To bring the expanse of our solar system down to a "workable" size presents some difficulty. For instance, the Sun is ~1,400,000 km in diameter (875,000 miles) or 109 Earth-diameters across and is ~150,000,000 kilometers (93,000,000 miles) from the Earth. The Sun on our model orreries is about 2 inches, and if we were to represent the Earth accurately, it would be a barely visible speck and would orbit over 12 feet away. The other planets would be correspondingly tiny and distant.
Because of these dimensional difficulties, we make an artist compromise in true scale to bring the planets into reproducable relative sizes to one another.