Final Competition!

It's here, finally! We had the treb all loaded up and ready the move in the morning, since the only way onto the field was going to have a carnival on it during the day. Once there, we encountered our first obstacle: a ditch. Granted it was a pretty steep deep, it seemed like a petty thing until the trebuchet in front of us slid off of it's trailer on the way up.
Luckily, we managed to get all set up behind the soccer goals. We had all the counterweight on when we where then informed that we would have to be on the field according to the safety permit. Fortunately for us, the competition were a friendly lot and lent us a hand. When it was time for our test launch, we way overshot it and threw clear across the field. The second shot was not so lucky. The gallon jug slipped out of the sling and was left spinning in the trough as the trebuchet dry-fired. After that, we tied the sling around each milk jug and threw the whole sling, along with the jug. The next hitch was a broken arm guide next the the third wheel. We tied it back using a cannibalized drawstring bag and it gave us no more trouble for the rest of the comp. For the rest of the competition, we had trouble throwing at a low enough angle. Each time the target moved another 5 yards away we figured out a way to get the angle lower, putting us within a few feet of the castle. All our shots landed withing 10 feet, and we got one direct hit. Next to us, the other trebuchets had varying success. The other floating arm, made by a couple of graduate students, hit the castle every time but two. Meanwhile, a tie-dye murlin down the line broke down and had to resort to having a crew member through the jug by hand. The Beta treb suffered from whip-back effect, in which the sling failed to released, then whips back and released, shooting it backwards. They were disqualified on their last shot, but their axle had sunk to about 30 degrees on either side, anyway. Speaking of which, we had about a 4" bend in our own counterweight axle. It managed to last through the comp, but was in pretty bad shape by the end. I guess 1" steel rod is just not enough.

We ended up getting 2nd overall, which we were pretty happy with. We plan on keeping the arm for next year, and getting rid of the frame. We managed to get most of the throws on a GoPro, which I put up here: http://www.youtube.com/watch?v=3sKrMhudwhU


Cheers!

Second Test!

First things first, we added some plywood on the outside of the rails, just in case. More importantly, we got a 7:1 hoist to lift the counterweight. However, we later discovered that the hoist significantly limits the height to which we can lift the arm. The baseball diamond was occupied, so we took the trebuchet to the varsity football field, instead. We got three shots off, the first with 4 45lb plates, and the others with 6, for a total of about 300 lbs with the bar. The triggering mechanism is of our own design, and has worked surprisingly well so far. There is a 2x6 spanning the vertical supports in top, to which the hoist is attached. When firing, we pull on a knot with two webbing length going from it. The shorter pulls out the triggering pin. With all the weight taken off of it, the 2x6 can then be pulled to the side by the second line, so that the arm doesn't hit it. A small line keeps the 2x6 from flying off towards the trigger man. After reviewing the video, we have concluded that we will need to make the bridle attaching the arm to the hoist shorter, so we may lift the arm higher. Also, we will make the sling shorter, as sling releases after the arm decelerates.
I tried to take the videos from different angles to make sure everything got captured at least once.