How Does a Ski Lift Work?
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Chairlifts
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There are many kinds of ski lifts which are divided in two main categories of aerial and surface lifts. These include tramways, gondolas, T-bars and rope-tows, but the most common ski lift is the chairlift from the aerial category. Chairlifts are built to seat two to eight people (double, quad, six-pack) and transport skiers from a base lodge area to either a tier mid-mountain where another lift starts or right to the top. Some ski lifts, called high-speed quads or six-packs, are faster due to their detachable chairs. They are all built with a circulating rope cable and supportive towers.
Cables and Capacity
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The rope cable is strung over supportive towers which make a chairlift recognizable from a distance. The distance between towers is determined during installation, based on how long and steep the lift needs to be and its expected capacity. Most chair lifts built during or after the 1990s are detachable grip lifts meaning each chair's top grip opens and closes at the point of loading or unloading. This allows it to slow down for skiers to get on or off without slowing the rest of the chairs. These grips are explained in depth on Skilifts.org. This type of lift can be twice the speed of a fixed grip chair but is more expensive. Grip chairs are woven right into the cable.
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Detachable Chairs
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At each end of the chair lift is a bullwheel. These are what keep the cable moving and redirect the chairs at loading and unloading points. One of these is the drive bullwheel, which usually electrically powers the lift. There is also a cam-braking structure on the bullwheels and surrounding sheaves. Tension is held by hydraulic rams or a counterweight system on the drive bullwheel, which is constantly changing due to differences in weight, temperature and friction. When a chair enters an end station it is briefly derailed (moving at a slower speed than the cable) while rounding the station and as it is leaving the station it re-grips the cable once again gaining speed and joining the procession.
Extra Safety
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Chairlifts are supervised and maintained during operation by lift operators who can slow or stop a lift in an emergency or unsafe situation. Most chairs have a passenger bar to help people stay safely in the seat. Other safety precautions include load testing with twice the intended weight and, in lighting prone areas, electrically grounding the lifts.
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Resources
- Photo Credit Double chair at Cannon Mtn. NH, Chairlift.org
