During the siege of Syracuse, one defense was Archimedes Claw . The claw consisted of long poles that dropped large weights or hooks through the Roman ships then lifted them, via levers , from the water and  dropped them, stern first, back into the sea.

Other defenses were systems of both catapult and crossbow with selective ranges allowing for a continuous assault on the Romans regardless of their range from the city.
 

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Build an Archimedes Water Screw in just one night with our easy, step by step plans and instructions. Great Project Invented in Egypt by the ancient Greek mathematician Archimedes , the Archimedes Screw , or water screw , as it is commonly known, was used for irrigation and lifting water from mines and ship bilges.  The water screw works wonderfully for science and history class assignments and science fair projects. Easy to Build All TrebuchetStore.com plans use common, inexpensive and easy to find building materials, available at your local hardware store or home center. Basic skills and tools are required, but the straightforward designs require no complicated layout or joinery. TrebuchetStore.com plans come complete with: • Parts Shopping List • Measured Drawings for all parts • Assembly Drawings • Step by step Assembly Instructions • Step by step Operating Instructions All the information you need to complete your project quickly and easily.