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Will
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Katy's Catapult (The Katypult!)

Here is an excellent little catapult that is very powerful and easy to build. It was submitted by a web visitor (Todd). His daughter Katy F. made it. And he tells us about how it was made.

This is a terrific little catapult!!!

 

Attached are photos of a catapult built by Katy, my daughter (with my help) for her physics class.  It is very simple, very strong and extremely effective.  We launched marshmallows as far as 50 feet.  Her  catapult out performed all her classmates entries and earned her a 100 for a grade.  More telling, her teacher said "this is awesome, can I keep it?"  He still has it.  I hope you like it.

 

 

 

 

We built it from scrap SPF wood I already had in the garage.  We used 5/16" dowels and carpenter glue to pin the wood frame together.  The throwing arm is made of an old plastic handle from a metal BBQ grill brush.  We thought the plastic would stand up to the repeated pounding better than wood which might crack along the grain, or near a knot.  We used self adhesive felt pads along the arm where it contacts the stop bar for a little cushion.  The bucket is a 1 Tbl spoon measuring scoop with the handle cut off. 

The pivot for the throwing arm is a 1/4" bolt and the stop arm is a 5/16" bolt.  There are multiple locations for the stop bar so we could judge the difference in range at various stop angles.  We found 45 degrees gave the most range by a wide margin. 

 

 

 

 

 


The springs were bought off the hardware rack at Lowe's.  Initially we used only one center mounted spring.  However we were dissatisfied with the range, so we went with dual side mounted springs.  We also moved the springs to arm attachment point closer to the bucket to add tension.  Afterwards, we were satisfied with the performance. 

The trigger consists of two hook eyes, one mounted to the bucket and one mounted to the frame base, with a 12 common nail run through them.  Just snatch the string attached to the nail and you get a clean, quick, consistent launch every time.

Its not a fancy as most of the catapults on your site, but its simplicity and functionality made it great for a high school physics project.  Having less than $10 in it makes it a perfect high school physics project.

 


 

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