Ornithopter models EV1 to EV4
Ornithopter model EV1
- first flight
- wing span
- weight
- max. wing chord
- flapping cycle
- flapping angle
- 1975
- 2.90 m
- 5.4 kg
- 0.44 m
- 0.8 s
- 60 deg
- [114 in]
- [190 oz]
- [17 in]
The first flying electric bird
(Elektro Vogel No. 1)
The inner (arm) portion of the wing was actively pitched and twisted. The outer (hand) portion of the wing twisted aeroelasticly.
EV1 at powered flight
EV1 at gliding flight
EV1 with wings at the upper final stroke positon.
The twisting along the whole span unfortunately was too small for powered flight. It was made harder by the large rigid trailing edge.
Wing twisting at downstroke
Fuselage of the EV1
Length 1.6 m, outer diameter 147 mm, fuselage side approx 10 mm, made of rigid foam rings, covered with polyester-glass laminate.
Open fuselage and wing attachment
EV1 was working with a wing root pitching.
Inside of each wing tongue
a mechanism was installed.
The wing wrists
in the center of the wing halfspan
were pitched with it additionally.
Electrical equipment in the front part of the fuselage
Left:
The drive motor and the servos to control the model.
Right:
Microswitches to reverse the motor and the resistance for a smooth starting.
Flapping mechanism
In the adjacent picture there are to be seen:
Left:
– The fitting for fixing the cord of the pulley of the rubber compensation spring in the rear part of the fuselage (next picture).
– Steel wires between the pulley and the angled lever which presses the main scotch yoke up and the wings down, respectively.
Centre:
– Fixing for leading the scotch yoke.
Right:
– Rods with spherical bearings to pitch the wing root.
– Underneath one can see a bit of the drive unit and right of this the blue micro switch for the gliding position.
– The spherical bearings of the main scotch yoke are pivoted inside the tube ends of the main spar.
Technical drawing
with a longitudinal section through the fuselage and the drive mechanism of the flapping wing.
Planetary gear drive unit for ornithopters
This special planetary gear mechanism converts the rotary motion of the electric motor into a straight line reciprocating motion of the crank pin (cardan gear mechanism). A scotch yoke was only used to switch between gliding and powered flight.
-
Glide is obtained by orienting the path line
of the main crank pin horizontally. -
Powered flight is obtained by orienting the
path line of the main crank pin vertically.
The 2 mm stagger between the main and the control crank pin is visible in the photograph.
On the top there are two triggers for two settings of glide to stop the motor at the dead center of the crank. In this way the glide position was locked.
This drive unit was used in the ornithopters EV1 to EV6.
For further details and technical data, please see Report,
my patent DE 26 28 846, application 1976
and the
Plans of the single parts
(PDF 1.4 MB)
18 pencil drawings, in German
You also can see an animation of this cardan gear mechanism with two crank pins.
Ornithopter model EV2
- first flight
- wing span
- weight
- max. wing chord
- 1976
- 2.96 m
- 5.4 kg
- 0.42 m
- [116 in]
- [190 oz]
- [16 in]
The active twisting of the wings resulted from the separate controlling of the main and auxiliary spars in stroke direction.
The spreading of the tubular spars was necessary for a relatively small twisting at the wingtip by a given stagger of the crank pins and a given distance between the main and auxiliary spars at the wing root.
There was no trailing edge. The ornithopter did not sustain flight, but good engineering progress was made (please take a look at the report).
For covering the wing the elastic foil type Platilon U
04
of the company Plate Bonn GmbH (Germany) was used for
the first time (thickness 0,03 and 0,05 mm).
EV1 in comparison with EV2, top view
EV2 opened
In front one can see the micro switches to reverse between gliding and powered flight.
The servos to modify the wing twisting are inside the front wing adapter rollers.
The main and the auxiliary spars was separately controlled by two steel wing levers.
To the rear one can see the cover of the steel spring used for lift force compensation (Data of the spring d = 4 mm, D_m = 40 mm, R = 3.26 N/mm, F_max = 536 N, W = 184 g [6.5 oz]).
The fuselage was divided. The rear part was detachable to change the batteries.
Single parts of the mechanism are shown in the report.
Ornithopter model EV3
No pictures
The EV3
did not get past the phase of design.
Only plans exist.
Ornithopter model EV4
- first flight
- wing span
- weight
- aspect ratio
- 1979
- 3.06 m
- 4.8 kg
- 10
- [120 in]
- [169 oz]
Run tests
Arm and hand wing sections was actively pitch controlled at the relevant section root. The arm wings were rigid. The hand wings should be twisted aeroelasticly. The twisting of the hand wing was appropriate for gliding.
Drive mechanism of the EV4
There is a picture series about the details of the mechanism. They reveal the design and function of the system.
Technical drawing
with a longitudinal section through the drive mechanism in the fuselage.
EV4 with stepped wing twisting
During powered flight, the twisting of the hand wings has been to small. During the downstroke, especially near the wing tips, the angle of incidence was not enough negative. But at that time, definite theoretical instruction about the distribution of this angle along the span was missing (e.g. handbook, 2001, chapter 6.5 to 6.7).
Adjusting works
The pitch of the hand wing could be modified in a small range.
At the wing root fairing one can see the high camber of the like
bird
airfoil.
EV4 with his wings at the lower final stroke positon.
To the Drive mechanism of the EV4