5Dump trucks work so hard Come along as dump trucks work together to move big loads of rocks, dirt, gravel, and more. Our Zippy Wheels series celebrates young children's fascination with all things "big rig," helps them learn some interesting things about their favorites, and even comes with rotating wheels. From fire trucks that help save lives, to dump trucks that drop heavy loads, to tractors that help around the farm, and diggers that clear the ground, there's always something to learn and see here.