Abstract: Two employees were leveling a carnival ride situated on a small flatbed trailer. The manually operated ride was a twirling sphere within a sphere (called a "Spaceball") that simulates a gyroscope and twirls in various directions. The "spheres" were constructed of 51-millimeter-diameter steel pipe formed into one or more interlocked circles. The operator helps the rider into the seat, straps the rider in, and then manually turns the middle sphere. After the operator gets that one in motion, he or she steps back and starts rotating the outer sphere. One of the two employees asked his coworker to try the ride to check make sure it was level. After the coworker was strapped in, the operator started turning the inner sphere, then stepped back and rotated the outer sphere. As he did this, he bent downward and inside the rotating outer sphere. The outer sphere struck the operator on the back of the head. He then pulled back and fell over backwards, suffering serious head injuries. The employee was hospitalized for his injuries.