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.

Trebuchet Progress

So far Emily and I have completed one side of the trebuchet and have begun work on the other side. We were working fairly slowly in the beginning because we weren't sure on what to do and had to discuss most things, but recently we have been doing things more automatically and it is progressing much faster. The main issue we have encountered is that the nails are too long for the materials we are using. Even if we use the smallest ones, they will still go all the way through the wood. This is an issue as it is splitting the wood and would definitely be weakening the structure. We have glued extra pieces over the top of parts that have been particularly affected by this to try to hold it together, but that is fairly time consuming and won't solve the problem completely. Other than that, the machines seem to be fairly crowded because it is such a large class, and it is quite slow when you have to return to them frequently to make small adjustments to angles. That can't really be helped though.

If we have time at the end we are going to add more supports to each side to strengthen them even further, so they will hopefully be able to hold even more weight. I am fairly sure we are on track to finish by the due date, and am quite confident that our trebuchet will operate well on the day.

Progress

Trebuchet

Recently we were given the design brief for our new task. We are to design and fabricate a trebuchet capable of propelling a golf ball as far as possible. I am going with Emily for this task, and we have decided that we would like to attempt to make a trebuchet instead of just a catapult, and if it doesn't work we can just revert back to the catapult design. This week we are working on designing our trebuchet, and researching some of the history surrounding them. Hopefully we'll be able to start in the workshop early next week.

Completing my car

A few days ago, my car crashed badly into the end of the track as there was not enough padding, and it slightly ruined my car. It jarred the axle housing, making the car not run straight. It also jammed the wire at the front into the gap at the end of the track and the wheels stopped staying on. It made the time drop from 2.856 seconds to about 3.8. I fixed it as best I could during lunch times as we did not have anymore lessons, and managed to get the time down to even faster than before. In one of my final runs, I got the time of 2.774, which was my fastest. After this I stopped racing it as I did not want to risk anymore complications.

Since my last post, I lubricated more, glued on one of the wheels to make it more steady, and shortened and soldered all of the wires. I also attached a windshield to the front of the car.

Below are some images of my finished car.

This has been one of my favourite units so far, and I wish we could have spent longer on it so we could experiment more with different designs. I am definitely looking forward to racing the cars on Monday, but am also slightly worried that mine will not perform as well as it has been because I have been experiencing complications lately. Hopefully everything will be fine, and even if it isn't, I know that I have made my car as well as I could have and am very satisfied with how it has done.