English for Agriculture - Beginners and Intermediate
The word "tractor" is related to words like "traction" and "tractive," from the Latin word "tractus" meaning drawing (pulling). A tractor is a machine designed for pulling heavy loads and powering implements attached to the back usually very slowly and surely. In the past, tractors were originally designed to replace working animals, such as oxen and horses, which people have been using to pull carts and plows since ancient times. One of the pioneers of modern tractors, American industrialist Henry Ford, was inspired on just to come up with something better than the horse for doing heavy farm work. Before tractors existed, horses made life much easier for farmers, but all they could really do was pull things. Because early tractors were only replacements for horses, pulling things were pretty much all they could do as well. Those early tractors were fueled by coal and known as steam traction engines. They looked like small steam locomotives and they came up at the end of the 19th century.
Tractors have large and powerful engine, that means they should be able to go incredibly fast, just like sports cars. But in a tractor, the engine's power is designed to be used in a different way: for pulling big and heavy loads. What makes this possible is the tractor's gearbox, which converts the high-speed revolutions of the powerful diesel engine into much lower-speed revolutions of the wheels, increasing the force the tractor can use for pulling things at the same time. If you know anything about gears, you will realize that a tractor's incredible pulling power must come at the expense of speed: if you ever see a tractor going really fast, it is carrying a heavy load. As well, if you are stuck in traffic in a road behind a tractor that is going slowly, that will be because the engine is probably working as hard as it can pull a heavy load.
Parts of a tractor
Carrying heavy loads is still one of the most important jobs that a tractor does for a farmer. Tractors pull implements or farm machines (such as plows, trailers, hay balers, manure spreaders, etc.) using a powerful cylinder called a drawbar, which makes a secure but very flexible link between the tractor and whatever is following it. The drawbar can turn so a tractor can easily pull its load around corners.
Modern tractors use a hydraulically powered lifting system at the back, known as a hydraulic hitch. This can raise and lower implements off the ground. The hitch makes it easy for a tractor to lower a plow when it is working on a field, and then raises it up again to drive it somewhere else.
Early traction engines could be used to power harvesters, elevators, and other kinds of equipment by parking them, separating their driving wheels, and then transmitting their power to another machine. Typically, this was done by putting a long rubber belt over the spinning wheel on top of the traction engine so it passed over a similar wheel on the machine that needed to be driven. It is the same as bicycle chain takes power from the pedals to the back wheel but using a rubber belt instead of a metal one.
Nowadays, modern tractors can power implements or machines using the power takeoff (PTO). It's a rotating cylinder, usually at the back of a tractor, from which power can be taken from the tractor's engine. To use the power takeoff, you need to hook up a special spinning cylinder between the tractor and the implement. A machine like a hay baler has spinning rakes, wheels, and gears inside it. When it's hooked to the back of a tractor, it's connected to the power takeoff so the tractor's engine powers the machinery inside the bailer as well as driving its own wheels. That's why tractors pulling powered machinery have to drive slowly. These power takeoff spinning cylinders spin at about 500rpm and can be dangerous if someone get close to it.
Tractors have large pneumatic (air filled) tires spread the weight of the tractor over a larger area and deep treads give excellent grip. By reducing the pressure on the ground, the tires stop it from sinking in to soil and mud that would quickly make a regular car get stuck. The more the tires spread the load, the less damage the tractor does to the soil.
Tractors are powered by large diesel engines, which are good at providing high pulling power at a very low speed. Smaller tractors may have gasoline engines and some are powered by LPG (liquified petroleum gas), usually to make them more economical or environmentally friendly.
Driving a tractor needs a great deal of skill. Power-assisted steering and braking are essential to help tractor drivers keep heavy loads safely under control. Since tractors are heavy and often have to work on inclined and unstable ground, there is always a risk they might overturn so modern tractors generally have reinforced cabs fitted with anti-roll bars. Although tractors could never be described as luxurious, most now have heated cabs, some have air conditioning, and a few are fitted with GPS satellite navigation to help farmers plan how they work their fields.