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A chairlift (technically, an elevated passenger ropeway), is a type of aerial lift, which consists of a continuously circulating steel cable loop strung between two end terminals and generally over intermediate towers, carrying a series of chairs. They are the primary transport at many ski areas, but are also found at amusement parks, various tourist attractions, and increasingly, in urban transport.

Passenger ropeways are both safe and efficient; depending on carrier size and loading efficiency, a passenger ropeway can move up 4000 people per hour, and the fastest lifts achieve operating speeds of up to 12 meters/second (27 mph, 43 km/h). 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 2.5 m/s. The four person detachable chairlift ("high speed quad") can transport 2400 people per hour with an average rope speed of 5 m/s. Some bi and tri cable elevated-ropeways and reversible tramways achieve much greater operating speeds. Fixed-grip lifts are usually shorter than detachable-grip lifts due to rope load; the maximum vertical rise for a fixed grip chairlift is 300-400 meters and a length of about 1200 m, while detachable quads can service a vertical rise of over 600 m and a line length of 2000 m.

Contents 1 Design and function 1.1 Terminology 1.2 Rope 1.3 Terminals and towers 1.3.1 Braking systems 1.3.2 Tensioning system 1.4 Prime mover and gearbox 1.4.1 Secondary and auxiliary movers 1.5 Carriers and grips 1.5.1 Restraining bar 1.5.2 Canopy 1.6 Control system 1.7 Safety systems 1.7.1 Grounding 1.7.2 Braking 1.7.3 Brittle bars 1.7.4 Collision 1.7.5 Communication 1.7.6 Evacuation 2 History 3 Future 4 See also 4.1 Ski and snowboard transport 4.2 Ski industry related 4.3 Other lift technology 5 References 6 External links

[edit] Design and function

A chairlift consists of numerous components to provide safe efficient transport.

[edit] Terminology

rope speed

the speed in feet per minute or meters per second that 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.

The capacity of a lift is constrained by the motive power (prime mover) versus 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 fast before loading efficiency decreases; usually an interval of at least five seconds is needed.

[edit] 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 is 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.

[edit] Terminals and towers

Image:Chairlift bullwheel.jpg Every lift involves at least two terminals and—usually—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 of the lift and the type of terrain it traverses. 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<ref>

 Greater top-drive efficiency assumes the chairlift predominately moves passengers uphill.
Glossary entry for Drive Terminal. skilifts.org. Retrieved on 2006-11-30. </ref>, practicalities of electric service might dictate bottom-drive.

[edit] Braking systems

The drive terminal is also the location of a lift's primary braking system, of which there are at least three. The service brake is located on the driveshaft, before the gearbox, while the emergency brake acts directly on the bullwheel. While not technically a brake, an anti-rollback device (usually a cam) also acts on the bullwheel. This prevents the potentially disastrous situation of runaway reverse operation. Many chairlifts have a braking system in the sheaves.<ref>Service Bulletin #2003-141 (pdf). Riblet Tramway Company (February 142003). Retrieved on 2006-11-28. </ref>

[edit] Tensioning system

The rope must be tensioned to compensate for sag caused by wind load and passenger weight, variations in rope length due to temperature and to maintain friction between the rope and the drive bullwheel. Tension is provided either by a counterweight system or by hydraulic rams, which adjust the position of the bullwheel carriage to maintain design tension.

[edit] Prime mover and gearbox

Either diesel engines or electric motors can function as prime movers. The power can range from under ten horsepower for the smallest of lifts, to several hundred for a long, fast detachable eight-seat up a steep slope. AC electric motors are the most common, though recent technological advances permit the installation of direct current motors, though this is still rare and expensive.

The driveshaft turns at high RPM, but with low torque. The gearbox transforms high RPM/low torque rotation into low RPM/high torque to drive the bullwheel. Higher horsepower is able to pull heavier loads, or sustain a higher rope speed.

[edit] Secondary and auxiliary movers

In most countries, the prime mover must have a backup drive; this is usually provided by a diesel engine, which can operate during power outages. The purpose of the backup is to permit clearing the rope to ensure the safety of passengers; it usually has much lower horsepower and is not used for normal operation. The secondary drive connects with the drive shaft before the gear box, usually with a chain coupling.

Some chairlifts are also equipped with an auxiliary drive, which can be used to continue regular operation in the event of a problem with the prime mover. Some lifts even have a hydrostatic coupling so the driveshaft of a snowcat can drive the chairlift.

