I do remember the "Rocket Speedway," although I for sure didn't remember the name. The Racing Derby was on the southeast corner of Playland, at the south end of the block within La Playa, Cabrillo, 48th Av., and Fulton. It was right next to Fulton St. It was housed like a Merry-Go-Round, and consisted of four ranks of horses. I think I remember that each radial group of 4 horses were on slotted tracks a few feet long, and crept forward and backward as the circular platform rotated. The platform itself was banked, or "dished" to the axle point, to counteract centrifugal force, as the whole works turned much faster than a Merry-Go-Round, when up to speed. The "race" was against the other 3 horses in your group of 4. I have no recollection of whether there were prizes or free rides for winning.