The sling: a giant stone-throwing engine
A man cranks a spoked wheel to bend the great arm of a sling-catapult
A large stone-throwing engine, captioned simply 'Frombola' (sling), dominates the sheet. A man drives a spoked wheel and windlass to bend down a long curved throwing arm mounted on a heavy timber frame, whose graduated arc carries a scale of tick marks for measuring the arm's travel. The engine is a lever machine that stores energy in the flexed arm to hurl a projectile. Following the Atlanticus classification, the folio also carries brief untranscribed writing and geometrical notes not included here.
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Sling engine for hurling stones
The whole drawing is labelled 'Frombola', a sling. It is a large military throwing machine whose long arm, flexed and released, casts a projectile — a siege weapon rather than a hand sling.
Crank, windlass and graduated arc
A man turns a large spoked wheel and windlass to draw down the sprung arm against a massive braced frame. A quarter-circle arc marked off in numbered graduations lets the arm's deflection be measured as it is bent back.