Note that we will be using colour consistently throughout this chapter: The black pieces are parts of the chassis, and the yellow one is obviously a steering wheel. That leaves four other important part:
a steering shaft (red) This is an axle that connects a steering wheel or a motor to the pinion of the rack-and-pinion gear set.
a rack-and-pinion gear set (grey) This gearset consists of a pinion (here, an 8-tooth gear) and a rack, which is a toothed plate, below it (see Figure 14-4); when the pinion rotates left or right, it makes the rack slide.