page_title: Polybolos
section_title: Design
hierarchical_section_title: Polybolos / Design
caption_attribution_description: Deutsch: Rekonstruktionen antiker mechanischer Artillerie im Saalburg-Museum in Hessen (Deutschland) Links stehend: Polybolos, ein semi-automatisches Katapult aus dem 3. Jh. v. Chr. (Rekonstruktion des deutschen Ingenieurs Erwin Schramm (1856–1935)) Rechts stehend: Philons Chalkotonon, ein Geschütz mit bronzenen Federn (von Schramm als "Erzspanngeschütz" rekonstruiert) Unten Mitte: Hölzerner Kettenantrieb des Polybolos Unten rechts: Philons Aerotonon, ein pneumatisches Katapult ausgestellt ohne Dreifuß (von Schramm als "Luftspanngeschütz" rekonstruiert) Hintergrund, an der Wand: Gastraphetes, eine griechische Armbrust English: Reconstructions of ancient mechanical artillery in the Saalburg Museum, Hesse, Germany Left standing: Polybolos, a 3rd century BC repeating catapult (reconstruction by the German engineer Erwin Schramm (1856–1935)) Right standing: Philo's Chalkotonon, a bronze-spring catapult (reconstructed by Schramm as "Erzspanngeschütz") Bottom center: Wooden chain-drive mechanism of the Polybolos Bottom right: Philo's Aerotonon, a pneumatic catapult displayed without tripod stand (reconstructed by Schramm as "Luftspanngeschütz") Background, on wall: Gastraphetes, a Greek crossbow
context_page_description: Polybolos, meaning "multi thrower" in Greek, was an ancient Greek repeating ballista reputedly invented by Dionysius of Alexandria, a 3rd-century BC Greek engineer at the Rhodes arsenal, and used in antiquity.
  Philo of Byzantium encountered and described a weapon similar to the polybolos, a catapult that like a modern machine gun could fire again and again without a need to reload. Philo left a detailed description of the gears that powered its chain drive, the oldest known application of such a mechanism, and that placed bolt after bolt into its firing slot.
context_section_description: The polybolos would have differed from an ordinary ballista in that it had a wooden hopper magazine, capable of holding several dozen bolts, that was positioned over the mensa (the cradle that holds the bolt prior to firing). The mechanism is unique in that it is driven by a flat-link chain connected to a windlass. The mensa itself was a sliding plank (similar to that on the gastraphetes) containing the claw latches used to pull back the drawstring and was attached to the chain link. When loading a new bolt and spanning the drawstring, the windlass is rotated counterclockwise by an operator standing on the left side of the weapon; this drives the mensa forward towards the bow string. At the very front, a metal lug at the front trigger the latching claws into catching the drawstring.  
  Once the string is held firm by the trigger mechanism, the windlass is then rotated clockwise; pulling the mensa back and drawing the bow string with it. At the same time, a round wooden pole in the bottom of the magazine is rotated via a spiral groove being driven by a rivet attached to the sliding mensa; dropping a single bolt from a carved notch in the rotating pole. With the drawstring pulled back and a bolt loaded on the mensa, the polybolos is ready to be fired.  As the windlass is rotated further back to the very back end, the claws on the mensa meets another lug like the one that pushed the claws into catching the string. This one causes the claws to disengage the drawstring and automatically fires the loaded bolt. Upon the bolt being fired, the process is repeated. The repetition provides the weapon's name, in Greek πολυβόλος,  "throwing many missiles", from πολύς (polys), "multiple, many" and -βόλος (-bolos) "thrower", in turn from βάλλω (ballo), "to throw, to hurl", literally a repeating weapon.
caption: Arsenal of ancient mechanical artillery in the Saalburg, Germany; left: polybolos reconstruction by the German engineer Erwin Schramm (1856–1935)
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