Mousetrap Challenge - 1.4: Written Debrief

I’ll begin by mentioning our process. In short, we (my team) scrambled for ideas since day one but managed to pull it all together on the final day: for that I am proud. We began by assembling a definition statement which was at least plausible to a certain extent. During this process however, we really struggled to come up with something other than because “Crompton told us to”. We were taking the challenge too literally, I for one know I often get frustrated when I don’t see “the point”. Obviously there is no real “point” to this vehicle, it is (I presume) only an introduction for what is to come and a prompter for creative thinking and design. Finally, we decided that “We need a way to propel a vehicle using a mouse trap’s centrifugal force for use as a form of short distance (5m) delivery.” By the time this was concluded we already had a good idea of what our design was going to be - or so we thought.

After a group member found Grant Thompson’s YouTube video of an only slightly modified “Mousetrap Gun” that was able to shoot BB pellets at a high enough velocity to knock over a wooden stand from 3 meters we thought we were done. But after learning the mousetrap was not to be modified in any way we experimented with simply putting an object on the mousetrap and catapulting it – success. A launched pen could fly four meters from the gray tables to the librarian’s desk with ease; therefore, an object with more weight and surfaces with constant width could probably double that distance. At this point, we had forgotten about our definition statement and research/empathy. A further class past before we realized this method didn’t really “deliver” anything. After a passionate catapult-supporter discussed with Mr. Crompton however, this too was resolved. It was determined a catapult delivers its payload as a gun delivers a bullet and is therefore a viable solution. The question did elicit warning however that projectiles are not recommended as aeronautical physics differ from ground-based physics. We didn’t mind though, and I still fail to see why that is applicable to designing a mousetrap vehicle. Calculating and knowing how much potential energy is in a mousetrap does not teach you how to better utilize or magnify it. Despite this, I went home with doubts forming. I thought that despite meeting the challenge criteria the catapult was just too easy and it didn’t satisfy the “empathy” consideration. I joked about how it could deliver packages by launching them into chimneys like Santa but in afterthought (thinking about it figuratively of course) I realized the potential for damage for too high.

On the fourth day, we scrapped almost everything we had. It turns out another group member had similar concerns about the creativity and risks of simply launching an object and dubbing it the vehicle. After much persuasion and even asking permission to temporarily split into two (which was denied) my ideas to restart came out on top and we began to ideate – again. I do admire how quickly and effectively we collectively didn’t hang on to our previous ideas and instead managed to focus on beginning again; the rest of the day was entirely dedicated to ideation and crude testing. Ultimately a working vehicle was produced from this, a cylindrical empty spool for 3-D printer fiber - it was perfect. The “package” could be placed inside as long as the cylinder’s ends were sealed. The idea, however, was less than ideal. The plan was to use a collection of pulleys to allow the mousetrap to quickly yank the vehicle towards the target location; but the transformation of the mousetrap’s circular motion to a lateral force was not effective. The pull was too small in distance to do much. One suggestion was to elongate the “arms” of the mousetrap to maximize the mousetraps imaginary circumference (arc made when the mousetrap is swinging) but that would take too much space and the added weight would sacrifice some of the mousetrap’s speed. For this purpose, the pulleys were also counterproductive. The pulleys would have to be attached to another surface and though the friction from a string is negligible the force exerted on the surface supporting the fulcrum is not.

It was not until the final day an idea agreed upon by all members was presented. After experimenting I found that resting the vehicle on the mousetrap in front of the firing arm caused the cylinder to roll a long distance. As evident by this and our preceding models we had decided not to attach the mousetrap to the vehicle itself to minimize weight. Its performance far exceeded our expectations – when it worked. About 40% of the time it would roll only two or three meters but when lucky it would occasionally roll seven or eight. This unreliability prompted us to control as many variables as we could; to do this we constructed a cardboard launching mat and rails for it to roll straight. For aesthetics and humor, we then added a small flag with the initials “CR” as per the wish of a much-delighted group member and coined the launcher “Amazon Roulette” for its utter unpredictability. The launching mat and rails didn’t seem to improve its reliability though, the vehicle usually rolled straight and if it was destined to turn it would only do so after at least a meter. Should the vehicle have actually hit a rail I’d imagine it wouldn't go very far after that anyways. The greatest contribution of the launching mat was in fact unintentional, the area where the cardboard and mousetrap met made a small indent where the vehicle more or less always rested before launching. It currently still gives too much leeway for us to find the optimal position but it did give me the idea to fabricate a secure and adjustable launching mat using 3-D printing for us to find the optimal position and utilize the energy to its fullest potential every time.

My group fared fantastically in the face of ever mounting pressure to successfully create a working design. Despite being sick on the testing day another classmate informed me my team's design rolled 25 feet or 7.62 meters. This is welcome news though I wonder how many attempts it took to reach 7.62 meters: our mission for iteration two is to achieve consistency. All things considered, in the face of so many dead-ends, I believe we managed our time well, explored as many ideas as possible, and as long as we continue to maintain the level of engagement displayed on the last day of production we will succeed. In retrospect, I have also realized we incorporated both of our primary two ideas into the final design. Despite being a revolution-based propulsion system the method of launching (putting the vehicle on the mousetrap) is very similar to how one would catapult it. I believe this is exemplary of how far we have come together, from a team considering temporarily disbanding to one where there is equal participation and team members that work to collaborate not compete.