A crawler tractor is a machine that operates on a set of tracks instead of tires. Commonly called bulldozers or cats from the brand name Caterpillar, these multipurpose vehicles are able to traverse the most treacherous terrain without becoming stuck. The tracks allow the tractor to exert less weight on the ground than a comparable-sized wheeled tractor. This allows the crawler tractor to be used in conditions where a wheeled vehicle cannot be used.
The advantages of a crawler tractor are its ability to disperse its weight out over a much greater area than that of a wheeled tractor. In doing so, a crawler tractor does not compact the soil as much as a wheeled tractor. This is monumental in farming where the soil suffers from compaction. The disadvantage of a track vehicle lies in the complexity of the tracks and the expense in repair over that of a tire.
The crawler tractor was the inspiration for the modern military tank. While the design has been improved since the first tank was built in England, the basic concept remains as it was in the 1800s. A continuous track vehicle was conceived and built in the late 1800s by a Russian farmer. The design has been adjusted and reworked by many since, resulting in the modern crawler tractor.
Most crawler tractors are used in heavy earth moving and construction. The basic tracked chassis is outfitted with a blade or crane attachment. Many tracked vehicles are also used in farming. The crawler tractor gained its popularity as a farming tool in the United States during The Great Dust Bowl. In many books and movies of that era, the symbol of the times is that of a crawler tractor making its way through the dusty fields of Oklahoma.
While the basic operation of a tracked vehicle is similar to a wheeled vehicle, the main difference lies in steering. Instead of a steering wheel, a track vehicle utilizes a twin stick braking system. The operator applies the brake on the track in the direction of the turn. To turn right, the right track is stopped and the left track drives the vehicle to the right. For a left turn, the brake is applied to the left track and the right track pushes the vehicle around to the left.
The crawler tractor is responsible for successful construction projects in areas which would have been impossible to traverse with a wheeled vehicle. It has been the basis for which military vehicles have been built and it has allowed farming to occur in soft dusty areas. They are also the inspiration for such recreational vehicles as snowmobiles.