Lego Car 2

With the extreme slowness of our first car in mind, we constructed another, smaller car. We initially wanted to use treads and a 1:15 gear ratio, but the treads were much too high-friction. We also encountered the problem of the 40-tooth gear being too large to be on the same axle as the wheel itself.

Next, we decided to try to change the wheel diameter in order to keep our 1:15 ratio. However, any larger wheels would collide with the overhanging axles of the gear train. This problem could have been solved by lengthening the axle of the wheels, but we were already using the longest available axle and were loath to connect smaller ones together due to the threat of bending.

Instead, we moved the motor to the top of the car, with the belt running diagonally down to the underbelly, and installed a 3-gear gear train diagonally (8-toothed to 40-toothed to 24-toothed, for a total ratio of 1:3 among the gears alone).

The diagonal gears of our 1:9 car

This arrangement, with a total ratio of 1:9, moved very fast without weight, but only very reluctantly and with a slow start would it move the weight. We noticed that the belt was kind of loose in attaching the motor, and after moving the motor one unit over, the belt was much tighter and the car started without any problems, even while carrying a weight. We timed this configuration and had a fast run of 6.2 sec!

In the official race, the car got a time of 6.5 sec. If we could change something, I would probably want to try lengthening the axles by connecting multiple ones together, despite the weakening, and use larger wheels.

The car featured a festive tropical theme