A skid loader, skid-steer loader, SSL, or skidsteer is any of a class of compact heavy equipment with lift arms that can attach to a wide variety of buckets and other labor-saving tools or attachments.
The wheels typically have no separate steering mechanism and hold a fixed straight alignment on the body of the machine. Turning is accomplished by differential steering, in which the left and right wheel pairs are operated at different speeds, and the machine turns by skidding or dragging its fixed-orientation wheels across the ground. Skid-steer loaders are capable of zero-radius turning, by driving one set of wheels forward while simultaneously driving the opposite set of wheels in reverse. This "zero-turn" capability (the machine can turn around within its own length) makes them extremely maneuverable and valuable for applications that require a compact, powerful and agile loader or tool carrier in confined-space work areas.
Like other front loaders, they can push material from one location to another, carry material in the bucket, load material into a truck or trailer and perform a variety of digging and grading operations.
History
The first three-wheeled, front-end loader was invented by brothers Cyril and Louis Keller in Rothsay, Minnesota, in 1957. The Kellers built the loader to help a farmer, Eddie Velo, mechanize the process of cleaning turkey manure from his barn. The light and compact machine, with its rear caster wheel, was able to turn around within its own length while performing the same tasks as a conventional front-end loader, hence its name.
The Melroe brothers, of Melroe Manufacturing Company in Gwinner, North Dakota, purchased the rights to the Keller loader in 1958 and hired the Kellers to continue refining their invention. As a result of this partnership, the M-200 Melroe self-propelled loader was introduced at the end of 1958. It featured two independent front-drive wheels and a rear caster wheel, a engine and a lift capacity. Two years later they replaced the caster wheel with a rear axle and introduced the M-400, the first four-wheel, true skid-steer loader. The M-440 was powered by a engine and had an rated operating capacity. Skid-steer development continued into the mid-1960s with the M600 loader. Melroe adopted the well-known Bobcat trademark in 1962.
By the late 1960s, competing heavy equipment manufacturers were selling machines of this form factor.
Operation
Skid-steer loaders are typically four-wheeled or tracked vehicles with the front and back wheels on each side mechanically linked together to turn at the same speed, and where the left-side drive wheels can be driven independently of the right-side drive wheels. This is accomplished by having two separate and independent transmissions; one for the left side wheels and one for the right side wheels. Earliest versions of skid steer loaders used forward and reverse clutch drives. Virtually all modern skid steers designed and built since the mid-1970s use two separate hydrostatic transmissions (one for the left side and one for the right side).
The differential steering, zero-turn capabilities and lack of visibility often exacerbated by carrying loads with these machines means that their safe operation requires the operator have a good field of vision, good hand eye coordination, manual dexterity and the ability to remember and perform multiple actions at once. Before allowing anyone, including adults, to operate a skid steer, they should be assessed on their ability to safely operate the machine and trained in its safe operation. In the US, it is illegal for youth under age 18 employed in non-agricultural jobs to operate a skid steer. For youth hired to work in agriculture, it is recommended they be at least 16 years old and have an adult assess their abilities using the Agricultural Youth Work Guidelines before being allowed to operate a skid steer.
Another thing to consider are beacon lights and reverse signal alarms that offer a warning to co-workers about the skid steer’s movements. These alarms are not always standard equipment on all farm or landscape skid steer machines, depending on factors like the age of the machine. Use and continued maintenance of these alarms greatly reduce the risk of incidents involving running over and/or pinning co-workers between the machine and an obstacle. Construction sites and their business contract requirements often call for landscapers to have operational skid steer reverse signal alarms and beacon lights.