When we were making our model, there were a few changes that had to be made in order to make it better. For example, we change our design to use a rubber band rather than string to pull the axle because we felt that rubber bands had more tension allowing the racer to move father. We also had to make cuts into our original base design because if we didn't the wheels wouldn't have been able to move how we wanted them to. But the overall idea for the racer remained the same.