A loader (also known as: bucket loader, front loader, front end loader, payloader, scoop loader, shovel, skip loader, and/or wheel loader) is a type of tractor, usually wheeled, sometimes on tracks, that has a front mounted square wide bucket connected to the end of two booms (arms) to scoop up loose material from the ground, such as dirt, sand or gravel, and move it from one place to another without pushing the material across the ground. A loader is commonly used to move a stockpiled material from ground level and deposit it into an awaiting dump truck or into a open trench excavation.
The loader assembly may be a removable attachment or permanently mounted. Often the bucket can be replaced with other devices or tools--for example, many can mount forks to lift heavy pallets or shipping containers, and a hydraulically-opening "clamshell" bucket allows a loader to act as a light dozer or scraper. The bucket can also be augmented with devices like a bale grappler for handling large bales of hay or straw.
Large loaders, such as the John Deere 844J, Caterpillar 950H, Volvo L120E, Case 921E, Caterpillar 966H, or Hitachi ZW310 usually have only a front bucket and are called Front Loaders, whereas small loader tractors are often also equipped with a small backhoe and are called backhoe loaders or loader backhoes.
The largest loader in the world is LeTourneau L-2350. Currently these large loaders are in production in the Longview, Texas facility. The L-2350 uses a diesel electric propulsion system simlilar to that used in a locomotive. Each rubber tired wheel is driven by its own independent electric motor.
Loaders are used mainly for uploading materials into trucks, laying pipe, clearing rubble, and digging. A loader is not the most efficient machine for digging as it cannot dig very deep below the level of its wheels, like a backhoe can. Their deep bucket can usually store about 3-6 cubic meters (exact number varies with the model) of earth. The front loader's bucket capacity is much bigger than a bucket capacity of a backhoe loader. Loaders are not classified as earthmoving machinery, as their primary purpose is other than earthmoving.
Unlike most bulldozers, most loaders are wheeled and not tracked, although track loaders are common. They are successful where sharp edged materials in construction debris would damage rubber wheels, or where the ground is soft and muddy. Wheels provide better mobility and speed and do not damage paved roads as much as tracks, but provide less traction.
In construction areas loaders are also used to transport building materials - such as bricks, pipe, metal bars, and digging tools - over short distances.
Loaders are also used for snow removal, using their bucket or a snowbasket, but usually using a snowplow attachment. They clear snow from streets, highways and parking lots. They sometimes load snow into dump trucks for transport.
High-tip buckets are suitable for light materials such as chip, peat and light gravel and when the bucket is emptied from a height.
Unlike backhoes or standard tractors fitted with a front bucket, many large loaders do not use automotive steering mechanisms. Instead, they steer by a hydraulically actuated pivot point set exactly between the front and rear axles. This is referred to as "articulated steering" and allows the front axle to be solid, allowing it to carry greater weight. Articulated steering provides better maneuverability for a given wheelbase. Since the front wheels and attachment rotate on the same axis, the operator is able to "steer" his load in an arc after positioning the machine, which can be useful. The tradeoff is that when the machine is "twisted" to one side and a heavy load is lifted high, it has a greater risk of turning over to the "wide" side.
Front loaders gained popularity during the last two decades, especially in urban engineering projects and small earthmoving works. Many engineering vehicle manufacturers offer a wide range of loaders, the most notable are those of John Deere, Caterpillar, Case, Volvo, Komatsu and Liebherr.
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