Draglines comprise some of the largest earthmoving equipment in the world. They are used primarily for excavating earth to uncover coal, minerals, and other bulk materials. The long boom and drag bucket makes the dragline an asset for digging deep holes or mines that other excavators would struggle with. It is capable of excavating a variety of materials from soft to hard, whether it is sand or blasted materials and abrasive rocks. One of the biggest ever to be produced in the world is the Big Muskie by dragline giant Bucyrus International. Costing as much as $250,000, draglines can tower more than 23 yards (21 m) from the ground and remove thousands of metric tons of earth.^[1]

Contents 1 History 1.1 Page's Draglines 1.2 Mobilizing Draglines 1.3 Ransomes & Rapier 1.4 Bucyrus vs. Marion 2 Features/How it Works 3 Common Manufacturers 4 References

[edit] History

[edit] Page's Draglines

The first dragline was invented by John W. Page in 1904. Page & Schnable used this machine to excavate materials for the Chicago Drainage Canal that year. Its success prompted Page to build more. He opened up the Page Engineering Co. in 1912 and set upon producing draglines. Page was also responsible for implementing the machines with diesel operation in 1924.^[2]

[edit] Mobilizing Draglines

Draglines didn’t learn to walk until after the mid-1920s but were made mobile with the help of crawler tracks after 1911. The early machines were usually mounted on rail tracks or rollers. In 1913, Oscar Martinson from Monighan Machine Co. aided in the evolution of the dragline by implementing two movable shoes on each side of the frame to make it mobile. Martinson experienced some success with a self-propelling method that could move the machine. He patented it shortly before it was purchased by Bucyrus-Erie Co. (now Bucyrus International).^[3]

Other manufacturers toyed with the idea of getting draglines to walk but the first dragline to do so successfully was Page’s 600 Walker Series, produced the 1930s. Page made major contributions to the evolution of draglines, including the improvement of dragline mobility, the invention of the archless bucket and continued to do improve on these machines until the company met its demise in 1988.

[edit] Ransomes & Rapier

The dragline business was a beneficial one to get into. Unlike other types of excavators, draglines could excavate heavy material far below the ground. A British firm called Ransomes & Rapier Ltd. designed its first dragline machine in 1938. The W170 was capable of carrying four cubic yards (3.05 m³) of earth and consisted of a 135-foot (41-m) long boom. Ransomes also launched one of the largest machines in the world at the time, the W1400, in 1961. Its drag bucket was 40 cubic yards (31 m³).

[edit] Bucyrus vs. Marion

Bucyrus and Marion Steam Shovel Co. hit the dragline market in a big way, each producing large machines to rival the other. When Marion emerged in 1939 with Model 7200, a five-cubic yard ( 3.8 m³) bucket and 120-foot (37-m) boom, the competition was not largely felt by other manufacturers. Within three years, however, Marion had produced the world’s largest dragline, the 7800 with a 30-cubic yard ( 23-m³) bucket on a 185-foot (56.4-m) boom. Marion tipped the scales yet again when it launched the Model 8800 in 1966, capable of extracting 130 cubic yards (99 m³) of dirt, followed by a version with a 145-cubic yard (111-m³) bucket.

Bucyrus countered this with the Big Muskie (Model 4250W), the biggest and most famous dragline ever to be constructed. The largest walking dragline was built in 1961 for the Central Ohio Coal Co. in 1969. It weighed in at 14,500 tons, consisting of a 220-cubic yard (168-m) bucket and a 310-foot boom (94-m). Capable of removing 608,000,000 metric tons of dirt, the Muskie had a capacity equivalent to excavating the Panama Canal twice over. The second largest mobile earthmoving machine in the world was dismantled in 1999.

Bucyrus and Marion were the kings of the dragline manufacturing industry until Bucyrus purchased Marion in 1997, leaving few dragline manufacturers in the business. There was, however, Harnischfeger Corp., a manufacturer that went on to purchase the first dragline business, Page Engineering Co., in 1988. The company created a series of draglines that were commonly used throughout Australia and Canada.

The world’s largest dragline at the moment goes to Bucryus. The 2570-WS is a super version of their 2570-W.^[4]

[edit] Features/How it Works

Draglines are best suited for a variety of applications, including excavating minerals and raw materials in open mine pits. The length of the boom makes them capable of excavating materials deeper in the ground than any other excavator. The capacity of the bucket to hold a large amount of dirt also adds to its benefit. To enable the dragline to accomplish this, it relies on a hoist cable that pulls and lowers the boom, which is also connected by cables to the bucket.

The bucket can come in a variety of sizes and is measured in cubic yards. The size required for the bucket depends largely on what needs to be excavated and the length of the boom. If the bucket is too heavy for the boom, it can tip the machine. Boom angles are typically at 35 degrees to ensure that tipping does become a risk.

The dragline also consists of drums that coordinate the cables that pull and release the bucket.

Draglines are essentially large boom cranes with an attached drag bucket. Instead of functioning through hydraulics, such as the hydraulic excavator would, the dragline uses a series of cables and operates through its own sheer weight. The dragline usually sits adjacent to the pit that it is excavating, and the wire cables suspend the boom and drag the bucket hoist and dump lines. The fairlead allows the cables to be pulled and released which is responsible for raising and lowering the bucket. It guides the cable to the drum and the bucket is loaded with materials. The cable enforces the pull motion to dig and when this is completed, it releases the drag cable to enable the bucket to empty the materials. The process is repeated as necessary. While it can dig and carry more dirt than most types of excavators, the dragline cannot ensure accuracy as it operates via cables rather than hydraulics.^[5]

[edit] Common Manufacturers

• Bucyrus International

[edit] References

1. ↑ Dragline. AB Heritage. 2008-09-24.
2. ↑ Sheryn, Hinton J. An Illustrated History of Excavators. Ian Allan Publishing: Shepperton, 2000.
3. ↑ Page Walking Draglines. Michael Bezilla. 2008-09-24.
4. ↑ Haddock, Keith. The Earthmover Encylopedia. Motorbooks: St. Paul, 2003
5. ↑ Peurifoy, Robert L. and Schexnayder, Clifford. Construction Planning, Equipment, and Methods. McGraw Hill: New York, 2002.