Post 1:
Our trebuchet was never shooting accurately before the challenge so we had no idea how it was going to shoot on performance day. It shot a lot better than we thought it would. We were fourth closest in our class at 0.69 meters from the target spot. We got three throws and 0.69 meters was the closest one.
To improve our trebuchet I would have used a sturdier bar to hold the arm. The one that we had couldn't handle the weight on it and sagged in the middle causing some problems. I would have also used a straighter piece of wood for the arm so it would shoot straighter- ours that we used was a little bit warped.
If I could have built a totally new trebuchet, I would have made it higher and not as long so the weight could have picked up more speed. I might've experimented with different pouches and string lengths.I think though that the use of wood for the trebuchet was a good idea- it was easy to build and supported the weight really well.
Post 2:
There were lots of things that went well on our trebuchet. The use of wood as the building material was a smart choice as well as an easy one. It made the building a lot easier but still supported the weight with ease. Our whole design worked really well. Other trebuches rocked a lot when they shot but ours stayed fairly solid on the ground. Our pouch and string length worked perfectly. We never had any trouble with the ball not staying in the pouch or not coming out of the pouch.
Recommendations for future trebuchet builders would be to make your trebuchet out of a material that is accessible and easy to work with for you. Don't make it harder than it needs to be. Also, don't be afraid to ask for help from someone who knows how to build with your material- it makes it way easier. For your pouch, try different styles and figure out what works best, same with the string length. Try not to get too frustrated if it doesn't work- troubles are bound to come up. Focus on working through it and getting it to shoot as good as you can. The biggest thing is if your trebuchet is shooting well and meeting requirements, don't change anything! Sometimes if you change one thing, it can throw everything off.
Friday, June 8, 2012
Posts 3: Performance Day
Post 3:
The theoretical range of our trebuchet was calculated using: 2h(M/m) Our theoretical range was 331.07 meters.
Five reasons why our trebuchet didn't achieve the theoretical range:
1. Friction between the moving parts of the trebuchet
2. Air resistance
3. Wind
4. Warped bar that the arm rotated on
5. Bad release from the pouch
Post 4:
Our trebuchet didn't perform up to our expectations on distance competition day. It started off strong but with each shot went a shorter distance. It started off shooting over 40 meters but by the end it was shooting under 25 meters. It had never given us any trouble before so we fiddled around with the weight and the angle of release and got it shooting mostly over 25 meters. Our average out of five shots was 27.85 meters.
For the accuracy part of the competition we plan to take out all the weights from our bucket. That will reduce the weight from 14.97 kg to 3.63kg. We also didn't pull the arm down as far- reducing the distance that the counterweight has to fall and slowing down the release. The rest of the tebuchet will stay the same.
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| Our trebuchet set and ready to shoot for distance. |
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| Janelle and I and our trebuchet on competition day. Picture compliments of Mr. Bertram. |
Tuesday, May 29, 2012
Post 2: Test Day
Janelle's and my trebuchet worked really smoothly. First we worked on distance. We loaded it up with 30 pounds and it consistently went around 40 meters. We were very happy with that considering it only needed to go 25. We didn't change anything on the trebuchet for distance.
Next we tried for accuracy- hitting a hula hoop at 15 meters. We took all our weights out and didn't pull the arm down as far when we loaded it. We were consistently within a foot of the hula hoop and made it inside the hoop once. We were changing how low the arm was and how tight we were pulling the sling. This affected the distance but it was inconsistent in how it changed. We didn't make any major changes. Everything worked very well and we were very happy with the results
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| Janelle and I and our trebuchet on test day. |
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| Loading up our trebuchet. |
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| Our trebuchet all set and ready to launch. This was for distance- the arm is pulled all the way down. |
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| The trebuchet ready to launch. This was for accuracy- the arm is pulled only partially down. |
Wednesday, May 23, 2012
Post 1
In physics class we made a cardboard trebuchet. This trebuchet had to hurl a wooden "marble" as close to 10 meters as we could get it, using washers as a counterweight.
The marble was a projectile- experiencing no other forces other than gravity. To get as far as possible we had to ensure that the release angle was at forty five degrees- which ensured the furthest distance.
In our design we had to make sure there was no friction that would slow down the action of the arm as it swung around. This would slow down the speed of the marble as it left the sling and therefore decrease its distance. Also along with friction, we had to make sure that when the bucket swung down that it wasn't hitting a support leg which would also slow down the release action of the marble.
