contoured to protect the riders' entire bodies. The odd, apostrophe-shaped capsules, spaced evenly along the perimeter of the boom, look very much like the rows of interlocking teeth on a zipper, the characteristic for which the ride was named. The passenger capsules travel around the perimeter of the boom at 4 revolutions per minute (rpm), not particularly fast, but the "flip" around the end of the oblong frame causes a sudden burst of speed and sends the compartments flipping end over end. The boom itself rotates at 7.5 rpm in the same direction as the pulley system. This combined but offset rotation provides each capsule with a unique and unpredictable experience. These rides rotate both clockwise and counter-clockwise, and most are run with several rotations in each direction constituting "one ride". If the riders shift enough body weight in one direction, they may be able to flip the car even when the boom and the attached cable are motionless. Each car allows limited space for riders. The restraint system for the riders are a lap bar and bars to hang on to. Not holding on to this bar when the ride suddenly jerks can cause a rider's head to hit the door in front of them. Riders also have the ability to attempt to shift their weight to try to flip their car as many times as possible during the ride, even with the little extra space available in the car. Safety issues and revisions The first fourteen Zippers manufactured spun at much higher speeds than modern models. The boom rotated at 11rpm and the cable system at 7rpm. These first-generation rides kept the passenger compartments spinning on their axes constantly, creating unsafe g-forces and causing impact-related injuries such as whiplash, bruises and back injuries. The safety hazard was quickly discovered and the mechanical rpms were permanently lowered to current speeds. On September 7, 1977, the U.S. Consumer Product Safety Commission issued a public warning, urging carnival-goers not to ride the Zipper after four deaths occurred due to compartment doors opening mid-ride. The safety restraints being attached to the door itself, riders are left unrestrained whenever the door is open. The four victims all died after falling from their compartments. The failure was traced to original spring-close latches on the doors wearing out and not being replaced. Compartments on currently operating Zippers are secured using the original latch, a redundant