CRANES (MACHINE HISTORY)

The principles of operation of today's CRANES is taken for granted, however, we thought you might be interested in learning a bit about the history of Cranes and their development into the modern age of technology.  Cranes are lifting machines equipped with a winder, wire ropes or chains and sheaves that can be used both to lift and lower materials and to move them horizontally. Put in basic terms, they use one or more simple machines to create mechanical advantage to enable the movement of loads beyond the normal capability of a human.

From the ancient Egyptians to the Greek and Roman Empires following through to the Middle Ages, the Industrial Revolution and into technologies available today, the concepts and ideas inspired by mankind's requirements to be able to lift heavy loads in order to construct towering buildings and enable other large scale engineering feats to become possible, is a fascinating source of reading material.  We hope you enjoy and find useful, the information provided.  There are also a large number of photographs to view and download.

ORIGINS OF MODERN DAY CRANES

CRANES AND THE CONSTRUCTION OF THE GOLDEN GATE BRIDGE

Linking San Francisco with Marin County the Golden Gate Bridge is a 1.7 mile-long suspension bridge that can be crossed by car, on bicycles or on foot.  There are parking and viewing areas at either end of the bridge.  As part of both U.S. Route 101 and California State Route 1, it connects the city of San Francisco on the northern tip of the San Francisco Peninsula to Marin County. The Golden Gate Bridge was the longest suspension bridge span in the world when it was completed during the year 1937, and has become an internationally recognised symbol of San Francisco and California. Since its completion, the span length has been surpassed by eight other bridges. It still has the second longest suspension bridge main span in the United States, after the Verrazano-Narrows Bridge in New York City. In 2007, it was ranked fifth on the List of America's Favorite Architecture by the American Institute of Architects.  Golden Gate refers to Golden Gate Strait, a name that originated around 1846.

Ocean tides flow through the Golden Gate four times a day, twice coming in and twice going out. The quantity of salt water in motion between high and low tides averages 390 billion gallons.  Water depth at the Golden Gate is more than 300 feet, but San Francisco Bay waters are, on average, just 14 feet deep. Thousands of animal species, including over 130 species of fish, call the bay home. Four distinct runs of Chinook salmon migrate through the bay on their way to spawn upstream.  San Francisco Bay is a drowned valley. At the end of the most recent Ice Age, 10,000 years ago, melting ice caused rising ocean levels. Water crept steadily through the Golden Gate and flooded the land beyond.

Before the bridge was built, the only practical short route between San Francisco and what is now Marin County was by boat across a section of San Francisco Bay. Ferry service began as early as 1820, with regularly scheduled service beginning in the 1840s for purposes of transporting water to San Francisco. The Sausalito Land and Ferry Company service, launched in 1867, eventually became the Golden Gate Ferry Company, a Southern Pacific Railroad subsidiary, the largest ferry operation in the world by the late 1920s. Once for railroad passengers and customers only, Southern Pacific's automobile ferries became very profitable and important to the regional economy. The ferry crossing between the Hyde Street Pier in San Francisco and Sausalito in Marin County took approximately 20 minutes and cost US$1.00 per vehicle, a price later reduced to compete with the new bridge. The trip from the San Francisco Ferry Building took 27 minutes.

Many wanted to build a bridge to connect San Francisco to Marin County. San Francisco was the largest American city still served primarily by ferry boats. Because it did not have a permanent link with communities around the bay, the city’s growth rate was below the national average. Many experts said that a bridge couldn’t be built across the 6,700 ft (2,042 m) strait. It had strong, swirling tides and currents, with water 500 ft (150 m) in depth at the center of the channel, and frequent strong winds. Experts said that ferocious winds and blinding fogs would prevent construction and operation.

 ARCHITECTS AND ENGINEERS THAT WORKED ON THE PROJECT

Although the idea of a bridge spanning the Golden Gate was not new, the proposal that eventually took place was made in a 1916 San Francisco Bulletin article by former engineering student James Wilkins. San Francisco's City Engineer estimated the cost at $100 million, impractical for the time, and fielded the question to bridge engineers of whether it could be built for less.

