An elevated passenger ropeway, or chairlift, is a type of aerial lift, which consists of a continuously circulating steel wire rope loop strung between two end terminals and usually over intermediate towers, carrying a series of chairs. They are the primary onhill transport at most ski areas (in such cases referred to as 'ski lifts'), but are also found at amusement parks and various tourist attractions.
Depending on carrier size and loading efficiency, a passenger ropeway can move up to 4000 people per hour, and the fastest lifts achieve operating speeds of up to or . The two-person double chair, which for many years was the workhorse of the ski industry, can move roughly 1200 people per hour at rope speeds of up to . The four person detachable chairlift ("high-speed quad") can transport 2400 people per hour with an average rope speed of . Some bi and tri cable elevated ropeways and reversible tramways achieve much greater operating speeds.
Design and function
A chairlift consists of numerous components to provide safe efficient transport.
Terminology
Especially at American ski areas, chairlifts are referred to with a ski industry vernacular. A one-person lift is a "single", a two-person lift is a "double", a three-person lift a "triple", four-person lifts are "quads", and a six-person lift is a "six pack". If the lift is a detachable chairlift, it is typically referred to as a "high-speed" or "express" lift, which results in an "express quad" or "high-speed six pack".
rope speed the speed in meters per second at which the rope moves
[load] interval the spacing between carriers, measured either by distance or time capacity the number of passengers the lift transports per hour efficiency the ratio of fully loaded carriers during peak operation, usually expressed as a percentage of capacity. Because fixed grip lifts move faster than detachables at load and unload, misloads (and missed unloads) are more frequent on fixed grips, and can reduce the efficiency as low as 80%. fixed grip each carrier is fastened to a fixed point on the rope detachable grip each carrier's grip opens and closes during regular operation allowing detachment from the rope and travel slowly for load and unload. Detachable grips allow a greater rope speed to be used, usually twice that of a fixed grip chair, while simultaneously having slower loading and unloading sections. See detachable chairlift.
The capacity of a lift is constrained by the motive power (prime mover), the rope speed, the carrier spacing, the vertical displacement, and the number of carriers on the rope (a function of the rope length). Human passengers can load only so quickly until loading efficiency decreases; usually an interval of at least five seconds is needed.
Rope
The rope is the defining characteristic of an elevated passenger ropeway. The rope stretches and contracts as the tension exerted upon it increases and decreases, and it bends and flexes as it passes over sheaves and around the bullwheels. The fibre core contains a lubricant which protects the rope from corrosion and also allows for smooth flexing operation. The rope must be regularly lubricated to ensure safe operation and long life.
Various techniques are used for constructing the rope. Dozens of wires are wound into a strand. Several strands are wound around a textile core, their twist oriented in the same or opposite direction as the individual wires; this is referred to as Lang lay and regular lay respectively.
Rope is constructed in a linear fashion, and must be spliced together before carriers are affixed. Splicing involves unwinding long sections of either end of the rope, and then winding each strand from opposing ends around the core. Sections of rope must be removed, as the strands overlap during the splicing process.
Terminals and towers
Every lift involves at least two terminals and may also have intermediate supporting towers. A bullwheel in each terminal redirects the rope, while sheaves (pulley assemblies) on the towers support the rope well above the ground. The number of towers is engineered based on the length and strength of the rope, worst case environmental conditions, and the type of terrain traversed. The bullwheel with the prime mover is called the drive bullwheel; the other is the return bullwheel. Chairlifts are usually electrically powered, often with Diesel or gasoline engine backup, and sometimes a hand crank tertiary backup. Drive terminals can be located either at the top or the bottom of an installation; though the top-drive configuration is more efficient, practicalities of electric service might dictate bottom-drive.