After taking measurements on the acrylic piece, we went to the Fabrication Lab (Fab Lab) to saw the larger pieces and drill holes where necessary. Also, since our measurements were off, especially for the placement of the holes, we had to drill again in the correct position. We also used the acrylic bender to bend the acrylic piece where necessary. There was a week where the saw blade was unavailable so we had to use the drill to saw wherever required. The only problem that could not be fixed was the short length of the screw needed to stop the ruler and store potential energy in the ruler. Other than that, we managed to create the desired parts without much difficulty. We were not able to test our design because we the motor was unavailable, and we could only test if the car could be assembled.
We were brought around the Fabrication Lab and briefed about how to operate the relevant machinery there. Then we proceeded to work on our design, fine-tuning it so that the process of cutting the materials to form the shape would be easier. We decided that one we would form a 'T' at the hitting end of the car, ensuring that the bottom of the vertical piece doesn't touch the bottom of the ground, but at the same time has enough clearance over the wheels. Obviously this will cause a moment when the ruler hits the can, causing the car to possibly be unaligned with it. For now we plan to either weigh the other end of the horizontal plane or supporting the base of the cart with weights (like how some construction trucks do when lifting heavy objects). We also made a bolt and nut design to swing the ruler.
After receiving the new car, we went about taking measurements of it, so we could build an accurate model. We also updated the mechanism to fit the car. We felt that if the motor was hung from the mechanism and was directly connected to the arm it would make designing easier, except we would have to counter the increased centre of gravity by weighing the base down. We also took into consideration the height of the platform of the mechanism from the ground because we need to accommodate the heigh of the ruler, ensuring that it doesn't hit the floor prematurely nor does the tires. We also thought of putting a rod that spins the ruler directly.
One of the main changes we did to the mechanism was changing the material of the arm from cardboard/acrylic to a flexible plastic ruler. Firstly the ruler is much lighter and would require less energy to move, but would have a higher kinetic energy and such cause the can to move further (KE = 1/2*mass*velocity^2). Making use of the ruler's flexible properties, we intend to a pole before the ruler strikes the can, to build up energy in the ruler. This will increase its kinetic energy and also the chances of the can crossing the line. Below is how the mechanism will roughly look like:
After being briefed on the task at hand, we decided on what kind of method we would want to use to get to move the can. Since our lecturer didn't advise on physically carrying the can, as he didn't talk about the programming of the motor, we finalised on hitting the can across the line.
Then was the case of hitting it vertically or horizontally. Hitting it horizontally seemed to induce inaccurate movement of the can, that is it tended to fly or roll more to the side rather than straight down. Hence a vertical swinging arm seemed more appropriate. Also, we decided to put a hook where the arm would strike the can, in a fashion comparable to gripping a rock with leather when using a slingshot. Theoretically it should hit the can at a similar angle every time. Also weighing the car down, identical to how trucks that have heavy moving machinery retract weights to that the truck itself is lifted of the ground, lowering the centre of gravity and as such making the car less prone to movements after striking the can.