To make sure that the marble was released properly we had to sew our sling in such a way that the marble would be held in it but at the same time be able to be released easily.
In order to increase the distance we added more weight to the bucket. This added weight caused the bucket to drop and swing the arm faster. This increased speed allowed the marble to be let go with more force and travel further.
Environmental factors that we had to deal with were gravity and air resistance. These we couldn't change but they affected our marble's flight. Air resistance was hardly noticeable but it was there. Gravity was an unavoidable force as it pulled our marble to the floor.
Performance factors were the angle of release, the counterweight, and alignment. These we could change to increase the performance of our trebuchet. The best angle of release was forty five degrees because it had equal x and y values that would cause it to go further. The counterweight we used was washers. The more we increased the weight, the faster the bucket would fall and the faster our marble was released. To get the trebuchet to go as far as possible we used as much weight as we could. To make it as accurate as possible, we took washers out until the trebuchet was shooting the right distance. Alignment was very important. We had to make sure that everything was running smoothly and nothing was rubbing or hitting as it was throwing the marble. The rubbing or hitting would cause friction which would slow down the arm's swing.
The marble was a projectile- experiencing no other forces other than gravity. To get as far as possible we had to ensure that the release angle was at forty five degrees- which ensured the furthest distance.
In our design we had to make sure there was no friction that would slow down the action of the arm as it swung around. This would slow down the speed of the marble as it left the sling and therefore decrease its distance. Also along with friction, we had to make sure that when the bucket swung down that it wasn't hitting a support leg which would also slow down the release action of the marble.
To make sure that the marble was released properly we had to sew our sling in such a way that the marble would be held in it but at the same time be able to be released easily.
In order to increase the distance we added more weight to the bucket. This added weight caused the bucket to drop and swing the arm faster. This increased speed allowed the marble to be let go with more force and travel further.
Environmental factors that we had to deal with were gravity and air resistance. These we couldn't change but they affected our marble's flight. Air resistance was hardly noticeable but it was there. Gravity was an unavoidable force as it pulled our marble to the floor.
Performance factors were the angle of release, the counterweight, and alignment. These we could change to increase the performance of our trebuchet. The best angle of release was forty five degrees because it had equal x and y values that would cause it to go further. The counterweight we used was washers. The more we increased the weight, the faster the bucket would fall and the faster our marble was released. To get the trebuchet to go as far as possible we used as much weight as we could. To make it as accurate as possible, we took washers out until the trebuchet was shooting the right distance. Alignment was very important. We had to make sure that everything was running smoothly and nothing was rubbing or hitting as it was throwing the marble. The rubbing or hitting would cause friction which would slow down the arm's swing.
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| Our trebuchet as it would look after we released the marble. |
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| Another angle of our trebuchet in the position after it would've shot the marble. |
Wednesday, February 29, 2012
Container Mass: 137.0 g
Container Dimensions: 27cm/26cm/11cm
Time of fall: 1.07 s
Fall Distance: 5 m
Condition of Egg: unbroken
Egg Points: 146
I found size to be the most limiting factor. We had to make a container smaller than 28cm by 28cm. We could have made our cardboard flaps much bigger and had our container fall much slower because of the increased resistance. This would have reduced impact at the floor and made it easier on our egg.
The most effective part of our design was the cardboard flaps. The flaps balanced the container and ensured that it landed on the right side. They also slowed the container down and lessened the impact.
The least effective part of our design was the sock wrapped around the toilet paper roll. It didn't really add anything to the container except mass, though it ensured that it all stayed together and held the egg more solidly in place.
To safely carry two eggs we would have to get a new toilet paper roll and cut two holes in the tissue with space between them. Everything else would be the same but just add another hole for the second egg.
Egg Drop Post 1
For test day we constructed a container to allow us to safely drop an egg from 5 meters. Our container was a cardboard box lined with bubble wrap. We had a smaller box filled with cotton balls inside the bubble wrap. Inside the cotton balls we had a small plastic container that held the egg. When we dropped the container from 5 meters on test day it smashed the egg. We decided to start over and design a whole new container. We decided to use a toilet paper roll. We cut a whole in the side of the roll through the tissue paper and through the one side of the cardboard structure. We placed a sock in the hole and wrapped it around the rest of the roll to give it support. We tested this container and the first time the egg was whole. The second time the egg was smashed. So we added cardboard flaps on all four sides to stabilize and slow down the fall. We tried it again and the egg was unbroken.
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