"This makes a great acquisition, that is in lifting and lowering, and this is because each screw is in six doubles, and in turning the females against the screws, each female makes a change of one-sixth braccio, so that, since there are six females, they make a change of one braccio"
This model represents a study of a complex
mechanism for the propulsion of the beating
wings, and one of the numerous systems
Leonardo drew in attempting to reduce
the pilot’s exertion by multiplying the effects
of his muscles. It is constituted of a wooden structure on which a pulley with two foot brackets are fixed, with cords and six endless screws vertically positioned at the center and connected by bolts and coupling rings. To the sides of the screws two horizontal iron bars are fixed, which in turn are united by two vertical bars connected by cords to the central pulley. Onto the upper screw, a bolt is screwed on which the bases for the two wing structures (not reconstructed) are inserted, and these pivot on two rings positioned on the bearing structure. Each of the six screws has six worms and the effects of their rotation inside the bolts accumulate so as to provoke alternating motion
of the arms of the wings inserted into the
upper bolt, much broader than the movement
impressed on the levers connected with the
two vertical iron staves. These are actuated,
by means of cords and pulleys, by the two
forward foot brackets, where the pilot’s feet go.
The model is based on the drawing:
- Manuscript B f. 77 r. (1486-1487)
Paris, Institut de France