Recent content by Jean Claude

  1. Jean Claude

    First jump takeoff in France

    Let me evaluate very roughly the possibility of takeoff with no run by pitch setting jump: Assuming the rotor pitch is adjusted abruptly to lift the weight of the gyrocopter in hover, the time during which the rotor energy due to overspeed will be available depends on the average power input...
  2. Jean Claude

    First jump takeoff in France

    If I understand correctly, the collective pitch increases when turning, since the controller automatically increases the pitch to prevent rpm from increasing. However, this may decrease the Vne. Conversely, if low g, the rrpm decreases less because the controler decrease the collective pitch.
  3. Jean Claude

    First jump takeoff in France

    As I said, I'm talking about constraints of rotation torque on the blade roots. I'm not even sure that gyrocopter blades are tested in the rotation plane, since a gyrocopter rotor is not supposed to receive the torque from its hub The pre-launch of usual gyrocopters is not limited by the motor...
  4. Jean Claude

    First jump takeoff in France

    It is not only the centrifugal stress that must be taken into account for the jump takeoff, it is mainly the over-torque applied by the hub to the blade roots: Between two and three times more than that of strong pre-launch of a standard takeoff.
  5. Jean Claude

    Wheel brakes

    Yes, when they are hydraulic, Woolfy. Disc mechanical brakes have a single moving pad pushed by a ball cam. This pad pushes the disc against the fixed pad. This requires easily flexible spokes
  6. Jean Claude

    Wheel brakes

    After thinking about it, I don't believe that the direction of the effort in the spokes is chosen for reasons of thermal expansion of the disk. This only produces a bending stress in plane for the spokes, whatever the direction of the stress. (See top picture) Rather, I believe that the spoke...
  7. Jean Claude

    Wheel brakes

    Thank you, Mike A link ?
  8. Jean Claude

    Reflex Airfoils

    "In the above The Cm of -.020 was converted to a positive number to increase the distance from leading edge to past AC...to make .27 chord." In the above the Cm discrepancy of -.020 shows the AC is not at 0.25 chord, but at 0.27 chord. So, around this point, the Cm is constant whatever the Cl...
  9. Jean Claude

    Wheel brakes

    No, this is the direction requested by the manufacturer
  10. Jean Claude

    Reflex Airfoils

    NACA TN 1998, fig 1 https://ntrs.nasa.gov/api/citations/19930082712/downloads/19930082712.pdf at RN = 1,800,000 Reynolds number = 70* Airfoil Velocity (m/s) * Chord (mm) And here your Clark YS according Airfoil Tools
  11. Jean Claude

    Reflex Airfoils

    According NACA TN 1998, we see that Cm = 0 when Cl = 0, and Cm = -0.020 when Cl = 1 This variation is due to the usual measurement relative to the point 0.25 c, instead of the accurate Aerodynamic Center. It is easy to obtain the precise Aerodynamic Center for which Cm is constant from Cl = 0...
  12. Jean Claude

    Wheel brakes

    All bicycle brake discs are mounted in the direction shown on this picture. That is to say with "spokes" working in compression rather than in traction (white arrows) This seems to me to take the unnecessary risk of buckling. Does anyone know the reason for this surprising direction?
  13. Jean Claude

    Reflex Airfoils

    1. Zero moment or moment more positive than negative at all angles of attack and airflow? Yes: Zero or slightly positive moment 2. Make sure that the CG or CoM of the blade remains at 25% of the chord? Yes: The point at 25-26% of the chord is called the Aerodynamic Center. This is where the...
  14. Jean Claude

    Reflex Airfoils

    Symmetrical profile works already well without tabs . Adding the tab would reduce the CL max and require more weight in the nose.
  15. Jean Claude

    First jump takeoff in France

    Michel never mentioned the use of special blades, neither reinforcement nor ballast at the tips. He only talked about the pitch regulator. Thus, I believe he uses standard gyroplane blades, without any weight at the end of the blade. Michel is a passionate experimenter who works mostly on feeling.
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