The most significant risk we have currently is about the mechanical design of the erasing system. After discussing with professors, we realized that the friction between the side of the rails and the wheels might prevent the wheels from moving. We will address this risk by adjusting the pressure applied on erasers, which is causing the friction between rails and wheels. We also identified some back up plans, in case the original design would not work. One is to make the wheels rotate vertically to the board, but this design might also face the issue of friction caused by gravity. Another more promising back up plan is to use a screw rod with non-captive stepper motors, but the shipping time of the components is long.
We made several changes to our current design. First is that we decided to remove the solenoid from our design, as a trade-off between functionality and stability. We think that erasing only part of the board, which is what solenoids are for, does not add too much to use case. On the other hand, solenoids add much risks and vulnerability to our physical design, because of the sudden push or pull force it exerts on the whole system. Second is that we decided to modify the eraser moving mechanism as described in the last paragraph. We now have 3 plans, and we will test each plan to see which one works best.
In response to those changes, we modified our schedule. First, the solenoid task is removed. Second, due to shipping delays, we postponed the task of building the mechanical system. We are unsure of when things will actually be delivered, but we will be working on other available parts of the project, while waiting for things to arrive.