Ballistae, Onagers and Trebuchets, Oh My!

Spring Break, Beaches, Sun or .......Catapults.  Yes, who needs the beach when you can build your own working models of ancient artillery?  With this book and the proper motivation, you can.

Rez and his friend decided that for the science fair they were going to experiment with which type of catapult shot the farthest.

I don't think they really thought about having to build said catapults.  

Luckily Rez has a mom that likes to build things and we had spring break, which is a good thing, because we worked on them every day, all week long.  Also, luckily that book had designs for each of the types they wanted to test.  Unluckily, I don't think the author actually had anyone build the catapults from his directions as they are printed, so you also had to use your noodle.  (You can not use a 1/2 inch bolt to attach anything to a dowel that is 1/2 inch in diameter.)

We started with the Ballista.  It is powered by torsion (twisted ropes).

Here it is without the strings attached.

And all set up ready to arm.  To shoot it, you pull the center block back and hold it with a hook and eye, add your ammunition, then release the hook.  The Ballista springs back to this position, shooting out your ammunition through a little hole in the front.

Next we made the Onager.  It is a traditional looking catapult, with an arm you pull back.  It is also powered by torsion (twisted ropes).  

I was smarter this time and glued it together, before nailing it.  This made for a more "squared" catapult.

I only had so many clamps, and so used large candles on the top to add some weight as it dried.

We also improvised on the "basket" that you put the ammunition in.  It called for a 2" fender washer that you then rounded with the ball end of a ball-peen hammer.  I could not find a 2" fender washer, nor do I have a ball-peen hammer.  We used an old cap from a baby food jar with a hole drilled in it.  It worked great.

Rez and his friend also added padding so it wasn't as loud and so they got a better angle on the catapult.

The Onager shot really well from off the steps.

The last catapult we built was a Trebuchet.  It is powered by a lever and a sling.

The model we built was for Ludgar, the War Wolf.  Back a long time ago the King of England went up against a Scottish castle.  He had 13 large catapults built in their view for the siege.  He put each one into use as soon as it was operational. The largest and last be built was Ludgar.  By the time it was operational, the Scotts had had enough.  They surrendered.  The King, though, had spent a lot of time and money on this grand machine and he wanted to see it in action.  The Queen had come out to see it also.  So, the King refused their surrender and ordered the Scotts back into their castle.  He then commenced to reduce the castle to rubble.  Only 30 Scotts survived.

Not a very nice King, I think.

The engineers who made Ludgar didn't leave any mechanical plans of it, there were only some pictures that our directions were based on, so our Ludgar did not work very well, but it looked nice.  We know that some trebuchets work really well.  The neighbor built one for his science fair project and it shot really far.  They boys wanted to use it for their trials, but it wasn't the same scale as their other catapults, so we built our own.

Here is Ludgar.

(and Rez's friend)

We had a little trouble getting the 6" pieces of wood cut with 30 degree angles on each end to make the triangles.  Our miter saw has a setting for 30 degrees, but it is 30 degrees from the center line, not from the  side edge that you hold the wood up to.  Trip is good at solving problems, so we figured out how to cut them.

We weighted the bottom with lots of metal washers and some lead fishing weights tucked inside.

Ocean is demonstrating how it works.  To shoot it, place an object in the sling, pull it all the way to the floor, and release.  The weight in the bottom pulls goes down and the throwing arm goes up, releasing the sling, shooting your object.

Rez discovered that the Ballista shoots nerf darts very well.  

He could run around shooting it like a cross bow.

He could even sight down the center for more accurate shooting. 

Finally after some fine-tuning, they were ready for their trials. 

Here they are lined up, ready to fire.

The Ballista (in the front) shot the farthest by far.  The way it is designed the ammunition shoots straight.  The marble we shot would fly out and skip across the ground like a stone skipping on the water.  It went up to 20 ft.  After the trials were done, Rez tightened the ropes more and got it to shoot up to 29 ft.