PASSIVE BRAKING SYSTEMS
Some of the more common passive braking systems include:
• Gravity: A gravity brake system involves simply tuning the arc of the cable to eliminate forward momentum at the end of the ride through uphill cable (sag) and reduced drop. Typically, this works well with relatively short and low-speed zip lines.
• Brake Blocks with bungee cords or ropes: A brake block is mounted on the zip cable near the end of the zip line and slides freely. When anchored to a bungee cord, the guest’s zip trolley makes contact with the block and pushes the block toward the end of the line. The bungee resists the movement and stops the rider, who rebounds to the landing pad or low point on the line. Alternatively, a rope can be attached to the brake block instead of a bungee. In this case, a guide then slows the rider by creating resistance on the rope. This eliminates recoil and can also be used to tow the rider to the landing. These widely used systems allow for flexibility in speed and rescue on the part of the guides.
Even a Prusik knot, which creates friction on the line, can assist with braking or be used as a back-up brake.
• Spring Brakes: Spring brakes stop a rider’s momentum at the end of the ride by compressing and then pushing a rider back to a stopping point, often via a one-way camming device on the cable. Multiple springs may be used in commercial operations to increase the braking distance at the end of the ride. Springs can also work well for movable/portable zip lines.
• Tires and pucks: Tires can be used to protect riders and equipment at the end of the ride when speeds are relatively low. These are often used as backups for bungee brakes and where precise stops are needed—for example, over a water feature. However, some operators consider tires archaic. Hockey pucks are also installed as back up brakes and stoppers on some lines.
• Magnetic Eddy Current Brakes: This relatively new and sophisticated, as well as most expensive, type of braking system works essentially on centrifugal force. When a rider hits an installed brake block on the cable, magnetic resistance is created at a rate proportionate to the kinetic energy (the combination of weight and speed) of the moving rider—the higher the kinetic energy, the higher the resistance. This accommodates varying rider weights and incoming speeds.
MAKING THE PASSIVE CASE
One of the most prominent names in magnetic passive braking is the ZipSTOP. “The top concerns for zip line operators are safety and throughput,” says Micah Salazar, senior business development manager of Head Rush Technologies, maker of the ZipSTOP. “The name of the game is ROI. If these guys have even one accident, they will likely lose their business, or take a huge hit in increased insurance and legal fees. Throughput is an obvious concern, and is directly tied to return on investment.
“Our ZipSTOP zip line brake meets these demands and offers automatic resetting of the brake, decreasing the risk of operator error or the risk of leaving braking in the hands of the guests,” says Salazar.
Zip-Flyer’s Lerner agrees that efficient and reliable passive braking is the future. “Our Zip-Runner and Zip-Flyer Trolleys offer in-flight braking, which governs the speed of every rider’s descent. For terminal braking we use tried and true braking solutions [i.e., graduated spring packs], but we also push the envelope with innovative, technologically advanced, redundant braking systems.”
One example: Zip-Flyer has forged a partnership with Head Rush Technologies to create the Hybrid zipSTOP. “We’ve incorporated these Hybrid zipSTOPs into our patented ZF Track Braking System, which can stop a 300-pound rider at speeds up to 140 mph,” Lerner says. This system ensures all riders big and small will offload at the exact same point every time, without the need for “massive towers or a football-field-sized landing zone” to accommodate a long line of springs, he notes.
Lerner adds that the system boasts three independent brakes, for triple redundancy, and the landing tower communicates with the launch tower—allowing the next rider to zip only when the brakes are fully reset and ready.