da vinci's cam hammer
grabcad
As you can see it was intended to be hand cranked. This would rotate the cam upon which the hammer mechanisms rests and follows. When the cam is rotated the weight of the hammer ensures that the bar connected to it always wants to be tight up against it due to the force of gravity. Eventually the hammer and its mechanism follow to cam all the way around until the cam suddenly drops off – this makes the hammer fall also. http://www.leonardodavincisinventions.com/mechanical-inventions/leonardo-da-vincis-cam-hammer/
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