Lab 0: Final Lab Write-up

1)
The axiom discussed in class "There is more than one way to skin a cat" proved true on many fronts during this lab. Not only was there a wide range of shooting mechanisms displayed during the competition, but even the smallest details of design and construction could be changed to perform the same function while "making do" with the available materials. We tried our best to build the device with re-purposed or off-the-shelf parts rather than custom pieces, and this lead to many difficulties with operation. Each of our axles, gears, and bearings could have benefited greatly from custom machined parts, but to save time, money, and stay true to our view of the intent of the lab, all of these fittings were "close enough" but not exacting. The "slop" in the system lead to a lot of vibration and wobbling. At the ball interface, we were able to account for this by choosing spongy tires which would grip the ball even if the wheels were spinning slightly off-center. The drive motor, on the other hand, suffered heavily from the extra vibrations because it was not capable of providing the extra torque required to spin the system at high speeds. Thus, or design was able to effectively launch balls in a consistent manner, but not with the desired range because of a lack of angular velocity at the wheels. This illustrates the biggest lesson from Lab 0; that when performing "quick and dirty" rapid-prototyping, certain areas are worth spending extra time and effort on, while others can hacked together and made to perform just fine.

We had a lot of fun with this project. In the typical style of engineers, one of our favorite parts was taking apart the toy and playing around with the components. Another highlight was seeing the design come together and certain parts begin working properly. The first successful ping pong ball launch was also exciting. Of course, there were a few not-so-fun times; early problems were not discouraging, because the trouble-shooting process can be fun, but malfunctions or deterioration in performance in the late stages of testing were problematic because of the added pressure of the time constraint. Also, watching every one of our balls "almost" make it in the bucket without actually going in was frustrating, especially because we had had success in previous trials.

2)
Brainstorming was an interesting process for us, because when we obtained our toy it was not evident which components would be relevant to the task at hand. In fact, we first assumed that we would probably have to use the springs in the pedals to create a sort of catapult design. However, disassembly revealed an electric motor and a full complement of gears, so we had to change our train of thoughts to incorporate motorized designs, which we of course ultimately picked. Our discussion focused both on simplicity and repeatability. A simple device is not only faster to design and assemble, but also has fewer pieces that could break or malfunction and also fewer weak links. Knowing that we would be aiming for small stationary targets, the ability to shoot a series of balls within a small cluster was extremely important. Thus, we wanted to come up with a design that would contact the ball at the same position with the same speed every time.

3)
The most robust aspect of our design turned out to be the tires, as discussed in #1 above. We did not have a single issue with the ball not being pulled through the gap no matter what was going on in the rest of the system. We could say that the motor was the least robust part of the device because it did not have enough power, but the root issue was the reducing play where the axles met the foam walls and also the wheel hub. Vibrations here caused problems with gear meshing, range and consistency.

4)
Mechatronically, our design was oriented more toward the mechanical side, so a lack of experience with mechatronics was never really an issue. The one problem we had with the electronics was the destruction of a potentiometer because we put too much power through it. This could have been avoided with more experience in using pots in high-power systems.