Testing with the Weight

Today we tested our trebuchet with the weights! It went fairly well, and thankfully didn't break. It went a bit further than the other ones I have seen, so I am pretty pleased with that. We didn't actually measure the distance it travelled or the time it took today because we just wanted to make sure that the angle for the cup holding the ball was right. We glued on the cup and the triangle that it sits on today, after making sure we were satisfied with everything. The wheels have also been made and attached. We also decided to spray some grease on the join between the washers on the arm and the nut, to ensure that the least possible amount of energy is lost due to friction.

The only issue that we are currently having is that unless it is set up with a lot of care, the weight will hit the sides. This means that it doesn't swing completely, and loses a lot of force and energy on the impact. However, this shouldn't be a problem on testing day, because now that we know it happens we can take care in making sure that it doesn't happen on the day.

Below is an image of our completed trebuchet.

Beginning Testing

Today, at the end of the lesson, we tested out trebuchet. We didn't attach the weights yet, but instead just pushed it down. We only wanted to see the angle that the ball would go in, so it didn't need to travel very far. As it was, it went reasonably well, but perhaps slightly too vertically. By changing the angle of the small triangle on the end of the arm, we could make it travel further in distance than it currently is. We did not have time to do this though, because we only began testing it in the last 15 minutes.

During the lesson we also attached the arm with the metal dowel, nuts, and washers, as well as drilling the hole through the end where the weights go. We are getting very close to finishing now, and only really need to do the wheels and adjust some angles on the arm, as well as possibly supporting some areas more if they are put under too much stress when the weights are attached. We are definitely well on our way to finishing, and I am really pleased with our progress. Some images of our trebuchet currently can be seen below. Part of the arm came off during testing, so it is currently being glued back on.

Nearly Completed

Emily and I have now nearly completed our trebuchet. We completed both sides and drilled the hole through the top. Then made the arm and attached it with just the wooden dowel for now. The only issue I have with it currently is that the holes are very slightly lopsided, so that one of the sides is slightly lower than the other. This will probably end up placing more pressure on this side, and could lead to our trebuchet's demise. Hopefully it will probably be fine, and if not we can just place extra supports on that side.

With the catapult arm, Mr Ward said it may be stronger if we glue three pieces of timbre together for the entire length, rather than just around the join. We have not done this, because it was said after we finished, but I still wouldn't have done it anyway, because it would add extra weight to the end with the ball that is being thrown. This would mean it would take more effort to throw the ball, and more energy would be lost, and that end of the arm really does not need to be supported because it will be lifting minimal weight. Instead, we have just reinforced the end with the weight itself, and the join, which I think would be more effective.

We still haven't actually gotten around to making our catapult into a trebuchet, and at the moment I am beginning to doubt that I'll have time. No one else has done one either yet, so it shouldn't matter too much. We could possibly go in to work on it in a few lunch times, but we are running out of time to even do that.