A Screw-Bent Saw for Cutting Iron; Crossbow Force Ratios
A silent file to free prisoners, and the proportion of derivative to primary motion
The recto's chief invention is a saw or file, drawn as a jaw-like tool at the head of the page, that is tightened by a screw so as to cut through any thick iron placed at m without making a noise — narrow like the back of a knife and wide toward the teeth at n — which Leonardo remarks is 'good for freeing prisoners.' Below and to the right are sketched block-and-guide mechanisms sliding on posts, and a small forked fitting lettered a, b, c. The accompanying text returns to the crossbow, stating that derivative motion stands to primary motion as the driving weights do, once the resistance of the air is reckoned in. A closing note gives the thickness at n c as one ounce and at m as two ounces.
On this page
Screw-tightened saw that cuts iron without noise
A saw or file that is bent by the force of a screw and cuts through any thick iron placed within it at m, making no noise. It is narrow like the back of a knife and wide toward the teeth, as shown at n, and is good for freeing prisoners.
Derivative versus primary motion in the crossbow
Derivative motion bears such proportion to primary as the weights causing them bear to each other. Since the weight is the cause of the crossbow's force, and that force in releasing drives a lesser weight, the bolt's flight relates to the string's discharge as the loading weight relates to the driven weight, once air resistance is allowed for.
Thicknesses of the blade at n c and m
Leonardo dimensions the tool: in each part it is one ounce thick, that is at n c, while at m it is two ounces thick.
Block-and-guide mechanisms sketched at right
To the right an isometric mechanism shows a fitted block riding on an upright post or guide, with a smaller forked bracket lettered a, b, c below it. Faint offset lines of a brick surface run behind the sketches.