A Ferris wheel (also known as an observation wheel or big wheel) is a non-building structure consisting of a rotating upright wheel with passenger cars (sometimes referred to as gondolas or capsules) attached to the rim in such a way that as the wheel turns, the cars are kept upright, usually by gravity. Some of the largest and most modern Ferris wheels have cars mounted on the outside of the rim, and electric motors to independently rotate each car to keep it upright. These wheels are sometimes referred to as observation wheels, and their cars referred to as capsules, however these alternative names are also sometimes used for wheels with conventional gravity-oriented cars.
The original Ferris Wheel was designed and constructed by George Washington Gale Ferris, Jr. Ferris was a graduate of Rensselaer Polytechnic Institute and a Pittsburgh, Pennsylvania, bridge-builder. He began his career in the railroad industry and then pursued an interest in bridge building. Ferris understood the growing need for structural steel and founded G.W.G. Ferris & Co. in Pittsburgh, a firm that tested and inspected metals for railroads and bridge builders.
With a height of 80.4 metres (264 ft) it was the largest attraction at the World’s Columbian Exposition in Chicago, Illinois, where it opened to the public on June 21, 1893. It was intended to rival the 324-metre (1,063 ft) Eiffel Tower, the centre piece of the 1889 Paris Exposition.The wheel rotated on a 71-ton, 45.5-foot axle comprising what was at that time the world’s largest hollow forging, manufactured in Pittsburgh by the Bethlehem Iron Company and weighing 89,320 pounds, together with two 16-foot-diameter (4.9 m) cast-iron spiders weighing 53,031 pounds. There were 36 cars, each fitted with 40 revolving chairs and able to accommodate up to 60 people, giving a total capacity of 2,160. The wheel carried some 38,000 passengers daily and took 20 minutes to complete two revolutions, the first involving six stops to allow passengers to exit and enter and the second a nine-minute non-stop rotation, for which the ticket holder paid 50 cents.
The Exposition ended in October 1893, and the wheel closed in April 1894 and was dismantled and stored until the following year. It was then rebuilt on Chicago’s North Side, near Lincoln Park, next to an exclusive neighborhood. This prompted William D. Boyce, then a local resident, to file a Circuit Court action against the owners of the wheel to have it removed, but without success. It operated there from October 1895 until 1903, when it was again dismantled, then transported by rail to St. Louis for the 1904 World’s Fair and finally destroyed by controlled demolition using dynamite on May 11, 1906.
Observation wheel is an alternative name for Ferris wheel. In 1892, when the incorporation papers for the Ferris Wheel Company (constructors of the original 1893 Chicago Ferris Wheel) were filed, the purpose of the company was stated as: [construction and operation of] “…wheels of the Ferris or other types for the purpose of observation or amusement”. Some Ferris wheels are marketed as observation wheels, any distinction between the two names being at the discretion of the operator, however the wheels whose operators reject the term Ferris wheel are often those having most in common with the original 1893 Chicago Ferris Wheel, especially in terms of scale and being an iconic landmark for a city or event.
Wheels with passenger cars mounted external to the rim and independently rotated by electric motors, as opposed to wheels with cars suspended from the rim and kept upright by gravity, are those most commonly referred to as observation wheels, and their cars are often referred to as capsules. However, these alternative names are also sometimes used for wheels with conventional gravity-oriented cars.
There are currently only three major Ferris wheels with motorised capsules.
The 165 m (541 ft) Singapore Flyer has cylindrical externally mounted motorised capsules and is described as an observation wheel by its operators, but credited as “world’s largest Ferris wheel” by the media.
The 135 m (443 ft) London Eye, typically described as a “giant Ferris wheel” by the media, has ovoidal externally mounted motorised capsules and is the “world’s tallest cantilevered observation wheel” according to its operators, who claim: “The London Eye is often mistakenly called a Ferris wheel. This is not the case: first, the passenger capsules are completely enclosed and are climate controlled; secondly, the capsules are positioned on the outside of the wheel structure and are fully motorised; and third, the entire structure is supported by an A-frame on one side only.” However, the operators of the Singapore Flyer claim their wheel is the “world’s largest observation wheel” despite it not being supported by an A-frame on one side only.
The 120 m (394 ft) Southern Star (which opened 20 December 2008, then closed the following month, and is currently dismantled for major repairs) has ovoidal externally mounted motorised capsules and is described by its operators as “the only observation wheel in the southern hemisphere”, but also as a Ferris wheel by the media.
A fourth wheel, the proposed 167.6 m (550 ft) High Roller, announced in August 2011 and scheduled for completion on the Las Vegas Strip in late 2013, is to feature externally mounted motorised capsules of a transparent spherical design, and is described as both a Ferris wheel and an observation wheel by the media.
Transportable Ferris wheels are designed to be operated at multiple locations, as opposed to fixed wheels which are usually intended for permanent installation. Small transportable designs may be permanently mounted on trailers, and can be moved intact. Larger transportable wheels are designed to be repeatedly dismantled and rebuilt, some using water ballast instead of the permanent foundations of their fixed counterparts.