[edit] Carriers and grips

Carriers (usually chairs, but sometimes gondolas), designed to seat one to eight people, are connected to the cable with a steel grip that is either clamped onto or weaved into the cable. For clamped systems, the carriers can be removed from or relocated along the rope by loosening the grip, especially for maintenance and servicing. Clamping systems use either a bolt system or coiled spring to provide clamping force.

[edit] Restraining bar

Many chairlifts have retractable restraining bars, sometimes with attached foot rests. In most configurations, a passenger may reach over and behind their head, grab the bar or a handle, and pull the restraint forward and down. Once the bar has rotated sufficiently, gravity assists positioning the bar to its down limit. Before disembarking, the bar must be rotated up, out of the way.

The physics of a passenger sitting properly in a chairlift do not require use of a restraining bar. If the chairlift stops suddenly (as from use of the system emergency brake), the carrier's arm connecting to the grip pivots smoothly forward—driven by inertia—and maintains friction between the seat and passenger. The restraining bar is useful for children—who do not fit comfortably into adult sized chairs—as well as apprehensive passengers, and for those who are disinclined or unable to sit still. The restraining bar is also useful in very strong wind and when the chair is coated by ice.

[edit] Canopy

Some lifts also have individual canopies which can be lowered to protect against inclement weather. The canopy, or bubble, is usually constructed of transparent plexiglass. In most designs, passenger legs are unprotected, however in rain or strong wind this is considerably more comfortable than no canopy.

[edit] Control system

To maintain safe operation, the chairlift's control system monitors and controls several system parameters and either compensates for variances or shuts down the system. In the event of shutdown, human inspection, repair or evacuation might be needed. Both fixed and detachable lifts have sensors to monitor rope speed and hold it within established limits for each defined system operating speed. Also, the minimum and maximum rope tension, and speed feedback redundancy are monitored.<ref>Service Bulletin #2000-137 (pdf). Riblet Tramway Company (December 182000). Retrieved on 2006-11-28. </ref> Detachable chairlift control systems measure grip tension during each detach and attach cycle, verify proper carrier spacing and verify correct movement of the detached carriers through the terminals.^{[citation needed]}

[edit] Safety systems

Aerial lifts have a variety of mechanisms to ensure safe operation over a lifetime often measured in decades.

[edit] Grounding

A steel line strung alongside a mountain is likely to attract lightning strikes. To protect against that and electrostatic buildup, all components of the system are electrically bonded together and connected to one or more grounding systems which connect the lift system to earth ground. In areas subject to frequent electrical strikes, a protective aerial line is fixed above the aerial ropeway.

[edit] Braking

As mentioned above, there are multiple redundant braking systems. Turning off the main drive will normally bring the rope to a stop in installations where it is transporting passengers uphill. A service brake and emergency brake on the bullwheel as well as drum brakes in the sheaves can stop the ropeway quickly.

[edit] Brittle bars

Some installations use brittle bars to detect several hazardous situations. Brittle bars alongside the sheaves detect the rope coming out of the track. They may also detect counterweight movement beyond safe parameters and detached carriers leaving the terminal's track. If a brittle bar breaks, it interrupts a circuit which causes the system controller to immediately stop the system.<ref> Glossary entry for Drive Terminal. skilifts.org. Retrieved on 2006-11-30. </ref>

[edit] Collision

Passenger loading and unloading is supervised by lift operators. Their primary purpose to ensure passenger safety by checking that passengers are suitably outfitted for the elements, not wearing or transporting items which could entangle towers, trees, etc. If a misload or misunload occurs—or is imminent—they slow or stop the lift to prevent carriers from colliding or dragging any person.

[edit] Communication

Lift operators at each terminal communicate with each other to assure all terminals are ready when restarting the system. Communication is used to warn of an arriving carrier with a passenger missing a ski, or otherwise unable to efficiently unload, such as patients being transported in a rescue toboggan. These uses are the chief reason each carrier has a visible identification number.

