A crank-and-rod wing drive converts rotary input into an oscillating wing lever. Explore one planar four-bar arrangement and see how its link lengths affect rocker sweep and endpoint travel.
Exact Four-Bar Wing-Drive Geometry
Enter the four rigid link lengths. The calculator closes the position loop through one full crank revolution and reports the resulting rocker-angle range and endpoint chord.
Equation Used
- All links are rigid, planar and joined by ideal revolute pins.
- The calculator follows one continuous circle-intersection branch and ignores backlash, compliance, inertia and collisions.
- The drawn wing is only a rigid extension of the rocker; aerodynamic force, twist, power and stability are excluded.
The calculation keeps all four link lengths fixed and solves the joint positions through a complete crank revolution. It reports rocker angles and endpoint chord, without predicting aerodynamic forces or flight performance.
Rotary crank to oscillating wing lever
Primary ornithopter patents document drives in which a rotating crank connects through a rod to a wing-flapping lever or flapper bar. The illustration represents that arrangement as one ideal planar four-bar loop.
The screen solves both circle constraints at every input angle, so the crank, coupler and rocker keep their entered lengths throughout the animation.
Geometry demonstration, not a flight design
Use the calculator to see how four declared link lengths change the angular sweep of one rocker. It cannot select a motor, gearbox, wing, material, frequency, pressure, power source or vehicle configuration.
Four-bar position closure
The moving crank pin A is known from input angle phi. The wing-lever joint B is the selected intersection of a radius-l circle around A and a radius-b circle around the fixed rocker pivot (d,0). Rocker angle is atan2(By,Bx-d).
Geometry example
For r=18 mm, l=95 mm, b=80 mm and d=105 mm, the selected branch moves from about -133.2 degrees to -106.1 degrees: a 27.1-degree rocker swing and a 37.5 mm chord at the rocker endpoint. Those are linkage-position results only.
Geometry and flight-performance limits
A real ornithopter requires its own mechanism, mass properties, structural dynamics, aeroelastic wing model, propulsion data, controls and flight testing.
Ornithopter-drive questions
Does one crank revolution produce one linkage cycle?
Yes, for this continuously rotating single-crank topology.
Does the rocker swing predict lift?
No. The calculator contains no aerodynamic model.
Is the shown geometry safe to build?
No. It is an ideal position model with no load, stress, fatigue, collision or stability analysis.
Primary mechanism references
- US20050269447A1, Ornithopter with independently controlled wings: final gear, crank piece, connecting rod, flapper bar and wing hinge.
- US20020173217A1, Ornithopter: output crank, connecting rod and wing-flapping lever.
- US20100308159A1, Flapping-wing flying vehicle: crank-and-connecting-rod ornithopter drives and the distinction between flapping frequency and amplitude control.
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