One who responded, Joseph Strauss, was an ambitious but dreamy engineer and poet who had, for his graduate thesis, designed a 55-mile (89 km) long railroad bridge across the Bering Strait. At the time, Strauss had completed some 400 drawbridges, most of which were inland, and nothing on the scale of the new project. Strauss's initial drawings were for a massive cantilever on each side of the strait, connected by a central suspension segment, which Strauss promised could be built for $17 million.

Local authorities agreed to proceed only on the assurance that Strauss alter the design and accept input from several consulting project experts. A suspension-bridge design was considered the most practical, because of recent advances in metallurgy.

Strauss spent more than a decade drumming up support in Northern California. The bridge faced opposition, including litigation, from many sources. The Department of War was concerned that the bridge would interfere with ship traffic; the navy feared that a ship collision or sabotage to the bridge could block the entrance to one of its main harbors. Unions demanded guarantees that local workers would be favored for construction jobs. Southern Pacific Railroad, one of the most powerful business interests in California, opposed the bridge as competition to its ferry fleet and filed a lawsuit against the project, leading to a mass boycott of the ferry service.

In May 1924, Colonel Herbert Deakyne held the second hearing on the Bridge on behalf of the Secretary of War in a request to use Federal land for construction. Deakyne, on behalf of the Secretary of War, approved the transfer of land needed for the bridge structure and leading roads to the "Bridging the Golden Gate Association" and both San Francisco County and Marin County, pending further bridge plans by Strauss.  Another ally was the fledgling automobile industry, which supported the development of roads and bridges to increase demand for automobiles.

The bridge's name was first used when the project was initially discussed in 1917 by M.H. O'Shaughnessy, city engineer of San Francisco, and Strauss. The name became official with the passage of the Golden Gate Bridge and Highway District Act by the state legislature in 1923.  Strauss was chief engineer in charge of overall design and construction of the bridge project. However, because he had little understanding or experience with cable-suspension designs, responsibility for much of the engineering and architecture fell on other experts.

Irving Morrow, a relatively unknown residential architect, designed the overall shape of the bridge towers, the lighting scheme, and Art Deco elements such as the streetlights, railing, and walkways.  Aesthetics was the foremost reason why the first design of Joseph Strauss was rejected. Upon re-submission of his bridge construction plan, he added details, such as lighting, to outline the bridge's cables and towers.

Senior engineer Charles Alton Ellis, collaborating remotely with famed bridge designer Leon Moisseiff, was the principal engineer of the project. Ellis was a Greek scholar and mathematician who at one time was a University of Illinois professor of engineering despite having no engineering degree (he eventually earned a degree in civil engineering from University of Illinois prior to designing the Golden Gate Bridge and spent the last twelve years of his career as a professor at Purdue University).

He became an expert in structural design, writing the standard textbook of the time. Ellis did much of the technical and theoretical work that built the bridge, but he received none of the credit in his lifetime. In November 1931, Strauss fired Ellis and replaced him with a former subordinate, Clifford Paine, ostensibly for wasting too much money sending telegrams back and forth to Moisseiff.  

Moisseiff produced the basic structural design, introducing his "deflection theory" by which a thin, flexible roadway would flex in the wind, greatly reducing stress by transmitting forces via suspension cables to the bridge towers. Although the Golden Gate Bridge design has proved sound, a later Moisseiff design, the original Tacoma Narrows Bridge, collapsed in a strong windstorm soon after it was completed, because of an unexpected aero-elastic flutter.

Ellis, obsessed with the project and unable to find work elsewhere during the Depression, continued working 70 hours per week on an unpaid basis, eventually turning in ten volumes of hand calculations.  With an eye toward self-promotion and posterity, Strauss downplayed the contributions of his collaborators who, despite receiving little recognition or compensation, are largely responsible for the final form of the bridge.

Strauss succeeded in having himself credited as the person most responsible for the design and vision of the bridge. Only much later were the contributions of the others on the design team properly appreciated. In May 2007, the Golden Gate Bridge district issued a formal report on 70 years of stewardship of the famous bridge and decided to right an old wrong by giving Ellis major credit for the design of the bridge.

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