM and lift amount readings.
You wish car tunnel details contact me, OK?
Nuff for now?

Hal [email protected]

ottogiro58

Hi Hal !! I got a big kick out of the mention of your "car tunnel" !!! That brings back memories of my first gyro experiments in the mid-'80's. I had a Buick Gran Sport Stage One Sun Coupe at the time, and would open the electric sunroof, hoist a stick with my experimental rotor head on it, and test its spinup and lift by driving through the neighborhood !!! The looks I would get from passer-byers were priceless !!! It was a great way to test the rotor heads, far easier than waiting for the right breezes or running down the block with rotor in hand. The Sun Coupe is long gone now, but I gained enough knowledge of teeter rotor performance back then to realize its potential. My control-line gyros fly great with a two- bladed teeter head (wingless). Spinup is quick and power-off glide is nice and gentle. I hope I have sparked a serious interest in the many experimenters out there. It would be a major accomplishment to perfect the two-bladed teeter rotor head for model use. I have spent countless hours working on the project, and in retrospect was very close to success when I turned to an alternate solution, the twin-contrarotating rotor layout. Though I am more than pleased with its performance, something inside me (the latent scientist !!) keeps telling me to finish what I had started. I really won't be satisfied until I am flying a wingless two-bladed teeter head. Hat's off to all of you who decide to take on this challenge !!! I wish you luck and many happy landings !!! Charlie Anderson

ottogiro58

Hi Sean !! It would be great to hear about your next experiments with thicker/wider rotor blades. The problems with using a teeter head are significant, but not insurmountable. Perhaps most significant (as you noted) is the fact that model rotors are very lightweight in comparison with full-scale blades. The lack of weight causes the blades to rise excessively because centrifical forces cannot pull on them enough to stabilize them. Therefore teeter head models will require more tail clearance to prevent strikes. There is a fine line between excessive weight, which causes slow spin up, and not enough weight, which may induce excessive teetering. Teeter heads also require built-in stops to prevent tail strikes. Other experiments seemed to show that having the teeter bolt slightly above the tips (plane) of the rotor blades induced a stability to the system. I also used a slight coning angle (dihedral) in my R/C teeter head to minimize necessary teetering. One good aspect about the blades rising/coning angle is that this induced dihedral allows these models to be easily contolled by rudder only. Rotor tilt should not be necessary. For a while, I was flying my control line gyro with pennies glued to the underside of the blades. This definately added stability. Spin up was slowed, however. On my C/L models (1/2A), it also caused the models to be a bit top heavy (total weight of the model was 10 1/2 ounces). As most of you already know, gyroplanes are balanced not only longitudinally, but vertically as well. It helps to have the thrust line passing through this vertical Center of Gravity. Finally, it would probably be easier to build a 2-bladed flex plate head. By using thicker/wider rotor blades (increasing solidity factor), more lift would be gained. This may necessitate the use of a slightly more rigid flex plate. By slightly increasing the rotor diameter, more centrifical force would be generated, perhaps eliminating the need for a more rigid flex plate. Good luck with your future experiments. I look forward to reading of yours, and of others, exploits. Keep it fun. Charlie Anderson

Spindizzy

Otto

I would love to have a teeter only system (without wings) so I will follow your progress with interest.
You also mentioned having the teeter bolt above the plane of rotation. This reminds me of the reason why teeter hubs on helicopters have the teeter bolt in this position also .It eliminates the need for lead/lag hinges due to the fact that as the blades rise and fall their c of g remains in the same plane of rotation therefore preservation of momentum rules are obeyed. This reduces vibration and blade stresses. Basically as a blade rises it also moves outward and vica versa when it falls........simple and very clever.

Have you considered using an delta hinge for the through bolt on the teeter hinge ? The whistler uses this to balance out the forces and reduce the amount of precession. As the hub teeters the angle of incidence is directly altered......I can photograph the relevant section of the plan if you wish ?

Sean

ottogiro58

Hi Sean !!! When I constructed the teeter head for my .15 powered Whizard conversion, I did not have a drill press and was somewhat sloppy with my drilling of the teeter bolt hole. This resulted in a delta type arrangement. This rotor head worked fine, but was rather inefficient (flew faster and did not have great lift) due to other reasons, namely flat non-airfoiled rotor blades, too much negative blade incidence (seemed to be needed at the time for quick spin-up), and too light of blades (inducing excessive teetering). I will incorporate several improvements into my next rotor head. Stay tuned for future developments. Charlie Anderson

ottogiro58

Hi Gang !!! OK, I'm making progress on the two-bladed teeter head project and will have gyro ready for test flights next weekend if all goes well. Rotor head is done, now I must finish the rotor blades. They are foam wings from an old Ace R/C Alpha .15 airplane kit. I will slightly modify the wings and add blade attachment points. Blade chord will be 5" or so. Blade thickness is @ 5/8". Pylon must also be constructed. I look forward to the test flights to come, and will keep my forum friends posted on my progress. When pix are available, I will post them also. Happy Landings !!! Charlie Anderson

ottogiro58

Hi Gang !!! Today was the big day. Would my new foam rotor blades do the trick ?? I mounted them to the latest version of my teeter head, and VOILA !! they work FINE !!! Spin up is very quick, and mega-lift is there. Teeter operation is smooth. Tail clearance may be a problem if I use the Whizard conversion. I may be forced to build a fuselage that will easily accomodate the big blades. The new 17" x 5" x 5/8" thick blades make the familiar old "chop-chop sound", like full scale blades. Total rotor span for the .15 powered gyroplane is 38 1/4". I may have to postpone test flights unless I can work out the blade clearance problem. It wouldn't take long to make a new fuselage, if needed. This new improved version should be worth the wait. I'm psyched. Charlie Anderson

Spindizzy

Otto

I eagerly await flight testing......and of course a few pics would be nice .

Sean

P.S Still building my small .10 powered co-axial design. This is the most stable type of gyro I have ever built ( I built a larger version first) and I hope to use it to encourage others in my club to have a go.

duggy

hi sean ,
i am a student pilot with a few hours in pusher gyros ; a friend of mine is building a single rotor tractor ; i am fascinated with the coax design ; if powered , the coax could take off like a helo and then fly forward in autorotation as a gyro ; have you considered powering the coax setup ?
duggy

soarrich

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I built this teeter head after seeing Whistlers fly in Indiana. Kind of got sidetracked, but I'm getting gyro psyched again.