Introduction: Ballista

Ya'll have fun with this one, it is pretty darn cool. After you get finished building it pull the rubber band back and put it in the two slots of the yellow pieces that is atached to the trigger system.

Step 1: First Part of the Catapult

Self explanatory

Step 2: Main Base

This is the trigger system.

Step 3: Trigger System Cont. (Parts)

Step 4: Trigger System Cont. (rubber Bands)

Attach the rubber bands to the white rod on the bottom of the trigger. After complete, then attach the two yellow pieces to the bottom grey rod on the first piece.

Step 5: Bottom Frame

The pieces may be off centered a little bit.

Step 6: Bullet's

self explanatory

Step 7: Rubber Band for First Piece

Insert the rubber band on both sides through the orange pieces and attach the ends to the top grey rod. In the middle of the rubber band, you need to wrap it with tape.

Step 8: The End Result

hope you enjoy this one. Don't shoot your eye out !!!

Remember not to shoot at other people.



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    We have a be nice policy.
    Please be positive and constructive.




    Not really a ballista- the trigger design makes it more like a crossbow.

    5 replies

    a ballista actually is a huge crossbow with weels, or on a standard you human XD haven't made it yet, need to get k'nex somehow :P alty

    here is an image of the greek ballista:

    and here is the roman ballista:

    Ballistae are torsionally powered.

    I could change the design and replace the picture.

    well acualy baslista is gust the german word for a normal crossbow, but we offten think of it as a huge cbow on wheels for the germans where one of the first 1s to make that

    4 replies

    Actually the romans were the first to make it.

    wrong dude. the greeks invented it and the romans perfected it and made it into a machine gun.

    i also belive the greeks made it for the seige that alexander did pree rome... but i ment that they were the first to make that name for romes big cbows (anyone know that latin word for ok)

    exactly. balista is german for crossbow but ballista was a greek long range weapon that could fire javelins or large metal balls and the romans improved the ballista by twisting the ropes more and also created the world's first machine gun, the repeating ballista.

    i just built it and whenever i shot it broke sorry your instructions dont cover how to put it all together.

    instead of using the blue spacers on the main base i used a mix of the single clips and "A" clips and made a handy ammo holder :D


    im gonna post a crossbow, i got the idea from you, so you get credit:D

    hey hey looks great and iv built it but there is something missing and i dont no what. how do you fire it?

    in step 4 it says After complete attach two yellow pieces to bottom grey rod of first piece I don't get it could someone explain

    That was uncalled for, and a violation of our "be nice" policy.

    Ballastae are a Greek invention, with a very good treatise on their design written something like 1,000 years before Rome existed. The heart of a ballista are the torsion springs (twisted bundles of rope are the usual) that power it. Don't have torsion springs, its something else.

    To address other comments, they weren't typically wheeled. They didn't move them, they were too heavy to easily move. Instead the builders marched to the battle site (usually a long term attack on a fortification), with the critical metal bits (like the trigger mechanism). When they got to the fort, they built them where they needed them, from locally sourced materials (trees).

    There are modern translations of the Greek text available. Whats interesting is that all the dimensions are given as a function of the diameter of the rope bundle. For example, you want the length of the bundle about 7-8 times the diameter, the arms a different multiple of the length, etc. They even give the timber sizes as a function of bundle size.

    To see a modern interpretation of the ancient Greek design check out (Pictures, videos, etc ) We used modern materials (steel, composites, and synthetic fiber) and we adapted some of the dimensions for lighter ammo, but the rest of the design is by-the-book. We even decided to learn the Greek names for the various bits, as they already went thru the trouble of inventing unique names for all the pieces.

    Founder: The New England Rubbish Deconstruction Society; The NERDS. The first American team to compete in Junkyard Wars.


    this is like dragono or w/e his name is crossbow ima try to build this it looks kool

    AAAAAAAAAAAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!i shot my sister in the head(not on purpus) with a cross bow and now i cant make knex guns for a week!!