Flywheel

A flywheel is ordinarily mounted near the rear main bearing, which is the longest and sometimes the largest of any of the main bearings in order to support the weight of the flywheel. The flywheel permits the engine to idle smoothly by carrying the pistons through those parts of the stroke cycle when power is not being produced.

The heavier the engine flywheel is the smoother the engine will idle. However an excessively heavy flywheel because of its inertia will cause the engine to accelerate and decelerate slowly.

For these reasons, heavy-duty or truck engines have large and heavy flywheels and racing car or high speed engines have light flywheels.

Because of the forces acting on the flywheel and crankshafts and the speed at which they revolve, it is necessary to balance them with great care.

They are first balanced statically and then balanced dynamically. To obtain static balance, the weight must be equal in all directions from the centre when the crankshaft is at rest.

Dynamic balance means balance while the crankshaft is turning. Dynamic balance is attained when centrifugal forces of rotation are equal in all directions at any point. The balancing operation requires special machinery and involves removal of metal at the heavy points or addition of metal at the light point.

But no matter how carefully the crankshaft and the parts attached to it are balanced, there will be certain speeds, at which vibration will occur. These are known as critical speeds are caused to occur at speeds outside the working speeds of the engine.

Задание 4. Закончите следующие предложения, используя текст “ Flywheel”.

1. A flywheel is ordinarily mounted...

2. The flywheel permits the engine...

3. To obtain static balance, the weight must...

4. Dynamic balance means...

5. Critical speeds are caused to occur...

Задание 5. Дайте антонимы к следующим словам.

Long, heavy, usual, mount, rear, main, accelerate, slow, high speed, static, equal, at rest, often, near, outside.

Задание 6. Найдите ответ, соответствующий содержанию текс­та.

1. Where is a flywheel usually mounted?

2. What is the function of a flywheel in an automobile?

3. What flywheels have heavy-duty vehicles?

4. Why must the flywheel and crankshaft be balanced with great care?

5. What are critical speeds?

Задание 7. Посмотрите на схему на с. 204 и ответьте на вопросы.

1. То what mechanism dоеs the flywheel refer?

2. What other parts are included into this mechanism?

Задание 8. Передайте содержание текста на английском языке, используя вопросы задания 6 как пункты плана пересказа.

При ответе используйте следующие выражения:

the text is about…; the text deals with the problem…; the main subject of the text is...; it should be noted, that....