Steering carts and three rotating loads
Why a four-wheeled cart must be jointed to steer, with three rotating loads of equal effort.
On f. 93v Leonardo contrasts two carts: a four-wheeled one, drawn with an articulated (jointed) frame because a rigid one cannot turn sideways without breaking its front wheels, and a two-wheeled one that turns easily either way without danger. Below are three rotating figures loaded with numbers (m 16295; n 8 8; f 4 4, 4 4), which he says must all be of equal effort when made to move in an equidistant circle. He notes that the centres of these weights, in following the motion, all lie on the drawn circle.
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Articulated four-wheeled cart
A four-wheeled cart cannot be bent or turned sideways without danger of breaking the front wheels unless it is made articulated. The upper figure shows the jointed frame Leonardo prescribes for steering.
Easily steered two-wheeled cart
The two-wheeled cart is very easy to turn to right or left without danger of collapse. It is drawn in the middle register as the simpler alternative to the four-wheeled type.
Three rotating loads of equal effort
Three figures loaded with the numbers shown (m 16295; n 8 8; f 4 4, 4 4) must all be of equal effort as the cause of their motion when made to move in an equidistant circle. Leonardo adds that the centres of these weights all fall on the circle he has drawn.