Mobile cranes were derived from the early steam cranes, and crawler cranes. They have a huge variety of uses in construction. And form an important part of construction plant history, as without then a lot of current machine designs are directly descended from.
Definition of a crane Edit
A crane is a mechanical lifting device equipped with a winder, wire ropes and sheaves that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human. Cranes are commonly employed in the transport industry for the loading and unloading of freight; in the construction industry for the movement of materials; and in the manufacturing industry for the assembling of heavy equipment.
Mobile crane Edit
The most basic type of mobile crane consists of a steel truss or telescopic boom mounted on a mobile platform, which may be rail, wheeled (including "truck" carriers) or caterpillar tracks. The boom is hinged at the bottom, and can be raised and lowered by cables or by hydraulic cylinders. A hook is suspended from the top of the boom by wire rope and sheaves. The wire ropes are operated by whatever prime movers the designers have available, operating through a variety of transmissions. Steam engines, electric motors and internal combustion engines (IC) have all been used. Older cranes' transmissions tended to be clutches. This was later modified when using IC engines to match the steam engines "max torque at zero speed" characteristic by the addition of a hydrokinetic element culminating in controlled torque converters. The operational advantages of this arrangement can now be achieved by electronic control of hydrostatic drives, which for size and other considerations is becoming standard. Some examples of this type of crane can be converted to a demolition crane by adding a demolition ball, or to an earthmover by adding a clamshell bucket or a dragline and scoop, although design details can limit their effectiveness.
To increase the horizontal reach of the hoist, the boom may be extended by adding a jib to the top. The jib can be fixed or, in more complex cranes, luffing (that is, able to be raised and lowered).
A telescopic crane has a boom that consists of a number of tubes fitted one inside the other. A hydraulic or other powered mechanism extends or retracts the tubes to increase or decrease the total length of the boom. These types of booms are often used for short term construction projects, rescue jobs, lifting boats in and out of the water, etc. The relative compactness of telescopic booms make them adaptable for many mobile applications, often of short duration.
Truck-mounted crane Edit
A crane mounted on a truck carrier provides the mobility for this type of crane.
Generally, these cranes are designed to be able to travel on streets and highways, eliminating the need for special equipment to transport a crane to the jobsite. When working on the jobsite, outriggers are extended horizontally from the chassis then down vertically to level and stabilize the crane while stationary and hoisting. Many truck cranes possess limited slow-travelling capability (just a few miles per hour) while suspending a load. Great care must be taken not to swing the load sideways from the direction of travel, as most of the anti-tipping stability then lies in the strength and stiffness of the chassis suspension. Most cranes of this type also have moving counterweights for stabilization beyond that of the outriggers. Loads suspended directly over the rear remain more stable, as most of the weight of the truck crane itself then acts as a counterweight to the load. Factory-calculated charts (or electronic safeguards) are used by the crane operator to determine the maximum safe loads for stationary (outriggered) work as well as pick and carry work (on-rubber) and safe travelling speeds.
Truck cranes range in lifting capacity from about 5 US tons to about 1300 US tons.
Rough Terrain crane Edit
A crane mounted on an undercarriage with four wheel drive on heavy duty rubber tires that is designed for pick-and-carry operations and for off-road and "rough terrain" applications. Outriggers that extend horizontally and vertically are used to level and stabilize the crane for hoisting.
These telescopic cranes are single-engine machines where the same engine is used for powering the undercarriage as is used for powering the crane hoist, similar to a crawler crane. However, in a rough terrain crane, the engine is usually mounted in the undercarriage rather than in the upper structure, like the crawler crane. Some versions can operate in pick and carry mode.
Crawler crane Edit
A crawler is a crane mounted on an undercarriage with a set of tracks (also commonly called crawlers) that provide for the stability and mobility of the crane. This type of crane has both advantages and disadvantages compared to wheeled or static units depending on their intended use. The main advantage of a crawler is that they can move on site and perform lifts with very little set-up, as the crane is stable on its tracks with no outriggers. In addition, a crawler crane is capable of travelling with a load. The main disadvantage of a crawler crane is that they are very heavy, and cannot easily be moved from one job site to the next without significant expense. Typically, a large crawler must be disassembled and moved by several trucks, rail cars or ships to be transported to its next location, often needing another crane to assist in the assembly/dismantling process.
Crawler cranes range in lifting capacity from about 40 US tons to 3500 US tons.
Compact crawler cranes Edit
A variation that is gaining in popularity is the Compact Crawler crane thathas low ground pressure due to being built on the base unit of 2 to 10 ton excavators. These units have applications for street works and inside or on the top of buildings and the idea appears to have come from the Far East and Japan.
Mini cranes (aka spider cranes in the UK) Edit
Are a modern compact crane on a crawler chassis that can in some cases pass through a door way. These fold up ultra compact, but the out rigger legs fold out like a "spider" to give a wide spaced but stable support. Often being used inside buildings or on the roof to install plant or glazing. capacities range from 0.5 to 10 ton for larger models, but vary depending on outrigger configuration. Being on tracks they have low ground pressure for travelling into working site and can be positioned easily by remote control.
