C-4 "Centenario" Autogiro project

Here are the results of my calculations for this four bladed rotor 8.5 x 0.225 m, assuming a total mass of 350 kg,
For 312 rpm pitch setting = -1.2° And at 20 m/s a1=0.3° b1 = 0.5° A.o.A shaft = 22° Rotor drag =1380 N

Such a high rrpm produces very high losses due to friction which requires a large angle of attack of the disc, and a negative pitch setting in compensation.
If you want to use 4 commercial blades of pitch setting suitable for an acceptable efficiency (i.e. about 3°), then each pair carrying only half the load, the rrpm will be about: 315/1.41 = 220 rpm which will not pose any safety problem as long as Mu does not exceed 0.35 (ie here about 125 km/h)

For example, with four bladed 8.5 x 0.225 when the pitch setting is +3°, my calculation gives:
223 rpm at 20 m/s a1=2.2° b1 = 0.7° A.o.A shaft = 9.5° Rotor drag =715 N
But in order for such unstayed blades to maintain their usual coning, it will be necessary to accept an 80 kg rotor and to allow for a few degrees of freedom between the two pairs, otherwise cracks will appear very quickly at the roots
 
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allow for a few degrees of freedom between the two pairs, otherwise cracks will appear very quickly at the roots
Jean Claude,

Could you please expound a little on this. Chuck and others repeatedly warned against paired teetering rotors because of rapid fatigue cracks at the root. If I have read your work correctly, in this thread, stays between the pairs, at some specific radius, helps structurally.

Thanks Jean Claude,

Jim
 
Jean Claude,

I re-read your posts 51, 53, 54, and 56. It seems to make sense to me now. Thank you.

If it is convenient, could you expound on the "stays" a little. Structure, material, any possibility of a modern interpretation to this type rotor?

Jim
 
Equi-distribution cables can only remove stresses in the roots if the below shrouds keep the blades with no coning.
But in this case, the additional drag is penalizing to high Rrpm. This becomes unacceptable when we aim for Vne above 55 mph.

Cable diameter required for 1000 lbs: at least 8 mm diameter. This is acceptable compared to a 0.7 m chord of blade, but not compared to a 0.22 m rope blade
 
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Elapsed time 243 days/ Pending time 115 days
We have already started the fabric covering.
The stabilizers and the wings are already finished.
The best of all is that we have had young people who want to help us.
Each day less time left!!
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The first trial will be using the conventional rotor that we know to minimize the risk, but we can do the four-blade rotor when the autogiro will be tested and the new way to fly tested and safe.

In any case, if we do the 4 blade rotor head, will be always a fix rotor, no cyclic input.

Our main concern is how to control the autogiro in the take-off and landing, as you know the autogiro will be controlled by the ailerons, and tail surfaces.

In a gyro the control is done by the cyclic so even we have cero airspeed we have control, but in our case, we need a minimum FW airspeed to control the autogiro.

From the other side, the current airstrips are runways, (longitudinal lines) with no possibility to align the take-off and landing path with the wind. In the old times were circular strips facing the wind.

This is our main concern.

How to control the autogiro in the case of cross wind?

We need a minimum speed to have “control” by the ailerons like a FW, but in a FW you can reduce the incidence angle of the wing after take-off to kill the lift. In our case the rotor will be turning, and our “wing” will have the chance to tip over the ship even when our forward speed will be cero.
There was of course an early of version of the C4 in which Cierva controlled roll directly (tilt head) rather than by ailerons and pitch by elevator. He did not pursue with this set up (and direct control for a while) as he found the loads and vibration to be very bad. He solved the vibration and load problem much later when he perfected direct control.

You could use this configuration (direct roll and elevators for pitch), it would be historically accurate and give you much more control in roll and alleviate your concern with crosswinds.
 
There was of course an early of version of the C4 in which Cierva controlled roll directly (tilt head) rather than by ailerons and pitch by elevator. He did not pursue with this set up (and direct control for a while) as he found the loads and vibration to be very bad. He solved the vibration and load problem much later when he perfected direct control.

You could use this configuration (direct roll and elevators for pitch), it would be historically accurate and give you much more control in roll and alleviate your concern with crosswinds.
Thanks Raghu, yes, we thought about that configuration. This was the first configuration used by de la Cierva, but he had so many problems that he changed to a fix rotor. This second configuration was the one that flew.
Yes, could be possible, but we are running out of time, few weeks left before January so now we are focused to do the idea we had at the beginning of the project, no time for changes.
We are at the limit to achieve the date, ………let see if we could do it.
After January 17 we would like to do some improvements because now we are doing the minimal work to have a “flying” ship.
 
The first radio control autogyro I built had a teeter bar with a delta 3 pivot angle, but it was fixed. The tractor gyro had wings with polyhedral tiplets at a 45deg. angle. (it looked like a Cierva with a lower aspect ratio wing) It had rudder and elevator control and the roll imparted by the tiplets worked very well, you could fly this gyro aerobatically.
I was able to do rolls and loops easily, but the power to weight ratio was ridiculous.....
 
Days elapsed 325/ Days pending 33
Also we did the first run. The ground stability was perfect.
Left side is not closed yet to have access to all the controls.
The wooden structure looks very nice.
Enjoy the videos!!


 
Arco,
On this picture, it seems to me to see a "flat four" engine with a gearbox.
Can you specify which one, please?

Sans titre.png
 
Finding a rotary was short of impossible. So, resorting to a Rotax 912 was a sensible option. This construction has been completed with lots of ingenuity and effort, and on a very tight budget...
 
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Hi,

we selected the Verner motor 80 hp, but we have two problems.
The first issue is lack of money, we are doing the whole project based on our own resources. We are in conversation with some institution and companies ( Airbus Helicopters and others) to get some financial support but up to now no money arrived. The only support is from ELA that gave by free a set of blades.
In theory, some money will be available by next year, let see.
From the other side, even having all the financial support, he deliver time is huge, the current status is from 7 to 8 months, and doesn't fit in our tight schedule.
The back up plan has been to use an old Rotax 80 cv from one member of the team. Just having financial support we will buy the Verner motor.
The autogiro will have the new motor installed in the best scenario by the very end of 2023 or in 2024.
 
Xavier,

You and your team are performing a marvelous job in constructing the C-4 replica. I just can't wait to see the video of the first flight!

Wayne
 
Xavier,

You and your team are performing a marvelous job in constructing the C-4 replica. I just can't wait to see the video of the first flight!

Wayne

Thanks, but I'm not a member of the construction team. I'm in frequent contact with Arco, and knew of the team's effort through a WhatsApp group...
 
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