New Physics

Isaac and I had to think pretty hard about physics that we had not used before. We have used kinematic equations, forces, and we have both taken wood shop (so no new physics can be used from that room). So, we tried to think a bit more about the core concepts in the trebuchet, more specifically the arm. We looked more into the concept online, and to put it simply, we looked into the following equation:
W1 * A1 = W2 * A2, where W stands for weight and A stands for arm length. If the two sides were equal, then the arm would be perfectly balanced. But, by having a shorter arm on the one side, with more weight on it, that creates more pull for the one side. And, by having a larger arm with the sling on it, it gets whipped around due to the large pull of the other side, and that is why it is able to fling so well. If the sling attached to the short side, the entire arm would whip around as quickly, and the arc would be smaller. It may be relatively simple physics, but Isaac and I had not worked with it before.

Outside Resource

Isaac and I had two outside resources for our project. Both Isaac's dad and Mr. Homkes helped us throughout our project. Isaac's dad helped us out a lot at the start. He was kind enough to buy us the wood that we would need, and he gave us some general tips on the best methods to go about actually making the trebuchet. His dad always had his phone, so if we were wondering the best way to screw something in (for example), he would respond within a few minutes about what we should try to do. Mr. Homkes was also very helpful. An example of when he helped, was when we were trying to hammer the metal axis rod though the throwing arm. We had a little hammer, and spent probably 10 minutes hammering and hammering away trying to get it through. We asked him if there was any better way, and he came back with a huge hammer, and a block of wood. He put the block of wood on the piece of metal, and with one hit, the entire metal rod fell exactly where we wanted it to be. We didn't think of a method like the one he used for us, but we were sure glad we asked, because hammering that could have taken all hour!

Mathematical Model

For our mathematical model, we tested different weights in our box, and tested to see how it would change how far our tennis ball threw out of our trebuchet. With our base amount of weight in the box, it was capable of throwing 486 inches (or 40.5 feet.) Then, we added different amounts of weight (in grams) to our box. We found that for every 500 grams that we added, it averaged an amount of about 40.5 (3.375 feet) inches extra per throw. So, we can estimate how far our trebuchet can throw based on how much weight we have added into our trebuchet. Our model would then be f(x) = 486 + 40.5x. This means that it will default throw that original 486 inches, and for every 500 grams that we add (1 extra x), it will throw that additional 40.5 inches.

Entry #12

Isaac and I have been really busy, and so we have forgotten to post to the blog. Isaac and I decided to take a break in making it look really nice, and focus more on functionality. So, we stopped spray painting, and started to work on the sling and box. The box is nearly done, and just needs to be put together, and the sling seems to be functioning with all of our test runs. Here is a picture of what we have so far, and it seems as though it is going to be working.

Entry #11

Isaac and I had to unscrew all of the vertical, in order to be able to have a straight hole through both vertical supports and the throwing arm. Also, we started the process of spray painting all of our project black, and it is possible that we will unscrew all the screws again and paint the tops of those a color that would look really cool with the black, if time permits it.

Entry #10

Today, Isaac and I made the tray that we are going to use to help guide the sling as it is taking off. We also made a few more supports between the  base to be able to support the tray more. We were not able to make the arm, because we did not have axle yet. Lastly, we sanded down the entire trebuchet, to prepare it to be spray painted.

Entry #9

Today, Isaac and I got all the supports up, and started to think of the best way to go about adding the arm. We found the best drill bit to hollow out the hole, and are in the process of thinking about the best way to prevent the bar from spinning around.

Entry #8

Hey! Look at that! We remembered to take a picture today! Anyways, Isaac and I worked on the supporting arms today, and decided to cut one a bit shorter than the other (because it looks cooler. Nothing sciency behind that). So we got one of the arms attached, and the other ones are already cut and ready to be put on. Overall, pretty productive.

Entry #7

Today, Isaac and I made the base of our trebuchet. We were working hard, and forgot to take a picture, but it is looking pretty good. We have it all planned out as to how we are going to make our entire project, and our model should be a pretty exact model, with little change. Thankfully, Mr. Homkes showed us where some really long screws were (which we didn't think to purchase, and that could have been an issue).

Entry #6

Today, Isaac and I just worked on Capa all class long. Instead of writing all of our dimensions down, we just decided to multiply all of the dimensions by 3.

Entry #5

Because we finished our model, we needed to figure out the dimensions of what our real project would be. Isaac wrote them down on his computer, and I do not have them, so I am not able to post them (we can post them tomorrow if I remember to ask him). After figuring it out, and planning the majority of what we will do, we drove around for about thirty minutes to different hardware stores. At these stores, we learned that wood is not a common thing for hardware stores to carry. Leaving woodless, we returned to school to start out capa.

Entry #4

This is kind of a bad picture, but you can see that we got the counter-weight to work. It is just a cup with some fishing wire holding the cup to some nails poking through the side. We also got the sling to work. If there was more weight, we would be able to launch things. However, because we don't have enough weight (the cup couldn't support it), it just gets held inside of the sling instead of actually launching. However, we can easily fix that with our real trebuchet, so we are pretty ready to start creation of the real trebuchet.

Entry #3

We struggled with the box a lot today, and we pretty much spent the entire hour trying to get it to actually work. We think that the problem is that the box is a bit too big, and that is preventing it from swinging easily. If we can't get it to work soon, we are just going to get something different for the box, or make a new one.

Entry #2

Today we attached the four supports, and we made the box for the weights. We also had to make the strings to attach them, and get the string so that it is able to launch.

Entry #1

We are almost done creating our model trebuchet. We just need to attach the side supports that we already made, and create the counter weight. It is going pretty well so far, and looks like it will work.

Week 1, Wednesday, 4/16

Today, Mr. Rink and I decided what our project would be. The classic physics project, a trebuchet, flung itself into our minds. We studied the previous miniature scaled models of past physics greats and decided to begin designing. We created a mock-up on paper, estimating what our dimensions should be.

Our current plans:
Height: 13 inches (1 foot plus one inch on base)
Base length: 20 inches
Base width: 8 inches
Support bar length: 14.21 inches
Arm 1 length: 15 inches
Arm 2 length: 4 inches
Weight in basket: tbd
Length of string: 8 inches
Width of channel: 2 inches