The screw and the toothed wheel
Leonardo methodically classified the different types of screw. He sought to measure their power and specify their potential applications in machines and mechanical operations. He also designed two screw-threading machines.
He devoted special attention to the toothed wheel, focusing on the teeth profiles and accurately classifying the different types of motion produced by various combinations of toothed wheels, pin-gear wheels, and pinions.
Pulleys, pulley blocks, axles, and bearings
Leonardo emphasized the advantages of the efficient use of pulley blocks and pulleys, notably for easier lifting of heavy loads.
He also analyzed many systems to support moving axles and shafts, in particular to diminish the effect of friction. His designs of ball bearings for vertical axles and of pressure-resistant ball bearings are especially noteworthy. He used the latter system to design a smoother-working screw-jack.
Crankshaft mechanisms and flywheels
Leonardo suggested the use of crankshaft mechanisms to turn rotary motion into reciprocal linear motion, as in the coil of the automatic winding machine of Madrid Ms. I.
He also analyzed in detail the role of flywheels in facilitating and regulating the motion of rotating shafts.
Springs and cams
Leonardo designed what can rightly be called a full visual catalogue of springs. He emphasized their usefulness in locks and clockwork, and proposed solutions to regulate their force. He also devised a spring-making machine.
His interest in cams, as well, is linked to the same determination to improve and regulate clocks, as shown in his studies on pendulum escapements and on escapements with propeller and sinusoidal cam.
Chains, rope- and belt-transmission systems, and shock absorbers
Leonardo produced a pictorial catalogue of several types of chains, which he especially recommended for lifting heavy loads.
He also proposed the use of ropes and belts to transmit circular motion.
Finally, Leonardo projected shock absorbers to cushion the ground impact of the flying machine in the event of a crash.