Siege Onager Jr : Upgrades

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Onager Jr : Upgrades
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After our trip to Maine, Onager Jr was used again at the 2001 History Channel Chunk, and at the 2001 Bennington High School Chunk. At the end of those two adventures, our third canvas pouch had disintegrated.

Amy used a pair of #35 knitting needles to create this pouch out of nylon clothes line. It is by far the sturdiest onager pouch to date. We used this pouch when we did a demonstration for the New England Model Engineering Society.

In July, we decided to rewind Onager Jr with some new rope. Here the old torsion bundle (yellow w/ bumps) is about to be replaced with two lengths of dynamic climbing rope (purple.) Climbing ropes are discarded when the sleeve wears through. This wear makes it hazardous to use in that it jams in equipment, and leaves it open for breaking while holding a critical load (ie: you.) As far as a torsion bundle is concerned, WHO CARES! The core is still stretchy and solid when I got a hold of it.

The yellow polypropalene rope served us well, but as you can see here, it did not take kindly to the abuse it was put through. This section wasn't over an epizygis, but was deep in the core of the bundle. This is what happens when you wrap a torsion bundle with some strands tighter than others.

Here is a quick look through the holes in the Onager. You can see the severe wear marks on the hole carriers.

Here is Roger on the other side as we rewind the torsion bundle with the new climbing rope. He is currently struggling trying to get the rope through the hole in the hole carrier.

When throwing rocks in Maine, the scutulas (hole carriers) bent in to the point where more torsion could not be added. Metal angle iron from a bedframe was added between pine layers to hold back all the force.

The onager has be rewound, and is ready to fire! You can see here that the rope bundle isn't full. We could probably fit in another 50' or more of rope. I found this rope to be very stretchy, and bad at a low number of twists, where the poly-p was better. We tightened this up to high power at the Mount Snow, Vermont.
Eric`s main concern was getting all the folks he works with a chance
to play with the catapults, and it was quite fortunate that the
management at Mount Snow was willing to give up some parking lot space
for the event.')">2002 Mount Snow/MathWorks chunk, and it would throw a 20oz soda bottle on a low flat trajectory over 130 ft. The Poly-p could throw 150ft with ease with a high arc once tighted up. This indicates that this type of rope is overpowering our projectile! Another aspect of this torsion bundle is that after a hard day use, it gets very wobbly and loose. Wait a day, and it returns to full tightness. Cool!

WHEELS! We suffered with the old bedframe wheels for some time. They didn't role well in the field, and grew flat spots. I finally replaced those small wheels with these big wheels scavenged off a gas grill. I placed them inside the frame so that when the onager is sitting on the ground, the don't touch the ground.

Once you pick it up from the front, however, the curves on the back beams allow the wheels to touch the ground. These wheels roll very smoothly and let me give Trevor a ride around the yard.

Additional Pages for Onager Jr
Onager Jr Onager Jr was our first torsion siege-engine of the medium scale that functioned well.
Onager Jr: Construction Onager Jr's basic construction is fairly simple. I thought it would be neat to make something that didn't use screws, but after assembling the bottom, screws were needed for much of the upper frame, and for the strengthening of structural members later.
Onager Jr : Flinging potatoes Loaded onto the car and ready for a drive to family reunion. I had finished it this morning, and the first test shot was 3 feet. How dissapointing.
Onager Jr : Rocks in Maine We rebuilt the machine, and brought it to Maine to fling rocks into the mud flats. We had rebuilt the breaker bar to be sturdier than before, and also added a winch.
Onager Jr : Upgrades After our trip to Maine, Onager Jr was used again at the 2001 History Channel Chunk, and at the 2001 Bennington High School Chunk. At the end of those two adventures, our third canvas pouch had disintegrated.
Onager Jr : Zucchini Upgrades In 2005, Onager Jr was destined to go to the zukapult contest in Ludlow Vermont. To accomplish this, Onager Jr needed to be upgraded to throw projectiles smaller than it had done so in the paste.
Onager Jr : Movies Here are some videos of the little guy in action. They were all taken during the 2001 History Chunk.

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