2-Position Synthesis of Ornithopter wing Mechanism.

The Flapping wing mechanism I've decided to implement in the Ornithopter is a 4-bar mechanism (for the primary part of the wing.)

The Primary Wing  will be providing most of the lift for the Ornithopter .
After some calculations it was concluded that the flapping angle should be less than 35 degrees for proper lift throughout flapping.

Hence the 2 extreme positions of the rocker (aka wing spar) is known.

The length of the rocker was taken to be 900mm.
(can be anything)

So for one complete rotation of the crank the rocker should rotate 35 degrees.

 Measure the distance between two end points.
This is the diameter of the circle which is described by the crank (or 2x crank lenght).

Now connecting the two end points of the rocker and extend the line.
Take a convenient length* of the coupler ( I chose 800mm).
*(Do make sure the dimensions chosen satisfy grashofs condition .)

Draw the coupler from one of the rocker ends.

Now draw a circle at the endpoint of the coupler with radius as the crank length.
The center of the circle is the joint between crank and the coupler.
The other end of the crank(the grounded end) lies on the 2 intersection points of the circle and the extended line.
Choose a point such that when the crank rotates you get your desired motion in the rocker,