Wheel for Perpetual Motion: Weight Beyond the Pole
Measuring the overbalancing weight, and the illusion that deceives the ignorant
An overbalancing wheel of radiating weighted arms is drawn above a ruled ground line, with a pivoted striking bar resting on a block at the lower right; the labels m and n mark the moving ball. Leonardo tells the reader to measure how much more weight lies beyond the pole than on the near side when the ball m stands at n, promising fuller proofs elsewhere in his treatment of motion and percussion. He adds that the device looks plausible to anyone ignorant of such instruments, who imagines that a small starting motion plus the added blow will keep the wheel going of itself.
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Measure the weight on each side of the pole
When the ball m stands at n, one must measure how much more weight remains on the far side of the pole than on the near side, and the truth will be clear. Leonardo sends these results briefly, promising to define them exactly elsewhere with their proofs, where motion and percussion are treated fully.
The illusion that deceives the ignorant
To someone ignorant of such machines the scheme seems truthful: he reasons that a little starting motion, maintained for a while of itself, plus an added blow, will easily sustain the motion once begun. Leonardo breaks off, noting that such a man does not know it will not do so.
Overbalancing wheel with striking bar
A toothed wheel carries arms tipped with weights radiating from the hub. At the lower right a pivoted bar rests on a block set on the ruled ground line, positioned to strike the wheel as it turns.