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How Ornithopters Fly

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Ornithopter model EV4

Content:

  1. Start preliminary
  2. Flight photographs
  3. Driving mechanism of the EV4
  4. Video of the EV4

The arm and hand wing sections were actively pitch controlled separately from the drive at the relevant section root. The arm wings were rigid. The hand wings should be twisted aeroelastic. The twisting of the hand wing was appropriate for gliding.

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1. Start preliminary

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2. Flight photographs

During powered flight, the twisting of the hand wings has been too small. During the downstroke, especially near the wing tips, the angle of incidence were not enough negative. But at that time, definite theoretical instruction about the distribution of this angle along the span was missing (e.g. 2001, handbook, chapter 6.5 to 6.7).

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3. Driving mechanism of the EV4

From right towards left in the picture:

  • Drive unit with a cardan gear mechanism. It is the same like in the model EV1. Main and control pins are provided with sliding blocks of polyamide. For specification of the cardan gear mechanism please look at the Report about the development of the EV-models. You also can see an animation of the cardan gear mechanism.
  • Main frame of the mechanism with side panels of rigid foam to adjust to the surface of the fuselage also made of rigid foam rings.
  • Sloped control scotch yoke, made of 1 mm epoxy plates and slide of steel. The slot is at an angle with the axis of the slider like the path line of the control crank pin in the glide situation.
  • 2 rods with spherical bearings
  • Lever arms to control the inner wing pitch, mounts onto the wing axis.
  • Wing axis was made of 6 mm spring steel, offset for a favourable fuselage-wing transition.
  • Wing adapter rollers (of the EV8) made of rigid foam and plywood and covered with epoxy-glass laminate, each with two inner 45 mm long lever arms.
  • 4 plywood linkages
  • Swing (frame of plywood) with the pressure vessel (about 5 bar) for the pneumatically spring made of epoxy-glass laminate. Ahead the frame is made of the main scotch yoke. At it are mounted the bearings for the control scotch yoke.
  • Cylinder or support ring made of epoxy-glass laminate, for the long-stroke bellows-like rolling-diaphragm below.
  • The piston of the pneumatic spring stands at the bottom of the fuselage and is not shown here.
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4. Video of the EV4 (1979)