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Mobile Excavator

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1998 Gradall XL5100 Mobile Excavator
Mobile excavators
have been a long time coming. Early excavators, albeit primitive, have been around for centuries and were innovated constantly to make them mobile for a variety of circumstances. The first excavators were made mobile by small wheels that could be used on railways.

Manufacturers started mounting excavators on the chassis of tractors and eventually, trucks. After the Second World War and the advent of a larger number of construction projects that were required to be completed in a short duration of time, manufacturers began producing the wheeled excavator as one component, hence the modern version of the mobile excavator that is seen today.

Mobile excavators function much like any other type of excavator. They are commonly used for digging rocks and soil, but with its many attachments it can also be used for cutting steel and breaking concrete, drilling holes in the earth, laying gravel onto the road prior to paving, crushing rocks, steel, and concrete, and even mowing landscapes.[1]

Contents

[edit] History

Excavators are one of the oldest types of earthmoving equipment. Even in their most primitive form, they contributed to the building of structures that continue to stand today, including the Great Pyramid in Giza, Egypt, a structure built approximately 4,600 years ago. With the help of the excavator, 1.6 million cubic yards (1.2 million m3) of the soil was removed.

[edit] Otis' Contributions

The first modern excavator was invented by William Otis in 1835 in Canton, Massachusetts. The Otis excavator resembled a quarry derrick and consisted of cables, an arm, and a bucket that was attached to a boom swing. The swing was pulled by ropes connected to a boom swing.[2]

Otis patented the self-propelled Otis Shovel in 1836 and seven were produced a year later. The Otis shovel used one bucket located on its arm to penetrate and lift earth It had a power thrust that could manipulate the radius of the cut of the soil. Like many excavators today, it could slew (swing), crowd, and hoist. The wheels were made of cast iron so it was limited in where it could travel.

When Otis died, his widow married a businessman by the name of Oliver S. Chapman in 1844. Chapman took over Otis’ company and produced the Otis-Chapman shovel in the 1870s. Some of his models were used in the building of the Welland Canal.

1996 Fiat-Hitachi FH150W-3 Mobile Excavator

[edit] Developments and Enhancements

Excavators were being built for a variety of purposes as manufacturers begin seeing what they were capable of. Developments such as the first excavator shovel for the railroad, as created by Harry Barnhart in 1884, propelled the exploration of the movement of excavators and how it could be improved upon. It was around this time that mobility became a factor in the production and demand for excavators.

Excavators were mounted on top of crawlers and tractors when wheeled excavators could not achieve the construction purpose. The first excavators on wheels were used primarily for railways and had small wheels that could not be utilized in other environments. Wheeled excavators such as the Vulcan “Little Giant” focused more on mobility with their self-propelling traction-focused wheels. This was particularly useful as excavators were increasingly used in urban areas where a lot of movement was necessary.[3]

Early on, companies such as Bucyrus, Marion, and Osgood detected the need for mobile excavators and produced railway shovels that could be transported via trains from one project to the next.

Some manufacturers took other measures to make their excavators more mobile. The German company, Menck & Hambrock, developed a shovel excavator with a partial slew in 1911 to make it easier to move. This excavator used large, steel rollers to travel short distances. Similarly, the American Speeder Machinery Co., which would later be known as Link-Belt, built a compact mobile shovel digger, the Tumblebug.

Even crawler excavators, with their ability to ride over the rough terrain that the railway excavators couldn’t, were limited in their mobility. To combat this, manufacturers began mounting excavators on trucks and anything with wheels to make it more mobile. Frederick O. Kilgore produced a hydraulic steam shovel that was mounted on wheels. This excavator could be driven on roadways and came in models 30t or 60t. It was capable of digging 1 to 2.1 cubic yards (0.95 to 1.9 m3) of earth.

After World War II, an emerging trend changed the way excavators moved. Increasingly, manufacturers were mounting them on trucks so they could travel from one job to the next without hassle, enabling jobs to be completed in a shorter duration. To disassemble a 17-ton steam excavator, for example, could take as much as 280 hours of manual labor, according to one source, Professor Garbotz. The amount of time a mounted excavator could shave off per application was worth the effort.[4]

The Bruneri brothers, Carlo and Mario, were perhaps the most responsible for mobile excavators. They produced an excavator with wheels in 1948. The excavator had a 360 degree slew swing and a fully hydraulic backacter bucket. SICAM also began producing excavators that were mounted on trucks in 1954. The Yumbo S25 and the H25 were self-propelled excavators mounted on trucks, the H25 weighing in at 7.4 tons. The AB1500, produced by Atlas Weyhausen in 1956 consisted of an excavator that was mounted on a truck with features such as a telescoping boom, shovel or a backhoe.[5]

The Michigan Power Shovel Co. built the TM-16, which was essentially an excavator mounted on the chassis of a highly mobile truck. The TM-16, a two-axle, all-wheel drive, was an incredibly popular machine in the 1950s, even being imported to Germany. Every component was top of the line to give it the mobility that was in demand, with an AB 100 “dragon” chassis was supplied by Krupp Sudwerke.

