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.
steering arms (blue) These arms around the connection to the chassis, and their rotation is controlled by the rack.
spindles (green) These are the axles in the wheels are mounted.