Competition Day

The theoretical range of our trebuchet was calculated to be 469.65 m. I believe that it didn't reach it's full potential due to these five factors:

1. Counterweight - The more weight used as a counterweight, the further the projectile will travel. The amount of weight we were able to use in our counterweight was limited to as much as we could fit in our bucket (3 chains). 
2. Air Resistance - The air resistance on competition day was pretty fierce, blowing from the north-east at over 20 km/h. This affected the path of the tennis ball while it was in the air, especially when the flight of your tennis ball is very steep. The higher the projectile is, the more it is affected by the wind.
3. Friction - Friction is a major factor in the range of the tennis ball, if there is a lot of friction between the arm and the axel, counterweight and the arm, etc. there is a greater chance that the ball will not travel it's full distance. 
4. Height of Counterweight - the further the counterweight has to fall, the longer gravity has to act on it, and the longer gravity has to act on it, the further the ball will be thrown. 
5. Length of Arm - The length of the arm is crucial to the range of the trebuchet, if the arm is too long, it will not throw correctly. If it is too short, it won't throw as far as possible. 

For our distance portion of competition day, we had 5 throws in 20 minutes and here they are as follows: 

1. 24.1 m
2. 25.3 m
3. 25.8 m
4. 30.5 m
5. 32 m

That turns out to be 27.5 m on average. 

For our accuracy component of the competition we are planning to leave the trigger how it is and just changing the weight of our counterweight to get as close to the target as possible.  

Test Day

On test day my partner and I unloaded our trebuchet from the back of the truck and set it up on the track. We locked our trigger system in place and loaded our counterweight (a bucket) with chains. We adjusted our trigger for maximum efficiency and loaded the tennis ball, ready to fire. When it was time to release our projectile traveled just under 25 meters, which quite surprised me. My expectations for our trebuchet weren't very high, i was prepared for much less than that. We attempted to adjust our trigger as the day went on, which slightly changed our range but no more than 2 or 3 meters. Another thing we tried was adding weight to our counterweight. We added an additional 20 lbs to it, but the extra chain that we added just ended up falling out, so we stuck to just 2 chains (40 lbs.).

Cardboard Trebuchet

This past week my partner and I have constructed a cardboard trebuchet. We both cut out the pieces and folded them into place. Shelby sewed the pouch and we created a trigger system. After we put it all together, we filled our bucket with 32 two washers and we perfected our release angle as best as possible. After everything was tweaked, we peaked at around 6-6.5 meters. For our accuracy test it took about 4-5 times to hit the target. Near the end of the testing our cardboard wasn't holding up as well, I'm glad we finished in time before it fell apart.

Egg Drop Competition Day!

The mass of our container on competition day, after our modifications, was 137.0 g. The containers final dimensions were 27cm/26cm/11cm and dropped from five meters in 1.07 seconds. Our drop was successful, scoring us a perfect 10. Our egg points were calculated out to be 146. I believe that the parachute rule really prevented our container from its full potential. With a parachute attached to our container, you could drop it as many times, and as high as you want and it wouldn't break. I think that the most effective part of our containers design was the flaps. The flaps allowed stabilization during the drop and also slowed down the fall. I don't really see any weaknesses in our design overall, every part of the container was essential for the success of the drop. If I were to carry two eggs I would alter our design by cutting two holes in the toilet roll and i believe that it would also help stabilize the container during the fall.

Egg Drop Test Day!

During testing day we used our design of a box inside of a box and took it to the top of the math staircase to try out our design. It failed, miserably. We decided to give up on that design and start from scratch once again. The next day we came back with a design that consisted of a roll of toilet paper with a hole cut into the side that would hold the egg. It was then wrapped in a sock to prevent the toilet paper roll from falling apart and to add extra cushioning. The whole in the toilet paper provided a tight fit and that prevented the egg from moving around on impact. We took that design back to the staircase to give it another shot, and passed! We decided to give it another go just to make sure that it was consistent. The second drop failed. After being baffled about why it failed the second time, we realized that it was very important to fluff up the bottom of the toilet paper to make sure the egg had a lot of material beneath it to cushion the blow on impact. Some things that we changed before the actual competition day were adding "flaps" or "wings" to our container to slow down the falling speed and keep it stable in the air while being dropped.

Post Race Reflection:

The results conducted from race day were as follows:

            Best distance - 22.2 meters, a new school record! (1st place)

            Drag time - 5:53 seconds. (5th place)

           

1. How would you modify your car design if you had the opportunity? If I could modify anything no our current design, I would cut out a notch in the mouse trap (side closest to the axle) to reduce friction on the string.  
2. What might you do differently if you could build a new car? I was quite impressed with our design of mousetrap car. If I had the choice, I would probably stick to the same design, just use bigger wheels. Another thing that I would consider is lighter materials. Example: aluminum axle instead of brass. The only thing that I could not make lighter would be the chassis. If I made the chassis any lighter, the mousetrap would spin around the axle when set off.
3. What could be tweaked to make your car perform better? One thing that we could have done to improve the performance of our mousetrap car would be to use bigger wheels to increase the final drive, or maybe a stronger string as our previous string broke.

Video's & Photo's from test day: 

 

Mousetrap Vehicle Test Day

These are the results we conducted on our mousetrap vehicle test day:
Does it work? Yes! The vehicle performed very well, even better than most of us expected!
Does it operate consistently? Yes, the vehicle was ran down the downstairs hallway and hit the end wall after every test.
Does it withstant repeated use? Yes, after several uses, the vehicle withstood it's same state as when we started.
Does it meet all design criteria? Yes, nothing was modified or tweaked.
Are risks minimized in design? Yes, the way that the trap is set, you just have to let go of the wheels, and it goes. This minimizes the risk of getting your finger caught in the trap.
Is it easily operated? To a point. The only difficult part is setting the trap, or putting the string through the axle.

Performance:
Did it run in a straight line? Not exactly, the vehicle always wanted to curve to the right after about the 20 meter mark. But it consistently curves to the right so we know how to set it to get the maximum distance out of it.
Distance traveled? 26-28 meters.