2018-01-08
537
Exercise 1.
1. The burring fuel causes a high temperature within the cylinder.
2. Self- propelled equipment requires specialized power transmission systems.
3. The harvested grain is directed to the grain tank.
4. Operating under heavy load conditions, engines may sometimes knock.
Exercise 2.
1. Reduced power requirements are especially significant when harvesting high moisture crop.
2. The types of tractors usually employed for work in agriculture include the row-crop to general-purpose tractors, standard wheel types, utility tractors and tracklayers.
3. Heavy and medium harrows are used for breaking of ploughed land.
4. When broken or worn, the knife sections can be easily removed and replaced.
Exercise 3.
1. Conventional reversible and disc ploughs are being produced now.
2. A plough is an implement with one or more moldboards cutting and turning the soil.
3. Producing very deep phoughing the digger type of plough body is generally used for root – crops.
4. While moving, any body does work.
Exercise 4.
1. The connecting- rod forming a link between piston and a crankshaft rotates the crankshaft.
2. The piston is moving within the cylinder.
3. Having passed across the field the operator turned the plough.
4. Mowing the body, we apply the force.
Exercise 5.
1. The tractor hydraulic system provides the power turning the plough.
2. The general- purpose type of plough body has become useful for the general ploughing work
3. The adjusted seat suits man better.
4. The several kinds of drills are distinguished by the type of furrow opener used.
Exercise 6.
1. Reduced fuel consumption is an important feature of the new hydraulic system.
2. A harvesting machine is divided into two sections.
|
|
|
3. Operating at higher speeds the driver needs an increased efficiency of the brakes and special devices for vibration isolation.
4. The cutting mechanism is usually controlled by hydraulic or electric lifts.
Exercise 7.
1. Soil compaction is being recognized as a problem on certain soil types.
2. Refined plant oil is very expensive in relation to diesel fuel.
3. When properly maintained tractor engines have higher operation efficiency.
4. Mowers being kept in good adjustment, tlu operator takes full advantage of their peak efficiency.
Exercise 8.
1. The smaller farmers with limited financial resources more often use tractor- powered implements.
2. In the following sections the design criteria of a tractor are being discussed.
3. We achieve a better power output using ethanol as a fuel in diesel engines.
4. Having many moving parts, grain harvesters have many places for wear.
Exercise 9.
1. The increasing use of agricultural machines has brought new technological problems.
2. In his cab, fully isolated from noise, vibration and dust, operator can work long hours.
3. Using the hydraulic system one can lift mounted implements.
4. The knife driven by a connecting rod lies through the fingers which are bolted to the cutter bar back.
Exercise 10.
1. The tractor hydraulic system provides the power turning the plough.
2. The present-day tractor is the most useful machine supplying its power to numerous farm tasks.
3. Harrows are used for various purposes.
4. All the cutting members being sharp, user takes full advantage of their peak efficiency.
ЗАВДАННЯ VII. Перепишіть та перекладіть текст на рідну мову.
TEXT 1.
DIESEL ENGINES
Diesel, or compression ignition engines are similar to the spark ignition engines in principle However, there are important differences. On the intake stroke of the Diesel engines air only enters the cylinder, and is compressed on the next to approximately 1.200 °F by decreasing its volume to about 1/16 of the original volume. This temperature; is known to be high enough to burn heavy fuel that is sprayed into the compressed and heated air by a specially high compression, its parts must be heavier and must fit more perfectly than in a spark ignition engine.
Although Diesel engines will theoretically operate on any oil that can be pumped through the injector, they operate much more efficiently on «Diesel Fuel” or fuel oil.
Some Diesel engines are designed on the two-cycle principle, performing the four necessary operations in two strokes. A blower is usually used to inject air into the cylinder, and to force burned gases out at end of the power stroke.
|
|
|
The most critical part of the Diesel engine is the fuel injecting system. The plungers are built to fit very closely.. Any dust or dirt in the fuel soon wears the injecting pumps until they cannot inject the fuel against the high compression in the cylinder. Special care must be taken with Diesel fuel to keep it clean and to deliver it clean to the injecting pumps.
As an added precaution, several very fine screens and filters are used in the supply line. These must be kept clean and operating efficiently as a protection to the pumps.
Manufacturer's instructions are particularly important in servicing Diesel.
Answer the questions:
1. What is the most critical part of the diesel engine?
2. What is the most important factor in servicing Diesel?
3. What is a blower is used for?
TEXT 2.
COOLING SYSTEMS
Let us examine cooling system arrangements in common use. The simplest is known as the thermo-syphon system. The cylinder block and head contain connected water passages. From the cylinder-head water passage a pipe extends into the top of the radiator From the bottom of the radiator, a pipe is connected to the waiter passage at the bottom of the cylinder block. Thus there is a complete circuit- A fan is provided to draw air through the radiator core.
When the engine is running, the water in the head and upper part of the cylinder block becomes hot and rises into the radiator. At the same time cooler water passes from the bottom of the radiator into the bottom of the cylinder block. The fan draws air through the core and dissipates some of the heat into the surrounding atmosphere. Thus the water circulates continually.