The majority of spider cranes are manufactured in Japan with Maeda having over 70% of the worldwide market.[citation (source) needed] Other manufacturers include Unic and Imai. The popularity of the these cranes has increased steadily throughout Europe over the past decade. The main advantages being their compact dimensions and low outrigger loads. This allows the cranes to be used closer to the lifting operation and therefore improving safety and reduce the need for a much larger crane. They are commonly used for Curtain walling / Glazing applications were they can move about as work proceeds and free up the tower crane for other tasks.
Tracked Access (specialist access & lifting company) are one of the leading rental companies for this type of crane in the UK. Pace Cranes are one of the leading rental companies in the Australia. These cranes are now becoming increasingly popular in the USA.
"Spider" is a registered trademark of SafeWorks, LLC, for use in the lifting and hoisting industry. Use of the term "spider" to refer to lifting and hoisting equipment, including but not limited to cranes, may be a violation of US trademark law. While these products may legitimately be called "spider" products in Europe, where SafeWorks does not own the trademark, the term may not be used in the United States. .
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Early cranes Edit
The first mobile cranes on vehicles were mounted on Steam Tractors, in the 1800s. Following the introduction of the Tractor and Crawler Tractor these were soon adapted to fit similar arms and a winch attached to the drive shaft soon followed.
- Self Erecting Tower Cranes - This is a tower crane which arrives on site ready assembled but folded. When electrical power is connected to the machine, it can be erected by means of its inbuilt hydraulics and ropes. This greatly reduces both the time taken to mobilise and the associated costs with mobilisation taking place within a few hours. Self Erecting Tower Cranes are usually operated through radio remote control, which allows the operator to move freely around the site. In some instances the crane operator can act as a slinger, which again makes the use of the equipment more versatile and cost effective.
- Goliath type are large mobile gantries that run on rails, usually used in shipyards and large engineering works. The best know being the pair at "Harland & Wolf" in Belfast. The largest was the ? crane in Finland (till it was sold to the Koreans).
- Rail cranes, built by Cowans-Sheldon in Carlise, started as steam cranes.
- Dock cranes, Built by Stothert & Pitt of Bath.
- Tower Cranes, Built by Comdil (Terex), Jost, Liebherr, Potain, Wolff and others.
- Scotch Derricks, A type of crane that was common in yards and Quaries. A central cab and winch mounted on a post supported by bracing legs that are anchored down by ballast weight. The design allows the boom and hook to cover a 250 degree arch. Some versions were used to erect early tall building and were mounted on the structure and grew with the building.
- John Allen of Oxford
- American Hoist now part of Terex
- Atlas Hydraulic Loaders Ltd Lorry loader cranes
- Casagrande - crawler cranes & piling rigs
- Chaseside - compact tractor mounted yard cranes.
- Clarke Chapman & Co. Ltd became NEI & now owns Stothert & Pitt
- Coles taken over by Grove of America
- Comedil Tower cranes part of Terex
- Henry Cooch cranes
- Cowan-Sheldon to by Clarke Chapman/NEI
- Faun now part of Tadano
- HIAB Lorry loader hydraulic cranes
- Hydrocon (Lambert Engineering)
- Jones Cranes
- Jost tower crane builder (new french firm)
- Koehring in uk built by Newton Chambers as NCK
- Krupp of Germany takem over by Grove
- Neil F. Lampson
- Liebherr- mobil and Tower cranes
- Link-Belt part of Manitowoc
- Manitowoc also took over Grove
- Mantis Cranes
- NCK Rapier formerly (NCK)
- R.H. Neal & Co. Taken over by Coles Cranes
- New Dafang Group Shipyard crane,concrete box girder crane,container crane,wind turbine crane
- P&H Cranes now part of Terex
- Palfinger Lorry loader cranes
- PPM now part of Terex
- Priestman t/o by sanderson, then RB International, now Clarke Chapman
- Ransomes & Rapier - steam cranes, crawler cranes, t/o by NCK to form NCK Rapier
- RB Cranes / Ruston-Bucyrus became RB International
- Ruston Proctor - steam cranes
- Thomas Smith & Sons (Rodley) Ltd
- Steel & Co. Ltd - took over Coles Cranes, Neal & F Taylor & Sons
- Stothert & Pitt - t/o by Clarke Chapman/NEI
- Taylor & Hubbard rail cranes
- F Taylor & Sons Merged with Coles Cranes
- Terex now owners of a number of other famous brands.
- Wolff tower cranes
UK Crane Hire firmsEdit
- Baldwins Crane Hire
- Crane Services
- Graystone White and Sparrow (GWS)
- Hewden Stuart
- Mantis Cranes
- Scott Greenham
- Stanley Davis
- Tracked Access
International Crane Hire firmsEdit
- http://www.kranliste.dk/ Crane details
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