|The final product|
|Though slight, the distorted angle of the rack is visible.|
|This picture shows the basic mechanism, which did not have|
enough support to function correctly.
For my second attempt, I used a combination of studded and studless pieces. While most technic builders have drifted away from studded beams, they have their merits. Their dimensions are more rigidly set, so a track using bricks and tiles virtually eliminated the vertical breathing room seen in the first model. However, bricks can pull apart vertically, which is why I reinforced it with studless beams crossing the casing vertically. When reinforcing in this way, it is important to note that there must be exactly two plates (two thirds of a brick) between two technic bricks in order for a beam to cross them vertically. This formula follows for greater distances, though it is sometimes easier to fiddle with it until it works than to calculate it. The new, sturdier casing has no vertical give, thus forcing the rack to mesh with the gears at all times. The casing is long enough that the rack can pull all the way off the gears when fully contracted, thus allowing the vehicle to coast.
|The rubber bands take up the space where the cockpit should|
be. Note that the diagonal beams keep the front end from
bending upward under high tension.
|This picture shows how the studless beams (in gray) reinforce|
the studded beams (green) of the main casing.
|This picture shows what it looks like when wound up to maximum.|
|This picture shows how the gears interact when wound up.|
|This one shows how the rack (black) does not mesh with|
the gray eight tooth gears when at rest. This allows the car
to coast after all the tension has been released.
Though outperformed by the one-piece Lego pull-back motors, I still managed to make it go about fifteen feet. The one-piece motors can go twice as far, but they are easy to find, and I tend not to do things the easy way. I enjoy knowing that I created a working mechanism, though not perfect. I encourage everyone to try to build something different, just to see if you can. Happy building!