[edit] Features/How it Works

[edit] The Arm

The excavator operates on different levels. The first is the arm of the vehicle. The arm is comprised of two hydraulic cylinders, a backet (the bucket-shaped component), and a boom (which is on the upper part of the arm). The arm moves in two parts just like a human arm would: at the wrist and the elbow.

Inside of the hydraulic cylinder is a rod (which is the inner part of the cylinder) and a piston, which is at the end of the cylinder and enables the arm to move with the help of oil. If there were no oil in the cylinder, the piston would drop to the bottom, but because of the nature of oil, its volume always stays the same.

Oil is pumped through the end of the piston and in turn pushes the rod through the cylinder, thus creating movement of one or both parts of the arm. By controlling the amount of oil pumped through the valve, the accuracy of the arm can be easily manipulated. This movement is activated by the use of control valves that are positioned inside the cab where the driver's seat is.

[edit] The Engine

1992 Akerman H7MC Mobile Excavator
Power in an automobile is normally received straight from the engine, but it works differently in a hydraulic excavator. Because the machine uses a lot of force, it is able to move by changing the energy it receives from the engine into hydraulic power. Excavators can alternatively operate with a diesel engine.

[edit] The Swing

One of the functions of this machine is its ability to turn. The swing of the excavator enables it to turn. The swing circle comprises of several components: an outer race, an inner race, ball bearings, and a pinion. As the outer race turns, the pinion runs alongside the unmoving inner race. The ball bearings work to ensure that this is done smoothly.

[edit] The Cab

The third part of the excavator is the upper structure where the driver’s seat is located and the controls are positioned. With the help of two levers on both sides and two in the front, the driver can move both at the same time to control direction and height.

[edit] The Feet

The mobile excavator has wheels that allow it to travel great distances and speed on gravel and some dirt roadways. It is most efficient for construction projects that require a great deal of mobility in a short amount of time. Wheels can be pneumatic and have a variety of traction patterns dependent on what is required.[6]

[edit] Types

“The Machine of Tomorrow” shovel appeared in adverts in 1947 for U.S. company General, which is now a part of Osgood. This model 105 excavator was described as “the most advanced machine ever produced in the industry,” and differed from other excavators in that it was not mounted on a truck. It had consisted of one engine and control position.

The first European wheeled excavator was built by Nordest and it featured pneumatic tires. The Supermobile had a low power of 45 horsepower while it was in transportation model and could obtain a maximum speed of 9.3 miles (15 km) per hour.[7]

One of the largest wheeled excavator was the Drott Yumbo 80R, produced in 1970.[8]

The largest mobile machine in the world is the BWE that was produced for a coalmine project in Rheinische Braunkohlenwerke AG (now known as RWE Rheinbraun in Cologne, Germany. The excavator weighted 6,120 tons and had a bucket capacity of 5,000 cubic yards (3,823 m3) per hour.[9]

[edit] Common Manufacturers

[edit] Additional Photos

1989 Case 1085B 4x4 Mobile Excavator
2004 Caterpillar M318C Mobile Excavator

[edit] References

  1. The Mechanism of a Hydraulic Excavator. Kenkenkikki. 2008-09-24.
  2. Grimshaw, Peter. Excavators. Blandford Press: 1985.
  3. Grimshaw, Peter. Excavators. Blandford Press: 1985.
  4. Cohrs, Heinz-Herbert. 500 Years of Construction. KHL Group:1995.
  5. Grimshaw, Peter. Excavators. Blandford Press: 1985.
  6. The Mechanism of a Hydraulic Excavator. Kenkenkikki. 2008-09-24.
  7. Cohrs, Heinz-Herbert. 500 Years of Construction. KHL Group:1995.
  8. Grimshaw, Peter N. The Amazing Story of Excavators. KHL Group: Wadhurst, 2002.
  9. Haddock, Keith. The Earthmover Encyclopedia. Motorbooks: St. Paul, 2003.