The 'sbaratrona' counterweight throwing engine
A sling-machine driven by a falling counterweight, with related mechanical sketches
The largest fragment mounted on this leaf shows an engine Leonardo names the SBARATRONA: a wheel that winds a counterweight, an arm and a sling (fromba) that hurls a load. He directs that the wheel's centre be set off its true place so the cord rests farther from the axis as the weight nears the end of its fall, that a second counterweight of equal weight be released at that moment, and that the sling's course pass clear through a pit a b so the sack does not tear. A heading at the top names three engines, Cismatica, Baratrona and Morrono, and a measure of 3 braccia is written within one drawing. Further untranscribed sketches are present on the mounted fragments, including a many-bladed rotary device and framed machines.
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The 'sbaratrona' throwing engine
The large drawing at upper right shows the engine Leonardo calls the sbaratrona. Its wheel, on which the counterweight winds, is set with its centre outside its true place, so that as the weight nears the end of its fall the cord rests farther from the axis. The slack sling-cord lets the arm snatch the load, whose course must pass clear through the pit a b so that it touches nothing on the way and the sack does not break.
Releasing a second counterweight to sustain the throw
As the counterweight has nearly finished its fall, a second counterweight of equal weight is to be released to add its pull. Offsetting the wheel's centre and springing this reserve weight are meant to keep the driving force strong through the whole cast.
Three named engines
The heading written across the top of the sheet names three engines: Cismatica, Baratrona and Morrono.
Scale of the mechanism
A measure of 3 braccia is written within one of the drawings, giving the scale of the mechanism.