The overall trebuchet experience was very fun and a learning experience for sure. Things that went well included the results of our trebuchet overall, I was very happy with the results and I think that we built our trebuchet to the best of our ability. As well we were lucky on all our days to have decent enough weather to be able to test our trebuchet. It was helpful that we picked our own groups because then we were able to pick partners whose schedules matched ours so working together was easy. It was also helpful that we made our trebuchet very early in advance because then we didn't have to spend time cramming near the end to get a working trebuchet and we were very lucky that it was consistent in its throws as well.
I would say that a big tip to help future students would be to get things done early as then it is over and done with and one less thing to worry about. As well that way if something goes wrong you have lots of time to fix it. I recommend as well that blog posts are done on time and not all at once because it can be hard to recall if left too long. It is also helpful to try out your trebuchet a number of times to make sure it is consistant and if it isn't then to work hard to make it consistant so that you are not crossing your fingers hoping it works. Besides this I would say just have fun with the trebuchet challenge, doing extra things like painting and personalizing your trebuchet also add to the fun and experience and time you get to spend with your group!
Thursday, May 26, 2011
Competition Reflection
Our trebuchet was very successful in the accuracy part of the challenge project with our closest throw to be within one meter of the center of the hula hoop. This earned us second place in the challenge! From that we scored 9/10 points in the accuracy part of the competition.
I would have improved our trebuchet by coming up with a more consistant way to make it accurate to 15m. I would have rather taken off the counterweights instead of added bungee cords because I feel it would more accurately place each throw at 15m. Even on competition day we had a few test trials that made us realize that we needed to alter the bungee cords. They were not the greatest choice because if they were slightly altered the whole overall performance of the trebuchet was compromised and that could have happened very easily, we were lucky that it didn't.
If I were going to build a brand new trebuchet there are not many things that I would change except for possibly raising the height that the counterweight had to fall and increasing the mass of the counterweight which would have increased the range. As well what I posted above I would do to alter the accuracy part of the competition.
I would have improved our trebuchet by coming up with a more consistant way to make it accurate to 15m. I would have rather taken off the counterweights instead of added bungee cords because I feel it would more accurately place each throw at 15m. Even on competition day we had a few test trials that made us realize that we needed to alter the bungee cords. They were not the greatest choice because if they were slightly altered the whole overall performance of the trebuchet was compromised and that could have happened very easily, we were lucky that it didn't.
If I were going to build a brand new trebuchet there are not many things that I would change except for possibly raising the height that the counterweight had to fall and increasing the mass of the counterweight which would have increased the range. As well what I posted above I would do to alter the accuracy part of the competition.
Distance Part of the Competition
Our trebuchet was very successful with distance it went the furthest out of all of the trebuchets. It's farthest distance was 51.22m. As well on the distance competition day every one of our throws was within a meter and a half of each other. This means that our trebuchet is consistant at achieving the long distance of around 51m.
In order to prepare for the accuracy part of the competition we are going to shorten the length of our throwing arm and add bungee cords around the top of our trebuchet. The bungee cords will stop the counterweight from falling the full height as well as restrict the throwing arm from swinging as fast as it normally would.
In order to prepare for the accuracy part of the competition we are going to shorten the length of our throwing arm and add bungee cords around the top of our trebuchet. The bungee cords will stop the counterweight from falling the full height as well as restrict the throwing arm from swinging as fast as it normally would.
Theoretical Range
Range = 2 x h x (M/m)
Range = 2 x 33 cm x (22.6796 kg / 0.057 kg)
Range = 26260.59 cm
Range = 262.6 m
Average distance= (51.69m + 50.99m + 42.11m + 50.29m + 51.00m) / 5
Average distance= 51.22 m
Difference between Range and Average distance= 262.6m - 51.22m
Difference between Range and Average distance= 211.38m
Five Reasons that kept our trebuchet from hurling the theoretical range:
Friction:
The friction between the moving parts of our trebuchet including between the swinging arm and the rod it is placed on cause the arm to not swing as fast and not hurl the ball to the full potential. As well the friction of the ball and pouch on the underside of the trebuchet as it is pulled upward by the swinging arm causes it to slow down and reduce the range.
Air Resistance:
The air resistance on the ball causes it to slow down and accelerate negatively causing the actual range to decrease. The ball we use is a tennis ball so it is not as aerodynamic as say a golf ball and therefore the tiny hairs on the ball cause more air resistance and reduce the range as well.
Pouch and Release Options:
In the theoretical range it is not considered that the pouch may not work in prime condition all the time. We had issues with our pouch at different times sometimes it did not release at the prime position it either held on too long to the ball or let go too early this caused the difference in actual range as compared to the theoretical range as well.
Release Angle:
Our trebuchet was supposed to be set with a release angle of 45 degrees, however we were not sure if it was ever actually exact on that value. It was difficult with transporting of the trebuchet and repeated use to say that it didn't change or was affected and possibly not the 45 degrees it was supposed to be. This affected and decreased our range as well.
Environment conditions:
The weather conditions affected our actual range as well reducing the range. Factors such as wind resistance and air density on that particular day caused our actual range to be less than the theoretical range as well.
Range = 2 x 33 cm x (22.6796 kg / 0.057 kg)
Range = 26260.59 cm
Range = 262.6 m
Average distance= (51.69m + 50.99m + 42.11m + 50.29m + 51.00m) / 5
Average distance= 51.22 m
Difference between Range and Average distance= 262.6m - 51.22m
Difference between Range and Average distance= 211.38m
Five Reasons that kept our trebuchet from hurling the theoretical range:
Friction:
The friction between the moving parts of our trebuchet including between the swinging arm and the rod it is placed on cause the arm to not swing as fast and not hurl the ball to the full potential. As well the friction of the ball and pouch on the underside of the trebuchet as it is pulled upward by the swinging arm causes it to slow down and reduce the range.
