Silk-winding machine with worm gear and spring tensioner
An endless screw driving a 100-tooth wheel, with crossbow-springs keeping the thread taut
Leonardo designs a machine for winding silk evenly. A worm screw (the 'endless screw') fixed at the centre passes through a hollow distaff and drives a wheel of 100 teeth, one tooth advancing per turn, so the thread is taken up steadily. A spring grips the single thread at the point a to keep constant tension, while paired crossbow-springs pull the spindles against one another so that the rod stays firmly drawn while the machine works. A lower figure shows the silk carried over a set of equal little wheels, all alike, so that it is always pulled in one and the same manner. The drawings render the spiral spring, the worm-and-wheel gearing, and the reeling frame.
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Endless screw driving a wheel of 100 teeth
The worm screw ('vite sanza fine') is to stay fixed at the centre and pass through the hollow distaff, engaging a wheel labelled with 100 teeth so that one tooth advances at each turn. This high-reduction worm gear meters the winding of the silk one increment at a time.
Spring gripping the single thread at a
Inside the upper figure a spring ('molla') clamps the single thread at the point a, holding it under steady tension as it is drawn onto the winder. The coiled spring is drawn at the upper left.
Crossbow-springs keeping the spindles taut
Paired crossbow-springs ('balestri') hold the spindles pulled one against the other so that the rod stays strongly drawn and always tensioned while the work goes on. This keeps the thread from slackening as the machine runs.
Winding the silk over equal rollers
At the foot Leonardo gives the method of turning the silk over equal little wheels, all made in one manner, so that the silk is always pulled in one and the same way. Uniform rollers give uniform take-up and even tension across the reel.