Spring Catapults and Their Loading Mechanisms
Two mounted sheets: a geared spring-arm engine and four catapults labelled compound and decomposed motion
The upper sheet (140a recto) shows a spring-armed throwing engine with a large toothed wheel and rack, loaded by an endless screw and released to hurl a stone, with detail views of the crank handle and a smaller device. The lower sheet (140b recto) sets out four catapults with curved spring arms, two labelled 'compound motion' and two 'decomposed motion.' Notes describe how to release the upper engine, how the crank winds the wheel before the little pole holding the stone is fitted, and advise using green, round, straight wood turned after each shot so that it never warps.
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Geared spring engine that hurls a stone
A framed engine carries a large toothed wheel and rack driving a long throwing arm tipped with a stone. A note explains that this is the way to let the instrument above run, that is, to release it once it has been loaded.
Crank that winds the throwing wheel
A detail shows the driver, or handle, that turns the wheel of the lower engine. The note directs that once the instrument is wound as far as it will go, the little pole that holds the stone is then set in place.
Catapults labelled compound and decomposed motion
Four catapults with curved spring arms are drawn on the lower sheet. Two are captioned 'compound motion' and two 'decomposed motion,' distinguishing the kinds of movement their arms perform.
Green-wood spring arm that resists warping
A note advises taking a green, round, straight length of wood for the arm and, after every shot, turning it to the opposite side, so that the wood will never stay warped.