Air Resistance:
The air resistance on the ball causes it to slow down and accelerate negatively causing the actual range to decrease. The ball we use is a tennis ball so it is not as aerodynamic as say a golf ball and therefore the tiny hairs on the ball cause more air resistance and reduce the range as well.
Pouch and Release Options:
In the theoretical range it is not considered that the pouch may not work in prime condition all the time. We had issues with our pouch at different times sometimes it did not release at the prime position it either held on too long to the ball or let go too early this caused the difference in actual range as compared to the theoretical range as well.
Release Angle:
Our trebuchet was supposed to be set with a release angle of 45 degrees, however we were not sure if it was ever actually exact on that value. It was difficult with transporting of the trebuchet and repeated use to say that it didn't change or was affected and possibly not the 45 degrees it was supposed to be. This affected and decreased our range as well.
Environment conditions:
The weather conditions affected our actual range as well reducing the range. Factors such as wind resistance and air density on that particular day caused our actual range to be less than the theoretical range as well.
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| Our colorful trebuchet loaded and ready to fire on competition day! |
Wednesday, May 18, 2011
Test Day
Test day for our trebuchet was very successful! We achieved a distance of 60m however the wind was quite strong that day so we expect it wouldn't go quite that far on a normal day. We did not make any changes to our trebuchet during test day as we had made it well in advance and had already made changes. One of these changes involved adding handles in order to easily carry the trebuchet around.
The only thing that was not completed on test day was the accuracy part of the challenge. We still had to find a way to make our trebuchet only go 15m as compared to its usual average of around 60m. We worked on this in the days following test day and found a way to make it work by restricting the drop in the counterweight and shortening the throwing arm.
The only other thing that we had to alter after test day was the pouch. Our pouch was simple in construction however very efficient. The only problem was that the stitching that surrounded the ball would occasionally loosen. In order to fix this we added additional stitching in order to support the ball better.\
The only thing that was not completed on test day was the accuracy part of the challenge. We still had to find a way to make our trebuchet only go 15m as compared to its usual average of around 60m. We worked on this in the days following test day and found a way to make it work by restricting the drop in the counterweight and shortening the throwing arm.
The only other thing that we had to alter after test day was the pouch. Our pouch was simple in construction however very efficient. The only problem was that the stitching that surrounded the ball would occasionally loosen. In order to fix this we added additional stitching in order to support the ball better.\
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| Our Successful Trebuchet! |
Wednesday, May 4, 2011
Cardboard Trebuchet
Creating our paper trebuchet was very fun and interesting and quite a learning experience. There was some difficulty in making it because of the somewhat fuzzy directions. It was sometimes difficult to tell which lines to cut and which lines to fold. The cutting and gluing was relatively easy and once we got going the process was easy to complete.
One of the things that a trebuchet cannot overcome is air resistance however in our small trebuchet air resistance was not really that prevelant as we were using such a small round ball, similar to a small version of a golf ball which is meant to go long distances with minimal air resistance. Air resistance may not have been very obvious however we know that it was still present.
Gravity was very much an obstacle that was shown in our paper trebuchet as we had to overcome it to, the best of our abilities in order to get our trebuchet to go as far as it could distance wise and as accurate as we could.
The last thing that we had to consider was the angle of release in order to get the optimal range out of our trebuchet we had to toy with the angle of release. Once we figured out that the optimal angle of release was 45 degrees we used this for our range.
As well a trebuchet must have a counterweight in order to use the full potential amount of gravitational pull. The larger this counterweight is the more gravity pulls it downward which causes the sling of the trebuchet to swing around faster.When we tested our paper trebuchet we used approximately 40 individual weights as a counterweight to get the longest range and we took out about 15 weights out in order to reach the right spot for accuracy by taking out weights this allows us to not have to change our angle of release which means we do not have to re-do the angle for distance again.
One of the things that a trebuchet cannot overcome is air resistance however in our small trebuchet air resistance was not really that prevelant as we were using such a small round ball, similar to a small version of a golf ball which is meant to go long distances with minimal air resistance. Air resistance may not have been very obvious however we know that it was still present.
Gravity was very much an obstacle that was shown in our paper trebuchet as we had to overcome it to, the best of our abilities in order to get our trebuchet to go as far as it could distance wise and as accurate as we could.
The last thing that we had to consider was the angle of release in order to get the optimal range out of our trebuchet we had to toy with the angle of release. Once we figured out that the optimal angle of release was 45 degrees we used this for our range.
As well a trebuchet must have a counterweight in order to use the full potential amount of gravitational pull. The larger this counterweight is the more gravity pulls it downward which causes the sling of the trebuchet to swing around faster.When we tested our paper trebuchet we used approximately 40 individual weights as a counterweight to get the longest range and we took out about 15 weights out in order to reach the right spot for accuracy by taking out weights this allows us to not have to change our angle of release which means we do not have to re-do the angle for distance again.
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| This is a picture of what our cardboard trebuchet looked similar to. |
Monday, March 14, 2011
Medical Physics Project
My team includes Toby, Keifer, and myself and we have chose to do our project on nuclear medicine -> Ultrasound. In the project Toby is to complete the fact sheet, Keifer is completing the report and I am completing the power point presentation and we are all going to work together in order to put together the demonstration. Along the way however we will all contribute to each other by assisting when our team members need us.
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