III. Reading.. Перевести.

Let’s suppose theme of the lesson. Look at the pictures. What do you think we’ll talk about?

III. Reading.

Перевести.

A grader, also commonly referred to as a road grader or a motor grader, is a construction machine with a long blade used to create a flat surface during the grading process. Although the earliest models were towed behind horses or other powered equipment, most modern graders contain an engine so are known as " motor graders". Typical models have three axles, with the engine and cab situated above the rear axles at one end of the vehicle and a third axle at the front end of the vehicle, with the blade in between. Most motor graders drive the rear axles in tandem, but some also add front wheel drive to improve grading capability. Many graders also have optional attachments for the rear of the machine which can be ripper, scarifier, blade, or compactor. In certain countries, for example in Finland, almost every grader is equipped with a second blade that is placed in front of the front axle. For snowplowing and some dirt grading operations, a side blade can also be mounted. Some construction personnel refer to the entire machine as " the blade". Capacities range from a blade width of 2. 50 to 7. 30 m (8 to 24 ft) and engines from 93–373 kW (125–500 hp). Certain graders can operate multiple attachments, or be designed for specialized tasks like underground mining.

In civil engineering, the grader's purpose is to " finish grade" (to refine or set precisely). The angle, tilt (or pitch) and height of the grader's blade can be adjusted to achieve precision grading of a surface. The " rough grading" is performed by heavy equipment or engineering vehicles such as scrapers and bulldozers.

Graders are commonly used in the construction and maintenance of dirt roads and gravel roads. In the construction of paved roads they are used to prepare the base course to create a wide flat surface upon which to place the road surface. Graders are also used to set native soilor gravel foundation pads to finish grade prior to the construction of large buildings. Graders can produce inclined surfaces, to give cant(camber or sideslope) to roads. In some countries they are used to produce drainage ditches with shallow V-shaped cross-sections on either side of highways.

Steering for a motor grader is typically accomplished via a steering wheel or joystick controlling the angle of the front wheels, but many models also allow frame articulation between the front and rear axles, which allows a smaller turning radius in addition to allowing the operator to adjust articulation angle to aid in the efficiency of moving material. Other implement functions are typically hydraulically powered, and can be directly controlled by levers, or by joystick inputs or electronic switches controlling Electrohydraulic servo valves.

A more recent innovation is the outfitting of graders with grade control technologies, such as those manufactured by Topcon Positioning Systems, Inc., Trimble Navigation, Leica Geosystems or Mikrofyn^[1] for precise grade control and (potentially) " stakeless" construction. Manufacturers such as Caterpillar have also began to integrate these technologies into their machines out of the factory.

scarifier [ˈ skɛ ə rɪ faɪ ə ] скарификатор, рыхлитель

stake [steɪ k] доля, ставка, пай

Electrohydraulic servo valves. Электрогидравлическиесервоклапаны.

Typically, graders managed (rotary) are the wheels of the front axle; certain types of graders have driven wheels front and rear axles, providing them with the possibility of rotation with a much smaller radius and allows forward movement in which the rear axle does not move in a completely finished road surface. This rotation control circuit has an auto grader D-426.

For convenience, the number of drive axles and axles with steerable wheels is often referred to in the technical literature:

L x B x V,

where

L - number of axles with driven wheels;

B - number of driving axes;

B is the total number of machine axes.

Using such a method of notation for the biaxial motor grader with two leading axles and all steering wheels wheel diagram will be denoted 2х2х2; for three-axle motor grader with two leading and one controlled axle wheel diagram will look like.

Обычно у автогрейдеров управляемыми (поворотными) являются колеса передней оси; некоторые типы автогрейдеров имеют управляемыми колеса передней и задней оси, что обеспечивает им возможность поворота со значительно меньшим радиусом и позволяет осуществлять поступательное движение, при котором колеса задней оси не движутся по окончательно отделанной поверхности дороги. Такую схему управления поворотом имеет автогрейдер Д-426.

Для удобства обозначения количества ведущих осей и осей, имеющих управляемые колеса, в технической литературе часто приводятся условные обозначения:

Л х Б х В,

где

Л — число осей с управляемыми колесами;

Б—число ведущих осей;

В — общее число осей машины.

Пользуясь таким способом обозначения, для двухосного автогрейдера с двумя ведущими осями и всеми управляемыми колесами колесная схема будет обозначаться 2х2х2; для автогрейдера трехосного с двумя ведущими и одной управляемой осью колесная схема будет иметь вид.

True - false