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Medieval Postal Service Prepping for the Chunk

We have gotten Medieval Postal Service set up and firing again in preparation for the 2009 World Championships of Punkin' Chunkin'. This past summer was spent doing a lot of rebuilding, modifying, and redesigning. After all this work, we took the machine down to our range on September 19, and began set-up. The weekend of the 26th was mostly a washout, and we got very little accomplished, but this past weekend we finished up and actually took some shots with a little counterweight and our 4-pound medicine ball, just to make sure that the modifications all work properly. They appear to be performing as well, and the three low-power shots we took were all very impressive. One shot actually nailed a tree dead center and came shooting back out of the treeline, which was an amusing moment.

Team Urban Siege Presents the New Site! has been totally revamped! The entire site has been converted from static .html pages to .php pages, allowing for dynamic generation of the pages. While this makes no difference for the bulk of the pages, it has allowed us to condense the launch logs and news blurbs into one cohesive, pseudo-blog. This blog generates the pages of news on its own, removing the need for manual editing and recoding of 2-3 pages every time we post a news update. Visitors to this site may have noticed that we have been very inconsistent in posting news, and a large part of the reason for that was the length of time it took to post such updates. No more. Perhaps now we will post updates more often.

We Present: Tennis Ball Trebuchet Plans!

Team Urban Siege is proud to present Ripcord's Tennis Ball Trebuchet Plans available for download right here. A server issue cause Ripcord's site to go offline several months ago, and there is no timeline for its return. But we have the plans right here for all to download, free of charge. Just remember who actually designed them (Ripcord, not us, we merely edited a few grammatical issues and tweaked the layout for better file reading), and that our disclaimer still applies (as does Ripcord's, which is inside the file). Enjoy the plans!

Straightening MPS's Tracks

This past Saturday we spent some time at Great Lakes Pressed Steel straightening the tracks to Medieval Postal Service. Both tracks had a bow in them from the original welding process last fall, and so we had to be very careful when clamping the carriages to the main axle. The tracks both bowed inward along their length such that the center of the tracks was about 1.5" tighter than at the ends. We had to adjust the carriage spacing so that the wheels were not too tight in the center, but still were not in danger of falling off the tracks. This took quite a bit of time to get right, and was an issue we were not happy about. We lived with it for 2008, luckily without too much trouble, but this issue did not help matters when we misfired our last shot at Delaware.

Page Added on Material Properties

There is a new page that discusses material properties and how to design for a given stress. This aims mainly at trebuchet axles and how to pick a material to survive the stresses, and is a lead-in to a soon-to-come axle stress calculation page for trebuchets.

MPS Video From 2008 WCPC

We've finally made a page for Medieval Postal Service Videos, and linked to our YouTube video of it performing in Delaware. Also, some updates have been made to the links page, and added some more links in there as well. More stuff is in the works, stay tuned!

Team Urban Siege Has a Domain and a New Home

We've officially moved the website to our own domain name. We had just about out grown the free hosting account at 50Webs, only 1.5 MB of space left, out of 60 MB. Since a move was clearly in order, we opted to get a domain name, since they are now so cheap and if we need to move in the future, you won't need to update your links. Our new hosting has nearly unlimited disk space and any just about features we want, still free (just have to pay the yearly domain fee - not much at all). It also seems to be a bit faster than the old host, though it is far from blazing fast. Still, it should serve our needs quite well. Please make sure to update all your links to the corresponding pages at

MPS Plans for 2009

We had a successful 2008 World Championships of Punkin' Chunkin', despite not meeting any of our goals for 2008: finish 4th and break 1000 feet. Really, these were hand-in-hand, as 1000 feet would have easily taken 4th place, as we figured. We failed, not due to the trebuchet not being as powerful as imagined, but due top a lack of testing. We actually think we have more power than initially imagined. We had originally thought that setting up the trebuchet for the first time in September would only take one to two weekends, but it ended up being more like 4-5 due to machining errors (some design-induced) and other little things that added up time-wise. Still, we lucked out in Delaware and got off 2 solid low-power competition shots. Now to get up to the full power level: 600 pounds of counterweight, which is what we designed for nearly one year ago. With the full counterweight, the arm should now stall correctly thanks to a more favorable mass ratio. In turn, we will be able to use a longer sling, and capture much more of the energy available into the throw.

WCPC 2008

The 23rd World Championships of Punkin' Chunkin', held from October 31 - November 2, 2008, was to be our first real hurling competition. We entered our new 8-foot Floating Axle King Arthur-style trebuchet, the Medieval Postal Service. Unfortunately, construction had taken so long to complete in the fall that we had yet to test fire with more than 200 pounds of counterweight and a 4-pound projectile. Entered in the Adult Trebuchet division (we were all too old to qualify for the Youth division - 17 and Under), we needed to be able to launch 8-10 pounders, and thus had some work to do. Despite the lack of true testing, we were still confident that we could take 4th place in the division, or at least be very competitive for it. Yankee Siege, Pumpkin Hammer, and the Magic of Merlin all figured to exceed 1500 feet and be the top three machines, but no one else was expected to break 1000 feet. We wanted to, but knew it probably would not happen this year.

Summer-Fall 2008

Most of the Summer and Fall of 2008 was spent building Medieval Postal Service. After the frame design was completed in late June, the first pieces, the bases naturally, were cut in early July. Throughout the course of the next month we would purchase wood (picking carefully through the pile at Home Depot, getting roughly 20 boards at a time), and cut more pieces. Come early August, most of the wood frame pieces were cut and the sub-assemblies built. However, the arm, hanger, tracks, carriages, and other assorted components were still being designed. And that process was stalled even further when in mid-August Matt left town for close to three weeks due to the impending death of a family member. Jason was also gone on vacation for close to two weeks during this time, and so not much got accomplished on Medieval Postal Service during the month of August.

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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!!!