The chief disadvantage of the thermo-syphon system is hat circulation tends to be sluggish, consequently a large radiator capacity, and connections are required.
To reduce these it is customary to fit a pump to assist circulation. Most cooling system pumps are the centrifugal impeller type, usually situated in the passage between cylinder head and radiator and driven by the fan-belt. This system is called the pump-assisted thermo-syphon.
Another device frequently incorporated in cooling systems is the thermostat. The purpose of this is to restrict the circulation of water to the engine until it has reached a predetermined temperature. This ensures that the engine warms up more quickly than it would if the whole of the water circulated,
The complete thermostat assembly is usually contained in the water passage between the cylinder head and the radiator And as long as the valve is closed, no considerable amount of water can pass into the top of the radiator. When the water around the engine reaches a given temperature, the valve opens and allows circulation through the radiator. The temperature at which the valve should open is usually stamped on the thermostat body.
Answer the questions:
1.What is the simplest cooling system?
2.What is the chief disadvantage of the termo-syphon system?
3.What device is used to restrict the circulation of water to the engine?
TEXT 3.
TRACTOR POWER
The basis of mechanization is the supply of power, in other words, it is the tractor. The actual source of farm power supply is the combustion of a fuel in the tractor engines. The engine produces power which the other tractor components make available at the drawbar, belt pulley and power take-off shaft.
The combustion of a mixture of air and fuel produces heat energy which is converted into mechanical energy by the engine. But considerable heat is inevitably lost with the exhaust gases and to the cooling water and mechanical losses of power occur in friction of the moving parts of the engine, in pumping the air of mixture into the cylinders and the burnt gases out of the cylinders and in driving the engine accessories (such as magneto, fan, etc.). Thus the power actually developed by the engine is very much less than the power equivalent latent in the fuel.
The ignition of a mixture of fuel and air in each cylinder gives rise to high pressure in the combustion space and forces the piston downwards; the piston is connected through a crank arrangement to a crankshaft and the pressure acting on each piston during the power stroke causes a turning effort on the crankshaft. The resultant crankshaft torque multiplied by the speed of crankshaft rotation gives the engine power output.
The major function of the tractor is to provide power at the draw bar for field work. Power at the engine flywheels is transmitted through a change-speed gearbox and various reduction gears to the rear wheels of tracks. The actual power at the rear wheel shafts will be lower than that at the engine flywheel because of the mechanical transmission.
Answer the questions:
1.What is the actual source of farm power supply?
2.How is mechanical power produced in a diesel engine?
3.What is the main function of the tractor?
TEXT 4.
DRILL SEEDERS
The grain drill is a machine designed and built to place the seeds of small grains and grasses in the ground in narrow rows spaced at 6 to 8 in (15.2 to 20.3 cm) apart at a uniform depth. The principal parts are the main frame, transport and drive wheels,a box for seed, a device to meter the seed out of the hopperin uniform quantities, furrow openers to open the furrows for t'hc seed, and covering devices.It is known that tractor-operated grain drills can be divided into two types, namely, trailing and mounted. Most of the trailing types are supported by a wheel at each end of the drill. This type is called an end-wheel drill. The wheels serve as ground traction drives to operate the moving parts of the drill.Large drills are divided so that each end wheel drives half of the feeds. Hydraulic remote-control cylinders raise and lower the drill on the end wheels. Trailing press-wheel drills are partly supported by the large press wheel at the rear and partly by the hitch bar in front.
Mounted grain drills are mounted on the tractor by the three- point hitch. The drill feeds and other moving parts are driven by the power take off of the tractor.
Answer the questions:
1. What is the grain drill?
2. How are grain drills classified?
3.How are grain drills mounted on the tractor?
TEXT 5.
CULTIVATOR — HARROWS
We know cultivators and harrows to be implements whose main use is in breaking up clods. For example, they are used after ploughs for breaking up the furrow slices and working the soil to a tilth in the preparation of seedbeds. Other uses include the destruction of weeds, mixing of fertilizers with the soil and covering of seeds. There is no essential difference between cultivators and harrows, but, generally speaking, cultivators are used to deal with heavy work and large clods, and harrows are later employed to continue the work of preparing a fine tilth. We believe the terms "cultivator" and "harrow" to be, however, loosely used; and implements which can bo used for either deep or shallow work are called "cultivator harrows",
|
|
|
The tines used on the older types of harrow are straight and are rigidly fixed in a perpendicular position in a "zig-zag" frame. The depth of penetration of such;u Implements is small; it depends upon the firmness of the soil, the size and shape of the tines and points, and the weight of the implement. Straight tines with the points inclined forward tend to penetrate deeper than vertically mounted ones. Such tines loosen the soil and lift weeds to the surface, while vertical tines compress the lower layers and do not pull out so much rubbish.
Answer the questions:
1. What is the purpose of cultivation?
2. Is there any difference between cultivators and harrows?
3. What does the depth of penetration of such implements depend upon?
TEXT 6.