[edit] Evacuation

Aerial ropeways always have several backup systems in the event of failure of the prime mover. An additional electric motor, diesel or gasoline engine—even a hand crank—allows movement of the rope to eventually unload passengers. In the event of a failure which prevents rope movement, staff may conduct emergency evacuation using a simple rope harness looped over the aerial ropeway to lower passengers to the ground one by one.<ref name="csm"> Information Center for Ropeway Studies (2006-03-17). About Ropeways. Colorado School of Mines - Arthur Lakes Library. Retrieved on 2006-11-30. </ref>

[edit] History

Aerial passenger ropeways were known in Asia well before the 1600s for crossing chasms in mountainous regions. Men would traverse a woven fiber line hand over hand. Evolutionary refinement added a harness or basket to also transport cargo.<ref name="csm" />

The first recorded mechanical ropeway appears to be Venetian Fausto Veranzio who designed a bicable passenger ropeway in 1616. The industry generally considers Dutchman Wybe Adam to have built the first operational system in 1644. Alpine regions of Europe developed the technology which rapidly advanced and expanded with the advent of wire rope and, especially, electric drive. World War I motivated extensive use of miltary tramways for warfare between Italy and Austria.<ref name="csm" />

The first known chairlift<ref> The "first known chairlift" depends on definition: Miners in Kennecott, Alaska used a mining tram to ski in the 1920s. There were other non-ski "chairlifts" in British Columbia at the turn of the century; Grass Valley (California) in 1896; Aspen (Colorado) in 1890; and British Columbia in 1874. </ref> was created for the ski resort in Sun Valley, Idaho in 1936. It was installed on Proctor Mountain, two miles east of the more famous Bald Mountain, the primary ski mountain of Sun Valley resort since 1939. The chairlift was developed by James Curran of Union Pacific's engineering department in Omaha during the summer of 1936. Prior to working for Union Pacific, Curran worked for Paxton and Vierling Steel, also in Omaha, which engineered banana conveyor systems to load cargo ships in the tropics. Curran reengineered the banana hooks with chairs and created a machine with greater capacity than the up-ski toboggan (cable car) and better comfort than the J-bar (rope tow), the two most common skier transports at the time—apart from mountain climbing. His basic design is still used for chairlifts today. W. Averell Harriman, Sun Valley's creator and former mayor of New York City, financed the project.<ref> Don Hibbard (July 1977). Sun Valley Ski Lifts (pdf). Idaho State Historical Society. Retrieved on 2006-11-21. </ref><ref> Sun Valley History. Retrieved on 2006-11-21. </ref>

The second chairlift was the Magic Mile chairlift on Mount Hood, Oregon in 1938 which was also the longest in the world.<ref> Other chairlifts preceded the Mile, but they were originally built for material transport and converted to chairlifts. </ref> <ref> Thomas P. Deering, Jr. (1986). Mountain Architecture: An Alternative Design Proposal for the Wy'East Day Lodge, Mount Hood Oregon. Master of Architecture Thesis, University of Washington. Retrieved on 2006-11-30. </ref> <ref> Alpenglow Ski Mountaineering History Project, Compendium of Northwest Skier Magazine (September 7, 2004). Retrieved on 2006-11-30. </ref>

[edit] Future

New chairlifts built since the 1990s are rarely fixed-grip. Existing fixed-grip lifts are being replaced with detachable chairlifts at most major ski areas. However the relative simplicity of the fixed-grip design results in lower installation, maintenance and—in many cases—lower operation costs. For this reason, they are likely to remain at low volume and community hills, and for short distances, such as beginner terrain.

[edit] See also

[edit] Ski and snowboard transport

• Heliskiing
• Aerial tramway
• Detachable chairlift
• Riblet tramway
• Gondola lift
• Magic carpet
• Platter lift
• Rope tow
• T-bar lift

[edit] Ski industry related

• List of aerial lift manufacturers
• Skiing and Skiing Topics

[edit] Other lift technology

• Aerial tramway (synonyms Cableway, Téléphérique and Seilbahn)
• Basket lift <ref> Lift-World.info list of Basket lifts. Retrieved on 2006-11-30. </ref>
• Cable car (railway)
• Elevator
• Funifor <ref> Lift-World.info list of Funifors. Retrieved on 2006-11-30. </ref>
• Funitel
• Hallidie ropeway
• Paternoster
• List of transport topics

[edit] References

[edit] External links

• Homebuilt Ski Tow
• Skilifts.org An online community dedicated to documenting all types of Ski Lifts
• Union Pacific Railroad The Chairlift's 70th Anniversary
• Chairlift.org preservation society
• Colorado Chairlift Locations
• The Colorado Skier Newsletter archive
• The first ski-lift in the world
• Riblet Tramway Company capacity engineering basicsbg:Лифт

ca:Telecadira cs:Sedačková lanová dráha de:Sesselbahn es:Telesilla fr:Télésiège id:Chairlift nl:Stoeltjeslift no:Stolheis sv:Stollift