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Code Name: Janus





Team Urban Siege has a new winter project. It seems that we cannot go too long without building a new machine, and this winter is no exception. The design? A Floating Axle King Arthur/Floating Axle Whipper trebuchet. That's right, we are finally going to try out a whipper design. But this trebuchet is also intended to help us try some small changes we are considering making to Medieval Postal Service, hence the King Arthur mode. Actually, there are a number of critical points that this new machine is intended to address:

1) Be a pseudo-test bed for Medieval Postal Service where we can play with some things and see how they work without having to deal with the massive beast.
2) Be able to set up in less than 6 hours, preferably 1. Yes, it takes us roughly 6 hours from start to finish to set up MPS for firing from when we roll onto a site.
3) Be able to reset and fire off shots in less than 30 min, the average it takes us on MPS if we push it. 5-10 min at most is the goal.
4) Try out the FAW/RAW design.
5) Be able to demonstrate how MPS works at Imagine RIT in the spring, we are intending to demo Melon Felon and this machine.

The machine has a 5' foot axle height (and long arm), with an adjustable short arm. This is basically 3 hanger axle holes, to allow for arm ratios of 4:1, 5:1, and 6:1. 4:1 is MPS's arm ratio, and 5:1 and 6:1 are typical whipper ratios. The hanger also has 3 holes to connect to the arm, so that the counterweight ends up at the same height after firing, no matter the arm ratio.

A projectile box has been designed, as has an adjustable prop. Whippers have the arm and hanger offset by a specific angle, referred to as the prop angle. Typically this angle is around 30 degrees, which our simulations have agreed with, but we are building in adjustability to allow for some changes, should they be needed. Basically we just have a threaded rod in the hanger with a swivel foot on the end. Turning the rod will adjust the prop angle. Nothing crazy.

O yea, what are we going to chunk? Up to 2.2 pound (1 kilogram) projectiles, with upwards of 200 pounds of counterweight. In theory, we may well break 1000 feet with this machine, we will see what actually results. Either way, it will throw way further than Jeckyl and Hyde ever hoped to. We are making the arm from aluminum, the hanger from steel, and there will be a v-grooved track with wheels.

We have begun frame construction, and as usual this machine will be able to break down for transportation. All of the vertical pieces will bolt onto the top and bottom beams, and the outriggers will bolt on as well. The base will be assembled with tee nuts, much like Medieval Postal Service in 2009.

Here are some screenshots of the CAD model rendering, we will update when we get some pictures taken:

straightening tracks thumbnail checking track straightness thumbnail done checking tracks thumbnail done checking tracks thumbnail straightening tracks thumbnail




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Use "common sense" when operating trebuchets and catapults. Even little ones can be dangerous. Do not place anything you are not willing to lose in the plane of the arm rotation (this includes yourself, body parts, car windshields, cameras, etc). These catapults and trebuchets are capable of throwing just as far backwards as forwards, and the use of a backstop of some sort is recommended, though the use of one does not make the region behind it safe.

Also, just because the throw got away safely downrange does not mean the end of the danger. The arm is likely still swinging wildly along with the counterweight, and there is a sling whipping around. One thing many people fail to take into account is this sling; some people put a metal ring on the slip end of the sling and this ring can HURT when whipping around!

Have fun hurling, but please KEEP IT SAFE!!!