Wheel for Perpetual Motion: Eight Balls in Twelve Channels
Counting the balls on each side of the pole to prove the wheel stable
A disc crossed by curved, interlacing channels holds rolling balls, drawn as a shaded pinwheel with the label m at its hub. Leonardo counts 8 balls in 12 channels, 4 on each side of the pole, and argues that when the run-out ball reaches m there are effectively only 2 balls against 5, since the lowest ball near the central line has little power. Applying his earlier check, he finds the wheel's stability certain, and refers the reader to the opposite figure to settle the objection from percussion.
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Eight balls in twelve channels
Of 8 balls in 12 channels, 4 lie on each side of the pole. When a ball has run out to m, the side of m holds effectively only 2 against 5, because the lowest ball, being near the central line, has little power; the earlier check then proves the wheel's stability certain.
The objection from percussion
One might object that when the weight moving away from the pole at m runs with percussion into the place where it halts, it would make the wheel turn strongly. Leonardo directs the reader to the figure set opposite, where the aforesaid proof will give the verdict.
Disc of curved ball-channels
The wheel is drawn as a shaded disc divided into curved, interlacing channels arranged like a pinwheel, along which the balls roll from the hub toward the rim; dots mark the balls at intervals.