Universal_Catapult-v03

The Universal Catapult for Seej

In the late 1700s Eli Whitney, the designer of the cot­ton gin, devel­oped mus­kets with inter­change­able parts to help the United States mil­i­tary. The man­u­fac­ture of objects with inter­change­able parts was soon a key fac­tor in the indus­trial rev­o­lu­tion. Mr. Whitney is per­haps a lit­tle anachro­nis­tic when brought along­side cas­tle and siege war­fare, but we can use the prin­ci­ples he cham­pi­oned to build a bet­ter piece of siege machin­ery.

In this spirit, and on July 4th, America’s Independence Day, I would like to share the Universal Catapult for Seej. Some friends and I started to play Seej, using the basic set. Maybe it was our tech­nique, maybe it was the rub­ber bands we had on hand, but we found the rubber-band-as-pivot to be woe­fully inac­cu­rate, almost unplayable. I set off to build a bet­ter cat­a­pult.

After two rounds of revi­sions, I’m post­ing the v03 Universal Catapult design. This cat­a­pult has three main fea­tures going for it:

Tension Keys — The ten­sion keys (pic­tured yel­low) pull the rub­ber bands instead of twist­ing them. This leads to fewer twisty knots and bet­ter lin­ear ten­sion.

Adjustable Strike Plate - I only have the one strike plate (pic­tured blue) for now, but in the­ory, you should be able to swap them out for plates of vary­ing depth. This allows for more fine con­trol of the angle of release.

Modular Base — Everything sits atop a base with mod­u­lar holes (pic­tured white and gray). If you would like to design a tre­buchet, bal­lista, or even gatling gun or death-laser, then feel free to skip rein­vent­ing the base and use this one. See the base detail image for exact mea­sure­ments.

The 3D mod­els and source files can be found on its Thingiverse page: http://www.thingiverse.com/thing:26265

Addendum: You might not know it, but this is ver­sion 3 of my cat­a­pult design.  If you would like to see more detail about the pre­vi­ous revi­sions, jump ahead to “The evo­lu­tion of a cat­pult.”

Posted in: MakerBot

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